PINNACLE WEST CAPITAL CORP, 10-K filed on 2/25/2025
Annual Report
v3.25.0.1
Cover Page - USD ($)
 12 Months Ended
Dec. 31, 2024
Feb. 20, 2025
Jun. 30, 2024
Entity Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2024    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 1-8962    
Entity Registrant Name PINNACLE WEST CAPITAL CORPORATION    
Entity Tax Identification Number 86-0512431    
Entity Incorporation, State or Country Code AZ    
Entity Address, Address Line One 400 North Fifth Street, P.O. Box 53999    
Entity Address, City or Town Phoenix    
Entity Address, State or Province AZ    
Entity Address, Postal Zip Code 85072-3999    
City Area Code (602)    
Local Phone Number 250-1000    
Title of 12(b) Security Common Stock,No Par Value    
Trading Symbol PNW    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 8,663,553,568
Entity Common Stock, Shares Outstanding   119,099,064  
Documents Incorporated by Reference
Portions of Pinnacle West Capital Corporation’s definitive Proxy Statement relating to its Annual Meeting of Shareholders to be held on May 21, 2025 are incorporated by reference into Part III hereof.
    
Entity Central Index Key 0000764622    
Amendment Flag false    
Document Fiscal Year Focus 2024    
Document Fiscal Period Focus FY    
Arizona Public Service Company      
Entity Information [Line Items]      
Document Type 10-K    
Document Period End Date Dec. 31, 2024    
Current Fiscal Year End Date --12-31    
Entity File Number 1-4473    
Entity Registrant Name ARIZONA PUBLIC SERVICE COMPANY    
Entity Tax Identification Number 86-0011170    
Entity Incorporation, State or Country Code AZ    
Entity Address, Address Line One 400 North Fifth Street, P.O. Box 53999    
Entity Address, City or Town Phoenix    
Entity Address, State or Province AZ    
Entity Address, Postal Zip Code 85072-3999    
City Area Code (602)    
Local Phone Number 250-1000    
Title of 12(g) Security Common Stock    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Public Float     $ 0
Entity Common Stock, Shares Outstanding   71,264,947  
Documents Incorporated by Reference
Arizona Public Service Company meets the conditions set forth in General Instruction I(1)(a) and (b) of Form 10-K and is therefore filing this form with the reduced disclosure format allowed under that General Instruction.
    
Entity Central Index Key 0000007286    
Amendment Flag false    
Document Fiscal Year Focus 2024    
Document Fiscal Period Focus FY    
v3.25.0.1
Audit Information
 12 Months Ended
Dec. 31, 2024
Auditor [Line Items]  
Auditor Name Deloitte & Touche LLP
Auditor Location Tempe, Arizona
Auditor Firm ID 34
Arizona Public Service Company  
Auditor [Line Items]  
Auditor Name Deloitte & Touche LLP
Auditor Location Tempe, Arizona
Auditor Firm ID 34
v3.25.0.1
CONSOLIDATED STATEMENTS OF INCOME - USD ($)
shares in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Income Statement [Abstract]      
OPERATING REVENUES (Note 2) $ 5,124,915 $ 4,695,991 $ 4,324,385
OPERATING EXPENSES      
Fuel and purchased power 1,822,566 1,792,657 1,629,343
Operations and maintenance 1,165,156 1,058,725 987,072
Depreciation and amortization 895,346 794,043 753,195
Taxes other than income taxes 227,395 224,013 220,370
Other expense 2,389 1,913 2,494
Total 4,112,852 3,871,351 3,592,474
OPERATING INCOME 1,012,063 824,640 731,911
OTHER INCOME (DEDUCTIONS)      
Allowance for equity funds used during construction (Note 1) 38,620 53,118 45,263
Pension and other postretirement non-service credits, net (Note 7) 48,870 40,648 98,487
Other income (Note 16) 48,614 33,666 7,916
Other expense (Note 16) (34,136) (25,056) (52,385)
Total 101,968 102,376 99,281
INTEREST EXPENSE      
Interest charges 425,742 374,887 283,569
Allowance for borrowed funds used during construction (Note 1) (48,270) (43,564) (28,030)
Total 377,472 331,323 255,539
INCOME BEFORE INCOME TAXES 736,559 595,693 575,653
INCOME TAXES (Note 4) 110,529 76,912 74,827
NET INCOME 626,030 518,781 500,826
Less: Net income attributable to noncontrolling interests (Note 17) 17,224 17,224 17,224
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS $ 608,806 $ 501,557 $ 483,602
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING — BASIC (in shares) 113,846 113,442 113,196
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING — DILUTED (in shares) 116,232 113,804 113,416
EARNINGS PER WEIGHTED-AVERAGE COMMON SHARE OUTSTANDING      
Net income attributable to common shareholders — basic (in dollars per share) $ 5.35 $ 4.42 $ 4.27
Net income attributable to common shareholders — diluted (in dollars per share) $ 5.24 $ 4.41 $ 4.26
v3.25.0.1
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Statement of Comprehensive Income [Abstract]      
NET INCOME $ 626,030 $ 518,781 $ 500,826
Derivative instruments:      
Net unrealized gain (loss), net of tax benefit (expense) of $(292), $234, and $615 (891) 713 1,873
Pension and other postretirement benefits activity, net of tax benefit (expense) of $(1,073), $801, and $(7,078) (Note 7) 3,093 (2,422) 21,553
Total other comprehensive income (loss) 2,202 (1,709) 23,426
COMPREHENSIVE INCOME 628,232 517,072 524,252
Less: Comprehensive income attributable to noncontrolling interests 17,224 17,224 17,224
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS $ 611,008 $ 499,848 $ 507,028
v3.25.0.1
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Statement of Comprehensive Income [Abstract]      
Net unrealized gain (loss), net of tax benefit (expense) $ (292) $ 234 $ 615
Pension and other postretirement benefits activity, net of tax benefit (expense) $ (1,073) $ 801 $ (7,078)
v3.25.0.1
CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
CURRENT ASSETS    
Cash and cash equivalents $ 3,838 $ 4,955
Customer and other receivables 525,608 513,892
Accrued unbilled revenues 176,903 167,553
Allowance for doubtful accounts (Note 2) (24,849) (22,433)
Materials and supplies (at average cost) 469,022 444,344
Income tax receivable (Note 4) 0 332
Fossil fuel (at average cost) 32,420 49,203
Assets from risk management activities (Note 15) 10,578 6,808
Assets held for sale (Note 20) 0 35,139
Deferred fuel and purchased power regulatory asset (Note 3) 287,597 463,195
Other regulatory assets (Note 3) 133,372 162,562
Other current assets 74,915 101,417
Total current assets 1,689,404 1,926,967
INVESTMENTS AND OTHER ASSETS    
Nuclear decommissioning trusts (Notes 12 and 18) 1,282,845 1,201,246
Other special use funds (Notes 12, 17 and 18) 408,357 362,781
Assets from risk management activities (Note 15) 5,980 0
Other assets 115,095 102,845
Total investments and other assets 1,812,277 1,666,872
PROPERTY, PLANT AND EQUIPMENT (Notes 1, 6 and 9)    
Plant in service and held for future use 25,860,950 24,211,167
Accumulated depreciation and amortization (9,027,426) (8,408,040)
Net 16,833,524 15,803,127
Construction work in progress 1,592,659 1,724,004
Palo Verde sale leaseback, net of accumulated depreciation of $268,894 and $264,624 (Note 17) 82,556 86,426
Intangible assets, net of accumulated amortization of $925,880 and $885,505 591,310 267,110
Nuclear fuel, net of accumulated amortization of $115,894 and $118,074 97,850 99,490
Total property, plant and equipment 19,197,899 17,980,157
DEFERRED DEBITS    
Regulatory assets (Notes 1, 3, 4 and 7) 1,389,489 1,390,279
Operating lease right-of-use assets (Note 8) 1,605,463 1,309,975
Assets for pension and other postretirement benefits (Note 7) 342,102 323,438
Other 66,126 63,465
Total deferred debits 3,403,180 3,087,157
TOTAL ASSETS 26,102,760 24,661,153
CURRENT LIABILITIES    
Accounts payable 485,426 442,455
Accrued taxes 175,863 166,833
Accrued interest 81,799 72,916
Common dividends payable 106,592 99,813
Short-term borrowings (Note 5) 568,450 609,500
Current maturities of long-term debt (Note 6) 800,000 875,000
Customer deposits 44,345 42,037
Liabilities from risk management activities (Note 15) 52,340 80,913
Liabilities for asset retirements (Note 11) 50,009 28,550
Operating lease liabilities (Note 8) 100,367 67,883
Regulatory liabilities (Note 3) 206,955 209,923
Other current liabilities 171,651 193,524
Total current liabilities 2,843,797 2,889,347
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 6) 8,058,648 7,540,622
DEFERRED CREDITS AND OTHER    
Deferred income taxes (Note 4) 2,444,473 2,416,480
Regulatory liabilities (Notes 1, 3, 4 and 7) 1,855,278 1,965,865
Liabilities for asset retirements (Note 11) 1,096,577 937,451
Liabilities for pension benefits (Note 7) 139,317 112,702
Liabilities from risk management activities (Note 15) 9,446 42,975
Customer advances 569,343 533,580
Coal mine reclamation 171,483 184,007
Deferred investment tax credit 249,490 257,743
Unrecognized tax benefits (Note 4) 44,233 33,861
Operating lease liabilities (Note 8) 1,520,877 1,210,189
Other 242,320 251,469
Total deferred credits and other 8,342,837 7,946,322
COMMITMENTS AND CONTINGENCIES (Note 10)
EQUITY    
Common stock, no par value; authorized 150,000,000 shares, 119,143,782 and 113,537,689 issued at respective dates 3,121,617 2,752,676
Treasury stock at cost; 46,968 and 113,272 shares at respective dates (3,323) (8,185)
Total common stock 3,118,294 2,744,491
Retained earnings 3,666,959 3,466,317
Accumulated other comprehensive loss (Note 19) (30,942) (33,144)
Total shareholders’ equity 6,754,311 6,177,664
Noncontrolling interests (Note 17) 103,167 107,198
Total equity 6,857,478 6,284,862
TOTAL LIABILITIES AND EQUITY $ 26,102,760 $ 24,661,153
v3.25.0.1
CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
PROPERTY, PLANT AND EQUIPMENT    
Accumulated depreciation of Palo Verde sale leaseback $ 268,894 $ 264,624
Accumulated amortization on intangible assets 925,880 885,505
Accumulated amortization on nuclear fuel $ 115,894 $ 118,074
EQUITY    
Common stock, authorized (in shares) 150,000,000 150,000,000
Common stock, issued (in shares) 119,143,782 113,537,689
Treasury stock at cost (in shares) 46,968 113,272,000
v3.25.0.1
CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
CASH FLOWS FROM OPERATING ACTIVITIES      
Net Income $ 626,030 $ 518,781 $ 500,826
Adjustments to reconcile net income to net cash provided by operating activities:      
Gain on sale relating to BCE (22,988) (6,423) 0
Depreciation and amortization including nuclear fuel 956,184 854,136 817,814
Deferred fuel and purchased power (250,288) (549,877) (291,992)
Deferred fuel and purchased power amortization 425,886 547,243 219,579
Allowance for equity funds used during construction (38,620) (53,118) (45,263)
Deferred income taxes (20,923) (24,310) 43,202
Deferred investment tax credit (8,253) 77,065 (5,893)
Change in derivative instruments fair value 0 (777) 777
Stock compensation 23,532 17,341 15,942
Changes in current assets and liabilities:      
Customer and other receivables (12,696) (61,983) (63,869)
Accrued unbilled revenues (9,350) (2,789) (30,784)
Materials, supplies and fossil fuel (7,895) (42,911) (83,469)
Income tax receivable 332 13,754 (6,572)
Other current assets (50,225) (19,550) 76,089
Accounts payable (7,214) (75,623) 90,076
Accrued taxes 9,030 2,393 (4,205)
Other current liabilities 47,329 40,510 (1,856)
Change in long-term regulatory assets 43,305 53,112 12,432
Change in long-term regulatory liabilities 9,416 28,495 (332,470)
Change in other long-term assets (132,563) (195,598) 159,030
Change in operating lease assets 98,214 90,525 105,359
Change in other long-term liabilities 24,794 63,080 170,359
Change in operating lease liabilities (93,214) (65,779) (103,671)
Net cash provided by operating activities 1,609,823 1,207,697 1,241,441
CASH FLOWS FROM INVESTING ACTIVITIES      
Capital expenditures (2,249,195) (1,846,370) (1,707,490)
Contributions in aid of construction 311,358 180,866 137,436
Proceeds from sale relating to BCE 84,322 23,400 0
Allowance for borrowed funds used during construction (48,270) (43,564) (28,030)
Proceeds from nuclear decommissioning trust sales and other special use funds 1,686,094 1,679,722 1,207,713
Investment in nuclear decommissioning trust and other special use funds (1,709,526) (1,681,845) (1,212,063)
Other (8,413) (6,458) (15,612)
Net cash used for investing activities (1,933,630) (1,694,249) (1,618,046)
CASH FLOWS FROM FINANCING ACTIVITIES      
Issuance of long-term debt 1,313,229 689,349 875,537
Repayment of long-term debt (875,000) (32,740) (150,000)
Short-term borrowings and (repayments) — net (241,050) 241,900 48,720
Short-term debt borrowings under term loan facility 550,000 0 0
Short-term debt repayments under term loan facility (350,000) 0 0
Dividends paid on common stock (394,663) (386,486) (378,881)
Common stock equity issuance and purchases — net 341,429    
Common stock equity issuance and purchases — net   (4,093) (2,653)
Capital activities by noncontrolling interests (21,255) (21,255) (21,255)
Net cash provided by financing activities 322,690 486,675 371,468
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS (1,117) 123 (5,137)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR 4,955 4,832 9,969
CASH AND CASH EQUIVALENTS AT END OF YEAR $ 3,838 $ 4,955 $ 4,832
v3.25.0.1
CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($)
$ in Thousands
Total
Common Stock
Treasury Stock
Retained Earnings
Accumulated Other Comprehensive Income (Loss)
Noncontrolling Interests
Beginning balance (in shares) at Dec. 31, 2021   113,014,528        
Beginning balance at Dec. 31, 2021 $ 6,021,460 $ 2,702,743 $ (6,401) $ 3,264,719 $ (54,861) $ 115,260
Beginning balance (in shares) at Dec. 31, 2021     (87,608)      
Increase (Decrease) in Shareholders' Equity            
Net Income 500,826     483,602   17,224
Other comprehensive income (loss) 23,426       23,426  
Dividends on common stock (387,975)     (387,975)    
Issuance of common stock (in shares)   232,661        
Issuance of common stock 21,996 $ 21,996        
Purchase of treasury stock (in shares) [1]     (77,152)      
Purchase of treasury stock [1] (5,152)   $ (5,152)      
Reissuance of treasury stock for stock-based compensation and other (in shares)     91,147      
Reissuance of treasury stock for stock-based compensation and other 6,548   $ 6,548      
Capital activities by noncontrolling interests (21,255)         (21,255)
Other 2 $ 1   1    
Ending balance (in shares) at Dec. 31, 2022   113,247,189        
Ending balance at Dec. 31, 2022 6,159,876 $ 2,724,740 $ (5,005) 3,360,347 (31,435) 111,229
Ending balance (in shares) at Dec. 31, 2022     (73,613)      
Increase (Decrease) in Shareholders' Equity            
Net Income 518,781     501,557   17,224
Other comprehensive income (loss) (1,709)       (1,709)  
Dividends on common stock (395,585)     (395,585)    
Issuance of common stock (in shares)   290,500        
Issuance of common stock 27,936 $ 27,936        
Purchase of treasury stock (in shares) [1]     (72,180)      
Purchase of treasury stock [1] (5,466)   $ (5,466)      
Reissuance of treasury stock for stock-based compensation and other (in shares)     32,521      
Reissuance of treasury stock for stock-based compensation and other 2,287   $ 2,287      
Capital activities by noncontrolling interests (21,255)         (21,255)
Other $ (3)   (1) (2)    
Ending balance (in shares) at Dec. 31, 2023 113,537,689 113,537,689        
Ending balance at Dec. 31, 2023 $ 6,284,862 $ 2,752,676 $ (8,185) 3,466,317 (33,144) 107,198
Ending balance (in shares) at Dec. 31, 2023 (113,272,000)   (113,272)      
Increase (Decrease) in Shareholders' Equity            
Net Income $ 626,030     608,806   17,224
Other comprehensive income (loss) 2,202       2,202  
Dividends on common stock (408,162)     (408,162)    
Issuance of common stock (in shares) [2]   5,606,093        
Issuance of common stock [2] 368,941 $ 368,941        
Purchase of treasury stock (in shares) [1]     (71,008)      
Purchase of treasury stock [1] (4,907)   $ (4,907)      
Reissuance of treasury stock for stock-based compensation and other (in shares)     137,312      
Reissuance of treasury stock for stock-based compensation and other 9,768   $ 9,768      
Capital activities by noncontrolling interests (21,255)         (21,255)
Other $ (1)   1 (2)    
Ending balance (in shares) at Dec. 31, 2024 119,143,782 119,143,782        
Ending balance at Dec. 31, 2024 $ 6,857,478 $ 3,121,617 $ (3,323) $ 3,666,959 $ (30,942) $ 103,167
Ending balance (in shares) at Dec. 31, 2024 (46,968)   (46,968)      
[1] Primarily represents shares of common stock withheld from certain stock awards for tax purposes.
[2] See Note 13 for information related to our equity forward sale agreements that were executed in February 2024 and November 2024. As of December 31, 2024, 5,377,115 shares of common stock have been issued as part of these agreements.
v3.25.0.1
CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical) - $ / shares
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dividends declared per common share (in dollars per share) $ 3.55 $ 3.49 $ 3.43
v3.25.0.1
ARIZONA PUBLIC SERVICE COMPANY - CONSOLIDATED STATEMENTS OF INCOME - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
OPERATING REVENUES (Note 2) $ 5,124,915 $ 4,695,991 $ 4,324,385
OPERATING EXPENSES      
Fuel and purchased power 1,822,566 1,792,657 1,629,343
Operations and maintenance 1,165,156 1,058,725 987,072
Depreciation and amortization 895,346 794,043 753,195
Taxes other than income taxes 227,395 224,013 220,370
Other expense 2,389 1,913 2,494
Total 4,112,852 3,871,351 3,592,474
OPERATING INCOME 1,012,063 824,640 731,911
OTHER INCOME (DEDUCTIONS)      
Allowance for equity funds used during construction (Note 1) 38,620 53,118 45,263
Pension and other postretirement non-service credits, net (Note 7) 48,870 40,648 98,487
Other income (Note 16) 48,614 33,666 7,916
Other expense (Note 16) (34,136) (25,056) (52,385)
Total 101,968 102,376 99,281
INTEREST EXPENSE      
Interest charges 425,742 374,887 283,569
Allowance for borrowed funds used during construction (Note 1) (48,270) (43,564) (28,030)
Total 377,472 331,323 255,539
INCOME BEFORE INCOME TAXES 736,559 595,693 575,653
INCOME TAXES (Note 4) 110,529 76,912 74,827
NET INCOME 626,030 518,781 500,826
Less: Net income attributable to noncontrolling interests (Note 17) 17,224 17,224 17,224
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS 608,806 501,557 483,602
Arizona Public Service Company      
OPERATING REVENUES (Note 2) 5,124,915 4,695,991 4,324,385
OPERATING EXPENSES      
Fuel and purchased power 1,822,566 1,792,657 1,629,343
Operations and maintenance 1,158,634 1,043,570 974,220
Depreciation and amortization 895,171 793,958 753,110
Taxes other than income taxes 227,307 223,962 220,277
Other expense 2,389 1,913 2,494
Total 4,106,067 3,856,060 3,579,444
OPERATING INCOME 1,018,848 839,931 744,941
OTHER INCOME (DEDUCTIONS)      
Allowance for equity funds used during construction (Note 1) 38,620 53,118 45,263
Pension and other postretirement non-service credits, net (Note 7) 49,489 41,577 98,945
Other income (Note 16) 21,094 27,072 5,888
Other expense (Note 16) (29,698) (18,264) (26,108)
Total 79,505 103,503 123,988
INTEREST EXPENSE      
Interest charges 360,481 323,719 262,815
Allowance for borrowed funds used during construction (Note 1) (48,270) (39,030) (26,839)
Total 312,211 284,689 235,976
INCOME BEFORE INCOME TAXES 786,142 658,745 632,953
INCOME TAXES (Note 4) 126,993 94,184 90,800
NET INCOME 659,149 564,561 542,153
Less: Net income attributable to noncontrolling interests (Note 17) 17,224 17,224 17,224
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS $ 641,925 $ 547,337 $ 524,929
v3.25.0.1
ARIZONA PUBLIC SERVICE COMPANY - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
NET INCOME $ 626,030 $ 518,781 $ 500,826
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX      
Pension and other postretirement benefits activity, net of tax benefit (expense) of $(1,022), $536, and $(6,332) (Note 7) 3,093 (2,422) 21,553
Total other comprehensive income (loss) 2,202 (1,709) 23,426
COMPREHENSIVE INCOME 628,232 517,072 524,252
Less: Comprehensive income attributable to noncontrolling interests 17,224 17,224 17,224
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS 611,008 499,848 507,028
Arizona Public Service Company      
NET INCOME 659,149 564,561 542,153
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX      
Pension and other postretirement benefits activity, net of tax benefit (expense) of $(1,022), $536, and $(6,332) (Note 7) 3,103 (1,623) 19,284
Total other comprehensive income (loss) 3,103 (1,623) 19,284
COMPREHENSIVE INCOME 662,252 562,938 561,437
Less: Comprehensive income attributable to noncontrolling interests 17,224 17,224 17,224
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS $ 645,028 $ 545,714 $ 544,213
v3.25.0.1
ARIZONA PUBLIC SERVICE COMPANY - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Pension and other postretirement benefits activity, net of tax benefit (expense) $ (1,073) $ 801 $ (7,078)
Arizona Public Service Company      
Pension and other postretirement benefits activity, net of tax benefit (expense) $ (1,022) $ 536 $ (6,332)
v3.25.0.1
ARIZONA PUBLIC SERVICE COMPANY - CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
PROPERTY, PLANT AND EQUIPMENT (Notes 1, 6 and 9)    
Plant in service and held for future use $ 25,860,950 $ 24,211,167
Accumulated depreciation and amortization (9,027,426) (8,408,040)
Net 16,833,524 15,803,127
Construction work in progress 1,592,659 1,724,004
Palo Verde sale leaseback, net of accumulated depreciation of $268,894 and $264,624 (Note 17) 82,556 86,426
Intangible assets, net of accumulated amortization of $925,880 and $884,371 591,310 267,110
Nuclear fuel, net of accumulated amortization of $115,894 and $118,074 97,850 99,490
Total property, plant and equipment 19,197,899 17,980,157
INVESTMENTS AND OTHER ASSETS    
Nuclear decommissioning trusts (Notes 12 and 18) 1,282,845 1,201,246
Other special use funds (Notes 12, 17 and 18) 408,357 362,781
Assets from risk management activities (Note 15) 5,980 0
Other assets 115,095 102,845
Total investments and other assets 1,812,277 1,666,872
CURRENT ASSETS    
Cash and cash equivalents 3,838 4,955
Customer and other receivables 525,608 513,892
Accrued unbilled revenues 176,903 167,553
Allowance for doubtful accounts (Note 2) (24,849) (22,433)
Materials and supplies (at average cost) 469,022 444,344
Fossil fuel (at average cost) 32,420 49,203
Income tax receivable (Note 4) 0 332
Assets from risk management activities (Note 15) 10,578 6,808
Deferred fuel and purchased power regulatory asset (Note 3) 287,597 463,195
Other regulatory assets (Note 3) 133,372 162,562
Other current assets 74,915 101,417
Total current assets 1,689,404 1,926,967
DEFERRED DEBITS    
Regulatory assets (Notes 1, 3, 4 and 7) 1,389,489 1,390,279
Operating lease right-of-use assets (Note 8) 1,605,463 1,309,975
Assets for pension and other postretirement benefits (Note 7) 342,102 323,438
Other 66,126 63,465
Total deferred debits 3,403,180 3,087,157
TOTAL ASSETS 26,102,760 24,661,153
CAPITALIZATION    
Retained earnings 3,666,959 3,466,317
Accumulated other comprehensive loss (Note 19) (30,942) (33,144)
Total shareholders’ equity 6,754,311 6,177,664
Noncontrolling interests (Note 17) 103,167 107,198
Total equity 6,857,478 6,284,862
Long-term debt less current maturities (Note 6) 8,058,648 7,540,622
CURRENT LIABILITIES    
Short-term borrowings (Note 5) 568,450 609,500
Current maturities of long-term debt (Note 6) 800,000 875,000
Accounts payable 485,426 442,455
Accrued taxes 175,863 166,833
Accrued interest 81,799 72,916
Common dividends payable 106,592 99,813
Customer deposits 44,345 42,037
Liabilities from risk management activities (Note 15) 52,340 80,913
Liabilities for asset retirements (Note 11) 50,009 28,550
Operating lease liabilities (Note 8) 100,367 67,883
Less: current regulatory liabilities 206,955 209,923
Other current liabilities 171,651 193,524
Total current liabilities 2,843,797 2,889,347
DEFERRED CREDITS AND OTHER    
Deferred income taxes (Note 4) 2,444,473 2,416,480
Regulatory liabilities (Notes 1, 3, 4 and 7) 1,855,278 1,965,865
Liabilities for asset retirements (Note 11) 1,096,577 937,451
Liabilities for pension benefits (Note 7) 139,317 112,702
Liabilities from risk management activities (Note 15) 9,446 42,975
Customer advances 569,343 533,580
Coal mine reclamation 171,483 184,007
Deferred investment tax credit 249,490 257,743
Unrecognized tax benefits (Note 4) 44,233 33,861
Operating lease liabilities (Note 8) 1,520,877 1,210,189
Other 242,320 251,469
Total deferred credits and other 8,342,837 7,946,322
COMMITMENTS AND CONTINGENCIES (Note 10)
TOTAL LIABILITIES AND EQUITY 26,102,760 24,661,153
Arizona Public Service Company    
PROPERTY, PLANT AND EQUIPMENT (Notes 1, 6 and 9)    
Plant in service and held for future use 25,860,068 24,207,706
Accumulated depreciation and amortization (9,026,544) (8,404,721)
Net 16,833,524 15,802,985
Construction work in progress 1,592,659 1,724,004
Palo Verde sale leaseback, net of accumulated depreciation of $268,894 and $264,624 (Note 17) 82,556 86,426
Intangible assets, net of accumulated amortization of $925,880 and $884,371 591,154 266,955
Nuclear fuel, net of accumulated amortization of $115,894 and $118,074 97,850 99,490
Total property, plant and equipment 19,197,743 17,979,860
INVESTMENTS AND OTHER ASSETS    
Nuclear decommissioning trusts (Notes 12 and 18) 1,282,845 1,201,246
Other special use funds (Notes 12, 17 and 18) 374,156 362,781
Assets from risk management activities (Note 15) 5,980 0
Other assets 49,673 43,625
Total investments and other assets 1,712,654 1,607,652
CURRENT ASSETS    
Cash and cash equivalents 3,815 4,549
Customer and other receivables 522,886 510,296
Accrued unbilled revenues 176,903 167,553
Allowance for doubtful accounts (Note 2) (24,849) (22,433)
Materials and supplies (at average cost) 469,022 444,344
Fossil fuel (at average cost) 32,420 49,203
Income tax receivable (Note 4) 5,463 0
Assets from risk management activities (Note 15) 10,578 6,808
Deferred fuel and purchased power regulatory asset (Note 3) 287,597 463,195
Other regulatory assets (Note 3) 133,372 162,562
Other current assets 65,754 64,311
Total current assets 1,682,961 1,850,388
DEFERRED DEBITS    
Regulatory assets (Notes 1, 3, 4 and 7) 1,389,489 1,390,279
Operating lease right-of-use assets (Note 8) 1,604,324 1,308,611
Assets for pension and other postretirement benefits (Note 7) 335,458 316,606
Other 65,606 63,059
Total deferred debits 3,394,877 3,078,555
TOTAL ASSETS 25,988,235 24,516,455
CAPITALIZATION    
Common stock 178,162 178,162
Additional paid-in capital 4,116,696 3,321,696
Retained earnings 3,992,423 3,759,299
Accumulated other comprehensive loss (Note 19) (14,116) (17,219)
Total shareholders’ equity 8,273,165 7,241,938
Noncontrolling interests (Note 17) 103,167 107,198
Total equity 8,376,332 7,349,136
Long-term debt less current maturities (Note 6) 7,190,878 7,041,891
Total capitalization 15,567,210 14,391,027
CURRENT LIABILITIES    
Short-term borrowings (Note 5) 339,900 532,850
Current maturities of long-term debt (Note 6) 300,000 250,000
Accounts payable 481,955 433,229
Accrued taxes 181,698 162,288
Accrued interest 79,308 72,548
Common dividends payable 107,200 99,800
Customer deposits 44,345 42,037
Liabilities from risk management activities (Note 15) 52,340 80,913
Liabilities for asset retirements (Note 11) 50,009 28,550
Operating lease liabilities (Note 8) 100,229 67,608
Less: current regulatory liabilities 206,955 209,923
Other current liabilities 177,019 211,773
Total current liabilities 2,120,958 2,191,519
DEFERRED CREDITS AND OTHER    
Deferred income taxes (Note 4) 2,419,937 2,431,697
Regulatory liabilities (Notes 1, 3, 4 and 7) 1,855,278 1,965,865
Liabilities for asset retirements (Note 11) 1,096,577 937,451
Liabilities for pension benefits (Note 7) 134,855 106,215
Liabilities from risk management activities (Note 15) 9,446 42,975
Customer advances 569,343 533,580
Coal mine reclamation 171,483 184,007
Deferred investment tax credit 249,490 257,743
Unrecognized tax benefits (Note 4) 48,725 33,861
Operating lease liabilities (Note 8) 1,519,683 1,208,857
Other 225,250 231,658
Total deferred credits and other 8,300,067 7,933,909
COMMITMENTS AND CONTINGENCIES (Note 10)
TOTAL LIABILITIES AND EQUITY $ 25,988,235 $ 24,516,455
v3.25.0.1
ARIZONA PUBLIC SERVICE COMPANY - CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
PROPERTY, PLANT AND EQUIPMENT    
Palo Verde sale leaseback, net of accumulated depreciation $ 268,894 $ 264,624
Intangible assets, net of accumulated amortization 925,880 885,505
Nuclear fuel, net of accumulated amortization 115,894 118,074
Arizona Public Service Company    
PROPERTY, PLANT AND EQUIPMENT    
Palo Verde sale leaseback, net of accumulated depreciation 268,894 264,624
Intangible assets, net of accumulated amortization 925,880 884,371
Nuclear fuel, net of accumulated amortization $ 115,894 $ 118,074
v3.25.0.1
ARIZONA PUBLIC SERVICE COMPANY - CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
CASH FLOWS FROM OPERATING ACTIVITIES      
Net Income $ 626,030 $ 518,781 $ 500,826
Adjustments to reconcile net income to net cash provided by operating activities:      
Depreciation and amortization including nuclear fuel 956,184 854,136 817,814
Deferred fuel and purchased power (250,288) (549,877) (291,992)
Deferred fuel and purchased power amortization 425,886 547,243 219,579
Allowance for equity funds used during construction (38,620) (53,118) (45,263)
Deferred income taxes (20,923) (24,310) 43,202
Deferred investment tax credit (8,253) 77,065 (5,893)
Changes in current assets and liabilities:      
Customer and other receivables (12,696) (61,983) (63,869)
Accrued unbilled revenues (9,350) (2,789) (30,784)
Materials, supplies and fossil fuel (7,895) (42,911) (83,469)
Income tax receivable 332 13,754 (6,572)
Other current assets (50,225) (19,550) 76,089
Accounts payable (7,214) (75,623) 90,076
Accrued taxes 9,030 2,393 (4,205)
Other current liabilities 47,329 40,510 (1,856)
Change in long-term regulatory assets 43,305 53,112 12,432
Change in long-term regulatory liabilities 9,416 28,495 (332,470)
Change in other long-term assets (132,563) (195,598) 159,030
Change in operating lease assets 98,214 90,525 105,359
Change in other long-term liabilities 24,794 63,080 170,359
Change in operating lease liabilities (93,214) (65,779) (103,671)
Net cash provided by operating activities 1,609,823 1,207,697 1,241,441
CASH FLOWS FROM INVESTING ACTIVITIES      
Capital expenditures (2,249,195) (1,846,370) (1,707,490)
Contributions in aid of construction 311,358 180,866 137,436
Allowance for borrowed funds used during construction (48,270) (43,564) (28,030)
Proceeds from nuclear decommissioning trust sales and other special use funds 1,686,094 1,679,722 1,207,713
Investment in nuclear decommissioning trust and other special use funds (1,709,526) (1,681,845) (1,212,063)
Other (8,413) (6,458) (15,612)
Net cash used for investing activities (1,933,630) (1,694,249) (1,618,046)
CASH FLOWS FROM FINANCING ACTIVITIES      
Issuance of long-term debt 1,313,229 689,349 875,537
Repayments of Other Long-Term Debt (875,000) (32,740) (150,000)
Short-term borrowings and (repayments) — net (241,050) 241,900 48,720
Short-term debt borrowings under term loan facility 550,000 0 0
Short-term debt repayments under term loan facility (350,000) 0 0
Dividends paid on common stock (394,663) (386,486) (378,881)
Capital activities of noncontrolling interests (21,255) (21,255) (21,255)
Net cash provided by financing activities 322,690 486,675 371,468
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS (1,117) 123 (5,137)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR 4,955 4,832 9,969
CASH AND CASH EQUIVALENTS AT END OF YEAR 3,838 4,955 4,832
Arizona Public Service Company      
CASH FLOWS FROM OPERATING ACTIVITIES      
Net Income 659,149 564,561 542,153
Adjustments to reconcile net income to net cash provided by operating activities:      
Depreciation and amortization including nuclear fuel 956,009 854,051 817,729
Deferred fuel and purchased power (250,288) (549,877) (291,992)
Deferred fuel and purchased power amortization 425,886 547,243 219,579
Allowance for equity funds used during construction (38,620) (53,118) (45,263)
Deferred income taxes (56,461) (10,314) (6,817)
Deferred investment tax credit (8,253) 77,065 (5,893)
Changes in current assets and liabilities:      
Customer and other receivables (13,570) (62,716) (60,930)
Accrued unbilled revenues (9,350) (2,789) (30,784)
Materials, supplies and fossil fuel (7,895) (42,911) (83,469)
Income tax receivable (5,463) 1,102 9,654
Other current assets (14,704) (20,243) 59,970
Accounts payable (2,500) (70,622) 79,492
Accrued taxes 19,410 5,542 4,734
Other current liabilities 31,982 62,212 1,190
Change in long-term regulatory assets 43,305 53,112 12,432
Change in long-term regulatory liabilities 9,416 28,495 (332,470)
Change in other long-term assets (159,940) (188,483) 170,587
Change in operating lease assets 97,989 90,234 105,058
Change in other long-term liabilities 27,202 58,574 168,503
Change in operating lease liabilities (93,076) (65,482) (103,361)
Net cash provided by operating activities 1,610,228 1,275,636 1,230,102
CASH FLOWS FROM INVESTING ACTIVITIES      
Capital expenditures (2,249,195) (1,825,585) (1,655,051)
Contributions in aid of construction 311,358 180,866 137,436
Allowance for borrowed funds used during construction (48,270) (39,030) (26,839)
Proceeds from nuclear decommissioning trust sales and other special use funds 1,686,094 1,679,722 1,207,713
Investment in nuclear decommissioning trust and other special use funds (1,684,526) (1,681,845) (1,212,063)
Other (1,660) (1,397) (727)
Net cash used for investing activities (1,986,199) (1,687,269) (1,549,531)
CASH FLOWS FROM FINANCING ACTIVITIES      
Issuance of long-term debt 445,842 496,025 524,852
Repayments of Other Long-Term Debt (250,000) 0 0
Short-term borrowings and (repayments) — net (192,950) 180,970 46,300
Short-term debt borrowings under term loan facility 350,000 0 0
Short-term debt repayments under term loan facility (350,000) 0 0
Dividends paid on common stock (401,400) (393,600) (385,800)
Equity infusion from Pinnacle West 795,000 150,000 150,000
Capital activities of noncontrolling interests (21,255) (21,255) (21,255)
Net cash provided by financing activities 375,237 412,140 314,097
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS (734) 507 (5,332)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR 4,549 4,042 9,374
CASH AND CASH EQUIVALENTS AT END OF YEAR $ 3,815 $ 4,549 $ 4,042
v3.25.0.1
ARIZONA PUBLIC SERVICE COMPANY - CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($)
$ in Thousands
Total
Common Stock
Retained Earnings
Accumulated Other Comprehensive Income (Loss)
Noncontrolling Interests
Arizona Public Service Company
Arizona Public Service Company
Common Stock
Arizona Public Service Company
Additional Paid-In Capital
Arizona Public Service Company
Retained Earnings
Arizona Public Service Company
Accumulated Other Comprehensive Income (Loss)
Arizona Public Service Company
Noncontrolling Interests
Beginning balance (in shares) at Dec. 31, 2021   113,014,528         71,264,947        
Beginning balance at Dec. 31, 2021 $ 6,021,460 $ 2,702,743 $ 3,264,719 $ (54,861) $ 115,260 $ 6,750,473 $ 178,162 $ 3,021,696 $ 3,470,235 $ (34,880) $ 115,260
Increase (Decrease) in Shareholders' Equity                      
Equity infusion from Pinnacle West           150,000   150,000      
Net Income 500,826   483,602   17,224 542,153     524,929   17,224
Other comprehensive income (loss) 23,426     23,426   19,284       19,284  
Dividends on common stock           (387,700)     (387,700)    
Capital activities by noncontrolling interests (21,255)       (21,255) (21,255)         (21,255)
Other 2 $ 1 1                
Ending balance (in shares) at Dec. 31, 2022   113,247,189         71,264,947        
Ending balance at Dec. 31, 2022 6,159,876 $ 2,724,740 3,360,347 (31,435) 111,229 7,052,955 $ 178,162 3,171,696 3,607,464 (15,596) 111,229
Increase (Decrease) in Shareholders' Equity                      
Equity infusion from Pinnacle West           150,000   150,000      
Net Income 518,781   501,557   17,224 564,561     547,337   17,224
Other comprehensive income (loss) (1,709)     (1,709)   (1,623)       (1,623)  
Dividends on common stock           (395,500)     (395,500)    
Capital activities by noncontrolling interests (21,255)       (21,255) (21,255)         (21,255)
Other $ (3)   (2)     (2)     (2)   0
Ending balance (in shares) at Dec. 31, 2023 113,537,689 113,537,689         71,264,947        
Ending balance at Dec. 31, 2023 $ 6,284,862 $ 2,752,676 3,466,317 (33,144) 107,198 7,349,136 $ 178,162 3,321,696 3,759,299 (17,219) 107,198
Increase (Decrease) in Shareholders' Equity                      
Equity infusion from Pinnacle West           795,000   795,000      
Net Income 626,030   608,806   17,224 659,149     641,925   17,224
Other comprehensive income (loss) 2,202     2,202   3,103       3,103  
Dividends on common stock           (408,800)     (408,800)    
Capital activities by noncontrolling interests (21,255)       (21,255) (21,255)         (21,255)
Other $ (1)   (2)     (1)     (1)   0
Ending balance (in shares) at Dec. 31, 2024 119,143,782 119,143,782         71,264,947        
Ending balance at Dec. 31, 2024 $ 6,857,478 $ 3,121,617 $ 3,666,959 $ (30,942) $ 103,167 $ 8,376,332 $ 178,162 $ 4,116,696 $ 3,992,423 $ (14,116) $ 103,167
v3.25.0.1
Summary of Significant Accounting Policies
 12 Months Ended
Dec. 31, 2024
Accounting Policies [Abstract]  
Summary of Significant Accounting Policies Summary of Significant Accounting Policies
Description of Business and Basis of Presentation
 
Pinnacle West is a holding company that conducts business through its subsidiaries, APS, El Dorado and PNW Power. APS, our wholly-owned subsidiary, is a vertically-integrated electric utility that provides either retail or wholesale electric service to substantially all of the state of Arizona, with the major exceptions of about one-half of the Phoenix metropolitan area, the Tucson metropolitan area and Mohave County in northwestern Arizona.  APS accounts for essentially all of our revenues and earnings and is expected to continue to do so.  El Dorado is a wholly-owned subsidiary that invests in energy-related and Arizona community-based ventures. PNW Power is a wholly-owned subsidiary that was created in September 2023 to hold certain investments in wind and transmission joint projects. See Note 20 for more information on PNW Power.
 
BCE was a Pinnacle West subsidiary that was formed in 2014. On August 4, 2023, Pinnacle West entered into a purchase and sale agreement pursuant to which all of our equity interest in BCE was sold. The sale was completed on January 12, 2024. See Note 20 for more information relating to the sale of BCE.

Pinnacle West’s Consolidated Financial Statements include the accounts of Pinnacle West and our subsidiaries, including APS, El Dorado, and PNW Power, as well as our former subsidiary BCE until its sale. Pinnacle West’s Consolidated Financial Statements also include the accounts of a VIE relating to a Captive Insurance Cell (“Captive”). APS’s Consolidated Financial Statements include the accounts of APS and certain VIEs relating to the Palo Verde sale leaseback.  Intercompany accounts and transactions between the consolidated companies have been eliminated.
 
We consolidate Variable Interest Entities (each a “VIE”) for which we are the primary beneficiary.  We determine whether we are the primary beneficiary of a VIE through a qualitative analysis that identifies which variable interest holder has the controlling financial interest in the VIE.  In performing our primary beneficiary analysis, we consider all relevant facts and circumstances, including the design and activities of the VIE, the terms of the contracts the VIE has entered into, and which parties participated significantly in the design or redesign of the entity.  We continually evaluate our primary beneficiary conclusions to determine if changes have occurred which would impact our primary beneficiary assessments.  We have determined that APS is the primary beneficiary of certain VIE lessor trusts relating to the Palo Verde sale leaseback, and therefore APS consolidates these entities. We have also determined that Pinnacle West is the primary beneficiary of a protected captive insurance cell VIE, and therefore Pinnacle West consolidates this insurance cell. See Note 17 for additional information.
 
Accounting Records and Use of Estimates
 
Our accounting records are maintained in accordance with accounting principles generally accepted in the United States of America (“GAAP”).  The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period.  Actual results could differ from those estimates.
Regulatory Accounting
 
APS is regulated by the ACC and FERC.  The accompanying financial statements reflect the rate-making policies of these commissions.  As a result, we capitalize certain costs that would be included as expense in the current period by unregulated companies.  Regulatory assets represent incurred costs that have been deferred because they are probable of future recovery in customer rates. Regulatory liabilities generally represent amounts collected in rates to recover costs expected to be incurred in the future or amounts collected in excess of costs incurred and are refundable to customers.
 
Management judgments include continually assessing the likelihood of future recovery of regulatory assets and/or a disallowance of part of the cost of recently completed plant, by considering factors such as applicable regulatory environment changes and recent rate orders to other regulated entities in the same jurisdiction.  This determination reflects the current political and regulatory climate in Arizona and is subject to change in the future.  If future recovery of costs ceases to be probable, the assets would be written off as a charge in current period earnings. Management judgments also include assessing the impact of potential commission-ordered refunds to customers on regulatory liabilities.
 
See Note 3 for additional information.
 
Electric Revenues
 
Revenues primarily consist of activities that are classified as revenues from contracts with customers. Our electric revenues generally represent a single performance obligation delivered over time. We have elected to apply the practical expedient that allows us to recognize revenue based on the amount to which we have a right to invoice for services performed.

We derive electric revenues primarily from sales of electricity to our regulated retail customers. Revenues related to the sale of electricity are generally recognized when service is rendered or electricity is delivered to customers. Unbilled revenues are estimated by applying an average revenue/kWh by customer class to the number of estimated kWhs delivered but not billed. Differences historically between the actual and estimated unbilled revenues are immaterial. We exclude sales taxes and franchise fees on electric revenues from both revenue and taxes other than income taxes.
 
Revenues from our regulated retail customers and non-derivative instruments are reported on a gross basis on Pinnacle West’s Consolidated Statements of Income. In the electricity business, some contracts to purchase electricity are netted against other contracts to sell electricity. This is called a “book-out” and usually occurs for contracts that have the same terms (quantities, delivery points and delivery periods) and for which power does not flow. We net these book-outs, which reduces both wholesale revenues and fuel and purchased power costs.

Certain cost recovery mechanisms may qualify as alternative revenue programs. For alternative revenue programs that meet specified accounting criteria, we recognize revenues when the specific events permitting billing of the additional revenues have been completed.

See Notes 2 and 3 for additional information.
Allowance for Doubtful Accounts
 
The allowance for doubtful accounts represents our best estimate of accounts receivable and accrued unbilled revenues that will ultimately be uncollectible due to credit loss risk. The allowance includes a write-off component that is calculated by applying an estimated write-off factor to retail electric revenues. The write-off factor used to estimate uncollectible accounts is based upon consideration of historical collections experience, the current and forecasted economic environment, changes to our collection policies, and management’s best estimate of future collections success.

See Note 2 for additional information.
 
Property, Plant and Equipment
 
Utility plant is the term we use to describe the business property and equipment that supports electric service, consisting primarily of generation, transmission, and distribution facilities.  We report utility plant at its original cost, which includes:

•material and labor;
•contractor costs;
•capitalized leases;
•construction overhead costs (where applicable); and
•AFUDC.

Pinnacle West’s property, plant and equipment included in the December 31, 2024, and 2023 Consolidated Balance Sheets is composed of the following (dollars in thousands):

Property, Plant and Equipment:20242023
Generation$11,111,915 $10,446,291 
Transmission4,135,970 3,773,253 
Distribution9,016,843 8,448,293 
General plant1,596,222 1,543,330 
Plant in service and held for future use25,860,950 24,211,167 
Accumulated depreciation and amortization(9,027,426)(8,408,040)
Net16,833,524 15,803,127 
Construction work in progress1,592,659 1,724,004 
Palo Verde sale leaseback, net of accumulated depreciation82,556 86,426 
Intangible assets, net of accumulated amortization591,310 267,110 
Nuclear fuel, net of accumulated amortization97,850 99,490 
Total property, plant and equipment$19,197,899 $17,980,157 

Property, plant and equipment balances and classes for APS are not materially different than Pinnacle West.

We expense the costs of plant outages, major maintenance and routine maintenance as incurred.  We charge retired utility plant to accumulated depreciation.  Liabilities associated with the retirement of tangible long-lived assets are recognized at fair value as incurred and capitalized as part of the related tangible long-lived assets.  Accretion of the liability due to the passage of time is an operating expense, and
the capitalized cost is depreciated over the useful life of the long-lived asset.  See Note 11 for additional information.

APS records a regulatory liability for the excess that has been recovered in regulated rates over the amount calculated in accordance with guidance on accounting for AROs.  APS believes it is probable it will recover in regulated rates, the costs calculated in accordance with this accounting guidance.
 
We record depreciation and amortization on utility plant on a straight-line basis over the remaining useful life of the related assets.  The approximate remaining average useful lives of our utility property at December 31, 2024, were as follows:

•Steam generation — 11 years;
•Nuclear plant — 25 years;
•Other generation — 18 years;
•Transmission — 38 years;
•Distribution — 33 years; and
•General plant — 7 years.
 
Depreciation of utility property, plant and equipment is computed on a straight-line, remaining-life basis. Depreciation expense was $723 million in 2024, $669 million in 2023, and $632 million in 2022. For the years 2022 through 2024, the depreciation rates ranged from a low of 1.37% to a high of 12.15%.  The weighted-average depreciation rate was 3.13% in 2024, 2.98% in 2023, and 3.03% in 2022.

Asset Retirement Obligations

APS has AROs for its Palo Verde nuclear facilities and certain other generation assets.  The Palo Verde ARO primarily relates to final plant decommissioning.  This obligation is based on the NRC’s requirements for disposal of irradiated property or plant and agreements APS reached with the ACC for final decommissioning of the plant.  The non-nuclear generation AROs primarily relate to requirements for removing portions of those plants at the end of the plant life or lease term and coal ash pond closures. Some of APS’s transmission and distribution assets have AROs because they are subject to right of way and easement agreements that require final removal.  These agreements have a history of uninterrupted renewal that APS expects to continue.  As a result, APS cannot reasonably estimate the fair value of the ARO related to such transmission and distribution assets. Additionally, APS has aquifer protection permits for some of its generation sites that require the closure of certain facilities at those sites.

See Note 11 for further information on Asset Retirement Obligations.

Allowance for Funds Used During Construction
 
AFUDC represents the approximate net composite interest cost of borrowed funds and an allowed return on the equity funds used for construction of regulated utility plant.  Both the debt and equity components of AFUDC are non-cash amounts within the Consolidated Statements of Income.  Plant construction costs, including AFUDC, are recovered in authorized rates through depreciation when completed projects are placed into commercial operation.
 
AFUDC was calculated by using a composite rate of 6.23% for 2024, 6.29% for 2023, and 5.75% for 2022.  APS compounds AFUDC semi-annually and ceases to accrue AFUDC when construction work is completed and the property is placed in service.

On June 30, 2020, FERC issued an order granting a waiver request related to the existing AFUDC rate calculation beginning March 1, 2020, through February 28, 2021.  On February 23, 2021, this waiver was extended until September 30, 2021. On September 21, 2021, it was further extended until March 31, 2022. The order provided a simplified approach that companies may elect to implement in order to minimize the significant distorted effect on the AFUDC formula resulting from increased short-term debt financing during the COVID-19 pandemic.  APS adopted this simplified approach to computing the AFUDC composite rate by using a simple average of the actual historical short-term debt balances for 2019, instead of current period short-term debt balances, and left all other aspects of the AFUDC formula composite rate calculation unchanged. This change impacted the AFUDC composite rate in 2021 and for the three-month period ended March 31, 2022.  Furthermore, the change in the composite rate calculation did not impact our accounting treatment for these costs. The change did not have a material impact on our financial statements.

Materials and Supplies
 
APS values materials, supplies and fossil fuel inventory using a weighted-average cost method.  APS materials, supplies and fossil fuel inventories are carried at the lower of weighted-average cost or net realizable value, unless evidence indicates that the weighted-average cost (even if in excess of market) will be recovered.
 
Fair Value Measurements
 
We apply recurring fair value measurements to cash equivalents, derivative instruments, investments held in the nuclear decommissioning trust and other special use funds. On an annual basis, we apply fair value measurements to plan assets held in our retirement and other benefits plans. Due to the short-term nature of short-term borrowings, the carrying values of these instruments approximate fair value.  Fair value measurements may also be applied on a nonrecurring basis to other assets and liabilities in certain circumstances such as impairments.  We also disclose fair value information for our long-term debt, which is carried at amortized cost. See Note 6 for additional information.
 
Fair value is the price that would be received for an asset or paid to transfer a liability (exit price) in the principal or most advantageous market which we can access for the asset or liability in an orderly transaction between willing market participants on the measurement date.  Inputs to fair value may include observable and unobservable data.  We maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value.
 
We determine fair market value using observable inputs such as actively-quoted prices for identical instruments when available.  When actively-quoted prices are not available for the identical instruments, we use other observable inputs, such as prices for similar instruments, other corroborative market information, or prices provided by other external sources.  For options, long-term contracts, and other contracts for which observable price data are not available, we use models and other valuation methods, which may incorporate unobservable inputs to determine fair market value.
The use of models and other valuation methods to determine fair market value often requires subjective and complex judgment.  Actual results could differ from the results estimated through application of these methods.
See Note 12 for additional information about fair value measurements.
Derivative Accounting
 
We are exposed to the impact of market fluctuations in the commodity price and transportation costs of electricity, natural gas, coal and in interest rates.  We manage risks associated with market volatility by utilizing various physical and financial instruments including futures, forwards, options, and swaps.  As part of our overall risk management program, we may use derivative instruments to hedge purchases and sales of electricity and natural gas as well as interest rate risk.  The changes in market value of such contracts have a high correlation to price changes in the hedged transactions.  We also enter into derivative instruments for economic hedging purposes.  Contracts that have the same terms (quantities, delivery points and delivery periods) and for which power does not flow are netted, which reduces both revenues and fuel and purchased power expenses in our Consolidated Statements of Income, but does not impact our financial condition, net income, or cash flows.
 
We account for our derivative contracts in accordance with derivatives and hedging guidance, which requires all derivatives not qualifying for a scope exception to be measured at fair value on the balance sheet as either assets or liabilities.  Transactions with counterparties that have master netting arrangements are reported net on the balance sheet. 

See Note 15 for additional information about our derivative instruments.
 
Loss Contingencies and Environmental Liabilities
 
Pinnacle West and APS are involved in certain legal and environmental matters that arise in the normal course of business.  Contingent losses and environmental liabilities are recorded when it is determined that it is probable that a loss has occurred, and the amount of the loss can be reasonably estimated.  When a range of the probable loss exists and no amount within the range is a better estimate than any other amount, Pinnacle West and APS record a loss contingency at the minimum amount in the range.  Unless otherwise required by GAAP, legal fees are expensed as incurred.
 
The Captive’s contingent losses may include an amount for losses incurred but not reported (“IBNR”). A reserve for IBNR is based upon a loss analysis prepared using actuarial assumptions and techniques. Such liabilities are necessarily based on estimates and the ultimate liability may be in excess of or less than the amount provided. The methods for making such estimates and for establishing the resulting liability are continually reviewed, and any adjustments for the review process as well as differences between estimates and ultimate payments are reflected in earnings currently. As of December 31, 2024, no IBNR reserve relating to our captive insurance cell has been recorded. See Note 17.
Retirement Plans and Other Postretirement Benefits
 
Pinnacle West sponsors a qualified defined benefit and account balance pension plan for the employees of Pinnacle West and its subsidiaries, in addition to a non-qualified pension plan.  We also sponsor another postretirement benefit plan for the employees of Pinnacle West and its subsidiaries that provides medical and life insurance benefits to retired employees.  Pension and other postretirement benefit expense are determined by actuarial valuations, based on assumptions that are evaluated annually. 

See Note 7 for additional information on pension and other postretirement benefits.
 
Nuclear Fuel
 
APS amortizes nuclear fuel by using the unit-of-production method.  The unit-of-production method is based on actual physical usage.  APS divides the cost of the fuel by the estimated number of thermal units it expects to produce with that fuel.  APS then multiplies that rate by the number of thermal units produced within the current period.  This calculation determines the current period nuclear fuel expense.
 
APS also charges nuclear fuel expense for the interim storage and permanent disposal of spent nuclear fuel.  The DOE is responsible for the permanent disposal of spent nuclear fuel and charged APS $0.001 per kWh of nuclear generation through May 2014, at which point the DOE reduced the fee to zero.  In accordance with a settlement agreement with the DOE in August 2014 for interim storage, we accrued a receivable and an offsetting regulatory liability through the settlement period ended December of 2024. See Note 10 for information on spent nuclear fuel disposal costs.
 
Income Taxes
 
Income taxes are provided using the asset and liability approach prescribed by guidance relating to accounting for income taxes and are based on currently enacted tax rates.  We file our federal income tax return on a consolidated basis, and we file our state income tax returns on a consolidated or unitary basis.  In accordance with our intercompany tax sharing agreement, federal and state income taxes are allocated to each first-tier subsidiary as though each first-tier subsidiary filed a separate income tax return.  Any difference between that method and the consolidated (and unitary) income tax liability is attributed to the parent company.  The income tax accounts reflect the tax and interest associated with management’s estimate of the largest amount of tax benefit that is greater than 50% likely of being realized upon settlement for all known and measurable tax exposures. See Note 4 for additional discussion.
Cash and Cash Equivalents

     We consider cash equivalents to be highly liquid investments with a remaining maturity of three months or less at acquisition.

The following table summarizes supplemental Pinnacle West cash flow information for each of the last three years (dollars in thousands):
Year Ended December 31,
202420232022
Cash paid during the period for:
Income taxes, net of refunds$133,968 $8,788 $46,227 
Interest, net of amounts capitalized360,349 310,996 245,271 
Significant non-cash investing and financing activities:
Accrued capital expenditures$257,494 $206,269 $114,999 
Dividends accrued but not yet paid106,592 99,813 97,895 
BCE Sale non-cash consideration (Note 20)
— 28,262 — 

The following table summarizes supplemental APS cash flow information for each of the last three years (dollars in thousands):
Year Ended December 31,
202420232022
Cash paid during the period for:
Income taxes, net of refunds$179,013 $21,734 $95,985 
Interest, net of amounts capitalized299,799 267,261 227,159 
Significant non-cash investing and financing activities:
Accrued capital expenditures$257,494 $206,269 $116,533 
Dividends accrued but not yet paid107,200 99,800 97,900 
Intangible Assets
 
We have separately disclosed intangible assets on Pinnacle West’s Consolidated Balance Sheets. The intangible assets relate primarily to APS’s internal-use software. We have no goodwill recorded. The intangible assets are amortized over their finite useful lives.  Amortization expense was $136 million in 2024, $90 million in 2023, and $84 million in 2022.  Estimated amortization expense on existing intangible assets over the next five years is $106 million in 2025, $77 million in 2026, $43 million in 2027, $25 million in 2028, and $14 million in 2029.  At December 31, 2024, the weighted-average remaining amortization period for intangible assets was 5 years.
 
Investments
 
El Dorado holds investments in both debt and equity securities.  Investments in debt securities are generally accounted for as held-to-maturity and investments in equity securities are accounted for using either the equity method (if significant influence) or the measurement alternative for investments without readily determinable fair values (if less than 20% ownership and no significant influence).
PNW Power holds investments in equity securities. Investments in equity securities are accounted for using either the equity method (if significant influence) or the measurement alternative for investments without readily determinable fair values (if less than 20% ownership and no significant influence).
 
Our investments in the nuclear decommissioning trusts, and other special use funds, are accounted for in accordance with guidance on accounting for investments in debt and equity securities. See Notes 12 and 18 for more information on these investments.

Leases

We determine if an agreement is a lease at contract inception. A lease is defined as a contract, or part of a contract, that conveys the right to control the use of an identified asset for a period of time in exchange for consideration. To control the use of an identified asset an entity must have both a right to obtain substantially all of the benefits from the use of the asset and the right to direct the use of the asset. If we determine an agreement is a lease, and we are the lessee, we recognize a right-of-use lease asset and a lease liability at the lease commencement date. Lease liabilities are recognized based on the present value of the fixed lease payments over the lease term. To present value lease liabilities we use the implicit rate in the lease if the information is readily available, otherwise we use our incremental borrowing rate determined at lease commencement. Our incremental borrowing rate is based on the rate of interest we would have to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. When measuring right-of-use assets and lease liabilities we exclude variable lease payments, other than those that depend on an index or rate or are in-substance fixed payments. For short-term leases with terms of 12 months or less, we do not recognize a right-of-use lease asset or lease liability. We recognize operating lease expense using a straight-line pattern over the periods of use.

APS enters into purchased power contracts that may contain leases. This occurs when a purchased power agreement designates a specific power plant or facility, APS obtains substantially all of the economic benefits from the use of the facility and has the right to direct the use of the facility. Purchased power lease contracts may also include energy storage facilities. Lease costs relating to purchased power lease contracts are reported in fuel and purchased power on the Consolidated Statements of Income and are subject to recovery under the PSA or RES. See Note 3. We also may enter into lease agreements related to vehicles, office space, land, and other equipment. See Note 8 for information on our lease agreements.

Business Segments
 
Pinnacle West’s reportable business segment is our regulated electricity segment, which consists of traditional regulated retail and wholesale electricity businesses (primarily electric service to Native Load customers) and related activities and includes electricity generation, transmission, and distribution. Our reportable segment activities are conducted through our wholly-owned subsidiary, APS. All other operating segment activities are insignificant to Pinnacle West.
For segment reporting purposes, Pinnacle West’s Chief Executive Officer performs the function of chief operating decision maker (“CODM”). The CODM uses net income to measure an operating segment’s profitability. When assessing the performance of an operating segment, and making decisions about allocating resources, the CODM evaluates net income actual results compared to budget. Net income is also used when implementing strategic initiatives and selecting projects to meet business objectives. Our reportable segment’s revenue streams are dependent upon regulated rate recovery, which is a primary factor in how we identify operating segments.

For information on our reportable business segment’s revenues, significant expenses, net income, assets, and other reportable segment items, see the APS’s Consolidated Income Statements, APS Consolidated Balance Sheets, and APS Consolidated Statements of Cash Flows. The following tables reconcile our reportable segment’s revenues, significant expenses, net income, and assets to the Pinnacle West Consolidated amounts (dollars in millions):

Year Ended December 31,
202420232022
Regulated Electricity SegmentOther Pinnacle West ConsolidatedRegulated Electricity SegmentOther Pinnacle West ConsolidatedRegulated Electricity SegmentOther Pinnacle West Consolidated
Operating Revenues$5,125 $— $5,125 $4,696 $— $4,696 $4,324 $— $4,324 
Fuel & Purchase Power (1,823)— (1,823)(1,793)— (1,793)(1,629)— (1,629)
Operations & Maintenance(1,159)(6)(1,165)(1,044)(15)(1,059)(974)(13)(987)
Depreciation & Amortization (895)— (895)(794)— (794)(753)— (753)
Taxes other than income taxes (227)— (227)(224)— (224)(220)— (220)
Pension and other postretirement non-service credits, net49 — 49 42 (1)41 99 (1)98 
Other income and expenses, net (a)28 22 50 60 — 60 22 (23)(1)
Interest expense and costs(312)(65)(377)(285)(46)(331)(236)(20)(256)
Income Taxes(127)16 (111)(94)17 (77)(91)16 (75)
Less: income related to noncontrolling interest(17)— (17)(17)— (17)(17)— (17)
Net Income (loss) $642 $(33)$609 $547 $(45)$502 $525 $(41)$484 
(a) See Note 16 for additional details regarding other income and other expenses. Other income includes allowance for equity funds used during construction, see the APS Consolidated Income Statements.

December 31, 2024December 31, 2023
Regulated Electricity SegmentOtherPNW ConsolidatedRegulated Electricity SegmentOtherPNW Consolidated
Total Assets$25,988 $115 $26,103 $24,516 $145 $24,661 
Preferred Stock

At December 31, 2024, Pinnacle West had 10 million shares of serial preferred stock authorized with no par value, none of which was outstanding, and APS had 15,535,000 shares of various types of preferred stock authorized with $25, $50, and $100 par values, none of which was outstanding.
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Revenue
 12 Months Ended
Dec. 31, 2024
Revenue from Contract with Customer [Abstract]  
Revenue Revenue
Sources of Revenue

The following table provides detail of Pinnacle West’s consolidated revenue disaggregated by revenue sources (dollars in thousands):
Year Ended December 31,
202420232022
Retail Electric Service
Residential$2,562,822 $2,289,196 $2,046,111 
Non-Residential2,334,925 2,048,416 1,767,616 
Wholesale Energy Sales96,857 208,985 383,126 
Transmission Services for Others119,038 138,631 116,628 
Other Sources11,273 10,763 10,904 
Total Operating Revenues$5,124,915 $4,695,991 $4,324,385 

Retail Electric Revenue. All of Pinnacle West’s retail electric revenue is generated by APS. Retail electric revenue is generated by the sale of electricity to our regulated customers within the authorized service territory at tariff rates approved by the ACC and based on customer usage. Revenues related to the sale of electricity are generally recognized when service is rendered, or electricity is delivered to customers. The billing of electricity sales to individual customers is based on the reading of their meters. We obtain customers’ meter data on a systematic basis throughout the month, and generally bill customers within a month from when service was provided. Customers are generally required to pay for services within 21 days of when the services are billed. See “Allowance for Doubtful Accounts” discussion below for additional details regarding payment terms.

Wholesale Energy Sales and Transmission Services for Others. Revenues from wholesale energy sales and transmission services for others represent energy and transmission sales to wholesale customers. These activities primarily consist of managing fuel and purchased power risks in connection with the cost of serving our retail customers’ energy requirements. We may also sell into the wholesale markets generation that is not needed for APS’s retail load. Our wholesale activities and tariff rates are regulated by FERC.
Revenue Activities

Our revenues primarily consist of activities that are classified as revenues from contracts with customers. We derive our revenues from contracts with customers primarily from sales of electricity to our regulated retail customers. Revenues from contracts with customers also include wholesale and transmission activities. Our revenues from contracts with customers for the year ended December 31, 2024, 2023 and 2022 were $5,073 million, $4,651 million, and $4,302 million, respectively.
We have certain revenues that do not meet the specific accounting criteria to be classified as revenues from contracts with customers. For the year ended December 31, 2024, 2023, and 2022 our revenues that do not qualify as revenue from contracts with customers were $52 million, $45 million, and $22 million, respectively. This amount includes revenues related to certain regulatory cost recovery mechanisms that are considered alternative revenue programs. We recognize revenue associated with alternative revenue programs when specific events permitting recognition are completed. Certain amounts associated with alternative revenue programs will subsequently be billed to customers; however, we do not reclassify billed amounts into revenue from contracts with customers. See Note 3 for a discussion of our regulatory cost recovery mechanisms.
Allowance for Doubtful Accounts
The allowance for doubtful accounts represents our best estimate of accounts receivable and accrued unbilled revenues that will ultimately be uncollectible due to credit loss risk. The allowance includes a write-off component that is calculated by applying an estimated write-off factor to retail electric revenues. The write-off factor used to estimate uncollectible accounts is based upon consideration of historical collections experience, the current and forecasted economic environment, changes to our collection policies, and management’s best estimate of future collections success. We continue to monitor the impacts of our disconnection policies, payment arrangements, among other considerations impacting our estimated write-off factor, and allowance for doubtful accounts.

The following table provides a rollforward of Pinnacle West’s allowance for doubtful accounts (dollars in thousands):

Year Ended December 31,
202420232022
Balance at beginning of period$22,433 $23,778 $25,354 
Bad debt expense35,799 23,399 17,006 
Actual write-offs(33,383)(24,744)(18,582)
Balance at end of period$24,849 $22,433 $23,778 
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Regulatory Matters
 12 Months Ended
Dec. 31, 2024
Regulated Operations [Abstract]  
Regulatory Matters Regulatory Matters
APS expects to file an application with the ACC for its next general rate case mid-year 2025 and is continuing to evaluate the timing of such filing.

2022 Retail Rate Case

APS filed an application with the ACC on October 28, 2022 (the “2022 Rate Case”) seeking an increase in annual retail base rates.

On January 25, 2024, an Administrative Law Judge issued a Recommended Opinion and Order (“ROO”) in the 2022 Rate Case, as corrected on February 6, 2024 (the “2022 Rate Case ROO”). The 2022 Rate Case ROO recommended, among other things, (i) a $523.1 million increase in the annual base rate revenue requirement, (ii) a 9.55% return on equity, (iii) a 0.25% return on the increment of fair value rate base greater than original cost, (iv) an effective fair value rate of return of 4.36%, (v) 12 months of post-
test year plant and the inclusion of the Four Corners Effluent Limitations Guideline (“ELG”) project, (vi) the approval of APS’s System Reliability Benefit (“SRB”) proposal with certain procedural and other modifications, (vii) no additional Coal Community Transition (“CCT”) funding, (viii) a 5.0% return on the prepaid pension asset and a return of 5.35% on the OPEB liability, and (ix) no disallowances on APS’s coal contracts.

The 2022 Rate Case ROO also recommended a number of changes to existing adjustors, including (i) the approval of modified DSM performance incentives and the requested DSM transfer to base rates, (ii) the retention of $1.9 million of Renewable Energy Adjustment Charge (“REAC”) in the adjustor rather than base rates, (iii) a partial transfer of $27.1 million of LFCR funds to base rates, and (iv) the adoption of an increase in the annual PSA cap to $0.006/kWh.

On February 22, 2024, the ACC approved a number of amendments to the 2022 Rate Case ROO that resulted in, among other things, (i) an approximately $491.7 million increase in the annual base revenue requirement, (ii) a 9.55% return on equity, (iii) a 0.25% return on the increment of fair value rate base greater than original cost, (iv) an effective fair value rate of return of 4.39%, (v) a return set at the Company’s weighted average cost of capital on the net prepaid pension asset and net other post-employment benefit liability in rate base, (vi) an adjustment to generation maintenance and outage expense to reflect a more reasonable level of test year costs, (vii) approval of the SRB mechanism with modifications to customer notifications, procedural timelines and the inclusion of any qualifying technology and fuel source bid received through an all-source request for proposal (“ASRFP”), and (viii) recovery of all DSM costs through the DSM Adjustment Charge (“DSMAC”) rather than through base rates.

The ACC’s decision results in an expected total net annual revenue increase for APS of approximately $253.4 million and a roughly 8% increase to the typical residential customer’s bill. The ACC issued the final order for the 2022 Rate Case on March 5, 2024, with the new rates becoming effective for all service rendered on or after March 8, 2024.

Six intervenors and the Attorney General of Arizona requested rehearing on various issues included in the ACC’s decision, such as the grid access charge (“GAC”) for solar customers, the SRB, and CCT funding. On April 15, 2024, the ACC granted, in part, the rehearing applications of the Attorney General, Arizona Solar Energy Industries Association, Solar Energy Industries Association, and Vote Solar specifically to review whether the GAC rate is just and reasonable, including whether it should be higher or lower, whether the GAC rate constitutes a discriminatory fee to solar customers, and whether omission of a GAC charge is discriminatory to non-solar customers. All other applications for rehearing were denied. A limited rehearing was held October 28 through November 1. Following the limited rehearing, an Administrative Law Judge issued a ROO (the “Limited Rehearing ROO”) on December 3, 2024. The Limited Rehearing ROO recommended affirming the GAC as just and reasonable and that the GAC is not discriminatory to solar customers and the absence of a GAC is not discriminatory to non-solar customers. On December 17, 2024, the ACC approved the Limited Rehearing ROO with an amendment that requires APS in its next rate case to propose a revenue allocation based on a site-load cost of service study in order to bring further parity in revenue collection between solar and non-solar customers. SEIA, AriSEIA, Vote Solar, the Arizona Attorney General, and two individual customers have filed requests for rehearing of the Commission’s December 17, 2024 decision on the rehearing. The Commission has taken no action on these requests. In addition, each of these parties have subsequently filed notices of appeal to the Arizona Court of Appeals seeking review of the Commission’s decisions regarding the GAC and on rehearing. APS cannot predict the outcome of these proceedings.
2019 Retail Rate Case

On October 31, 2019, APS filed an application with the ACC for an annual increase in retail base rates (the “2019 Rate Case”). On August 2, 2021, an Administrative Law Judge issued a ROO in the 2019 Rate Case (the “2019 Rate Case ROO”) and issued corrections on September 10 and September 20, 2021.

On November 2, 2021, the ACC approved the 2019 Rate Case ROO, with various amendments, that resulted in, among other things, (i) a return on equity of 8.70%, which included a 20 basis points penalty; (ii) the recovery of the deferral and rate base effects of the operating costs and construction of the Four Corners selective catalytic reduction (“SCR”) project, with the exception of $215.5 million (see “Four Corners SCR Cost Recovery” below); (iii) the CCT plan including the following components: (a) a payment of $1 million to the Hopi Tribe within 60 days of the 2019 Rate Case decision, (b) a payment of $10 million over three years to the Navajo Nation, (c) a payment of $0.5 million to the Navajo County communities within 60 days of the 2019 Rate Case decision, (d) up to $1.25 million for electrification of homes and businesses on the Hopi reservation, and (e) up to $1.25 million for the electrification of homes and businesses on the Navajo Nation reservation; and (iv) a change in the residential on-peak time-of-use period from 3 p.m. to 8 p.m. to 4 p.m. to 7 p.m. Monday through Friday, excluding holidays. The 2019 Rate Case ROO, as amended, resulted in a total annual revenue decrease for APS of $4.8 million, excluding temporary payments and expenditures, under the CCT plan.

Consistent with the 2019 Rate Case decision, APS completed the following payments that are being recovered through rates related to the CCT: (i) $10 million to the Navajo Nation; (ii) $0.5 million to the Navajo County communities; and (iii) $1 million to the Hopi Tribe. Consistent with APS’s commitment to the impacted communities, APS has also completed the following payments: (i) $1.5 million to the Navajo Nation for CCT; (ii) $1.1 million to the Navajo County communities for CCT and economic development; and (iii) $1.25 million to the Hopi Tribe for CCT and economic development. The ACC also authorized $1.25 million to be spent for electrification of homes and businesses on each of the Navajo Nation and Hopi reservations. Expenditure of the recoverable funds for electrification of homes and businesses on the Navajo Nation and the Hopi reservations is contingent upon completion of a census of the unelectrified homes and businesses in each that are also within APS service territory. The census work was completed in November 2022 and disbursement of the funds for electrification of homes and businesses is planned to be finalized after discussions with the Navajo Nation and the Hopi Tribe are completed. On February 22, 2024, the ACC voted to not approve any further CCT funding.

APS filed a Notice of Direct Appeal to the Arizona Court of Appeals on December 17, 2021 requesting review of certain aspects of the 2019 Rate Case. On March 6, 2023, the Court issued its opinion in this matter, affirming in part and reversing in part the ACC’s decision in the 2019 Rate Case. The Court vacated the 20 basis points penalty included in the ACC’s allowed return on equity, as the Court determined the use of customer service metrics to justify the reduction exceeded the ACC’s ratemaking authority. Additionally, the Court vacated the disallowance of $215.5 million of APS’s Four Corners SCR investment. The Court remanded the issue to the ACC for further proceedings.

On June 14, 2023, APS and the ACC Legal Division filed a joint resolution with the ACC to allow recovery of the $215.5 million in costs related to the installation of the Four Corners SCR, a reversal of the 20 basis points reduction to APS’s return on equity from 8.9% to 8.7% as a result of the 2019 Rate Case decision, and recovery of $59.6 million in revenue lost by APS between December 2021 and June 20, 2023. On June 21, 2023, the ACC approved the joint resolution and proposals therein for recovery through
the Court Resolution Surcharge (“CRS”) mechanism, which became effective on July 1, 2023. See “Court Resolution Surcharge” below for more information.

Regulatory Lag Docket

On January 5, 2023, the ACC opened a new docket to explore the possibility of modifications to the ACC’s historical test year rules. The ACC requested comments and held two workshops exploring ways to reduce regulatory lag, including alternative ratemaking structures such as future test years, hybrid test years, and formula rates. On December 3, 2024, the ACC approved a policy statement regarding formula rate plans. The policy statement allows regulated utilities to propose formula rate plans in future rate cases. Proposed plans must be based on a historical test year, include an annual update with a true-up and an earnings test to ensure a utility earns within a 20 basis points band of its authorized return on equity. Proposed plans should also include an annual meeting and challenge periods for stakeholder feedback. Utilities that implement formula rates also must file a full rate case at least every five years unless an alternate schedule is set by the ACC. APS cannot predict the outcome of this matter.

Cost Recovery Mechanisms
 
APS has received regulatory decisions that allow for more timely recovery of certain costs outside of a general retail rate case through the following recovery mechanisms. See “2022 Retail Rate Case” above for modifications of adjustment mechanisms in the 2022 Rate Case.
 
Renewable Energy Standard. In 2006, the ACC approved the RES. Under the RES, electric utilities that are regulated by the ACC must supply an increasing percentage of their retail electric energy sales from eligible renewable resources, including, for example, solar, wind, biomass, biogas and geothermal technologies. In order to achieve these requirements, the ACC allows APS to include a RES surcharge as part of customer bills to recover the approved amounts for use on renewable energy projects. Each year, APS is required to file a five-year implementation plan with the ACC and seek approval for funding the upcoming year’s RES budget.

In June 2021, the ACC adopted a clean energy rules package which would require APS to meet certain clean energy standards and technology procurement mandates, obtain approval for its action plan included in its Integrated Resource Plan (“IRP”), and seek cost recovery in a rate process. Since the adopted clean energy rules differed substantially from the original ROO, supplemental rulemaking procedures were required before the rules could become effective. On January 26, 2022, the ACC reversed its prior decision and declined to send the final draft energy rules through the rulemaking process. Instead, the ACC opened a new docket to consider ASRFP requirements and the IRP process. See “Energy Modernization Plan” below for more information.

On July 1, 2021, APS filed its 2022 RES Implementation Plan and proposed a budget of approximately $93.1 million. APS filed an amended 2022 RES Implementation Plan on December 9, 2021, with a proposed budget of $100.5 million. This budget included funding for programs to comply with the decision in the 2019 Rate Case, including the ACC authorizing spending $20 million to $30 million in capital costs for the continuation of the APS Solar Communities program each year for a period of three years from the effective date of the 2019 Rate Case decision. APS’s budget proposal supported existing approved projects and commitments and requested a waiver of the RES residential and non-residential distributed energy requirements for 2022. On May 18, 2022, the ACC approved the 2022
RES Implementation Plan, including an amendment requiring a stakeholder working group convene to develop a community solar program for the ACC’s consideration at a future date.

On July 1, 2022, APS filed its 2023 RES Implementation Plan and proposed a budget of approximately $86.2 million, excluding any funding offsets. This budget contained funding for programs to comply with ACC-approved initiatives, including the 2019 Rate Case decision. APS’s budget proposal supported existing approved projects and commitments and requested a waiver of the RES residential and non-residential distributed energy requirements for 2023. On November 10, 2022, the ACC approved the 2023 RES Implementation Plan, including APS’s requested waiver of the distributed energy requirement for 2023.

On June 30, 2023, APS filed its 2024 RES Implementation Plan and proposed a budget of approximately $95.1 million. APS’s budget proposal supports existing approved projects and commitments and requests a waiver of the RES renewable energy credit requirements to demonstrate compliance with the Annual Renewable Energy Requirement for 2023. The ACC has not yet ruled on the 2024 RES Implementation Plan. APS cannot predict the outcome of this proceeding.

On July 1, 2024, APS filed its 2025 RES Implementation Plan and proposed a budget of approximately $92.7 million. APS’s budget proposal supports existing approved projects and commitments and requests a waiver of the RES renewable energy credit requirements to demonstrate compliance with the Annual Renewable Energy Requirement for 2024. The ACC has not yet ruled on the 2025 RES Implementation Plan. APS cannot predict the outcome of this proceeding.

On June 14, 2021, APS filed an application for approval of its Green Power Partners Program (“GPP”). On September 1, 2021, the ACC approved the application. On June 28, 2024, APS filed an application for approval of modifications to the GPP and requested a renewable generation renewable energy credits waiver. The ACC has not yet ruled on the GPP application. APS cannot predict the outcome of this proceeding.

Demand Side Management Adjustor Charge. The ACC Electric Energy Efficiency Standards require APS to submit a DSM Implementation Plan annually for review and approval by the ACC. Verified energy savings from APS’s resource savings projects can be counted toward compliance with the Electric Energy Efficiency Standards; however, APS is not allowed to count savings from systems savings projects toward determination of the achievement of performance incentives, nor may APS include savings from these system savings projects in the calculation of its LFCR mechanism. See below for discussion of the LFCR.

On December 17, 2021, APS filed its 2022 DSM Implementation Plan in accordance with an extension granted in 2021. The 2022 DSM Plan requested a budget of $78.4 million and represents an increase of approximately $14 million in DSM spending above 2021. On November 10, 2022, the ACC approved the 2022 DSM Implementation Plan, including a proposed performance incentive.

On June 1, 2022, APS filed its 2023 Transportation Electrification Plan (“2023 TE Plan”). The 2023 TE Plan detailed APS’s efforts to support transportation electrification in Arizona, including the Take Charge AZ Pilot Program and customer education and outreach related to transportation electrification. Subsequently, APS filed an amended 2023 TE Plan on November 30, 2022, that included a request for a $5 million budget. On December 12, 2023, the ACC approved the 2023 TE Plan without including the
Take Charge AZ Program and its budget going forward, but allowed APS to complete projects already underway. Additionally, the ACC discontinued the residential EV SmartCharger rebate and approved modifications to the EV rate plan.

On November 30, 2022, APS filed its 2023 DSM Implementation Plan, which requested a budget of $88 million. On May 31, 2023, APS filed an amended 2023 DSM Implementation Plan. The amended plan maintained the originally proposed budget of $88 million. Subsequent to filing the amended 2023 DSM Implementation Plan and prior to the ACC approving it, on November 30, 2023, APS filed its 2024 DSM Implementation Plan. The 2024 DSM Implementation Plan requested a total budget of $91.5 million and incorporated all elements of the amended 2023 DSM Implementation Plan as well as the 2024 TE Implementation Plan. On April 26, 2024, APS filed an amendment to the 2024 DSM Implementation Plan. The amended 2024 DSM Implementation Plan includes an updated budget of $90.9 million to reflect removal of incentive funds for the Level 2 Smart Charger rebate within the EV Charging Demand Management Pilot, an update on the performance incentive calculation, and the withdrawal of tranches two and three of the residential battery pilot. The ACC has not yet ruled on the amended 2024 DSM Implementation Plan. In a letter filed May 31, 2024, APS said it would not file a 2025 DSM Implementation Plan pending ACC review of the amended 2024 DSM Implementation Plan. APS cannot predict the outcome of this proceeding.

Power Supply Adjustor Mechanism and Balance. The PSA provides for the adjustment of retail rates to reflect variations primarily in retail fuel and purchased power costs. The PSA is subject to specified parameters and procedures, including the following:

•APS records deferrals for recovery or refund to the extent actual retail fuel and purchased power costs vary from the Base Fuel Rate;
•an adjustment to the PSA rate is made annually each February 1 (unless otherwise approved by the ACC) and goes into effect automatically unless suspended by the ACC;
•the PSA uses a forward-looking estimate of fuel and purchased power costs to set the annual PSA rate, which is reconciled to actual costs experienced for each PSA Year (February 1 through January 31) (see the following bullet point);
•the PSA rate includes (a) a “forward component,” under which APS recovers or refunds differences between expected fuel and purchased power costs for the upcoming calendar year and those embedded in the Base Fuel Rate; (b) a “historical component,” under which differences between actual fuel and purchased power costs and those recovered or refunded through the combination of the Base Fuel Rate and the forward component are recovered during the next PSA Year; and (c) a “transition component,” under which APS may seek mid-year PSA changes due to large variances between actual fuel and purchased power costs and the combination of the Base Fuel Rate and the forward component; and
•the PSA rate may not be increased or decreased more than $0.006 per kWh in a year without permission of the ACC.
The following table shows the changes in the deferred fuel and purchased power regulatory asset for 2024 and 2023 (dollars in thousands):
 Year Ended December 31,
 20242023
Balance at beginning of period$463,195 $460,561 
Deferred fuel and purchased power costs250,288 549,877 
Amounts charged to customers
(425,886)(547,243)
Balance at end of period$287,597 $463,195 

On November 30, 2021, APS filed its PSA rate for the PSA year beginning February 1, 2022. That rate was $0.007544 per kWh, which consisted of a forward component of $(0.004842) per kWh and a historical component of $0.012386 per kWh. The 2022 PSA rate was a $0.004 per kWh increase compared to the 2021 PSA year, which is the maximum permitted under the Plan of Administration for the PSA. These rates went into effect as filed on February 1, 2022.

On April 1, 2022, the ACC filed a final report of its third-party audit findings regarding APS’s fuel and purchased power costs for the period January 2019 through January 2021. The report contained an in-depth review of APS’s fuel and purchased power contracts, its monthly fuel accounting activities, its forecasting and dispatching procedures, and its monthly PSA filings, among other fuel-related activities. The report found that APS’s fuel processing accounting practices, dispatching procedures, and procedures for hedging activity were reasonable and appropriate. The report included several recommendations for the ACC’s consideration, including review of current contracts, maintenance schedules, and certain changes and improvements to the schedules in APS’s monthly PSA filings. On December 27, 2022, ACC Staff filed a proposed order supporting adoption of the recommendations in the third-party audit report, and the ACC approved the proposed order on February 22, 2023.

On November 30, 2022, APS filed its PSA rate for the PSA year beginning February 1, 2023. In this filing, APS also requested that one of three different options be adopted to address the growing undercollected PSA balance. On February 23, 2023, the ACC approved an overall PSA rate of $0.019074 per kWh, which consisted of a forward component of $(0.005527) per kWh, a historical component of $0.013071 per kWh and a transition component of $0.011530 per kWh, that will continue until further notice of the ACC. The rate became effective with the first billing cycle in March 2023 and is designed to bring the PSA balancing account to near-zero over a 24-month period. On November 30, 2023, APS notified the ACC that it will be maintaining the current PSA rate of $0.019074 per kWh and an updated PSA adjustment schedule would not be filed at that time. In Decision No. 79293 in the 2022 Rate Case, the ACC approved a permanent increase in the annual PSA adjustor rate cap from $0.004 per kWh to $0.006 per kWh and a requirement that APS report to the ACC for possible action when the overall PSA balance reaches $100 million. As part of the 2022 Rate Case decision, the ACC also approved an overall PSA rate of $0.011977 per kWh, which consisted of a forward component of $(0.012624) per kWh, a historical component of $0.013071 per kWh, and a transition component of $0.011530 per kWh. The overall PSA rate was reduced to offset an increase in base fuel prices. The rate became effective on March 8, 2024.

On November 27, 2024, APS filed its PSA rate for the PSA year beginning February 1, 2025. The overall PSA rate of $0.013977 per kWh consists of a forward component of $(0.000281) per kWh, a
historical component of $0.008728 per kWh, and a transition component of $0.005530. This overall PSA rate is an increase of $0.002 per kWh over the prior overall rate approved in the 2022 Rate Case decision, and it is below the annual PSA rate increase cap of $0.006 per kWh. On February 5, 2025, the ACC voted to approve this request, with a rate effective date of the first billing cycle in March 2025.

Environmental Improvement Surcharge. On March 5, 2024, the ACC approved the elimination of the EIS, and the surcharge is no longer in effect. The EIS permitted APS to recover the capital carrying costs (rate of return, depreciation and taxes) plus incremental operations and maintenance expenses associated with environmental improvements made outside of a test year to comply with environmental standards set by federal, state, tribal, or local laws and regulations. APS’s February 1, 2023, EIS application requested an increase in the charge to $14.7 million, or $3.3 million over the prior-period charge. On March 10, 2023, APS filed an amended application requesting an EIS charge of $4.0 million, a decrease of $10.7 million from the February EIS request, and a decrease of $7.5 million from the prior-period charge. The revised 2023 EIS became effective with the first billing cycle in April 2023; however, with the elimination of the surcharge, it is no longer in effect, and any remaining amounts are being collected through base rates.
 
Transmission Rates, Transmission Cost Adjustor and Other Transmission Matters. APS’s retail transmission charges’ formula rate is updated each year effective June 1 on the basis of APS’s actual cost of service, as disclosed in APS’s FERC Form 1 report for the previous fiscal year. Items to be updated include actual capital expenditures made as compared with previous projections, transmission revenue credits and other items. APS reviews the proposed formula rate filing amounts with the ACC Staff. Any items or adjustments which are not agreed to by APS and the ACC Staff can remain in dispute until settled or litigated with FERC. Settlement or litigated resolution of disputed issues could require an extended period of time and could have a significant effect on the Retail Transmission Charges because any adjustment, though applied prospectively, may be calculated to account for previously over- or under-collected amounts. The resolution of proposed adjustments can result in significant volatility in the revenues to be collected.

Effective June 1, 2022, APS’s annual wholesale transmission revenue requirement for all users of its transmission system decreased by approximately $33 million for the 12-month period beginning June 1, 2022, in accordance with the FERC-approved formula. Of this net amount, wholesale customer rates decreased by approximately $6.4 million and retail customer rates would have decreased by approximately $26.6 million. However, since changes in Retail Transmission Charges are reflected through the TCA after consideration of transmission recovery in retail base rates and the ACC-approved balancing account, the retail revenue requirement decreased by $2.4 million, resulting in a reduction to the residential rate and increases to commercial rates. An adjustment to APS’s retail rates to recover FERC-approved transmission charges went into effect automatically on June 1, 2022.

Effective June 1, 2023, APS’s annual wholesale transmission revenue requirement for all users of its transmission system increased by approximately $34.7 million for the 12-month period beginning June 1, 2023, in accordance with the FERC-approved formula. Of this net amount, wholesale customer rates increased by approximately $20.7 million and retail customer rates would have increased by approximately $14 million. However, since changes in Retail Transmission Charges are reflected through the TCA after consideration of transmission recovery in retail base rates and the ACC-approved balancing account, the retail revenue requirement decreased by $10 million, resulting in reductions to the residential
and commercial rates. An adjustment to APS’s retail rates to recover FERC-approved transmission charges went into effect automatically on June 1, 2023.

Effective June 1, 2024, APS’s annual wholesale transmission revenue requirement for all users of its transmission system increased by approximately $27.4 million for the 12-month period beginning June 1, 2024 in accordance with the FERC-approved formula. Of this net amount, wholesale customer rates increased by approximately $16.6 million and retail customer rates would have increased by approximately $10.8 million. However, since changes in Retail Transmission Charges are reflected through the TCA after consideration of transmission recovery in retail base rates and the ACC-approved balancing account, the retail revenue requirement increased by $8.8 million, resulting in an increase to residential and commercial rates over 3 MW and a decrease to commercial rates less than or equal to 3 MW. An adjustment to APS’s retail rates to recover FERC-approved transmission charges went into effect automatically on June 1, 2024.

Lost Fixed Cost Recovery Mechanism. The LFCR mechanism permits APS to recover on an after-the-fact basis a portion of its fixed costs that would otherwise have been collected by APS in the kWh sales lost due to APS energy efficiency programs and to DG such as rooftop solar arrays. The adjustment to the LFCR has a year-over-year cap of 1% of retail revenues. Any amounts left unrecovered in a particular year because of this cap can be carried over for recovery in a future year. The kWhs lost from energy efficiency are based on a third-party evaluation of APS’s energy efficiency programs. DG sales losses are determined from the metered output from the DG units.
 
On February 15, 2022, APS filed its 2022 annual LFCR adjustment, requesting that effective May 1, 2022, the annual LFCR recovery amount be increased to $59.1 million (a $32.5 million increase from previous levels, which was inclusive of a $11.8 million balance from APS’s 2021 LFCR filing). On May 9, 2022, the ACC Staff filed its revised report and proposed order regarding APS’s 2022 LFCR adjustment, concluding that APS calculated the adjustment in accordance with its Plan of Administration. On May 18, 2022, the ACC approved the 2022 LFCR adjustment, with a rate effective date of June 1, 2022.

On February 15, 2023, APS filed a letter to the ACC docket stating that, in accordance with Decision No. 78585, APS and ACC Staff have agreed to move the filing date for the annual LFCR adjustment to July 31 each year. On September 5, 2023, APS filed an updated LFCR Plan of Administration, which was approved by ACC Staff on December 8, 2023. On July 31, 2023, APS filed its 2023 annual LFCR adjustment, requesting that the annual LFCR recovery amount be increased to $68.7 million (a $9.6 million increase from previous levels). On October 19, 2023, a request for intervention was filed, which was granted. Consistent with an October 25, 2023, Procedural Order, the parties met and conferred and conducted limited discovery. As a result of Decision No. 79293 in the 2022 Rate Case, APS transferred $27.1 million from the LFCR to base rates.

On March 8, 2024, APS filed conforming LFCR schedules to incorporate changes required as a result of Decision No. 79293 in the 2022 Rate Case. On April 9, 2024, the ACC approved the 2023 annual LFCR adjustment, with new rates effective in the first billing cycle of May 2024.

On June 5, 2024, APS filed a revised LFCR Plan of Administration in accordance with Decision No. 79293. The ACC approved the revised Plan of Administration on October 8, 2024.
On July 31, 2024, APS filed its 2024 annual LFCR adjustment, requesting that effective November 1, 2024, the annual LFCR recovery amount be increased to $49.6 million (an $8 million increase from previous levels). On December 3, 2024, the ACC approved the 2024 annual LFCR adjustment, with new rates effective in the first billing cycle of January 2025.

Tax Expense Adjustor Mechanism.  The TEAM helps address potential federal income tax reform and enable the pass-through of certain income tax effects to customers. The TEAM expressly applies to APS’s retail rates with the exception of a small subset of customers taking service under specially-approved tariffs. As part of the 2019 Rate Case decision, there remains small true up balances in the TEAM balancing account. In the 2022 Rate Case, these true up balances are being recovered and amortized through 2032.

Court Resolution Surcharge. The CRS mechanism permits APS to recover certain costs associated with investments and expenses for APS’s purchase and installation of SCR technology for Four Corners Units 4 and 5 and a change in APS’s allowable return on equity as required by the Arizona Court of Appeals and approved by the ACC in Decision No. 78979. The CRS went into effect on July 1, 2023, at a rate of $0.00175 per kWh. The rate is designed to recover $59.6 million in revenue lost by APS between December 2021 and June 20, 2023, and the prospective recovery of ongoing costs related to the SCR investments and expense and the allowable return on equity difference in current base rates. The portion of the CRS representing the recovery of the $59.6 million of lost revenue between December 2021 and June 20, 2023, $26.2 million of which has been collected as of December 31, 2024, will cease upon full collection of the lost revenue. Additionally, the CRS tariff was updated to remove the return on equity component and account for SCR-related depreciation and deferral adjustments approved in Decision No. 79293 in the 2022 Rate Case. See “2019 Retail Rate Case” above for more information.

Net Metering

The ACC’s decision from APS’s 2017 rate case (the “2017 Rate Case Decision”) provides that payments by utilities for energy exported to the grid from residential DG solar facilities will be determined using a Resource Comparison Proxy (“RCP”) methodology as determined in the ACC’s generic Value and Cost of Distributed Generation docket. RCP is a method that is based on the most recent five-year rolling average price that APS incurs for utility-scale solar photovoltaic projects. The price established by this RCP method is updated annually (between general retail rate cases) but cannot be decreased by more than 10% per year.

On April 29, 2022, APS filed an application to decrease the RCP price from 9.4 cents per kWh, which had been in effect since October 1, 2021, to 8.46 cents per kWh, reflecting a 10% annual reduction, to become effective September 1, 2022. On July 12, 2022, the ACC approved the RCP as filed.

On May 1, 2023, APS filed an application for revisions to the RCP. This application would decrease the RCP price to 7.619 cents per kWh, reflecting a 10% annual reduction, to become effective September 1, 2023. On August 25, 2023, the ACC approved the RCP as filed.

On May 1, 2024, APS filed an application for revisions to the RCP. This application would decrease the RCP price to 6.857 cents per kWh, reflecting a 10% annual reduction, to become effective September 1, 2024. On August 13, 2024, the ACC approved the RCP as filed.
On October 11, 2023, the ACC voted to open a new general docket to hold a hearing to explore potential future changes to the 10% annual reduction cap in the solar export rate paid by utilities to distributed solar customers for exports to the grid and the 10-year rate lock period for those customers that were approved in the ACC’s Value and Cost of Distributed Generation Docket. A procedural conference was held on November 1, 2023, to discuss the process going forward. As a result of the procedural conference, ACC Staff issued a request for information to investigate the issues related to this matter. A status conference was held on March 20, 2024 to determine if ACC Staff is prepared to present a recommendation on this matter at that time. Stakeholders provided responses to the ACC Staff’s request for information on March 21, 2024. Another status conference took place on May 20, 2024 and ACC Staff issued a request for additional information to investigate the issues related to the matter on May 31, 2024. Stakeholders provided responses to the ACC Staff’s request for additional information on July 1, 2024, and on October 15, 2024, the ACC Staff filed a report finding that the RCP is working as intended and recommending no changes to the RCP at this time. The ACC Staff also recommended that the ACC close the docket without a hearing or further action. The ACC has not yet acted on the ACC Staff’s recommendation, and APS cannot predict the outcome of this matter.

Energy Modernization Plan

On May 26, 2023, the ACC opened a new docket to review articles within the Arizona Administrative Code related to Resource Planning, the Renewable Energy Standard and Tariff, and Electric Energy Efficiency Standards. On January 9, 2024, the ACC approved a rulemaking process for this matter. During the ACC Open Meeting on February 6, 2024, the ACC approved motions to direct ACC Staff to include recommendations to repeal the current Electric Energy Efficiency and Renewable Energy Standard rules during the rulemaking process. On August 21, 2024, the ACC Staff filed separate reports for each set of rules, including its recommendations to repeal the Electric Energy Efficiency and Renewable Energy Standard rules along with required preliminary economic, small business, and consumer impact statements. APS and other interested parties have filed comments about the ACC Staff reports. APS cannot predict the outcome of this matter.

Integrated Resource Planning

ACC rules require utilities to develop triennial 15-year IRPs which describe how the utility plans to serve customer load in the plan time frame. The ACC reviews each utility’s IRP to determine if it meets the necessary requirements and whether it should be acknowledged. In February 2022, the ACC acknowledged APS’s 2020 IRP filed on June 26, 2020. The ACC also approved certain amendments to the IRP process, including, setting an EES of 1.3% of retail sales annually (averaged over a three-year period) and a demand-side resource capacity of 35% of 2020 peak demand by January 1, 2030.

On May 1, 2023, APS, Tucson Electric Power Company, and UNS Electric, Inc. filed a joint request for an extension to file the IRPs from August 1, 2023, to November 1, 2023. On June 21, 2023, the ACC granted the extension. As a result, APS filed its 2023 IRP on November 1, 2023. On January 31, 2024, stakeholders filed comments regarding the IRP, and APS filed its response to stakeholder comments on May 31, 2024. On July 31, 2024, the ACC held an IRP workshop where utilities and stakeholders presented on the 2023 IRPs. On October 8, 2024, the ACC acknowledged APS’s 2023 IRP and approved certain amendments to the IRP process, including requirements for APS to demonstrate resource adequacy prior to exiting Four Corners as well as analysis of impacts from western market participation and planned resource requirements in the next IRP. See “Energy Modernization Plan” above for information regarding proposed changes to the IRP filings.
Equity Infusions

On October 27, 2023, APS filed a notice of intent to increase Pinnacle West’s equity in APS in 2024. APS sought approval to receive from Pinnacle West in 2024 up to $500 million in additional equity infusions above the previously authorized limit of $150 million annually. The ACC approved the increased equity infusion limit for 2024 on January 9, 2024.

On April 19, 2024, APS submitted a request to the ACC to permanently modify Pinnacle West’s permitted yearly equity infusions to equal up to 2.5% of APS’s consolidated assets each calendar year on a three-year rolling average basis. On December 17, 2024, the ACC issued a financing order that approved an annual equity infusion allowance of 2.5% of APS’s consolidated assets on a three-year rolling average basis.

Public Utility Regulatory Policies Act

Under the Public Utility Regulatory Policies Act of 1978 (“PURPA”), qualifying facilities are provided the right to sell energy and/or capacity to utilities and are granted relief from certain regulatory burdens. On December 17, 2019, the ACC mandated a minimum contract length of 18 years for qualifying facilities over 100 kW in Arizona and established that the rate paid to qualifying facilities must be based on the long-term avoided cost. “Avoided cost” is generally defined as the price at which the utility could purchase or produce the same amount of power from sources other than the qualifying facility on a long-term basis.

Residential Electric Utility Customer Service Disconnections

In accordance with the ACC’s service disconnection rules, APS uses a calendar-based method to suspend the disconnection of customers for nonpayment from June 1 through October 15 each year (“Annual Disconnection Moratorium”). Pursuant to an ACC order, customers with past due balances of $75 or greater as of approximately one month prior to the end of the Annual Disconnection Moratorium are automatically placed on six-month payment arrangements. In addition, APS voluntarily began waiving late payment fees of its customers (“Late Fee Waivers”) on March 13, 2020. Effective February 1, 2023, late payment fees for residential customers were reinstated. Late payment fees for commercial and industrial customers were reinstated effective May 1, 2022. Since the suspensions and moratoriums on disconnections began, APS has experienced an increase in bad debt expense and the related write-offs of delinquent customer accounts.

Retail Electric Competition Rules

On November 17, 2018, the ACC voted to re-examine the facilitation of a deregulated retail electric market in Arizona. On July 1 and July 2, 2019, ACC Staff issued a report and initial proposed draft rules regarding possible modifications to the ACC’s retail electric competition rules. On February 10, 2020, two ACC Commissioners filed two sets of draft proposed retail electric competition rules. On February 12, 2020, ACC Staff issued its second report regarding possible modifications to the ACC’s retail electric competition rules. During a July 15, 2020, ACC Staff meeting, the ACC Commissioners discussed the possible development of a retail competition pilot program, but no action was taken. In April 2022, the Arizona Legislature passed, and the Governor signed a bill that repealed the electric deregulation law that
had been in place in Arizona since 1998. On August 27, 2024, the ACC administratively closed this docket due to inactivity and obsolescence.

Four Corners SCR Cost Recovery

On December 29, 2017, in accordance with the 2017 Rate Case Decision, APS filed a Notice of Intent to file its SCR Adjustment to permit recovery of costs associated with the installation of SCR equipment at Four Corners Units 4 and 5. APS filed the SCR Adjustment request in April 2018. The SCR Adjustment request provided that there would be a $67.5 million annual revenue impact that would be applied as a percentage of base rates for all applicable customers. Also, as provided for in the 2017 Rate Case Decision, APS requested that the adjustment become effective no later than January 1, 2019. The hearing for this matter occurred in September 2018. At the hearing, APS accepted ACC Staff’s recommendation of a lower annual revenue impact of approximately $58.5 million. The Administrative Law Judge issued a ROO finding that the costs for the SCR project were prudently incurred and recommending authorization of the $58.5 million annual revenue requirement related to the installation and operation of the SCRs. The ACC did not issue a decision on this matter. APS included the costs for the SCR project in the retail rate base in its 2019 Rate Case filing with the ACC.

On November 2, 2021, the 2019 Rate Case decision was approved by the ACC allowing approximately $194 million of SCR related plant investments and cost deferrals in rate base and to recover, depreciate and amortize in rates based on an end-of-life assumption of July 2031. The decision also included a partial and combined disallowance of $215.5 million on the SCR investments and deferrals. APS believes the SCR plant investments and related SCR cost deferrals were prudently incurred, and on December 17, 2021, APS filed its Notice of Direct Appeal at the Arizona Court of Appeals requesting review of the $215.5 million disallowance. The Arizona Court of Appeals heard oral arguments on November 30, 2022. On March 6, 2023, the Court of Appeals issued its order in the matter, vacating the ACC’s disallowance of the SCR investment and remanding the matter back to the ACC for further review in accordance with ACC rules and the order of the Court of Appeals. On June 21, 2023, the ACC approved a joint settlement filed by APS and the ACC’s Legal Division that resolved all issues relating to the 2019 Rate Case decision, including recovery of the cost of the Four Corners SCRs. See above for further discussion on the 2019 Rate Case decision.

Cholla

On September 11, 2014, APS announced that it would close Unit 2 of the Cholla Power Plant (“Cholla”) and cease burning coal at the other APS-owned units (Units 1 and 3) at the plant by the mid-2020s, if the EPA approved a compromise proposal offered by APS to meet required environmental and emissions standards and rules. On April 14, 2015, the ACC approved APS’s plan to retire Unit 2, without expressing any view on the future recoverability of APS’s remaining investment in the unit. APS closed Unit 2 on October 1, 2015. In early 2017, EPA approved a final rule incorporating APS’s compromise proposal, which took effect on April 26, 2017. In December 2019, PacifiCorp notified APS that it planned to retire Cholla Unit 4 by the end of 2020 and the unit ceased operation in December 2020. APS is required to cease burning coal at its remaining Cholla units by April 2025.

Previously, APS estimated Cholla Unit 2’s end of life to be 2033. APS has been recovering a return on and of the net book value of the unit in base rates. APS is allowed continued recovery of the net book value of the unit and the unit’s decommissioning and other retirement-related costs, $28.1 million as
of December 31, 2024, in addition to a return on its investment. In accordance with GAAP, in the third quarter of 2014, Unit 2’s remaining net book value was reclassified from property, plant and equipment to a regulatory asset. In accordance with the 2019 Rate Case decision, the regulatory asset is being amortized through 2033.

On August 14, 2024, APS filed a request with the ACC for a deferral order associated with unrecovered book value and closure costs of the remaining Cholla units. This order would authorize APS to defer, for future recovery in rates, both the expenses necessary to close and decommission coal-fired power plant infrastructure at Cholla, including legally required site environmental remediation, CCR corrective actions, the closure of CCR management facilities, and any unrecovered plant investment and operating costs incurred through and after April 2025. APS cannot predict the outcome of this matter.

Navajo Plant

The Navajo Plant ceased operations in November 2019. The co-owners and the Navajo Nation executed a lease extension on November 29, 2017, that allows for decommissioning activities to begin after the plant ceased operations. In accordance with GAAP, in the second quarter of 2017, APS’s remaining net book value of its interest in the Navajo Plant was reclassified from property, plant and equipment to a regulatory asset.

APS has been recovering a return on and of the net book value of its interest in the Navajo plant in base rates over its previously estimated life through 2026. Pursuant to the 2019 Rate Case decision described above, APS will be allowed continued recovery of the book value of its remaining investment in the Navajo plant, $33.4 million as of December 31, 2024, in addition to a return on the net book value, with the exception of 15% of the annual amortization expense in rates. In addition, APS will be allowed recovery of other costs related to retirement and closure, including the Navajo coal reclamation regulatory asset, $7.9 million as of December 31, 2024. The disallowed recovery of 15% of the annual amortization does not have a material impact on APS financial statements.

Fire Mitigation

On August 14, 2024, APS filed a request with the ACC for a deferral order that would authorize APS to defer, for future recovery in rates, operations and maintenance expenses associated with wildfire management, including increased insurance costs. APS cannot predict the outcome of this matter.
Regulatory Assets and Liabilities

The detail of regulatory assets is as follows (dollars in thousands):
December 31,
Amortization Through20242023
Pension(a)$750,976 $696,476 
Deferred fuel and purchased power (b) (c)2025287,597 463,195 
Income taxes — AFUDC equity2054192,936 189,058 
Ocotillo deferral2034114,775 128,636 
SCR deferral (e)203883,123 89,477 
Lease incentives(g)70,541 46,615 
Retired power plant costs203368,380 83,536 
Deferred fuel and purchased power — mark-to-market (Note 15)
202742,275 120,214 
FERC Transmission true up202635,159 616 
Income taxes — investment tax credit basis adjustment205634,834 34,230 
Deferred compensation203633,108 33,972 
Deferred property taxes202723,918 32,488 
Palo Verde VIEs (Note 17)
204620,611 20,772 
Power supply adjustor - interest202511,525 19,416 
Active Union Medical Trust(f)9,673 12,747 
Mead-Phoenix transmission line contributions in aid of construction (“CIAC”)20508,384 8,716 
Navajo coal reclamation20267,905 10,883 
Loss on reacquired debt20386,682 7,965 
Tax expense adjustor mechanism (b)20314,534 5,190 
Four Corners cost deferral2024— 7,922 
OtherVarious3,522 3,912 
Total regulatory assets (d)$1,810,458 $2,016,036 
Less: current regulatory assets$420,969 $625,757 
Total non-current regulatory assets$1,389,489 $1,390,279 
(a)This asset represents the future recovery of pension benefit obligations and expense through retail rates.  If these costs are disallowed by the ACC, this regulatory asset would be charged to OCI and result in lower future revenues.  As a result of the 2019 Rate Case decision, the amount authorized for inclusion in rate base was determined using an averaging methodology, which resulted in a reduced return in retail rates. The 2022 Rate Case decision allows for the full return on the pension asset in rate base. See Note 7 for further discussion.
(b)See “Cost Recovery Mechanisms” discussion above.
(c)Subject to a carrying charge.
(d)There are no regulatory assets for which the ACC has allowed recovery of costs, but not allowed a return by exclusion from rate base. FERC rates are set using a formula rate as described in “Transmission Rates, Transmission Cost Adjustor and Other Transmission Matters.”
(e)See “Four Corners SCR Cost Recovery” discussion above.
(f)Collected in retail rates.
(g)Amortization periods vary based on specific terms of lease contract.
The detail of regulatory liabilities is as follows (dollars in thousands):
December 31,
Amortization Through20242023
Excess deferred income taxes - ACC — Tax Cuts and Jobs Act (a)2046$888,896 $930,344 
Excess deferred income taxes - FERC — Tax Cuts and Jobs Act (a)2058207,400 214,667 
Asset retirement obligations and removal costs(d)358,403 486,751 
Other postretirement benefits(c)238,113 226,726 
Four Corners coal reclamation203877,532 68,521 
Renewable energy standard (b)202568,523 60,667 
Income taxes — deferred investment tax credit205666,327 55,917 
Income taxes — change in rates205359,133 43,251 
Spent nuclear fuel202726,818 33,154 
Demand side management (b)202523,927 14,374 
Sundance maintenance203123,086 19,989 
TCA Balancing Account (b)202614,834 3,425 
Property tax deferral20274,785 10,850 
Tax expense adjustor mechanism (b)20324,343 4,835 
OtherVarious113 2,317 
Total regulatory liabilities$2,062,233 $2,175,788 
Less: current regulatory liabilities$206,955 $209,923 
Total non-current regulatory liabilities$1,855,278 $1,965,865 
(a)For purposes of presentation on the Statement of Cash Flows, amortization of the regulatory liabilities for excess deferred income taxes are reflected as “Deferred income taxes” under Cash Flows From Operating Activities.
(b)See “Cost Recovery Mechanisms” discussion above.
(c)See Note 7.
(d)In accordance with regulatory accounting, APS accrues removal costs for its regulated assets, even if there is no legal obligation for removal.
v3.25.0.1
Income Taxes
 12 Months Ended
Dec. 31, 2024
Income Tax Disclosure [Abstract]  
Income Taxes Income Taxes
Certain assets and liabilities are reported differently for income tax purposes than they are for financial statement purposes.  The tax effect of these differences is recorded as deferred taxes.  We calculate deferred taxes using currently enacted income tax rates.    

APS has recorded regulatory assets and regulatory liabilities related to income taxes on its Consolidated Balance Sheets in accordance with accounting guidance for regulated operations.  The regulatory assets are for certain temporary differences, primarily the allowance for equity funds used during construction, investment tax credit (“ITC”) basis adjustment and tax expense of Medicare subsidy.  The regulatory liabilities primarily relate to the change in income tax rates and deferred taxes resulting from ITCs.    

In accordance with regulatory requirements, APS ITCs are deferred and are amortized over the life of the related property with such amortization applied as a credit to reduce current income tax expense in the Statements of Income.
On January 30, 2024, Pinnacle West entered into a tax credit transfer agreement to purchase from Ameresco $23 million of investment tax credits from the BCE Los Alamitos project for $21 million. See Note 20 for more information about the BCE Sale.

As a part of the Inflation Reduction Act of 2022 (“IRA”), a new PTC for nuclear energy produced by existing nuclear energy plants (“Nuclear PTC”) was enacted. Energy produced and sold by APS from Palo Verde between 2024 and 2032 is eligible for this credit subject to a credit phase out based upon APS’s gross receipts from nuclear sales. The Company continues to await guidance from the U.S. Treasury Department related to the definition of “gross receipts from nuclear sales” for purposes of the credit phase-out. Without such guidance, the Company is unable to accurately determine the benefit the Nuclear PTC may provide. Due to the lack of guidance, no income tax benefits have been recognized related to the Nuclear PTC as of December 31, 2024.

Net income associated with the Captive and Palo Verde sale leaseback VIEs is not subject to tax.  As a result, there is no income tax expense associated with the VIEs recorded on the Pinnacle West Consolidated and APS Consolidated Statements of Income. See Note 17 for additional details related to Palo Verde sale leaseback VIEs.

The following is a tabular reconciliation of the total amounts of unrecognized tax benefits, excluding interest and penalties, at the beginning and end of the year that are included in accrued taxes and unrecognized tax benefits (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 202420232022202420232022
Total unrecognized tax benefits, January 1$44,274 $43,097 $45,086 $44,274 $43,097 $45,086 
Additions for tax positions of the current year1,271 1,473 1,399 1,271 1,473 1,399 
Additions for tax positions of prior years2,031 419 2,069 2,031 419 2,069 
Reductions for tax positions of prior years for:      
Changes in judgment(2,043)661 (3,495)(2,043)661 (3,495)
Settlements with taxing authorities— — — — — — 
Lapses of applicable statute of limitations(1,184)(1,376)(1,962)(1,184)(1,376)(1,962)
Total unrecognized tax benefits, December 31$44,349 $44,274 $43,097 $44,349 $44,274 $43,097 

Included in the balances of unrecognized tax benefits are the following tax positions that, if recognized, would decrease our effective tax rate (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 202420232022202420232022
Tax positions, that if recognized, would decrease our effective tax rate$27,899 $28,762 $28,246 $27,899 $28,762 $28,246 

As of the balance sheet date, the tax year ended December 31, 2021, and all subsequent tax years remain subject to examination by the IRS.  With a few exceptions, we are no longer subject to state income tax examinations by tax authorities for years before 2020.
We reflect interest and penalties, if any, on unrecognized tax benefits in the Pinnacle West Consolidated and APS Consolidated Statements of Income as income tax expense.  The amount of interest expense or benefit recognized related to unrecognized tax benefits are as follows (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 202420232022202420232022
Unrecognized tax benefit interest expense/(benefit) recognized
$2,743 $452 $(139)$2,743 $452 $(139)

Following are the total amounts of accrued liabilities for interest recognized related to unrecognized benefits that could reverse and decrease our effective tax rate to the extent matters are settled favorably (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 202420232022202420232022
Unrecognized tax benefit interest accrued $4,376 $1,633 $1,181 $4,376 $1,633 $1,181 

Additionally, as of December 31, 2024, we have recognized approximately $2.1 million of interest expense to be paid on the underpayment of income taxes for certain adjustments that we have filed, or will file, with the IRS.

The components of income tax expense are as follows (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 Year Ended December 31,Year Ended December 31,
 202420232022202420232022
Current:   
Federal$137,342 $21,272 $35,617 $165,653 $26,405 $103,349 
State2,392 2,854 1,950 26,054 1,027 161 
Total current139,734 24,126 37,567 191,707 27,432 103,510 
Deferred:      
Federal(53,228)37,273 23,693 (69,075)44,922 (31,860)
State24,023 15,513 13,567 4,361 21,830 19,150 
Total deferred(29,205)52,786 37,260 (64,714)66,752 (12,710)
Income tax expense/(benefit)$110,529 $76,912 $74,827 $126,993 $94,184 $90,800 
The following chart compares pretax income at the 21% statutory federal income tax rate to income tax expense (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 Year Ended December 31,Year Ended December 31,
 202420232022202420232022
Federal income tax expense at statutory rate$154,677 $125,095 $120,887 $165,090 $138,337 $132,920 
Increases (reductions) in tax expense resulting from:      
State income tax net of federal income tax benefit24,218 18,024 17,740 25,639 19,832 19,000 
State income tax credits net of federal income tax benefit(3,349)(3,513)(5,482)(1,611)(1,775)(3,744)
Excess deferred income taxes — Tax Cuts and Jobs Act(36,559)(36,558)(36,241)(36,559)(36,558)(36,241)
Allowance for equity funds used during construction (Note 1)
(2,545)(5,964)(4,629)(2,545)(5,964)(4,629)
Palo Verde VIE noncontrolling interest (Note 17)
(3,617)(3,617)(3,617)(3,617)(3,617)(3,617)
Investment tax credit amortization(9,425)(9,495)(5,608)(9,425)(9,495)(5,608)
   Federal production tax credit(15,206)(8,441)(3,146)(12,110)(5,460)— 
   Other federal income tax credits(3,881)(3,453)(7,721)(1,551)(2,803)(7,721)
Other6,216 4,834 2,644 3,682 1,687 440 
Income tax expense/(benefit)$110,529 $76,912 $74,827 $126,993 $94,184 $90,800 
     The components of the net deferred income tax liability were as follows (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 December 31,December 31,
 2024202320242023
DEFERRED TAX ASSETS  
Risk management activities$14,539 $31,411 $14,539 $31,411 
Regulatory liabilities:   
Excess deferred income taxes — Tax Cuts and Jobs Act271,004 283,161 271,004 283,161 
Asset retirement obligation and removal costs81,308 113,312 81,308 113,312 
Unamortized investment tax credits66,327 68,521 66,327 68,521 
Other postretirement benefits58,862 56,070 58,862 56,070 
Other47,671 39,857 47,671 39,857 
Operating lease liabilities400,771 316,067 400,442 315,670 
Pension liabilities39,070 33,294 36,100 29,918 
Coal reclamation liabilities42,391 45,505 42,391 45,505 
Renewable energy incentives14,571 17,261 14,571 17,261 
Credit and loss carryforwards7,682 43,940 — 3,031 
Employee benefit liabilities57,853 49,222 56,561 48,551 
Other44,412 28,643 44,412 29,314 
Total deferred tax assets1,146,461 1,126,264 1,134,188 1,081,582 
DEFERRED TAX LIABILITIES   
Plant-related(2,562,990)(2,572,495)(2,562,990)(2,572,495)
Risk management activities(4,089)(1,682)(4,089)(1,682)
Pension and other postretirement assets(83,401)(78,853)(82,925)(78,297)
Other special use funds(55,146)(56,550)(55,146)(56,550)
Operating lease right-of-use assets(400,771)(316,067)(400,443)(315,670)
Regulatory assets:   
Allowance for equity funds used during construction(47,694)(46,754)(47,694)(46,754)
Deferred fuel and purchased power(84,393)(149,078)(84,393)(149,078)
Pension benefits(185,641)(172,239)(185,641)(172,239)
Ocotillo deferral(28,372)(31,812)(28,372)(31,812)
SCR deferral(20,548)(22,128)(20,548)(22,128)
Retired power plant costs (16,904)(20,659)(16,904)(20,659)
Other(57,602)(38,320)(57,602)(38,320)
Other(43,383)(36,107)(7,378)(7,595)
Total deferred tax liabilities(3,590,934)(3,542,744)(3,554,125)(3,513,279)
Deferred income taxes — net$(2,444,473)$(2,416,480)$(2,419,937)$(2,431,697)
As of December 31, 2024, Pinnacle West consolidated deferred tax assets for credit and loss carryforwards relate to federal and state credit carryforwards, net of federal benefit, of $12 million, which first begin to expire in 2029. Pinnacle West consolidated credit and loss carryforwards amount above has been reduced by $4 million of unrecognized tax benefits.
As of December 31, 2024, APS consolidated does not have any deferred tax assets for credit and loss carryforwards relating to federal or state carryforwards due to APS utilizing all available federal and state credits in 2024.
v3.25.0.1
Lines of Credit and Short-Term Borrowings
 12 Months Ended
Dec. 31, 2024
Debt Disclosure [Abstract]  
Lines of Credit and Short-Term Borrowings Lines of Credit and Short-Term Borrowings
Pinnacle West and APS maintain committed revolving credit facilities in order to enhance liquidity and provide credit support for their commercial paper programs, to refinance indebtedness, and for other general corporate purposes.
The table below presents the consolidated credit and term loan facilities and the amounts available and outstanding (dollars in thousands): 
December 31, 2024December 31, 2023
Pinnacle WestAPSTotalPinnacle WestAPSTotal
Commitments under Credit and Term Loan Facilities$400,000 $1,650,000 $2,050,000 $200,000 $1,250,000 $1,450,000 
Outstanding short-term borrowings(228,550)(339,900)(568,450)(76,650)(532,850)(609,500)
Amount of Credit and Term Loan Facilities Available$171,450 $1,310,100 $1,481,550 $123,350 $717,150 $840,500 
Weighted-Average Commitment Fees0.225%0.175%0.170%0.120%
Pinnacle West

On August 2, 2024, Pinnacle West amended its $200 million revolving credit facility, extending the maturity date from April 10, 2028 to April 10, 2029, and providing a mechanism to either update the Sustainability Table (as defined in the Pinnacle West revolving credit facility), which provides for a sustainability-linked pricing feature, or, in certain circumstances, terminate the sustainability-linked pricing feature for the final year. Pinnacle West has the option to increase the amount of the facility up to a total of $300 million upon the satisfaction of certain conditions and with the consent of the lenders. Interest rates are based on Pinnacle West’s senior unsecured debt credit ratings and the agreement includes a sustainability-linked pricing metric which permits an interest rate reduction or increase by meeting or missing targets related to specific environmental and employee health and safety sustainability objectives. The facility is available to support Pinnacle West’s general corporate purposes, including support for Pinnacle West’s $200 million commercial paper program, for bank borrowings or for issuances of letters of credit. At December 31, 2024, Pinnacle West had no outstanding borrowings under its revolving credit facility, no letters of credit outstanding under its credit facility, and $29 million of outstanding commercial paper borrowings. The weighted-average interest rate for the outstanding borrowings on December 31, 2024, was 4.58%.

On December 5, 2024, Pinnacle West entered into an agreement with a new 364-day $200 million term loan facility that matures on December 4, 2025. Borrowings under the facility bear interest at SOFR plus 0.95% per annum. On December 20, 2024, Pinnacle West drew the full amount of $200 million. On December 20, 2024, Pinnacle West repaid $200 million of the Pinnacle West term loan which matured in December 2024.
APS

On August 2, 2024, APS amended its $1.25 billion revolving credit facility, extending the maturity date from April 10, 2028 to April 10, 2029, and providing a mechanism to either update the Sustainability Table (as defined in the APS revolving credit facility), which provides for a sustainability-linked pricing feature, or, in certain circumstances, terminate the sustainability-linked pricing feature for the final year. APS has the option to increase the amount of the facility by up to a maximum of $400 million, for a total of $1.65 billion, upon the satisfaction of certain conditions and with the consent of the lenders. Interest rates are based on APS’s senior unsecured debt credit ratings and the agreement includes a sustainability-linked pricing metric which permits an interest rate reduction or increase by meeting or missing targets related to specific environmental and employee health and safety sustainability objectives. The facility is available to support APS’s general corporate purposes, including support for APS’s commercial paper program, which was increased from $750 million to $1 billion on April 10, 2023, for bank borrowings or for issuances of letters of credit. At December 31, 2024, APS had no outstanding borrowings under its revolving credit facility, no letters of credit outstanding under the credit facility, and $340 million of outstanding commercial paper borrowings. The weighted-average interest rate for the outstanding borrowings on December 31, 2024, was 4.62%.

On December 12, 2023, APS entered into an agreement for a new 364-day $350 million term loan facility that matured on December 10, 2024. Borrowings under the facility boar interest at SOFR plus 1.0% per annum. On February 9, 2024, APS drew the full amount of $350 million, which APS subsequently paid off in full on June 10, 2024.

On December 5, 2024, APS entered into a $400 million 364-Day Term Loan Agreement that matures on December 4, 2025. Borrowings under the facility bear interest at SOFR plus 0.90% per annum. As of the date of this report, APS has not drawn on this term loan.

See “Financial Assurances” in Note 10 for a discussion of other outstanding letters of credit.
Debt Provisions
 
On December 17, 2024, the ACC issued a financing order that reaffirmed APS’s short-term debt authorization equal to the sum of (i) 7% of APS’s capitalization, and (ii) $500 million (which is required to be used for costs relating to purchases of natural gas and power) and increased the long-term debt limit to $9.5 billion and made certain changes to permitted annual equity infusions into APS. See Note 6 for additional long-term debt provisions
v3.25.0.1
Long-Term Debt and Liquidity Matters
 12 Months Ended
Dec. 31, 2024
Debt Disclosure [Abstract]  
Long-Term Debt and Liquidity Matters Long-Term Debt and Liquidity Matters
All of Pinnacle West’s and APS’s debt is unsecured.  The following table presents the components of long-term debt on the Consolidated Balance Sheets outstanding (dollars in thousands):
 MaturityInterestDecember 31,
 Dates (a)Rates20242023
APS    
Pollution control bonds:    
Variable2029(b)$163,975 $163,975 
Total pollution control bonds  163,975 163,975 
Senior unsecured notes2025-2050
2.20%-6.88%
7,380,000 7,180,000 
Unamortized discount  (14,252)(14,197)
Unamortized premium  9,955 11,162 
Unamortized debt issuance cost(48,800)(49,049)
Total APS long-term debt  7,490,878 7,291,891 
Less current maturities 300,000 250,000 
Total APS long-term debt less current maturities  7,190,878 7,041,891 
Pinnacle West    
Senior unsecured notes2025-2027
1.30%-4.75%
1,025,000 500,000 
Floating rate note2026(c)350,000 — 
Term loans2024(d)— 625,000 
Unamortized discount(5)(15)
Unamortized debt issuance cost(7,225)(1,254)
Total Pinnacle West long-term debt1,367,770 1,123,731 
Less current maturities500,000 625,000 
Total Pinnacle West long-term debt less current maturities867,770 498,731 
TOTAL LONG-TERM DEBT LESS CURRENT MATURITIES
$8,058,648 $7,540,622 
(a)    This schedule does not reflect the timing of redemptions that may occur prior to maturities.
(b)    The weighted-average interest rate for the variable rate pollution control bonds was 4.01% at December 31, 2024, and 4.11% at December 31, 2023.
(c)    The weighted-average interest rate was 5.88% at December 31, 2024, and was not applicable at December 31, 2023. See additional details below.
(d)    The weighted-average interest rate was not applicable at December 31, 2024, and was 6.20% at December 31, 2023. See additional details below.
The following table shows principal payments due on Pinnacle West’s and APS’s total long-term debt (dollars in thousands):
YearPinnacle West ConsolidatedAPS Consolidated
2025$800,000 $300,000 
2026600,000 250,000 
2027825,000 300,000 
2028— — 
2029568,975 568,975 
Thereafter6,125,000 6,125,000 
Total$8,918,975 $7,543,975 
 
Debt Fair Value
 
Our long-term debt fair value estimates are classified within Level 2 of the fair value hierarchy. The following table represents the estimated fair value of our long-term debt, including current maturities (dollars in thousands):
 As of December 31, 2024As of December 31, 2023
 Carrying
Amount		Fair ValueCarrying
Amount		Fair Value
Pinnacle West$1,367,770 $1,393,744 $1,123,731 $1,095,935 
APS7,490,878 6,525,248 7,291,891 6,459,718 
Total$8,858,648 $7,918,992 $8,415,622 $7,555,653 
 
Credit Facilities and Debt and Equity Issuances

Pinnacle West

On December 16, 2022, Pinnacle West entered into a $175 million term loan facility that matured on December 16, 2024. The proceeds were received on January 6, 2023, and used for general corporate purposes. We recognized the term loan facility as long-term debt upon settlement on January 6, 2023. On June 10, 2024 Pinnacle West repaid the full $175 million term loan, that matured on December 16, 2024.

On February 28, 2024, Pinnacle West entered into equity forward sale agreements (the “February 2024 Forward Sale Agreements”), which may be settled with Pinnacle West common stock or cash. In December 2024, Pinnacle West partially settled the 2024 Forward Sale Agreements by issuing 5,377,115 shares of common stock and receiving net proceeds of $345 million. The proceeds were recorded in equity. At December 31, 2024, Pinnacle West could have settled the remaining February 2024 Forward Sale Agreements with the issuance of 5,863,486 shares of common stock, which would have provided cash liquidity to Pinnacle West of approximately $377 million. See Note 13.

On November 8, 2024, Pinnacle West entered into an equity forward sale agreement under the ATM program (the “November 2024 ATM Forward Sale Agreement”), which may be settled with Pinnacle West common stock or cash. At December 31, 2024, Pinnacle West could have settled the November 2024 ATM Forward Sale Agreement with the issuance of 552,833 shares of common stock, which would have provided cash liquidity to Pinnacle West of approximately $50 million. See Note 13.
Convertible Senior Notes. In June 2024, Pinnacle West issued $525 million of 4.75% convertible senior notes due 2027 (the “Convertible Notes”), which are senior unsecured obligations of Pinnacle West, and will mature on June 15, 2027. The Convertible Notes bear interest at a fixed rate of 4.75% per year, payable semiannually in arrears on June 15 and December 15 of each year, beginning on December 15, 2024. Proceeds from the Convertible Notes were used to repay APS’s 364-day $350 million term loan facility that matured on December 10, 2024 and commercial paper borrowings.

Prior to March 15, 2027, the holders of the Convertible Notes may elect at their option to convert all or any portion of their Convertible Notes under the following limited circumstances:

•during any calendar quarter (and only during such calendar quarter), if the sale price of Pinnacle West common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter, is greater than or equal to 130% of the conversion price on each applicable trading day;

•during the five business day period after any 10 consecutive trading day period (“Measurement Period”) in which the trading price per $1,000 principal amount of Convertible Notes for each trading day of the Measurement Period was less than 98% of the product of the last reported sale price of Pinnacle West common stock and the conversion rate on such trading day; or

•upon the occurrence of certain corporate events, as defined in the Convertible Notes’ indenture.

On or after March 15, 2027, until the maturity date, the holders of the Convertible Notes may elect at their option to convert all or any portion of their notes. Upon conversion, Pinnacle West will pay cash up to the aggregate principal amount of the Convertible Notes converted and at Pinnacle West’s sole discretion, pay or deliver cash, shares of Pinnacle West common stock or a combination of both, in respect to the remainder, if any, of Pinnacle West’s conversion obligation in excess of the aggregate principal amount of the Convertible Notes being converted. The initial conversion rate, which is subject to certain adjustments as set forth in the indenture, is 10.8338 shares of common stock per $1,000 principal amount of Convertible Notes, which is equivalent to an initial conversion price of approximately $92.30 per share of Pinnacle West’s common stock. The conversion rate is not subject to adjustment for any accrued and unpaid interest.

If Pinnacle West undergoes a fundamental change, as defined in the Convertible Notes’ indenture, then, subject to certain conditions, holders of the Convertible Notes may require Pinnacle West to repurchase for cash all or any portion of its Convertible Notes at a repurchase price equal to 100% of the principal amount of the Convertible Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

As of December 31, 2024, the conditions allowing holders to convert their Convertible Notes were not met, and as a result, the Convertible Notes were classified as long term debt on Pinnacle West’s Consolidated Balance Sheets with a carrying amount of $525 million, including unamortized debt issuance costs of $8 million. The estimated fair value of the Convertible Notes as of December 31, 2024 was $552 million (Level 2 within the fair value hierarchy).
As of December 31, 2024, based on Pinnacle West’s average stock price and the relevant terms of the Convertible Notes, there were no shares of Pinnacles West’s common stock included in basic or diluted EPS relating to the potential conversion of the Convertible Notes. See Note 13.

Floating Rate Notes. In June 2024, Pinnacle West completed the sale of $350 million Floating Rate Notes due 2026 (the “Floating Rate Notes”). The Floating Rate Notes are senior unsecured obligations of Pinnacle West and will mature on June 10, 2026. The Floating Rate Notes bear a variable interest rate of Compounded SOFR (as defined in the Fifth Supplemental Indenture dated as of June 10, 2024) plus 82 basis points per year. Proceeds were used to repay a portion of Pinnacle West’s $450 million term loan that matured in December 2024 and the full amount of Pinnacle West’s $175 million term loan that matured in December 2024.

On June 10, 2024, Pinnacle West repaid $250 million of its $450 million term loan which matured in December 2024. On December 20, 2024, Pinnacle West repaid the remaining $200 million of the term loan.

On June 10, 2024 Pinnacle West repaid the full $175 million term loan, that matured on December 16, 2024.

APS

APS was previously authorized to receive up to $150 million annually in equity infusions from Pinnacle West without seeking ACC approval. In 2023, APS sought approval for an additional $500 million in equity infusions and received approval in early 2024. Subsequently, APS requested and the ACC issued a new financing order that approved a limit on yearly equity infusions equal to 2.5% of APS’s total assets each calendar year on a three-year rolling average basis, subject to APS’s equity ratio remaining below the most recently approved rate case capital structure plus 50 basis points.

On June 12, 2024, Pinnacle West contributed $450 million into APS in the form of an equity infusion. APS used this contribution to repay short-term indebtedness. On December 23, 2024, Pinnacle West contributed $345 million into APS in the form of an equity infusion. APS used this contribution to repay a portion of commercial paper borrowings and for other general corporate purposes.

On May 9, 2024, APS issued $450 million of 5.7% senior unsecured notes that mature August 15, 2034. The net proceeds from the sale were used to repay short-term indebtedness consisting of commercial paper and for general corporate purposes.

On June 17, 2024, APS repaid its $250 million 3.35% senior unsecured notes at maturity from commercial paper borrowings.

See “Lines of Credit and Short-Term Borrowings” in Note 5 and “Financial Assurances” in Note 10 for discussion of APS’s separate outstanding letters of credit.

BCE

On February 11, 2022, a special purpose subsidiary of BCE entered into a credit agreement to finance capital expenditures and related costs for the development of a 31 megawatt (“MW”) solar and 20 megawatt hour (“MWh”) battery storage project in Los Alamitos, California (“Los Alamitos”). The credit
agreement consisted of an equity bridge loan facility, a non-recourse construction facility, a letter of credit facility, and a related interest rate swap. On August 4, 2023, Pinnacle West entered into a purchase and sale agreement with Ameresco, Inc. (“Ameresco”), pursuant to which we agreed to sell all our equity interest in BCE to Ameresco (the “BCE Sale”). See Note 20. As a part of the BCE Sale closing, the $36 million construction facility, the letter of credit facility, and the interest rate swap were transferred to Ameresco. On August 4, 2023, concurrent with the BCE Sale, Pinnacle West paid in full the outstanding $31 million equity bridge loan balance. As of December 31, 2024, there is no outstanding balance on our Consolidated Balance Sheets relating to this credit agreement.

On April 18, 2023, and on December 29, 2023, Pinnacle West issued performance guarantees in connection with BCE’s Kūpono Solar investment project financing. BCE held an equity method investment relating to the Kūpono Solar project that was included in the BCE Sale relating to the stage of the BCE Sale that closed on January 12, 2024. The performance guarantees did not transfer in the BCE Sale, and Pinnacle West continues to retain these performance guarantees. See Note 10.
 
Debt Provisions
 
Pinnacle West’s and APS’s debt covenants related to their respective bank financing arrangements include maximum debt to capitalization ratios. Pinnacle West and APS comply with this covenant.  For both Pinnacle West and APS, this covenant requires that the ratio of consolidated debt to total consolidated capitalization not exceed 65%.  At December 31, 2024, the ratio was approximately 59% for Pinnacle West and 49% for APS.  Failure to comply with such covenant levels would result in an event of default, which, generally speaking, would require the immediate repayment of the debt subject to the covenants and could cross-default other debt.  See further discussion of “cross-default” provisions below.
 
Neither Pinnacle West’s nor APS’s financing agreements contain “rating triggers” that would result in an acceleration of the required interest and principal payments in the event of a rating downgrade.  However, our bank credit agreements contain a pricing grid in which the interest rates we pay for borrowings thereunder are determined by our current credit ratings.
 
All of Pinnacle West’s loan agreements contain “cross-default” provisions that would result in defaults and the potential acceleration of payment under these loan agreements if Pinnacle West or APS were to default under certain other material agreements.  All of APS’s bank agreements contain “cross-default” provisions that would result in defaults and the potential acceleration of payment under these bank agreements if APS were to default under certain other material agreements.  Pinnacle West and APS do not have a material adverse change restriction for credit facility borrowings.

Although provisions in APS’s articles of incorporation and ACC financing orders establish maximum amounts of preferred stock and debt that APS may issue, APS does not expect any of these provisions to limit its ability to meet its capital requirements.

On April 19, 2024, APS submitted an application to the ACC requesting to increase the long-term debt limit from $8.0 billion to $9.5 billion and to increase Pinnacle West’s permitted yearly equity infusions to equal up to 2.5% of APS’s consolidated assets each calendar year on a three-year rolling average basis. On December 17, 2024, the ACC issued a financing order approving the increase of the long-term debt limit to $9.5 billion and the permitted yearly equity infusions to equal to 2.5% of APS’s total assets each calendar year on a three-year rolling average basis, subject to APS’s equity ratio
remaining below the most recently approved rate case capital structure plus 50 basis points. See Note 5 for additional short-term debt provisions.
v3.25.0.1
Retirement Plans and Other Postretirement Benefits
 12 Months Ended
Dec. 31, 2024
Retirement Benefits [Abstract]  
Retirement Plans and Other Postretirement Benefits Retirement Plans and Other Postretirement Benefits
Pinnacle West sponsors a qualified defined benefit and account balance pension plan (The Pinnacle West Capital Corporation Retirement Plan) and a non-qualified supplemental excess benefit retirement plan for the employees of Pinnacle West and its subsidiaries.  All new employees participate in the account balance plan.  Defined benefit plans specify the amount of benefits a plan participant is to receive using information about the participant.  The pension plan covers nearly all employees.  The supplemental excess benefit retirement plan covers officers of the Company and highly compensated employees designated for participation by the Board of Directors.  Our employees do not contribute directly to the plans.  We calculate the benefits based on age, years of service and pay.

Pinnacle West also sponsors other postretirement benefit plans (Pinnacle West Capital Corporation Group Life and Medical Plan and Pinnacle West Capital Corporation Post-65 Retiree Health Reimbursement Arrangement “HRA”) for the employees of Pinnacle West and its subsidiaries.  These plans provide medical and life insurance benefits to retired employees.  Employees must retire to become eligible for these retirement benefits, which are based on years of service and age.  For the medical insurance plan, retirees make contributions to cover a portion of the plan costs.  For the life insurance plan, retirees do not make contributions.  We retain the right to change or eliminate these benefits.

Pinnacle West uses a December 31 measurement date each year for its pension and other postretirement benefit plans.  The market-related value of our plan assets is their fair value at the measurement date.  See Note 12 for further discussion of how fair values are determined.  Due to subjective and complex judgments, which may be required in determining fair values, actual results could differ from the results estimated through the application of these methods.

A significant portion of the changes in the actuarial gains and losses of our pension and postretirement plans is attributable to APS and are recoverable in rates.  Accordingly, these changes are recorded as a regulatory asset or regulatory liability. Our retail rates provide for the inclusion of annual benefit expense, which allows for recovery or return of this regulatory asset/liability. See Note 3.
The following table provides details of the plans’ net periodic benefit costs and the portion of these costs charged to expense (including administrative costs and excluding amounts capitalized as overhead construction or billed to electric plant participants) (dollars in thousands):
Pension PlansOther Benefits Plans
 202420232022202420232022
Service cost-benefits earned during the period$43,641 $39,461 $55,473 $9,955 $8,567 $16,470 
Non-service costs (credits):
Interest cost on benefit obligation148,643 153,561 107,492 22,169 22,509 17,491 
Expected return on plan assets(188,651)(182,938)(185,775)(46,834)(43,486)(46,042)
Amortization of:
Prior service credit (a)— — — (37,789)(37,789)(37,789)
Net actuarial loss (gain)
41,915 38,420 17,515 (8,676)(9,614)(12,835)
Net periodic benefit costs (credits)
$45,548 $48,504 $(5,295)$(61,175)$(59,813)$(62,705)
Portion of costs (credits) charged to expense
$23,652 $27,029 $(16,431)$(45,557)$(43,408)$(45,042)
(a)    Prior-service costs or credits reflect the impact of modifications to the pension or postretirement plan benefits. The impact of these modifications is amortized over a period which reflects the demographics of the impacted population. In 2014, Pinnacle West made changes to the postretirement benefits offered to Medicare eligible retirees which resulted in prior-service credits. We have been amortizing these prior-serviced credits since 2015 with the last full-year amortization occurring in 2024.
The following table shows the plans’ changes in the benefit obligations and funded status (dollars in thousands):
 Pension PlansOther Benefits Plans
 2024202320242023
Change in Benefit Obligation    
Benefit obligation at January 1$2,908,063 $2,809,529 $430,434 $409,461 
Service cost43,641 39,461 9,955 8,567 
Interest cost148,643 153,561 22,169 22,509 
Benefit payments(216,238)(210,737)(30,516)(30,784)
Actuarial (gain) loss(91,800)116,249 (71,952)20,681 
Benefit obligation at December 312,792,309 2,908,063 360,090 430,434 
Change in Plan Assets    
Fair value of plan assets at January 12,835,549 2,829,485 696,494 652,287 
Actual return on plan assets4,518 199,098 32,816 67,317 
Benefit payments(200,205)(193,034)(27,118)(23,110)
Fair value of plan assets at December 312,639,862 2,835,549 702,192 696,494 
Funded (Underfunded) Status at December 31$(152,447)$(72,514)$342,102 $266,060 

The following table shows information for pension plans with an accumulated obligation in excess of plan assets (dollars in thousands):
As of December 31,
 20242023
Accumulated benefit obligation$113,541 $123,701 
Fair value of plan assets— — 
 The Pinnacle West Capital Corporation Retirement Plan is more than 100% funded on an accumulated benefit obligation basis at December 31, 2024, and December 31, 2023, therefore, the only pension plan with an accumulated benefit obligation in excess of plan assets in 2024 and 2023 is a non-qualified supplemental excess benefit retirement plan.

The following table shows information for pension plans with a projected benefit obligation in excess of plan assets (dollars in thousands):
As of December 31,
 20242023
Projected benefit obligation$2,792,309 $129,891 
Fair value of plan assets2,639,862 — 

The Pinnacle West Capital Corporation Retirement Plan, on a projected benefit obligation basis, was 99% funded at December 31, 2024 and 102% funded at December 31, 2023. For 2024, we included both the projected benefit obligation and the fair value of plan assets for our qualified pension plan and a non-qualified supplemental excess benefit retirement plan. In 2023, the only plan that was underfunded was the non-qualified supplemental excess benefit retirement plan.

The following table shows the amounts recognized on the Consolidated Balance Sheets (dollars in thousands):
 Pension PlansOther Benefits Plans
 2024202320242023
Noncurrent asset$— $57,378 $342,102 $266,060 
Current liability(13,130)(17,190)— — 
Noncurrent liability(139,317)(112,702)— — 
Net amount recognized (funded status)$(152,447)$(72,514)$342,102 $266,060 
 
The following table shows the details related to accumulated other comprehensive loss (gain) as of December 31, 2024, and 2023 (dollars in thousands): 
 Pension PlansOther Benefits Plans
 2024202320242023
Net actuarial loss (gain)$793,421 $743,003 $(237,889)$(188,630)
Prior service credit— — (1,265)(39,054)
APS’s portion recorded as a regulatory (asset) liability(750,976)(696,476)238,113 226,726 
Income tax expense (benefit)(10,354)(11,506)611 691 
Accumulated other comprehensive loss (gain)$32,091 $35,021 $(430)$(267)
 
The following table shows the weighted-average assumptions used for both the pension and other benefits to determine benefit obligations and net periodic benefit costs:
 Benefit Obligations
As of December 31,		Benefit Costs
Year Ended December 31,
 20242023202420232022
Discount rate – pension plans5.68 %5.21 %5.21 %5.56 %2.92 %
Discount rate – other benefits plans5.71 %5.23 %5.23 %5.58 %2.98 %
Rate of compensation increase4.50 %4.52 %4.52 %4.57 %4.00 %
Expected long-term return on plan assets - pension plansN/AN/A6.90 %6.70 %5.00 %
Expected long-term return on plan assets - other benefit plansN/AN/A6.85 %6.80 %5.35 %
Initial healthcare cost trend rate (pre-65 participants)6.50 %6.25 %6.25 %6.50 %6.00 %
Ultimate healthcare cost trend rate (pre-65 participants)4.50 %4.75 %4.75 %4.75 %4.75 %
Number of years to ultimate trend rate (pre-65 participants)65453
Initial healthcare cost trend rate (post-65 participants)1.00 %2.00 %2.00 %2.00 %2.00 %
Ultimate healthcare cost trend rate (post-65 participants)— %2.00 %2.00 %2.00 %2.00 %
Interest crediting rate – cash balance pension plans4.66 %4.54 %4.54 %4.50 %4.50 %

In selecting the pretax expected long-term rate of return on plan assets, we consider past performance and economic forecasts for the types of investments held by the plan.  For 2025, we are assuming a 7.05% long-term rate of return for pension assets and 7.15% (before tax) for other benefit assets, which we believe is reasonable given our asset allocation in relation to historical and expected performance.

In selecting our healthcare trend rates, we consider past performance and forecasts of healthcare costs. 

Plan Assets
 
The Board of Directors has delegated oversight of the pension and other postretirement benefit plans’ assets to an Investment Management Committee (“Committee”).  The Committee has adopted investment policy statements (“IPS”) for the pension and the other postretirement benefit plans’ assets. The investment strategies for these plans include external management of plan assets.
 
The overall strategy of the pension plan’s IPS is to achieve an adequate level of trust assets relative to the benefit obligations.  To achieve this objective, the plan’s investment policy provides for mixes of investments including long-term fixed income assets and return-seeking assets.  The target allocation between return-seeking and long-term fixed income assets is defined in the IPS.  The plan’s funded status is reviewed on at least a monthly basis.
 
Changes in the value of long-term fixed income assets, also known as liability-hedging assets, are intended to offset changes in the benefit obligations due to changes in interest rates.  Long-term fixed income assets consist primarily of fixed income debt securities issued by the U.S. Treasury and other government agencies, U.S. Treasury futures contracts, and fixed income debt securities issued by corporations.  Long-term fixed income assets may also include interest rate swaps, and other instruments.
 
Return-seeking assets are intended to provide a reasonable long-term rate of investment return with a prudent level of volatility.  Return-seeking assets are composed of U.S. equities, international equities, and alternative investments.  International equities include investments in both developed and emerging markets.  Alternative investments may include investments in real estate, private debt and various other strategies.  The plan may also hold investments in return-seeking assets by holding securities in partnerships, common and collective trusts, and mutual funds.

Based on the IPS, the target and actual allocation for the pension plan at December 31, 2024, are as follows:
 Target AllocationActual Allocation
Long-term fixed income assets80 %79 %
Return-seeking assets20 %21 %
Total100 %100 %

The permissible range is within +/-5% of the target allocation shown in the above table, and also considers the plan’s funded status.

The following table presents the additional target allocations, as a percent of total pension plan assets, for the return-seeking assets:
Target Allocation
Equities in US and other developed markets12 %
Equities in emerging markets4 %
Alternative investments4 %
Total20 %

The pension plan IPS does not provide for a specific mix of long-term fixed income assets but does expect the average credit quality of such assets to be investment grade. 

As of December 31, 2024, the asset allocation for other postretirement benefit plan assets is governed by the IPS for those plans, which provides for different asset allocation target mixes depending on the characteristics of the liability. The following table presents the actual allocations of the investment for the other postretirement benefit plan at December 31, 2024:
Actual Allocation
Long-term fixed income assets61 %
Return-seeking assets39 %
Total100 %
See Note 12 for a discussion on the fair value hierarchy and how fair value methodologies are applied.  The plans invest directly in fixed income, U.S. Treasury Futures Contracts, and equity securities, in addition to investing indirectly in fixed income securities, equity securities and real estate through the use of mutual funds, partnerships and common and collective trusts.  Equity securities held directly by the plans are valued using quoted active market prices from the published exchange on which the equity security trades and are classified as Level 1.  U.S. Treasury Futures Contracts are valued using the quoted active market prices from the exchange on which they trade and are classified as Level 1. Fixed income securities issued by the U.S. Treasury held directly by the plans are valued using quoted active market
prices and are classified as Level 1.  Fixed income securities issued by corporations, municipalities, and other agencies are primarily valued using quoted inactive market prices, or quoted active market prices for similar securities, or by utilizing calculations which incorporate observable inputs such as yield, maturity, and credit quality.  These instruments are classified as Level 2.
 
Mutual funds, partnerships, and common and collective trusts are valued utilizing a net asset value (“NAV”) concept or its equivalent. Mutual funds, which includes exchange traded funds (“ETFs”), are classified as Level 1, and valued using a NAV that is observable and based on the active market in which the fund trades.

Common and collective trusts are maintained by banks or investment companies and hold certain investments in accordance with a stated set of objectives (such as tracking the performance of the S&P 500 Index).  The trust’s shares are offered to a limited group of investors and are not traded in an active market. Investments in common and collective trusts are valued using NAV as a practical expedient and, accordingly, are not classified in the fair value hierarchy. The NAV for trusts investing in exchange traded equities, and fixed income securities is derived from the market prices of the underlying securities held by the trusts. The NAV for trusts investing in real estate is derived from the appraised values of the trust’s underlying real estate assets. 

Investments in partnerships are also valued using the concept of NAV as a practical expedient and, accordingly, are not classified in the fair value hierarchy. The NAV for these investments is derived from the value of the partnerships’ underlying assets. The plan’s partnerships holdings relate to investments in high-yield fixed income instruments. Certain partnerships also include funding commitments that may require the plan to contribute up to $50 million to these partnerships; as of December 31, 2024, approximately $38 million of these commitments have been funded.
 
The plans’ trustee provides valuation of our plan assets by using pricing services that utilize methodologies described to determine fair market value.  We have internal control procedures to ensure this information is consistent with fair value accounting guidance.  These procedures include assessing valuations using an independent pricing source, verifying that pricing can be supported by actual recent market transactions, assessing hierarchy classifications, comparing investment returns with benchmarks, and obtaining and reviewing independent audit reports on the trustee’s internal operating controls and valuation processes.
The fair value of Pinnacle West’s pension plan and other postretirement benefit plan assets at December 31, 2024, by asset category, are as follows (dollars in thousands):
 
 Level 1Level 2Other (a)Total
Pension Plan:   
Cash and cash equivalents$9,055 $— $— $9,055 
Fixed income securities:   
Corporate— 1,325,833 — 1,325,833 
U.S. Treasury561,317 — — 561,317 
Other (b)— 133,254 — 133,254 
Common stock equities (c)74,939 — — 74,939 
Mutual funds (d)102,722 — — 102,722 
Common and collective trusts:
Equities— — 244,734 244,734 
Real estate— — 127,397 127,397 
Other (e)— — 60,611 60,611 
Total$748,033 $1,459,087 $432,742 $2,639,862 
Other Benefits:    
Cash and cash equivalents$840 $— $— $840 
Fixed income securities:   
Corporate— 186,435 — 186,435 
U.S. Treasury204,274 — — 204,274 
Other (b)— 12,585 — 12,585 
Common stock equities (c)89,685 — — 89,685 
Mutual funds (d)23,415 — — 23,415 
Common and collective trusts:   
Equities— — 140,178 140,178 
Real estate— — 19,474 19,474 
Other (e)19,145 — 6,161 25,306 
Total$337,359 $199,020 $165,813 $702,192 
(a)These investments primarily represent assets valued using NAV as a practical expedient and have not been classified in the fair value hierarchy.
(b)This category consists primarily of debt securities issued by municipalities and asset backed securities.
(c)This category primarily consists of U.S. common stock equities.
(d)These funds invest in international common stock equities.
(e)Primarily relates to short-term investment funds and includes plan receivables and payables.


 
The fair value of Pinnacle West’s pension plan and other postretirement benefit plan assets at December 31, 2023, by asset category, are as follows (dollars in thousands):
 Level 1Level 2Other (a)Total
Pension Plan:   
Fixed income securities:   
Corporate$— $1,415,346 $— $1,415,346 
U.S. Treasury622,273 — — 622,273 
Other (b)— 135,184 — 135,184 
Common stock equities (c)150,657 — — 150,657 
Mutual funds (d)112,791 — — 112,791 
Common and collective trusts:
   Equities— — 192,945 192,945 
   Real estate— — 140,613 140,613 
Other (e)— — 65,740 65,740 
Total $885,721 $1,550,530 $399,298 $2,835,549 
Other Benefits:    
Fixed income securities:   
Corporate$— $189,902 $— $189,902 
U.S. Treasury207,665 — — 207,665 
Other (b)— 8,372 — 8,372 
Common stock equities (c)139,952 — — 139,952 
Mutual funds (d)22,256 — — 22,256 
Common and collective trusts:
   Equities— — 81,724 81,724 
   Real estate— — 20,001 20,001 
Other (e)21,146 — 5,476 26,622 
Total $391,019 $198,274 $107,201 $696,494 
(a)These investments primarily represent assets valued using NAV as a practical expedient and have not been classified in the fair value hierarchy.
(b)This category consists primarily of debt securities issued by municipalities and asset backed securities.
(c)This category primarily consists of U.S. common stock equities.
(d)These funds invest in U.S. and international common stock equities.
(e)
Contributions
 
Future year contribution amounts are dependent on plan asset performance and plan actuarial assumptions.  In 2024 and 2023, we did not make any contributions to our pension plan. The expected minimum required cash contributions for the pension plan are zero for the next three years and we do not expect to make any voluntary contributions in 2025, 2026 or 2027.  With regard to contributions to our other postretirement benefit plan, we did not make a contribution in 2024 or 2023 and do not expect to make any contributions in 2025, 2026 or 2027. The Company was reimbursed $27 million in 2024, $23 million in 2023, and $26 million in 2022 for prior years retiree medical claims from the other postretirement benefit plan trust assets.
Estimated Future Benefit Payments
 
Benefit payments, which reflect estimated future employee service, for the next five years and the succeeding five years thereafter, are estimated to be as follows (dollars in thousands):
YearPension PlansOther Benefits Plans
2025$241,762 $28,753 
2026223,562 28,747 
2027230,335 28,276 
2028233,617 27,880 
2029232,591 27,645 
Years 2030-20341,147,273 137,301 
 
Electric plant participants contribute to the above amounts in accordance with their respective participation agreements.

Employee Savings Plan Benefits
 
Pinnacle West sponsors a defined contribution savings plan for eligible employees of Pinnacle West and its subsidiaries.  In 2024, costs related to APS’s employees represented 99% of the total cost of this plan.  In a defined contribution savings plan, the benefits a participant receives result from regular contributions participants make to their own individual account, the Company’s matching contributions and earnings or losses on their investments.  Under this plan, the Company matches a percentage of the participants’ contributions in cash which is then invested in the same investment mix as participants elect to invest their own future contributions.  Pinnacle West recorded expenses for this plan of approximately $14 million for 2024, $12 million for 2023, and $12 million for 2022.
v3.25.0.1
Leases
 12 Months Ended
Dec. 31, 2024
Leases [Abstract]  
Leases Leases
 
We lease certain land, buildings, vehicles, equipment, and other property through operating rental agreements with varying terms, provisions, and expiration dates. APS also has certain purchased power and energy storage agreements that qualify as lease arrangements. Our leases have remaining terms that expire in 2025 through 2073. Substantially all of our leasing activities relate to APS.

In 1986, APS entered into agreements with three separate lessor trust entities in order to sell and lease back interests in Palo Verde Unit 2 and related common facilities.  These lessor trust entities have been deemed VIEs for which APS is the primary beneficiary.  As the primary beneficiary, APS consolidated these lessor trust entities.  The impacts of these sale leaseback transactions are excluded from our lease disclosures as lease accounting is eliminated upon consolidation.  See Note 17 for a discussion of VIEs.

APS has purchased power lease agreements that allow APS the right to the generation capacity from certain natural-gas fueled generators during certain months of each year throughout the term of the arrangements. As APS only has rights to use the assets during certain periods of each year, the leases have non-consecutive periods of use. APS does not operate or maintain the leased assets. APS controls the dispatch of the leased assets during the months of use and is required to pay a fixed monthly capacity payment during these periods of use. For these types of leased assets, APS has elected to combine both the
lease and non-lease payment components and accounts for the entire fixed payment as a lease obligation. In addition to the fixed monthly capacity payments, APS must also pay variable charges based on the actual production volume of the assets. The variable consideration is not included in the measurement of our lease obligation.

APS has executed various energy storage purchased power lease agreements that allow APS the right to charge and discharge energy storage facilities. APS pays a fixed monthly capacity price for rights to use the lease assets. The agreements generally have 20-year lease terms and provide APS with the exclusive use of the energy storage assets through the lease term. APS does not operate or maintain the energy storage facilities and has no purchase options or residual value guarantees relating to these lease assets. For this class of energy storage lease assets, APS has elected to separate the lease and non-lease components. These leases are accounted for as operating leases, with lease terms that commenced between September 2023 and August 2024.

The following table provides information related to our lease costs (dollars in thousands):
Year Ended December 31,
202420232022
Operating Lease Cost - Purchased Power & Energy Storage Lease Contracts$147,313 $126,655 $104,001 
Operating Lease Cost - Land, Property, and Other Equipment20,120 19,235 18,061 
Total Operating Lease Cost167,433 145,890 122,062 
Variable Lease Cost (a)144,108 135,007 122,040 
Short-term Lease Cost20,653 21,530 9,928 
Total Lease Cost$332,194 $302,427 $254,030 
(a)     Primarily relates to purchased power lease contracts.

Lease costs are primarily included as a component of operating expenses on our Consolidated Statements of Income. Lease costs relating to purchased power and energy storage lease contracts are recorded in fuel and purchased power on the Consolidated Statements of Income and are subject to recovery under the PSA or RES. See Note 3. The tables above reflect the lease cost amounts before the effect of regulatory deferral under the PSA and RES. Variable lease costs are recognized in the period the costs are incurred, and primarily relate to renewable purchased power lease contracts. Payments under most renewable purchased power lease contracts are dependent upon environmental factors, and due to the inherent uncertainty associated with the reliability of the fuel source, the payments are considered variable and are excluded from the measurement of lease liabilities and right-of-use lease assets. Certain of our lease agreements have lease terms with non-consecutive periods of use. For these agreements, we recognize lease costs during the periods of use. Leases with initial terms of 12 months or less are considered short-term leases and are not recorded on the balance sheets.
The following table provides information related to the maturity of our operating lease liabilities (dollars in thousands):
December 31, 2024
YearPurchased Power & Energy Storage Lease ContractsLand, Property & Equipment LeasesTotal
2025 $158,363 $16,834 $175,197 
2026172,087 14,830 186,917 
2027198,007 12,249 210,256 
2028201,804 9,591 211,395 
2029205,741 7,465 213,206 
Thereafter1,140,971 61,855 1,202,826 
Total lease commitments2,076,973 122,824 2,199,797 
Less imputed interest536,948 41,605 578,553 
Total lease liabilities$1,540,025 $81,219 $1,621,244 
    
We recognize lease assets and liabilities upon lease commencement. At December 31, 2024, we have various lease arrangements that have been executed, but have not yet commenced. We expect the total fixed consideration paid for these arrangements, which includes both lease and non-lease payments, will approximate $16.7 billion over the terms of the agreements. These arrangements primarily relate to energy storage assets. We expect lease commencement dates ranging from March 2025 through June 2028, with lease terms expiring through June 2048. The lease commencement dates for certain arrangements have experienced delays. As a result of these delays and other events, APS has received cash proceeds from certain lessors prior to lease commencement. Proceeds received from lessors relating to energy storage PPA leases are accounted for as lease incentives on our Consolidated Balance Sheets, and upon lease commencement are amortized over the associated lease term. For regulatory purposes, the proceeds received by APS relating to these PPA leases are treated as a reduction to fuel and purchased power costs through the PSA in the period proceeds are received. See Note 3.
The following tables provide other additional information related to operating lease liabilities (dollars in thousands):
Year Ended December 31,
202420232022
Cash paid for amounts included in the measurement of lease liabilities — operating cash flows:$143,950 $123,472 $118,463 
Right-of-use operating lease assets obtained in exchange for operating lease liabilities:393,702 (a)602,301 (b)16,990 


December 31, 2024December 31, 2023
Weighted average remaining lease term11 years10 years
Weighted average discount rate (c)4.90 %4.53 %

(a)Primarily relates to the three new energy storage operating lease agreements that commenced in 2024.
(b)Primarily relates to the two purchased power operating lease agreements that were modified in January 2023.
(c)Most of our lease agreements do not contain an implicit rate that is readily determinable. For these agreements we use our incremental borrowing rate to measure the present value of lease liabilities. We determine our incremental borrowing rate at lease commencement based on the rate of interest that we would have to pay to borrow, on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. We use the implicit rate when it is readily determinable.
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Jointly-Owned Facilities
 12 Months Ended
Dec. 31, 2024
Jointly Owned Utility Plant, Net Ownership Amount [Abstract]  
Jointly-Owned Facilities Jointly-Owned Facilities
 
APS shares ownership of some of its generating and transmission facilities with other companies.  We are responsible for our share of operating costs which are included in the corresponding operating expenses on our Consolidated Statements of Income. We are also responsible for providing our own financing.  Our share of operating expenses and utility plant costs related to these facilities is accounted for using proportional consolidation.  The following table shows APS’s interests in those jointly-owned facilities recorded on the Consolidated Balance Sheets at December 31, 2024 (dollars in thousands):

 Percent
Owned		 Plant in
Service		Accumulated
Depreciation		Construction
Work in
Progress
Generating facilities:     
Palo Verde Units 1 and 329.1 %$2,010,346 $1,081,321 $20,694 
Palo Verde Unit 2 (a)16.8 %709,414 397,235 9,076 
Palo Verde Common28.0 %(b)898,401 366,027 47,962 
Palo Verde Sale Leaseback (a)351,050 268,494 — 
Four Corners Generating Station 63.0 %1,848,412 705,667 56,226 
Cholla Common Facilities (c)50.5 %301,035 231,170 1,743 
Transmission facilities:     
Arizona Nuclear Power Project 500kV System33.3 %(b)134,713 60,174 7,174 
Navajo Southern System24.7 %(b)88,528 38,797 626 
Palo Verde — Yuma 500kV System25.5 %(b)24,260 8,120 142 
Four Corners Switchyards58.0 %(b)84,367 23,886 309 
Phoenix — Mead System17.1 %(b)39,788 21,173 330 
Palo Verde — Rudd 500kV System50.0 %95,785 34,254 1,808 
Morgan — Pinnacle Peak System63.2 %(b)117,500 29,013 287 
Round Valley System50.0 %548 213 — 
Palo Verde — Morgan System87.5 %(b)266,547 46,327 208 
Hassayampa — North Gila System80.0 %154,330 27,739 — 
Cholla 500kV Switchyard85.7 %8,454 2,859 35 
Saguaro 500kV Switchyard60.0 %29,850 15,768 101 
Kyrene — Knox System50.0 %578 349 — 
Agua Fria Switchyard10.0 %— — 82 
(a)See Note 17.
(b)Weighted-average of interests.
(c)PacifiCorp owns Cholla Unit 4 (see Note 3 for additional information), and APS operated the unit for PacifiCorp.  Cholla Unit 4 was retired on December 24, 2020. The common facilities at Cholla are jointly-owned.
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Commitments and Contingencies
 12 Months Ended
Dec. 31, 2024
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies Commitments and Contingencies
 
Palo Verde Generating Station
 
Spent Nuclear Fuel and Waste Disposal
 
On December 19, 2012, APS, acting on behalf of itself and the participant owners of Palo Verde, filed a second breach of contract lawsuit against the DOE in the United States Court of Federal Claims (“Court of Federal Claims”). The lawsuit sought to recover damages incurred due to DOE’s breach of the Contract for Disposal of Spent Nuclear Fuel and/or High Level Radioactive Waste (“Standard Contract”) for failing to accept Palo Verde’s spent nuclear fuel and high level waste from January 1, 2007, through June 30, 2011, pursuant to the terms of the Standard Contract and the Nuclear Waste Policy Act. On August 18, 2014, APS and DOE entered into a settlement agreement, which required DOE to pay the Palo Verde owners for certain specified costs incurred by Palo Verde during the period January 1, 2007, through June 30, 2011. In addition, the settlement agreement provided APS with a method for submitting claims and getting recovery for costs incurred through December 31, 2016, which was extended to December 31, 2025.

APS has recovered costs for ten claims pursuant to the terms of the August 15, 2014 settlement agreement, for ten separate time periods during July 1, 2011, through October 31, 2023. The DOE has approved and paid approximately $156.7 million for these claims (APS’s share is approximately $45.6 million). The amounts recovered were primarily recorded as adjustments to a regulatory liability and had no impact on reported net income. In accordance with the 2017 Rate Case Decision, this regulatory liability is being refunded to customers. See Note 3. On October 31, 2024, APS filed its eleventh claim pursuant to the terms of the August 15, 2014, settlement agreement in the amount of approximately $18 million (APS’s share is approximately $5.3 million). In February 2025, the DOE approved approximately $17.6 million of this claim.

Nuclear Insurance
 
Public liability for incidents at nuclear power plants is governed by the Price-Anderson Nuclear Industries Indemnity Act (“Price-Anderson Act”), which limits the liability of nuclear reactor owners to the amount of insurance available from both commercial sources and an industry-wide retrospective payment plan. This insurance limit is subject to an adjustment every five years based upon the aggregate percentage change in the Consumer Price Index. The most recent adjustment took effect on January 1, 2024. As of that date, in accordance with the Price-Anderson Act, the Palo Verde participants are insured against public liability for a nuclear incident up to approximately $16.3 billion per occurrence. Palo Verde maintains the maximum available nuclear liability insurance in the amount of $500 million, which is provided by American Nuclear Insurers.  The remaining balance of approximately $15.8 billion of liability coverage is provided through a mandatory, industry-wide retrospective premium program. If losses at any nuclear power plant covered by the program exceed the accumulated funds, APS could be responsible for retrospective premiums. The maximum retrospective premium per reactor under the program for each nuclear liability incident is approximately $165.9 million, subject to a maximum annual premium of approximately $24.7 million per incident.  Based on APS’s ownership interest in the three Palo Verde units, APS’s maximum retrospective premium per incident for all three units is approximately $144.9 million, with a maximum annual retrospective premium of approximately $21.6 million.
The Palo Verde participants maintain insurance for property damage to, and decontamination of, property at Palo Verde in the aggregate amount of $2.8 billion.  APS has also secured accidental outage insurance for a sudden and unforeseen accidental outage of any of the three units. The property damage, decontamination, and accidental outage insurance are provided by Nuclear Electric Insurance Limited (“NEIL”).  APS is subject to retrospective premium adjustments under all NEIL policies if NEIL’s losses in any policy year exceed accumulated funds. The maximum amount APS could incur under the current NEIL policies totals approximately $23.1 million for each retrospective premium assessment declared by NEIL’s Board of Directors due to losses.  Additionally, at the sole discretion of the NEIL Board of Directors, APS would be liable to provide approximately $64.1 million in deposit premium within 20 days of request as assurance to satisfy any site obligation of retrospective premium assessment.  The insurance coverage discussed in this, and the previous paragraph, is subject to certain policy conditions, sublimits, and exclusions.
 
Captive Insurance Cell

Pinnacle West has established a captive insurance program to supplement third-party insurance coverage for certain risks. The Captive insures Pinnacle West and its subsidiaries for terrorism coverage, excess liability including certain wildfire coverage, excess property insurance, and excess employment practice liability. These coverages may be supplemented with third-party insurance policies. The Captive policies exclude nuclear liability at Palo Verde. See Note 10. The Captive may hold investment assets in cash, cash equivalents, and equity and fixed income instruments, which in the event of an insured loss would be available to pay covered claims. In the event of an insured loss event, Pinnacle West may be required to provide additional funding to the Captive. The Captive is a VIE, and Pinnacle West is the primary beneficiary of the VIE and consolidates the assets and liabilities of the Captive. See Note 17 for additional details.

Fuel and Purchased Power Commitments and Purchase Obligations
APS is party to various fuel and purchased power contracts and purchase obligations with terms expiring between 2025 and 2048 that include required purchase provisions.  APS estimates the contract requirements to be approximately $1,540 million in 2025; $1,742 million in 2026; $1,973 million in 2027; $2,142 million in 2028; $2,115 million in 2029; and $27.2 billion thereafter.  However, these amounts may vary significantly pursuant to certain provisions in such contracts that permit us to decrease required purchases under certain circumstances. These amounts include estimated commitments relating to purchased power lease contracts. See Note 8.
 
Of the various fuel and purchased power contracts mentioned above, some of those contracts for coal supply include take-or-pay provisions.  The current coal contracts with take-or-pay provisions have terms expiring through 2031.
 
The following table summarizes our estimated coal take-or-pay commitments (dollars in thousands):
 
 
Year Ended December 31,
 20252026202720282029Thereafter (b)
Coal take-or-pay commitments (a)$208,984 $214,090 $212,529 $217,820 $223,291 $463,752 
 
(a)Total take-or-pay commitments are approximately $1.5 billion.  The total net present value of these commitments using a 4.81% discount rate is approximately $1.3 billion.
(b)Through 2031.
 
    APS may spend more to meet its actual fuel requirements than the minimum purchase obligations in our coal take-or-pay contracts. The following table summarizes actual amounts purchased under the coal contracts which include take-or-pay provisions for each of the last three years (dollars in thousands):

 
Year Ended December 31,
 202420232022
Total purchases$237,821 $255,219 $305,502 
 
Renewable Energy Credits
 
APS has entered into contracts to purchase renewable energy credits to comply with the RES.  APS estimates the contract requirements to be approximately $27 million in 2025; $24 million in 2026; $21 million in 2027; $18 million in 2028; $16 million in 2029; and $36 million thereafter.  These amounts do not include purchases of renewable energy credits that are bundled with energy.
 
Coal Mine Reclamation Obligations
APS must reimburse certain coal providers for final and contemporaneous coal mine reclamation.  We account for contemporaneous reclamation costs as part of the cost of the delivered coal.  We utilize site-specific studies of costs expected to be incurred in the future to estimate our final reclamation obligation.  These studies utilize various assumptions to estimate the future costs.  Based on the most recent reclamation studies, APS recorded an obligation for the coal mine final reclamation of approximately $171 million at December 31, 2024, and $184 million at December 31, 2023. Under our current coal supply agreements, APS expects to make payments for the final mine reclamation as follows: $20 million in 2025; $21 million in 2026; $22 million in 2027; $23 million in 2028; and $2 million thereafter. These funds are held in an escrow account and will be distributed to certain coal providers under the terms of the applicable coal supply agreements.  Any amendments to current coal supply agreements may change the timing of the contribution or cost of final reclamation. The annual payments to the escrow account and final distribution to certain coal providers may be subject to adjustments based on escrow earnings.
Superfund and Other Related Matters
 
The Comprehensive Environmental Response Compensation and Liability Act (“Superfund” or “CERCLA”) establishes liability for the cleanup of hazardous substances found contaminating the soil, water or air.  Those who released, generated, transported to or disposed of hazardous substances at a
contaminated site are among the parties who are potentially responsible (each a “PRP”).  PRPs may be strictly, jointly, and severally liable for clean-up.  On September 3, 2003, EPA advised APS that EPA considers APS to be a PRP in the Motorola 52nd Street Superfund Site, Operable Unit 3 (“OU3”) in Phoenix, Arizona.  APS has facilities that are within this Superfund site.  APS and Pinnacle West have agreed with EPA to perform certain investigative activities of the APS facilities within OU3.  In addition, on September 23, 2009, APS agreed with EPA and one other PRP to voluntarily assist with the funding and management of the site-wide groundwater remedial investigation and feasibility study (“RI/FS”).  The RI/FS for OU3 was finalized and submitted to EPA at the end of 2022. EPA notified APS that the RI/FS was approved on September 11, 2024. APS’s estimated costs related to this investigation and study is approximately $3 million. APS anticipates incurring additional expenditures in the future, but because the final costs associated with remediation requirements set forth in the RI/FS are not yet finalized, at the present time expenditures related to this matter cannot be reasonably estimated.
 
In connection with APS’s status as a PRP for OU3, since 2013 APS and at least two dozen other parties have been defendants in various CERCLA lawsuits stemming from allegations that contamination from OU3 and elsewhere has impacted groundwater wells operated by the Roosevelt Irrigation District (“RID”). At this time, only one active lawsuit remains pending in the U.S. District Court for Arizona, which concerns $8.3 million in remediation legal expenses. APS is unable to predict the outcome of any further litigation related to this claim or APS’s share of liability related to that claim; however, APS does not expect the outcome to have a material impact on its financial position, results of operations or cash flows.

On February 28, 2022, EPA provided APS with a request for information under CERCLA related to APS’s Ocotillo power plant site located in Tempe, Arizona. In particular, EPA seeks information from APS regarding APS’s use, storage, and disposal of substances containing per-and polyfluoroalkyl (“PFAS”) compounds at the Ocotillo power plant site in order to aid EPA’s investigation into actual or threatened releases of PFAS into groundwater within the South Indian Bend Wash (“SIBW”) Superfund site. The SIBW Superfund site includes the APS Ocotillo power plant site. APS filed its response to this information request on April 29, 2022. On January 17, 2023, EPA contacted APS to inform APS that it would be commencing on-site investigations within the SIBW site, including the Ocotillo power plant, and performing a remedial investigation and feasibility study related to potential PFAS impacts to groundwater over the next two to three years. APS estimates that its costs to oversee and participate in the remedial investigation work will be approximately $1.7 million. At the present time, we are unable to predict the outcome of this matter, and any further expenditures related to necessary remediation, if any, or further investigations cannot be reasonably estimated.

Environmental Matters

APS is subject to numerous environmental laws and regulations affecting many aspects of its present and future operations, including air emissions of both conventional pollutants and greenhouse gases, water quality, wastewater discharges, solid waste, hazardous waste, and CCRs. These laws and regulations can change from time to time, imposing new obligations on APS resulting in increased capital, operating, and other costs. Associated capital expenditures or operating costs could be material. APS intends to seek recovery of any such environmental compliance costs through our rates but cannot predict whether it will obtain such recovery. The following proposed and final rules could involve material compliance costs to APS.
 
Coal Combustion Waste. On December 19, 2014, EPA issued its final regulations governing the handling and disposal of CCR, such as fly ash and bottom ash. The rule regulates CCR as a non-hazardous waste under Subtitle D of the Resource Conservation and Recovery Act (“RCRA”) and establishes national minimum criteria for existing and new CCR landfills and surface impoundments and all lateral expansions. These criteria include standards governing location restrictions, design and operating criteria, groundwater monitoring and corrective action, closure requirements and post closure care, and recordkeeping, notification, and internet posting requirements. The rule generally requires any existing unlined CCR surface impoundment to stop receiving CCR and either retrofit or close, and further requires the closure of any CCR landfill or surface impoundment that cannot meet the applicable performance criteria for location restrictions or structural integrity. Such closure requirements are deemed “forced closure” or “closure for cause” of unlined surface impoundments and are the subject of the regulatory and judicial activities described below.

Since these regulations were finalized, EPA has taken steps to substantially modify the federal rules governing CCR disposal. While certain changes have been prompted by utility industry petitions, others have resulted from judicial review, court-approved settlements with environmental groups, and statutory changes to RCRA. The following lists the pending regulatory changes that, if finalized, could have a material impact as to how APS manages CCR at its coal-fired power plants:

•Following the passage of the Water Infrastructure Improvements for the Nation (“WIIN”) Act in 2016, EPA possesses authority to either authorize states to develop their own permit programs for CCR management or issue federal permits governing CCR disposal both in states without their own permit programs and on tribal lands. At this time, Arizona Department of Environmental Quality (“ADEQ”) has taken steps to develop a CCR permitting program and plans to propose state regulations governing CCR permitting over the summer of 2024. It remains unclear when EPA would approve that permitting program pursuant to the WIIN Act. On December 19, 2019, EPA proposed its own set of regulations governing the issuance of CCR management permits, which would impact facilities like Four Corners located on the Navajo Nation. The proposal remains pending.

•On March 1, 2018, as a result of a settlement with certain environmental groups, EPA proposed adding boron to the list of constituents that trigger corrective action requirements to remediate groundwater impacted by CCR disposal activities. Apart from a subsequent proposal issued on August 14, 2019, to add a specific, health-based groundwater protection standard for boron, EPA has yet to take action on this proposal.

•With respect to APS’s Cholla facility, APS’s application for alternative closure was submitted to EPA on November 30, 2020. While EPA has deemed APS’s application administratively “complete,” the Agency’s approval remains pending. If granted, this application would allow the continued disposal of CCR within Cholla’s existing unlined CCR surface impoundments until the required date for ceasing coal-fired boiler operations in April 2025. This application will be subject to public comment and, potentially, judicial review. We expect to have a proposed decision from EPA regarding Cholla in 2025.

We cannot predict the outcome of these regulatory proceedings or when EPA will take final action on those matters that are still pending. Depending on the eventual outcome, the costs associated with
APS’s management of CCR could materially increase, which could affect our financial condition, results of operations, or cash flows.

On April 25, 2024, EPA took final action on a proposal to expand the scope of federal CCR regulations to address the impacts from historical CCR disposal activities that would have ceased prior to 2015. This new class of CCR management units (“CCRMUs”), which contain at least 1,000 tons of CCR, broadly encompass any location at an operating coal-fired power plant where CCR would have been placed on land. As proposed, this would include not only historically closed landfills and surface impoundments but also prior applications of CCR beneficial use (with exceptions for historical roadbed and embankment applications). Existing CCR regulatory requirements for groundwater monitoring, corrective action, closure, post-closure care, and other requirements will be imposed on such CCRMUs. At this time, APS is still evaluating the impacts of this final regulation on its business, with initial CCRMU site surveys due to be completed by February 2026 and final site investigation reports to be finalized by February 2027. Based on the information available to APS at this time, APS cannot reasonably estimate the fair value of the entire CCRMU asset retirement obligation. Depending on the outcome of those evaluations and site investigations, the costs associated with APS’s management of CCR could materially increase, which could affect our financial condition, results of operations, or cash flows.

APS currently disposes of CCR in ash ponds and dry storage areas at Cholla and Four Corners. The Navajo Plant disposed of CCR only in a dry landfill storage area. Additionally, the CCR rule requires ongoing, phased groundwater monitoring. As of October 2018, APS has completed the statistical analyses for its CCR disposal units that triggered assessment monitoring. APS determined that several of its CCR disposal units at Cholla and Four Corners will need to undergo corrective action. In addition, under the current regulations, all such disposal units must have ceased operating and initiated closure as of April 11, 2021 (except for those disposal units subject to alternative closure). APS completed the assessments of corrective measures on June 14, 2019; however, additional investigations and engineering analyses that will support the remedy selection are still underway. In addition, APS has also solicited input from the public and hosted public hearings as part of this process. APS’s estimates for its share of corrective action and monitoring costs at Four Corners and Cholla are captured within the Asset Retirement Obligations. As APS continues to implement the CCR rule’s corrective action assessment process, the current cost estimates may change. Given uncertainties that may exist until we have fully completed the corrective action assessment and final remedy selection process, we cannot predict any ultimate impacts to APS; however, at this time APS does not believe that any potential changes to the cost estimate from the CCR rule’s corrective action assessment process for Four Corners or Cholla would have a material impact on its financial condition, results of operations, or cash flows.

EPA Power Plant Carbon Regulations. EPA’s regulation of carbon dioxide emissions from electric utility power plants has proceeded in fits and starts over most of the last decade. Starting on August 3, 2015, EPA finalized the Clean Power Plan, which was the Agency’s first effort at such regulation through system-wide generation dispatch shifting. Those regulations were subsequently repealed by the EPA on June 19, 2019 and replaced by the Affordable Clean Energy (“ACE”) regulations, which were a far narrower set of rules. While the U.S. Court of Appeals for the D.C. Circuit subsequently vacated the ACE regulations on January 19, 2021, and ordered a remand for EPA to develop replacement regulations consistent with the original 2015 Clean Power Plan, the U.S. Supreme Court subsequently reversed that decision on June 30, 2022, holding that the Clean Power Plan exceeded EPA’s authority under the Clean Air Act.
In the final regulations governing power plant carbon dioxide emissions, released April 25, 2024, EPA issued emission standards and guidelines for various subcategories of new and existing power plants. Unlike EPA’s Clean Power Plan regulations from 2015, which took a broad, system-wide approach to regulating carbon emissions from electric utility fossil-fuel burning power plants, these new federal regulations are limited to measures that can be installed at individual power plants to limit planet-warming carbon-dioxide emissions.

As such, for new natural gas-fired combustion turbine power plants, EPA is proposing that carbon emission performance standards apply based on the annual capacity factors. For the highest utilization combustion turbines, EPA is therefore proposing that such facilities be retrofitted for carbon capture and sequestration or utilization controls (“CCS”) by 2032. For intermediate or low-load natural gas fired combustion turbines, those with 40% or less capacity factors, EPA’s regulations would not require add-on pollution controls. Instead, natural gas-fired combustion turbines with capacity factors of up to 20% would be effectively unregulated, while such turbines with capacity factors over 20% and up to 40% would be subject to carbon dioxide emission rate limitations. EPA did not finalize standards for existing natural gas-fired combustion turbines but has indicated that it will propose a new set of standards, initiating a separate rulemaking, for these existing gas-fired power plants within the next year.

For coal-fired power plants, instead of imposing regulations based on capacity and utilization, EPA has finalized subcategories based on planned retirement dates. This means that facilities retiring before 2032 are effectively exempt from regulation, those that retire between 2032 and 2038 must co-fire with natural gas starting in 2030, and those that retire in 2039 or later must install CCS controls by 2032.

As of May 10, 2024, several states, electric utility companies, affiliated trade associations, and other entities filed petitions for review of these regulations in the D.C. Circuit Court of Appeals. APS is participating in that litigation as part of an ad hoc coalition of electric utility companies, independent power producers, and trade groups, called Electric Generators for a Sensible Transition. We cannot predict the outcome of the litigation challenging EPA’s latest carbon emission standards for power plants. In addition, the Trump administration has stated that it intends to reverse or substantially revise these standards. We cannot predict the outcome of future rulemaking or other regulatory proceedings aimed at changing or eliminating the current EPA emission standards for power plants.

If this regulation remains in effect, it will likely lead to a material increase in APS’s costs to build, operate, and maintain new, frequently operated gas-fired power plants. The regulatory deadlines in 2032 by which new, frequently operated gas-fired power plants must install carbon capture and sequestration and achieve 90% capture efficiency may not be feasible. Future resource plans and procurement efforts implicating the development of such new generation remains pending and, as such, at this time APS is not able to quantify the financial impact associated with EPA’s GHG regulations for power plants.

Effluent Limitation Guidelines. EPA published effluent limitation guidelines (“ELG”) on October 13, 2020, and, based off those guidelines, APS completed a National Pollutant Discharge Elimination System (“NPDES”) permit modification for Four Corners on December 1, 2023. The ELG standards finalized in October 2020 relaxed the “zero discharge” standard for bottom ash transport waters EPA finalized in September 2015. However, on April 25, 2024, EPA finalized new ELG regulations that once again require “zero discharge” standards for flows of bottom ash transport water at power plants like Four Corners. Nonetheless, for power plants that permanently cease operations by December 31, 2034, such facilities can continue to comply with the 2020 ELG standards. APS is currently evaluating its
compliance options for Four Corners based on the ELG regulations finalized in April 2024 and is assessing what impacts the new standards will have on our financial condition, results of operations, or cash flows.

EPA Good Neighbor Proposal for Arizona. On March 15, 2023, EPA issued its final Good Neighbor Plan for 23 states in order to ensure that the cross-state transport of ozone forming emissions does not interfere with downwind state compliance with the National Ambient Air Quality Standards (“NAAQS”). Thermal power plant emission limitations are a key aspect of these regulations, which involve emission allowance trading for nitrogen oxide (“NOx”) emissions. While Arizona was not among the 23 states subject to EPA’s March 2023 final action, EPA announced on January 23, 2024, that it was proposing to add Arizona and New Mexico (along with two other additional states) to EPA’s NOx emission allowance trading program finalized last year. That proposal involves adding these states to the Good Neighbor Plan and disapproving the corresponding provisions of each state’s State Implementation Plan. Because APS operates thermal power plants within Arizona and those portions of the Navajo Nation within New Mexico, APS’s power plants would be subject to EPA’s Good Neighbor Plan upon finalization of this proposal. EPA’s final Good Neighbor Plan is subject to ongoing judicial review in the D.C. Circuit Court of Appeals. On June 27, 2024, the U.S. Supreme Court granted a motion to stay the effectiveness of EPA’s final Good Neighbor Plan pending the resolution of the litigation. As such, APS will not be impacted by the Good Neighbor Plan until the outcome of this litigation is finalized. In addition, on December 19, 2024, EPA announced that it was withdrawing its proposal to add Arizona (along with other western states) to the federal Good Neighbor Plan. As such, while EPA may elect to resume work on and finalize this proposal in the future, it is unlikely to do so over a near-term horizon. APS cannot predict the outcome of any future EPA efforts to add Arizona to the federal Good Neighbor Plan (which depends on action disapproving the Arizona State Implementation Plan) or whether the Good Neighbor Plan itself will remain in effect pending the outcome of judicial review in the D.C. Circuit Court of Appeals. Should the Good Neighbor Plan ultimately be imposed on APS and its operations in Arizona and New Mexico, it would have material impact on both the costs to operate current APS power plants and APS’s ability to develop new thermal generation to serve load. At this time, APS cannot predict the impact on the Company’s financial condition, results of operations, or cash flows.

Revised Mercury and Air Toxics Standard (“MATS”) Proposal. On April 25, 2024, EPA finalized revisions to the existing MATS regulations governing emissions of toxic air pollution from existing coal-fired power plants. The final regulations increase the stringency of filterable particulate matter limits used to demonstrate compliance with MATS and require the use of continuous emissions monitoring systems to ensure compliance (as opposed to periodic performance testing). These final regulations will take effect for existing coal-fired power plants, such as Four Corners, within three years of publication in the Federal Register. Based on APS’s assessment of the revised MATS regulations, this final rule is unlikely to have a material impact on plant operations or require significant capital expenditures to ensure compliance.

Other environmental rules that could involve material compliance costs include those related to effluent limitations, the ozone national ambient air quality standard and other rules or matters involving the Clean Air Act, Clean Water Act, Endangered Species Act, RCRA, Superfund, the Navajo Nation, and water supplies for our power plants. The financial impact of complying with current and future environmental rules could jeopardize the economic viability of APS’s fossil-fuel powered plants or the willingness or ability of power plant participants to fund any required equipment upgrades or continue their participation in these plants. The economics of continuing to own certain resources, particularly our coal plants, may deteriorate, warranting early retirement of those plants, which may result in asset impairments.
APS would seek recovery in rates for the book value of any remaining investments in the plants, as well as other costs related to early retirement, but cannot predict whether it would obtain such recovery.
 
Four Corners National Pollutant Discharge Elimination System (“NPDES”) Permit

The latest NPDES permit for Four Corners was issued on September 30, 2019. Based upon a November 1, 2019, filing by several environmental groups, the Environmental Appeals Board (“EAB”) took up review of the Four Corners NPDES Permit. The EAB denied the environmental group petition on September 30, 2020. While on January 22, 2021, the environmental groups filed a petition for review of the EAB’s decision with the U.S. Court of Appeals for the Ninth Circuit, the parties to the litigation (including APS) finalized a settlement on May 2, 2022. This settlement requires investigation of thermal wastewater discharges from Four Corners, administratively closes the litigation filed in January 2021, and APS does not expect the outcome to have a material impact on its financial condition, results of operations, or cash flows.

BCE Kūpono Solar

BCE and Ameresco jointly owned a special purpose entity that sponsored the Kūpono Solar Project. This project is a 42 MW solar and battery storage facility in Oʻahu, Hawaii that supplies energy and capacity under a 20-year power purchase agreement with Hawaiian Electric Company, Inc. The Kūpono Solar Project achieved commercial operations in June 2024. On April 18, 2023, the Kūpono special purpose entity entered into a $140 million non-recourse construction financing agreement. On August 14, 2024, the construction financing converted into long-term financing in the form of a sale-leaseback. In connection with the project financing, Pinnacle West issued performance guarantees relating to the Kūpono Solar Project. Investments in the Kūpono Solar Project were included in the BCE Sale which closed on January 12, 2024, and as a result of the BCE Sale, Pinnacle West holds no equity or ownership interest in the Kūpono Solar Project. As of December 31, 2024, Pinnacle West continues to maintain performance guarantees relating to the Kūpono Solar Project sale-leaseback financing (see additional information below regarding these guarantees). See Note 20 for information relating to the BCE Sale.

Financial Assurances
 
In the normal course of business, we obtain standby letters of credit and surety bonds from financial institutions and other third parties. These instruments guarantee our own future performance and provide third parties with financial and performance assurance in the event we do not perform. These instruments support commodity contract collateral obligations and other transactions. As of December 31, 2024, standby letters of credit totaled approximately $18 million and surety bonds totaled approximately $23 million; both will expire through 2025. The underlying liabilities insured by these instruments are reflected on our balance sheets, where applicable. Therefore, no additional liability is reflected for the letters of credit and surety bonds themselves.
 
We enter into agreements that include indemnification provisions relating to liabilities arising from or related to certain of our agreements. Most significantly, APS has agreed to indemnify the equity participants and other parties in the Palo Verde sale leaseback transactions with respect to certain tax matters. Generally, a maximum obligation is not explicitly stated in the indemnification provisions and, therefore, the overall maximum amount of the obligation under such indemnification provisions cannot be
reasonably estimated. Based on historical experience and evaluation of the specific indemnities, we do not believe that any material loss related to such indemnification provisions is likely.
 
Pinnacle West has issued parental guarantees and has provided indemnification under certain surety bonds for APS which were not material at December 31, 2024. In connection with the sale of 4C Acquisition, LLC’s 7% interest to Navajo Transitional Energy Corporation (“NTEC”), Pinnacle West is guaranteeing certain obligations that NTEC will have to the other owners of Four Corners. Pinnacle West has not needed to perform under this guarantee. A maximum obligation is not explicitly stated in the guarantee and, therefore, the overall maximum amount of the obligation under such guarantee cannot be reasonably estimated; however, we consider the fair value of this guarantee, including expected credit losses, to be immaterial.

In connection with PNW Power’s investments in minority ownership positions in the Clear Creek wind farm in Missouri and Nobles 2 wind farm in Minnesota, Pinnacle West has guaranteed the obligations of PNW Power to make production tax credit funding payments to borrowers of the projects (the “PTC Guarantees”). The amounts guaranteed by Pinnacle West are reduced as payments are made under the respective guarantee agreements. As of December 31, 2024, there is approximately $29 million of remaining guarantees relating to these PTC Guarantees that are expected to terminate by 2031.

Pinnacle West has issued various performance guarantees in connection with the Kūpono Solar Project investment financing and is exposed to losses relating to these guarantees upon the occurrence of certain events that we consider to be remote. Subsequent to the BCE Sale, Pinnacle West continues to maintain these guarantees. See Note 20. Pinnacle West has not needed to perform under these guarantees. Maximum obligations are not explicitly stated in the guarantees and cannot be reasonably estimated. Ameresco is obligated to reimburse Pinnacle West for any payments made by Pinnacle West under such guarantees. We consider the fair value of these guarantees, including expected credit losses, to be immaterial. The details of the guarantees are as follows:

•Pinnacle West committed to certain performance guarantees tied to the Kūpono Solar Project achieving certain construction and operation milestones. These performance guarantees expired in August 2024. Pinnacle West has no on-going exposure under these construction-related guarantees.
•Under the Kūpono Solar Project sale-leaseback financing, Pinnacle West has committed to certain performance guarantees that may apply upon the occurrence of specified events, such as uninsured loss events. Ameresco has agreed to make efforts to refinance the project and eliminate these guarantees prior to 2030.
v3.25.0.1
Asset Retirement Obligations
 12 Months Ended
Dec. 31, 2024
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligations Asset Retirement Obligations
 
In 2024, the Company revised its cost estimates for existing AROs for the following:

•Cholla coal-fired power plant related to the closure of ponds and facilities, which resulted in an increase to the ARO of approximately $63 million, primarily due to cost estimates associated with the CCR Rule.
•Four Corners coal-fired power plant, which resulted in an increase of approximately $82 million, primarily due to cost estimates associated with the CCR Rule.
•Navajo, a decommissioned coal-fired power plant, which resulted in an increase of approximately $8 million.
•Palo Verde nuclear plant, which resulted in an increase of approximately $1 million.
•Solar, which resulted in a decrease to the ARO of approximately $11 million, primarily due to the reduced cost of solar panel disposal.

APS has also recorded the initial investigation and assessment costs related to the newly signed EPA rule for Legacy Impoundments and CCRMUs. At this time, APS is still estimating the financial impacts of this final regulation on its business, with initial CCRMU site surveys due to be completed by February 2026 and final site investigation reports to be finalized by February 2027. Based on the information available to APS at this time, APS cannot reasonably estimate the fair value of the entire CCRMU asset retirement obligation. Depending on the outcome of those evaluations and site investigations, the costs associated with APS’s management of CCR could materially increase, which could affect our financial condition, results of operations, or cash flows.

In 2023, the Company revised its cost estimates for existing ARO for the following:

•Cholla coal-fired power plant related to the closure of ponds and facilities, which resulted in an increase to the ARO of approximately $71 million, primarily due to changes in the planned pond closure methodology and increased corrective action cost estimates associated with the CCR Rule.
•Four Corners coal-fired power plant, which resulted in a decrease of approximately $7 million.
•Navajo coal-fired plant, a decommissioned coal-fired power plant, which resulted in an increase of approximately $8 million.
•Palo Verde received a new decommissioning study, which resulted in an increase to the ARO in the amount of $63 million, an increase in the plant in service of $59 million and a decrease in the regulatory liability of $4 million.

See additional details in Notes 3 and 10.

The following table shows the change in our asset retirement obligations (dollars in thousands):

 20242023
Asset retirement obligations at the beginning of year
$966,001 $797,762 
Changes attributable to:  
Accretion expense56,143 44,269 
Settlements(18,379)(14,039)
Estimated cash flow revisions142,821 135,323 
Newly incurred obligation— 2,686 
Asset retirement obligations at the end of year
$1,146,586 $966,001 
 
In accordance with regulatory accounting, APS accrues removal costs for its regulated utility assets, even if there is no legal obligation for removal.  See Note 3 for detail of regulatory liabilities.
v3.25.0.1
Fair Value Measurements
 12 Months Ended
Dec. 31, 2024
Fair Value Disclosures [Abstract]  
Fair Value Measurements Fair Value Measurements
 
We classify our assets and liabilities that are carried at fair value within the fair value hierarchy.  This hierarchy ranks the quality and reliability of the inputs used to determine fair values, which are then classified and disclosed in one of three categories.  The three levels of the fair value hierarchy are:
 
Level 1 — Inputs are unadjusted quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 2 — Other significant observable inputs, including quoted prices in active markets for similar assets or liabilities; quoted prices in markets that are not active, and model-derived valuations whose inputs are observable (such as yield curves). 
 
Level 3 — Valuation models with significant unobservable inputs that are supported by little or no market activity.  Instruments in this category may include long-dated derivative transactions where valuations are unobservable due to the length of the transaction, options, and transactions in locations where observable market data does not exist.  The valuation models we employ utilize spot prices, forward prices, historical market data and other factors to forecast future prices.
 
Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement.  Thus, a valuation may be classified in Level 3 even though the valuation may include significant inputs that are readily observable.  We maximize the use of observable inputs and minimize the use of unobservable inputs.  We rely primarily on the market approach of using prices and other market information for identical and/or comparable assets and liabilities.  If market data is not readily available, inputs may reflect our own assumptions about the inputs market participants would use.  Our assessment of the inputs and the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of fair value assets and liabilities as well as their placement within the fair value hierarchy levels.  We assess whether a market is active by obtaining observable broker quotes, reviewing actual market activity, and assessing the volume of transactions.  We consider broker quotes observable inputs when the quote is binding on the broker, we can validate the quote with market activity, or we can determine that the inputs the broker used to arrive at the quoted price are observable.
Certain instruments have been valued using the concept of Net Asset Value (“NAV”) as a practical expedient. These instruments are typically structured as investment companies offering shares or units to multiple investors for the purpose of providing a return. These instruments are similar to mutual funds; however, their NAV is generally not published and publicly available, nor are these instruments traded on an exchange. Instruments valued using NAV as a practical expedient are included in our fair value disclosures; however, in accordance with GAAP are not classified within the fair value hierarchy levels.
Recurring Fair Value Measurements
 
We apply recurring fair value measurements to cash equivalents, derivative instruments, and investments held in the nuclear decommissioning trusts and other special use funds. On an annual basis, we apply fair value measurements to plan assets held in our retirement and other benefit plans. See Note 7 for fair value discussion of plan assets held in our retirement and other benefit plans.
 
Cash Equivalents
 
Cash equivalents represent certain investments in money market funds that are valued using quoted prices in active markets.

Risk Management Activities — Energy Derivative Instruments
 
Exchange traded commodity contracts are valued using unadjusted quoted prices.  For non-exchange traded commodity contracts, we calculate fair value based on the average of the bid and offer price, discounted to reflect net present value.  We maintain certain valuation adjustments for a number of risks associated with the valuation of future commitments.  These include valuation adjustments for liquidity and credit risks.  The liquidity valuation adjustment represents the cost that would be incurred if all unmatched positions were closed out or hedged.  The credit valuation adjustment represents estimated credit losses on our net exposure to counterparties, taking into account netting agreements, expected default experience for the credit rating of the counterparties and the overall diversification of the portfolio.  We maintain credit policies that management believes minimize overall credit risk.
 
Certain non-exchange traded commodity contracts are valued based on unobservable inputs due to the long-term nature of contracts, characteristics of the product, or the unique location of the transactions.  Long-dated energy transactions may consist of observable valuations for the near-term portion and unobservable valuations for the long-term portions of the transaction.  We rely primarily on broker quotes to value these instruments.  When our valuations utilize broker quotes, we perform various control procedures to ensure the quote has been developed consistent with fair value accounting guidance.  These controls include assessing the quote for reasonableness by comparison against other broker quotes, reviewing historical price relationships, and assessing market activity.  When broker quotes are not available, the primary valuation technique used to calculate the fair value is the extrapolation of forward pricing curves using observable market data for more liquid delivery points in the same region and actual transactions at more illiquid delivery points.
 
When the unobservable portion is significant to the overall valuation of the transaction, the entire transaction is classified as Level 3. 
 
Investments Held in Nuclear Decommissioning Trusts and Other Special Use Funds
 
The nuclear decommissioning trusts and other special use funds invest in fixed income and equity securities. Other special use funds include the coal reclamation escrow account, the active union employee medical account, and the Captive. See Note 18 for additional discussion about our investment accounts.

We value investments in fixed income and equity securities using information provided by our trustees and escrow agent. Our trustees and escrow agent use pricing services that utilize the valuation methodologies described below to determine fair market value. We have internal control procedures designed to ensure this information is consistent with fair value accounting guidance. These procedures include assessing valuations using an independent pricing source, verifying that pricing can be supported by actual recent market transactions, assessing hierarchy classifications, comparing investment returns with benchmarks, and obtaining and reviewing independent audit reports on the trustees’ and escrow agent’s internal operating controls and valuation processes.
Fixed Income Securities

Fixed income securities issued by the U.S. Treasury are valued using quoted active market prices and are typically classified as Level 1.  Fixed income securities issued by corporations, municipalities, and other agencies, including mortgage-backed instruments, are valued using quoted inactive market prices, quoted active market prices for similar securities, or by utilizing calculations which incorporate observable inputs such as yield curves and spreads relative to such yield curves.  These fixed income instruments are classified as Level 2.  Whenever possible, multiple market quotes are obtained which enables a cross-check validation.  A primary price source is identified based on asset type, class, or issue of securities.

Fixed income securities may also include short-term investments in certificates of deposit, variable rate notes, time deposit accounts, U.S. Treasury and Agency obligations, U.S. Treasury repurchase agreements, commercial paper, and other short-term instruments. These instruments are valued using active market prices or utilizing observable inputs described above.

Equity Securities

The nuclear decommissioning trusts’ equity security investments are held indirectly through commingled funds.  The commingled funds are valued using the funds’ NAV as a practical expedient. The funds’ NAV is primarily derived from the quoted active market prices of the underlying equity securities held by the funds. We may transact in these commingled funds on a semi-monthly basis at the NAV.  The commingled funds are maintained by a bank and hold investments in accordance with the stated objective of tracking the performance of the S&P 500 Index.  Because the commingled funds’ shares are offered to a limited group of investors, they are not considered to be traded in an active market. As these instruments are valued using NAV, as a practical expedient, they have not been classified within the fair value hierarchy.

The nuclear decommissioning trusts and other special use funds may also hold equity securities that include exchange traded mutual funds and money market accounts for short-term liquidity purposes. These short-term, highly-liquid investments are valued using active market prices.
Fair Value Tables

The following table presents the fair value at December 31, 2024, of our assets and liabilities that are measured at fair value on a recurring basis (dollars in thousands):

Level 1Level 2Level 3OtherTotal
ASSETS
Cash equivalents$23 $— $— $— $23 
Risk management activities — derivative instruments:
Commodity contracts— 13,152 7,176 (3,770)(a)16,558 
Nuclear decommissioning trusts:
Equity securities11,859 542 — 3,335 (b)15,736 
U.S. commingled equity funds— — — 423,069 (c)423,069 
U.S. Treasury debt367,396 — — — 367,396 
Corporate debt— 203,180 — — 203,180 
Mortgage-backed securities— 208,533 — — 208,533 
Municipal bonds— 37,429 — — 37,429 
Other fixed income— 27,502 — — 27,502 
Subtotal nuclear decommissioning trusts379,255 477,186 — 426,404 1,282,845 
Other special use funds:
Cash equivalents25,000 — — — (d)$25,000 
Equity securities24,962 — — 2,851 (b,d)27,813 
U.S. Treasury debt355,544 — — — 355,544 
Subtotal other special use funds (d)405,506 — — 2,851 408,357 
Total assets$784,784 $490,338 $7,176 $425,485 $1,707,783 
LIABILITIES
Risk management activities — derivative instruments:
Commodity contracts$— $(40,388)$(22,215)$817 (a)$(61,786)
(a)Represents counterparty netting, margin, and collateral. See Note 15.
(b)Represents net pending securities sales and purchases.
(c)Valued using NAV as a practical expedient and, therefore, are not classified in the fair value hierarchy.
(d)All amounts relate to APS, with the exception of $34.2 million related to Pinnacle West’s Captive investments that are classified within Level 1, $25.0 million in cash equivalents and $9.2 million related to equity securities. See Note 17.
 The following table presents the fair value at December 31, 2023, of our assets and liabilities that are measured at fair value on a recurring basis (dollars in thousands):
 
Level 1Level 2Level 3OtherTotal
ASSETS
Cash equivalents$10 $— $— $— $10 
Risk management activities — derivative instruments:
Commodity contracts— 1,881 6,616 (1,689)(a)6,808 
Nuclear decommissioning trusts:
Equity securities11,064 — — (767)(b)10,297 
U.S. commingled equity funds— — — 409,616 (c)409,616 
U.S. Treasury debt319,734 — — — 319,734 
Corporate debt— 188,317 — — 188,317 
Mortgage-backed securities— 208,306 — — 208,306 
Municipal bonds— 59,323 — — 59,323 
Other fixed income— 5,653 — — 5,653 
Subtotal nuclear decommissioning trusts330,798 461,599 — 408,849 1,201,246 
Other special use funds:
Equity securities40,991 — — 2,196 (b)43,187 
U.S. Treasury debt319,594 — — — 319,594 
Subtotal other special use funds360,585 — — 2,196 362,781 
Total assets$691,393 $463,480 $6,616 $409,356 $1,570,845 
LIABILITIES
Risk management activities — derivative instruments:
Commodity contracts$— $(127,016)$(1,695)$4,823 (a)$(123,888)
(a)Represents counterparty netting, margin, and collateral. See Note 15.
(b)Represents net pending securities sales and purchases.
(c)Valued using NAV as a practical expedient and, therefore, are not classified in the fair value hierarchy.
Fair Value Measurements Classified as Level 3
 
The significant unobservable inputs used in the fair value measurement of our energy derivative contracts include broker quotes that cannot be validated as an observable input primarily due to the long-term nature of the quote or other characteristics of the product.  Significant changes in these inputs in isolation would result in significantly higher or lower fair value measurements.  Changes in our derivative contract fair values, including changes relating to unobservable inputs, typically will not impact net income due to regulatory accounting treatment. See Note 3.
 
Because our forward commodity contracts classified as Level 3 are currently in a net purchase position, we would expect price increases of the underlying commodity to result in increases in the net fair value of the related contracts.  Conversely, if the price of the underlying commodity decreases, the net fair value of the related contracts would likely decrease.

Other unobservable valuation inputs include credit and liquidity reserves which do not have a material impact on our valuations; however, significant changes in these inputs could also result in higher or lower fair value measurements.

The following tables provide information regarding our significant unobservable inputs used to value our risk management derivative Level 3 instruments at December 31, 2024, and December 31, 2023:

December 31, 2024
 Fair Value (thousands) 		ValuationSignificantWeighted-Average
Commodity ContractsAssetsLiabilitiesTechniqueUnobservable InputRange (b)
Electricity Forward Contracts (a)$708 $21,890 Discounted cash flowsElectricity forward price (per MWh)
$25.25
-
$151.11
$106.06
Natural Gas Forward Contracts (a)6,468 325 Discounted cash flowsNatural gas forward price (per MMBtu)
$(0.89)
-
$1.47
$0.71
Total$7,176 $22,215 
(a)Includes swaps and physical and financial contracts.
(b)Unobservable inputs were weighted by the relative fair value of the instrument.

December 31, 2023
 Fair Value (thousands) 		ValuationSignificantWeighted-Average
Commodity ContractsAssetsLiabilitiesTechniqueUnobservable InputRange(b)
Electricity Forward Contracts (a)$6,587 $658 Discounted cash flowsElectricity forward price (per MWh)$37.79 -$259.04$158.08
Natural Gas Forward Contracts (a)29 1,037 Discounted cash flowsNatural gas forward price (per MMBtu)$0.00-$0.08$0.03
Total$6,616 $1,695 
(a)Includes swaps and physical and financial contracts.
(b)Unobservable inputs were weighted by the relative fair value of the instrument.
The following table shows the changes in fair value for our risk management activities’ assets and liabilities that are measured at fair value on a recurring basis using Level 3 inputs (dollars in thousands):

 Year Ended December 31,
Commodity Contracts20242023
Balance at beginning of period$4,921 $(4,888)
Total net losses realized/unrealized:
Deferred as a regulatory asset or liability(60,965)(70,214)
Settlements44,156 69,706 
Transfers into Level 3 from Level 2(4,635)(1,289)
Transfers from Level 3 into Level 21,484 11,606 
Balance at end of period$(15,039)$4,921 
Net unrealized gains/losses included in earnings related to instruments still held at end of period$— $— 

             Transfers in or out of Level 3 are typically related to our long-dated energy transactions that extend beyond available quoted periods.

Financial Instruments Not Carried at Fair Value
 
The carrying value of our short-term borrowings approximate fair value and are classified within Level 2 of the fair value hierarchy.  See Note 6 for our long-term debt fair values.
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Common Stock Equity and Earnings Per Share
 12 Months Ended
Dec. 31, 2024
Earnings Per Share [Abstract]  
Common Stock Equity and Earnings Per Share Common Stock Equity and Earnings Per Share
ATM Program

On November 8, 2024, Pinnacle West entered into an equity distribution sales agreement, pursuant to which Pinnacle West may sell, from time to time, up to $900 million of its common stock through an ATM program, which includes the ability to enter into forward sale agreements. As of December 31, 2024, approximately $850 million of common stock is available to be issued under the ATM Program, which takes into account the forward sale agreement in effect as of December 31, 2024.

As of December 31, 2024, Pinnacle West had an outstanding forward sale agreement under the ATM program relating to approximately $50 million of common stock (the “November 2024 ATM Forward Sale Agreement”). The November 2024 ATM Forward Sale Agreement may be settled at Pinnacle West’s discretion no later than June 30, 2026. On a given settlement date, Pinnacle West will issue shares of common at the then-applicable forward sales price. The terms of the November 2024 ATM Forward Sale Agreement also allow Pinnacle West, at its option, to settle the agreements with the counterparties by delivering cash, in lieu of shares.

The initial forward sales price for the November 2024 ATM Forward Sale Agreement was approximately $89.73, subject to certain adjustments. On December 31, 2024, Pinnacle West could have settled the outstanding November 2024 ATM Forward Sale Agreement with the physical delivery of 552,833 shares of Pinnacle West common stock in exchange for cash of approximately $50 million. As of December 31, 2024, Pinnacle West has not received any proceeds relating to the November 2024 Forward
Sale Agreement. Pinnacle West will receive proceeds, if any, when settlement occurs, and will record the proceeds, if any, in equity.

Non-ATM February 2024 Forward Sale Agreements

On February 28, 2024, Pinnacle West executed equity forward sale agreements, relating to 11,240,601 shares of Pinnacle West common stock (“February 2024 Forward Sale Agreements”). The February 2024 Forward Sale Agreements may be settled at our discretion no later than September 4, 2025, and were not issued under the ATM program discussed above. On a settlement date, Pinnacle West will issue shares of Pinnacle West common stock and receive cash, if any, at the then-applicable forward sales price. The terms of the February 2024 Forward Sale Agreements also allow Pinnacle West, at its option, to settle the agreements with the counterparties by delivering cash, in lieu of shares.

The initial forward sales price for the February 2024 Forward Sale Agreements was initially, approximately $64.51 per share and is subject to adjustment based on the terms of the agreements. In December 2024, Pinnacle West partially settled the February 2024 Forward Sale Agreements with the issuance of 5,377,115 shares of common stock and received net proceeds of $345 million. The proceeds were recorded in equity.

At December 31, 2024, Pinnacle West could have settled the remaining February 2024 Forward Sale Agreements with the issuance of 5,863,486 shares of common stock in exchange for cash of $377 million. We will not receive any additional proceeds, if any, from the February 2024 Forward Sale Agreements until settlement occurs.

Convertible Notes

In June 2024, Pinnacle West issued $525 million of 4.75% convertible senior notes that will mature on June 15, 2027. The Convertible Notes conversion options are indexed to Pinnacle West’s common stock. See Note 5.
Earnings Per Share

The following table presents the calculation of Pinnacle West’s basic and diluted EPS (in thousands, except per share amounts):
 202420232022
Net income attributable to common shareholders$608,806 $501,557 $483,602 
Weighted average common shares outstanding — basic113,846 113,442 113,196 
Net effect of dilutive securities:   
Contingently issuable performance shares and restricted stock units480 362 220 
Dilutive shares related to equity forward sale agreements (a)1,906 — — 
Total contingently issuable shares2,386 362 220 
Weighted average common shares outstanding — diluted116,232 113,804 113,416 
Earnings per weighted-average common share outstanding
Net income attributable to common shareholders — basic$5.35 $4.42 $4.27 
Net income attributable to common shareholders — diluted$5.24 $4.41 $4.26 
(a)    For the years ended December 31, 2024, 2023 and 2022, diluted weighted average common shares excludes 1,038,463, 0 and 0 shares, respectively, relating to the Convertible Notes and the ATM equity forward. These potentially issuable shares were excluded from the calculation of diluted shares as their inclusion would have been antidilutive.
The November 2024 ATM Forward Sale Agreements and the February 2024 Forward Sale Agreements are classified as equity transactions, and are not recorded on the Pinnacle West Consolidated Balance Sheets. Delivery of shares to settle equity forward agreements result in dilution to basic earnings per share (EPS) upon settlement. Prior to settlement, the potentially issuable shares are reflected in our diluted EPS calculations using the treasury stock method. Under this method, the number of shares, if any, that would be issued upon settlement less that number of shares that could be purchased by Pinnacle West in the market with the proceeds received from issuance (based on the average market price during the reporting period). Share dilution occurs when the average market price of our stock during the reporting period is higher than the adjusted forward sale price as of the end of the reporting period.
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Stock-Based Compensation
 12 Months Ended
Dec. 31, 2024
Share-Based Payment Arrangement [Abstract]  
Stock-Based Compensation Stock-Based Compensation
 
Pinnacle West has incentive compensation plans under which stock-based compensation is granted to officers, key employees, and non-officer members of the Board of Directors. Awards granted under the 2021 Long-Term Incentive Plan, as amended (“2021 Plan”), may be in the form of stock grants, restricted stock units, stock units, performance shares, restricted stock, dividend equivalents, performance share units, performance cash, incentive and non-qualified stock options, and stock appreciation rights.  The 2021 Plan authorizes up to 4.3 million common shares to be available for grant.  As of December 31, 2024, 2.9 million common shares were available for issuance under the 2021 Plan. During 2024, 2023 and 2022, the Company granted awards in the form of restricted stock units, stock units, stock grants, and performance shares. Awards granted from 2012 to May 2021 were issued under the 2012 Long-Term Incentive Plan (“2012 Plan”), and awards granted from 2007 to 2011 were issued under the 2007 Long-Term Incentive Plan (“2007 Plan”). No new awards may be granted under the 2012 or 2007 Plans.
Stock-Based Compensation Expense and Activity
 
Compensation cost included in net income for stock-based compensation plans was $24 million in 2024, $17 million in 2023, and $16 million in 2022.  The compensation cost capitalized is immaterial for all years. Income tax benefits related to stock-based compensation arrangements were $6 million in 2024, $3 million in 2023, and $2 million in 2022.

As of December 31, 2024, there were approximately $38 million of unrecognized compensation costs related to nonvested stock-based compensation arrangements. We expect to recognize these costs over a weighted-average period of two years. 

The total fair value of shares vested was $24 million in 2024, $24 million in 2023, and $25 million in 2022.
 
The following table is a summary of awards granted and the weighted-average grant date fair value for each of the last three years:
Restricted Stock Units, Stock Grants, and Stock Units (a)Performance Shares (b)
 202420232022202420232022
Units granted261,808 192,295 174,791 225,516 202,562 208,736 
Weighted-average grant date fair value$71.10 $74.32 $69.66 $72.89 $79.61 $77.63 
(a)The Units granted does not include awards that will be cash settled in 2024, 2023 or 2022. See below for additional information on restricted stock unit grants.
(b)Reflects the target payout level.
 
The following table shows the change of nonvested awards:

Restricted Stock Units, Stock Grants, and Stock UnitsPerformance Shares
SharesWeighted-Average
Grant Date
Fair Value		Shares (b)Weighted-Average
Grant Date
Fair Value
Nonvested at December 31, 2023
374,367 $73.29 347,283 $77.29 
Granted261,808 71.10 225,516 72.89 
Vested(155,345)74.54 (165,194)76.55 
Forfeited (c)(20,039)71.32 (17,054)75.69 
Nonvested at December 31, 2024
460,791 (a)71.72 390,551 77.29 
Vested Awards Outstanding at December 31, 2024
70,851 165,194 
(a)Includes 11,750 of awards that will be cash settled.
(b)The performance shares are reflected at target payout level. 
(c)We account for forfeitures as they occur.

Share-based liabilities paid relating to restricted stock units were $8 million, $6 million, and $3 million in 2024, 2023 and 2022, respectively. This includes cash used to settle restricted stock units of $2
million, $3 million, and $3 million in 2024, 2023 and 2022, respectively. Restricted stock units that are cash settled are classified as liability awards. All performance shares are classified as equity awards.
 
Restricted Stock Units, Stock Grants, and Stock Units
 
Restricted stock units are granted to officers and key employees and typically vest and settle in equal annual installments over a 4-year period after the grant date.  Vesting is typically dependent upon continuous service during the vesting period.

Beginning in 2022, restricted stock unit awards are issued in stock. Awards include a dividend equivalent feature that allows each award to accrue dividends and treat them as reinvested, from the date of grant until the applicable vesting date. If the award is forfeited the employee is not entitled to the accrued reinvested dividends on those shares. Awards granted to retirement-eligible employees will vest on a pro-rata basis upon the employee’s retirement.

Prior to 2022, awardees typically elected to receive payment in either 100% stock, 100% cash, or 50% in cash and 50% in stock.  Awards included a dividend equivalent feature that accrued dividend rights from the date of grant until the applicable vesting date, plus interest compounded quarterly. If the award was forfeited, the employee was not entitled to the accrued dividends on those shares. Awards granted to retirement-eligible employees typically vested upon the employee’s retirement.

Compensation cost for restricted stock unit awards is based on the fair value of the award, with the fair value being the market price of our stock on the measurement date. Restricted stock unit awards that will be settled in cash are accounted for as liability awards, with compensation cost initially calculated on the date of grant using the Company’s closing stock price and remeasured at each balance sheet date. Restricted stock unit awards that will be settled in shares are accounted for as equity awards, with compensation cost calculated using the Company’s closing stock price on the date of grant. Compensation cost is recognized over the requisite service period based on the fair value of the award.
 
Stock grants are issued to non-officer members of the Board of Directors. They may elect to receive the stock grant, or to defer receipt until a later date and receive stock units in lieu of the stock grant. Beginning in 2023, payments for stock units are issued in stock and include a dividend equivalent feature that allows each award to accrue dividends and treat them as reinvested, from the date of grant until the applicable vesting date. Prior to 2023, members of the Board of Directors who elected to defer could elect to receive payment in either 100% stock, 100% cash, or 50% in cash and 50% in stock.  The stock units prior to 2023 included a dividend equivalent feature that accrues dividend rights from the date of grant to the date of payment, plus interest compounded quarterly.
 
Performance Share Awards
 
Performance share awards are granted to officers and key employees.  The awards contain separate performance metric criteria that affect the number of shares that may be received if, after the end of a 3-year performance period, the performance criteria are met.

Beginning in 2022, performance share awards contain three separate, unrelated performance criteria. The first performance criteria is based upon Pinnacle West’s total shareholder return (“TSR”) in relation to the TSR of other companies in a specified utility index (i.e., the TSR component). The second performance criteria is based upon Pinnacle West’s earnings per share (“EPS”) performance relative to an
approved target (i.e., the EPS component). The third performance criteria is based upon APS’s clean MW installed of renewable or other carbon free resources compared to the approved target (i.e., the Clean component). The exact number of shares issued is calculated separately for each performance component and can vary from 0% to 200% of the target award for each separate performance criteria. Shares received include a dividend equivalent feature that treats accrued dividends as reinvested, from the date of grant until the date of payment, equal to the number of vested performance shares. If the award is forfeited or if the performance criteria are not achieved, the employee is not entitled to the dividends on those shares. Awards granted to retirement-eligible employees will vest on a pro-rata basis upon the employee’s retirement.

Prior to 2022, performance share awards had two performance criteria. The first performance criteria was based upon non-financial performance metrics (i.e., the Metric component). The second performance criteria was based upon Pinnacle West’s TSR in relation to the TSR of other companies in a specified utility index (i.e., the TSR component). The exact number of shares issued will vary from 0% to 200% of the target award. Shares received included a dividend equivalent feature that allows accrued dividend rights from the date of grant until the date of payment, plus interest compounded quarterly, equal to the number of vested performance shares. If the award was forfeited, the employee was not entitled to the accrued dividends on those shares. Awards granted to retirement-eligible employees typically vested upon the employee’s retirement.
 
Performance share awards are accounted for as equity awards, with compensation cost based on the fair value of the award on the grant date. Compensation cost relating to the EPS and Clean metric component of the respective awards is based on the Company’s closing stock price on the date of grant, with compensation cost recognized over the requisite service period based on the number of shares expected to vest. Management evaluates the probability of meeting the EPS and Clean metric component at each balance sheet date. If the EPS and Clean metric component criteria are not ultimately achieved, no compensation cost is recognized relating to the EPS and Clean metric component, and any previously recognized compensation cost is reversed. Compensation cost relating to the TSR component of the respective awards is determined using a Monte Carlo simulation valuation model, with compensation cost recognized ratably over the requisite service period, regardless of the number of shares that actually vest.
v3.25.0.1
Derivative Accounting
 12 Months Ended
Dec. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Derivative Accounting Derivative Accounting
 
Derivative financial instruments are used to manage exposure to commodity price and transportation costs of electricity, natural gas, emissions allowances, and interest rates.  Risks associated with market volatility are managed by utilizing various physical and financial derivative instruments, including futures, forwards, options, and swaps.  As part of our overall risk management program, we may use derivative instruments to hedge purchases and sales of electricity and natural gas.  Derivative instruments that meet certain hedge accounting criteria may be designated as cash flow hedges and are used to limit our exposure to cash flow variability on forecasted transactions.  The changes in market value of such instruments have a high correlation to price changes in the hedged transactions.  Derivative instruments are also entered into for economic hedging purposes.  While economic hedges may mitigate exposure to fluctuations in commodity prices, these instruments have not been designated as accounting hedges.  Contracts that have the same terms (quantities, delivery points and delivery periods) and for which power does not flow are netted, which reduces both revenues and fuel and purchased power costs in our Consolidated Statements of Income, but does not impact our financial condition, net income, or cash flows.
  
Our derivative instruments, excluding those qualifying for a scope exception, are recorded on the balance sheets as an asset or liability and are measured at fair value.  See Note 12 for a discussion of fair value measurements.  Derivative instruments may qualify for the normal purchases and normal sales scope exception if they require physical delivery, and the quantities represent those transacted in the normal course of business.  Derivative instruments qualifying for the normal purchases and sales scope exception are accounted for under the accrual method of accounting and excluded from our derivative instrument discussion and disclosures below.

See Note 13 for details relating to Pinnacle West’s equity forward sale agreements and Note 5 for Pinnacle West’s Convertible Notes. These equity-linked transactions are indexed to Pinnacle West common stock and qualify for a derivative scope exception, and as such, are not subject to mark-to-market accounting and are excluded from the derivative disclosures below.

Energy Derivatives

For its regulated operations, APS defers for future rate treatment 100% of the unrealized gains and losses on energy derivatives pursuant to the PSA mechanism that would otherwise be recognized in income.  Realized gains and losses on energy derivatives are deferred in accordance with the PSA to the extent the amounts are above or below the Base Fuel Rate. See Note 3.  Gains and losses from energy derivatives in the following tables represent the amounts reflected in income before the effect of PSA deferrals.

The following table shows the outstanding gross notional volume of energy derivatives, which represent both purchases and sales (does not reflect net position):
Quantity
CommodityUnit of MeasureDecember 31, 2024December 31, 2023
PowerGWh1,051 1,212 
GasBillion cubic feet235 200 
 
Gains and Losses from Energy Derivative Instruments
For the years ended December 31, 2024, 2023 and 2022, APS had no energy derivative instruments in designated accounting hedging relationships.
The following table provides information about gains and losses from energy derivative instruments not designated as accounting hedging instruments (dollars in thousands):
Financial Statement Year Ended December 31,
Commodity ContractsLocation202420232022
Net Gain (Loss) Recognized in Income
Fuel and purchased power (a)(88,522)(370,145)307,287 
(a)Amounts are before the effect of PSA deferrals.
Energy Derivative Instruments in the Consolidated Balance Sheets

Our energy derivative transactions are typically executed under standardized or customized agreements, which include collateral requirements and, in the event of a default, would allow for the netting of positive and negative exposures associated with a single counterparty.  Agreements that allow for the offsetting of positive and negative exposures associated with a single counterparty are considered master netting arrangements.  Transactions with counterparties that have master netting arrangements are offset and reported net on the Consolidated Balance Sheets.  Transactions that do not allow for offsetting of positive and negative positions are reported gross on the Consolidated Balance Sheets.

We do not offset a counterparty’s current energy derivative contracts with the counterparty’s non-current energy derivative contracts, although our master netting arrangements would allow current and non-current positions to be offset in the event of a default.  These types of transactions may include non-derivative instruments, derivatives qualifying for scope exceptions, trade receivables and trade payables arising from settled positions, and other forms of non-cash collateral (such as letters of credit).  These types of transactions are excluded from the offsetting tables presented below.

The following tables provide information about the fair value of APS’s risk management activities reported on a gross basis and the impacts of offsetting.  These amounts relate to commodity contracts and are located in the assets and liabilities from risk management activities lines of APS’s Consolidated Balance Sheets.
As of December 31, 2024:
 (dollars in thousands) 		Gross 
Recognized 
Derivatives
 (a)		Amounts 
Offset
(b)		Net
 Recognized
 Derivatives		Other
 (c)		Amounts 
Reported on 
Balance Sheets
Current assets$13,718 $(3,158)$10,560 $18 $10,578 
Investments and other assets6,610 (630)5,980 — 5,980 
Total assets20,328 (3,788)16,540 18 16,558 
Current liabilities(52,527)3,158 (49,369)(2,971)(52,340)
Deferred credits and other(10,076)630 (9,446)— (9,446)
Total liabilities(62,603)3,788 (58,815)(2,971)(61,786)
Total$(42,275)$— $(42,275)$(2,953)$(45,228)
(a)All of our gross recognized derivative instruments were subject to master netting arrangements.
(b)No cash collateral has been provided to counterparties, or received from counterparties, that is subject to offsetting.
(c)Represents cash collateral and cash margin that is not subject to offsetting. Amounts relate to non-derivative instruments, derivatives qualifying for scope exceptions, or collateral and margin posted in excess of the recognized derivative instrument.  Includes cash collateral received from counterparties of $2,971 thousand and cash margin provided to counterparties of $18 thousand.
As of December 31, 2023:
 (dollars in thousands) 		Gross
 Recognized
 Derivatives
 (a)		Amounts
Offset 
(b)		Net
 Recognized
 Derivatives		Other
 (c)		Amounts
 Reported on
 Balance Sheets
Current assets$8,497 $(1,694)$6,803 $5 $6,808 
Investments and other assets— — — — — 
Total assets8,497 (1,694)6,803 5 6,808 
Current liabilities(85,736)10,894 (74,842)(6,071)(80,913)
Deferred credits and other(42,975)— (42,975)— (42,975)
Total liabilities(128,711)10,894 (117,817)(6,071)(123,888)
Total$(120,214)$9,200 $(111,014)$(6,066)$(117,080)
(a)All of our gross recognized derivative instruments were subject to master netting arrangements.
(b)Includes cash collateral provided to counterparties of $9,200 thousand that is subject to offsetting.
(c)Represents cash collateral and cash margin that is not subject to offsetting.  Amounts relate to non-derivative instruments, derivatives qualifying for scope exceptions, or collateral and margin posted in excess of the recognized derivative instrument.  Includes cash collateral received from counterparties of $6,071 thousand and cash margin provided to counterparties of $5 thousand.

Credit Risk and Credit Related Contingent Features
 
We are exposed to losses in the event of nonperformance or nonpayment by energy derivative counterparties and have risk management contracts with many energy derivative counterparties. As of December 31, 2024, we have one counterparty for which our exposure represents approximately 26% of Pinnacle West’s $16.6 million of risk management assets. This exposure relates to an ISDA master agreement with the respective counterparty. The counterparty is rated as investment grade by Standard & Poor’s. Our risk management process assesses and monitors the financial exposure of all counterparties.  Despite the fact that the great majority of our trading counterparties’ debt is rated as investment grade by the credit rating agencies, there is still a possibility that one or more of these counterparties could default, resulting in a material impact on consolidated earnings for a given period. Counterparties in the portfolio consist principally of financial institutions, major energy companies, municipalities and local distribution companies.  We maintain credit policies that we believe minimize overall credit risk to within acceptable limits.  Determination of the credit quality of our counterparties is based upon a number of factors, including credit ratings and our evaluation of their financial condition.  To manage credit risk, we employ collateral requirements and standardized agreements that allow for the netting of positive and negative exposures associated with a single counterparty.  Valuation adjustments are established representing our estimated credit losses on our overall exposure to counterparties.
 
Certain of our energy derivative instrument contracts contain credit-risk-related contingent features including, among other things, investment grade credit rating provisions, credit-related cross-default provisions, and adequate assurance provisions.  Adequate assurance provisions allow a counterparty with reasonable grounds for uncertainty to demand additional collateral based on subjective events and/or conditions.  For those energy derivative instruments in a net liability position, with investment grade credit contingencies, the counterparties could demand additional collateral if our debt credit rating were to fall below investment grade (below BBB- for Standard & Poor’s or Fitch or Baa3 for Moody’s).
 
The following table provides information about our energy derivative instruments that have credit-risk-related contingent features (dollars in thousands):
 December 31, 2024
Aggregate fair value of derivative instruments in a net liability position$62,603 
Additional collateral in the event credit-risk related contingent features were fully triggered (a)32,728 
(a)This amount is after counterparty netting and includes those contracts which qualify for scope exceptions, which are excluded from the derivative details above.
 
We also have energy related non-derivative instrument contracts, including energy storage lease contracts, with investment grade credit-related contingent features, which could also require us to post additional collateral of approximately $416 million if our debt credit ratings were to fall below investment grade.
v3.25.0.1
Other Income and Other Expense
 12 Months Ended
Dec. 31, 2024
Other Income and Expenses [Abstract]  
Other Income and Other Expense Other Income and Other Expense
 
The following table provides detail of Pinnacle West’s Consolidated other income and other expense for 2024, 2023, and 2022 (dollars in thousands):
 202420232022
Other income:   
Interest income$24,322 (a)$27,242 (a)$7,326 
Gain on sale of BCE (Note 20)
22,988 6,205 — 
Miscellaneous1,304 219 590 
Total other income$48,614 $33,666 $7,916 
Other expense:
Non-operating costs$(27,370)(b)$(15,260)$(18,619)
Investment losses — net(1,418)(3,402)(20,537)(c)
Miscellaneous(5,348)(6,394)(13,229)
Total other expense$(34,136)$(25,056)$(52,385)
(a)The 2023 and 2024 Interest income is primarily related to PSA Interest. See Note 3.
(b)The 2024 Non-operating cost is primarily related to corporate giving.
(c)The 2022 investment loss is primarily related to an impairment of PNW Power’s Clear Creek wind farm investment.
The following table provides detail of APS’s other income and other expense for 2024, 2023, and 2022 (dollars in thousands):
 202420232022
Other income:   
Interest income (a)$21,088 (a)$26,853 (a)$5,332 
Miscellaneous6 219 556 
 Total other income$21,094 $27,072 $5,888 
Other expense:
Non-operating costs$(26,588)(b)$(14,070)$(15,579)
Miscellaneous(3,110)(4,194)(10,529)
Total other expense$(29,698)$(18,264)$(26,108)
(a)The 2023 and 2024 Interest income is primarily related to PSA Interest. See Note 3.
(b)The 2024 Non-operating cost is primarily related to corporate giving.
v3.25.0.1
Variable Interest Entities
 12 Months Ended
Dec. 31, 2024
Variable Interest Entities [Abstract]  
Variable Interest Entities Variable Interest Entities
 
Pinnacle West

Captive Insurance Cell VIE

To support our overall insurance program, Pinnacle West established a captive insurance cell to insure certain risks of Pinnacle West and our subsidiaries. The Captive is a protected separate cell captive insurance company sponsored by Energy Insurance Services, Inc (“EISI”). EISI is owned by Energy Insurance Mutual Limited Company and allows participating member sponsoring organizations, such as Pinnacle West, to insure risks using captive entities. Pinnacle West, through its contractual rights, has a controlling financial interest in the separate protected Captive cell’s assets. Pinnacle West obtains all the benefits from the Captive and makes all the primary controlling decisions that economically impact the Captive. As a separate protected cell, Pinnacle West is the Captive’s only participant. The Captive is a VIE for which Pinnacle West is the primary beneficiary. Accordingly, Pinnacle West consolidates the Captive.

Under a mutual business program participation agreement between the Captive and EISI, EISI will issue policies, make claim disbursements, claim expenses and other underwriting fees on behalf of the Captive, as necessary.

The Captive insures Pinnacle West and its subsidiaries for terrorism coverage, excess liability including certain wildfire coverage, excess property insurance, and excess employment practice liability. The Captive policies exclude nuclear liability at Palo Verde. See Note 10 for details regarding nuclear liability insurance. Claim payments to the insureds can only be made up to the amount of the Captive’s available assets. In the event that claims exceed the Captive’s available assets, Pinnacle West may be required to provide additional funding to the Captive. In addition to policies obtained through the Captive, Pinnacle West also has insurance policies purchased through third-party insurers that may provide coverage if a loss event occurs.

As a result of consolidation, we eliminate intercompany transactions between Pinnacle West and the Captive and record the Captive’s assets, liabilities and third-party operating activities. In consolidation,
the Captive’s insurance premium revenues derived from Pinnacle West policies is eliminated against the insurance premium expense recorded by Pinnacle West and our subsidiaries relating to insurance policy coverage provided by the Captive. Consolidation primarily resulted in Pinnacle West reflecting the Captive’s investment holdings on our Consolidated Balance Sheets, and the Captive’s investment gains and losses reflected through earnings on our Consolidated Income Statements.

Consolidation of the Captive resulted in an increase in Pinnacle West net income of $5 million for 2024, and zero for 2023 and 2022. These amounts are fully attributable to Pinnacle West shareholders. Consolidation impacts Pinnacle West Consolidated Income Statement’s operations and maintenance expense and other income line items.

Pinnacle West’s Consolidated Balance Sheets as of December 31, 2024 include $34 million of assets relating to the Captive that is reported within the other special use funds line item. See Notes 12 and 18 for additional details on these investment holdings. Our Consolidated Balance Sheets as of December 31, 2023, include $5 million of assets relating to the Captive that is reported within the other assets line item.

APS’s financial statements are not impacted by Pinnacle West’s consolidation of the Captive VIE.

APS

Palo Verde Sale Leaseback VIEs

In 1986, APS entered into agreements with three separate VIE lessor trust entities in order to sell and lease back interests in Palo Verde Unit 2 and related common facilities. APS will retain the assets through 2033 under all three lease agreements. APS will be required to make payments relating to the three leases in total of approximately $21 million annually for the period 2025 through 2033. At the end of the lease period, APS will have the option to purchase the leased assets at their fair market value, extend the leases for up to two years, or return the assets to the lessors.
 
The leases’ terms give APS the ability to utilize the assets for a significant portion of the assets’ economic life, and therefore provide APS with the power to direct activities of the VIEs that most significantly impact the VIEs’ economic performance. Predominantly due to the lease terms, APS has been deemed the primary beneficiary of these VIEs and therefore consolidates the VIEs.
As a result of consolidation, we eliminate lease accounting and instead recognize depreciation expense, resulting in an increase in net income of $17 million for each of 2024, 2023 and 2022. The increase in net income is entirely attributable to the noncontrolling interests.  Income attributable to Pinnacle West shareholders is not impacted by the consolidation.
Our Consolidated Balance Sheets include the following amounts relating to these VIEs (dollars in thousands):
 December 31, 2024December 31, 2023
Palo Verde sale leaseback property, plant and equipment, net of accumulated depreciation$82,556 $86,426 
Equity — Noncontrolling interests103,167 107,198 
 
Assets of the VIEs are restricted and may only be used for payment to the noncontrolling interest holders.  These assets are reported on our consolidated financial statements.
 
APS is exposed to losses relating to these VIEs upon the occurrence of certain events that APS does not consider to be reasonably likely to occur.  Under certain circumstances (for example, the NRC issuing specified violation orders with respect to Palo Verde or the occurrence of specified nuclear events), APS would be required to make specified payments to the VIEs’ noncontrolling equity participants and take title to the leased Unit 2 interests, which, if appropriate, may be required to be written-down in value.  If such an event were to occur during the lease periods, APS may be required to pay the noncontrolling equity participants approximately $345 million beginning in 2025, and up to $501 million over the lease extension terms.
 
For regulatory ratemaking purposes, the agreements continue to be treated as operating leases and, as a result, we have recorded a regulatory asset relating to the arrangements.
v3.25.0.1
Investments in Nuclear Decommissioning Trusts and Other Special Use Funds
 12 Months Ended
Dec. 31, 2024
Investments, Debt and Equity Securities [Abstract]  
Investments in Nuclear Decommissioning Trusts and Other Special Use Funds Investments in Nuclear Decommissioning Trusts and Other Special Use Funds
 
We have investments in debt and equity securities held in Nuclear Decommissioning Trusts and Other Special Use funds. Investments in debt securities are classified as available-for-sale securities. We record both debt and equity security investments at their fair value on our Consolidated Balance Sheets. See Note 12 for a discussion of how fair value is determined and the classification of the investments within the fair value hierarchy. The investments in each trust or account are restricted for use and are intended to fund specified costs and activities as further described for each fund below.

Nuclear Decommissioning Trusts — APS established external decommissioning trusts in accordance with NRC regulations to fund the future costs APS expects to incur to decommission Palo Verde.  Third-party investment managers are authorized to buy and sell securities per stated investment guidelines.  The trust funds are invested in fixed income securities and equity securities. Earnings and proceeds from sales and maturities of securities are reinvested in the trusts. Because of the ability of APS to recover decommissioning costs in rates, and in accordance with the regulatory treatment, APS has deferred realized and unrealized gains and losses (including credit losses) in other regulatory liabilities.

Coal Reclamation Escrow Account — APS has investments restricted for the future coal mine reclamation funding related to Four Corners. This escrow account is primarily invested in fixed income securities. Earnings and proceeds from sales of securities are reinvested in the escrow account. Because of the ability of APS to recover coal reclamation costs in rates, and in accordance with the regulatory treatment, APS has deferred realized and unrealized gains and losses (including credit losses) in other regulatory liabilities. Activities relating to APS coal mine reclamation escrow account investments are included within the other special use funds in the table below.
Active Union Employee Medical Account — APS has investments restricted for paying active union employee medical costs. These investments may be used to pay active union employee medical costs incurred in the current and future periods. In 2024 and 2023, APS was reimbursed $14 million for each year, for prior year active union employee medical claims from the active union employee medical account. The account is invested primarily in fixed income securities. In accordance with the ratemaking treatment, APS has deferred the unrealized gains and losses (including credit losses) in other regulatory assets and liabilities. Activities relating to active union employee medical account investments are included within the other special use funds in the table below.

Captive Insurance Cell — Pinnacle West has investments in the Captive that may be used to pay insurance losses in the event of certain insured loss events. The Captive may hold investment assets in cash, cash equivalents, and equity and fixed income instruments. These investments are restricted for insured loss events.

Pinnacle West Consolidated investment holdings reflected in the tables below primarily relate to APS, with the exception of the Captive’s investments included within Other Special Use Funds.

The following tables present the unrealized gains and losses based on the original cost of the investment and summarizes the fair value of the nuclear decommissioning trusts and other special use fund assets (dollars in thousands): 
December 31, 2024
 Fair ValueTotal
Unrealized
Gains		Total
Unrealized
Losses
Investment Type:Nuclear Decommissioning TrustsOther Special Use FundsTotal
Equity securities$435,470 $24,962 $460,432 $359,127 $(176)
Available for sale-fixed income securities844,040 355,544 1,199,584 (a)7,717 (31,960)
Other3,335 27,851 31,186 (b)— — 
Total$1,282,845 $408,357 $1,691,202 (c)$366,844 $(32,136)
(a)As of December 31, 2024, the amortized cost basis of these available-for-sale investments is $1,224 million.
(b)Represents net pending securities sales and purchases.
(c)All amounts pertain to APS, with the exception of $34 million of Other Special Use Fund investments in equity securities relating to the Captive.

December 31, 2023
 Fair ValueTotal
Unrealized
Gains		Total
Unrealized
Losses
Investment Type:Nuclear Decommissioning TrustsOther Special Use FundsTotal
Equity securities$420,680 $40,991 $461,671 $336,555 $— 
Available for sale-fixed income securities781,333 319,594 1,100,927 (a)21,518 (40,868)
Other(767)2,196 1,429 (b)39 — 
Total$1,201,246 $362,781 $1,564,027 (c)$358,112 $(40,868)
(a)As of December 31, 2023, the amortized cost basis of these available-for-sale investments is $1,120 million.
(b)Represents net pending securities sales and purchases.
(c)All amounts pertain to APS.
 Year Ended December 31,
 Nuclear Decommissioning TrustsOther Special Use FundsTotal
2024
Realized gains$75,690 $372 $76,062 
Realized losses$(21,966)$— $(21,966)
Proceeds from the sale of securities (a)$1,330,940 $355,154 $1,686,094 
2023
Realized gains$111,922 $172 $112,094 
Realized losses$(41,212)$(568)$(41,780)
Proceeds from the sale of securities (a)$1,324,978 $354,744 $1,679,722 
2022
Realized gains$9,017 $420 $9,437 
Realized losses$(40,239)$— $(40,239)
Proceeds from the sale of securities (a)$979,639 $227,558 $1,207,197 
(a)Proceeds are reinvested in the nuclear decommissioning trusts and other special use funds, excluding amounts reimbursed to the Company for active union employee medical claims from the active union employee medical account.
    
Fixed Income Securities Contractual Maturities

The fair value of APS’s fixed income securities, summarized by contractual maturities, at December 31, 2024, is as follows (dollars in thousands):
 
 Nuclear Decommissioning TrustsCoal Reclamation Escrow AccountActive Union Employee Medical AccountTotal
Less than one year$19,868 $87,424 $39,090 $146,382 
1 year – 5 years268,974 58,598 154,768 482,340 
5 years – 10 years198,464 — 15,664 214,128 
Greater than 10 years356,734 — — 356,734 
Total$844,040 $146,022 $209,522 $1,199,584 
v3.25.0.1
Changes in Accumulated Other Comprehensive Loss
 12 Months Ended
Dec. 31, 2024
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]  
Changes in Accumulated Other Comprehensive Loss Changes in Accumulated Other Comprehensive Loss
 
The following table shows the changes in Pinnacle West’s consolidated accumulated other comprehensive loss, including reclassification adjustments, net of tax, by component (dollars in thousands): 
 Pension and Other Postretirement BenefitsDerivative InstrumentsTotal
Balance at December 31, 2022
$(32,332)$897 $(31,435)
Other comprehensive income/(loss) before reclassifications
(4,420)713 (3,707)
Amounts reclassified from accumulated other comprehensive loss
1,998 (a)— 1,998 
Balance at December 31, 2023
(34,754)1,610 (33,144)
Other comprehensive income/(loss) before reclassifications
1,039 (891)148 
Amounts reclassified from accumulated other comprehensive loss
2,054 (a)— 2,054 
Balance at December 31, 2024
$(31,661)$719 $(30,942)
(a)These amounts primarily represent amortization of actuarial loss and are included in the computation of net periodic pension cost. See Note 7.
The following table shows the changes in APS’s consolidated accumulated other comprehensive loss, including reclassification adjustments, net of tax, by component (dollars in thousands): 
 Pension and Other Postretirement Benefits
Balance at December 31, 2022
$(15,596)
Other comprehensive (loss) before reclassifications
(3,383)
Amounts reclassified from accumulated other comprehensive loss
1,760 (a)
Balance at December 31, 2023
(17,219)
Other comprehensive income before reclassifications
1,255 
Amounts reclassified from accumulated other comprehensive loss
1,848 (a)
Balance at December 31, 2024
$(14,116)
(a)These amounts primarily represent amortization of actuarial loss and are included in the computation of net periodic pension cost. See Note 7.
v3.25.0.1
Sale of Bright Canyon Energy
 12 Months Ended
Dec. 31, 2024
Discontinued Operations and Disposal Groups [Abstract]  
Sale of Bright Canyon Energy Sale of Bright Canyon Energy
On August 4, 2023, Pinnacle West entered into a purchase and sale agreement pursuant to which we agreed to sell all of our equity interest in our wholly-owned subsidiary, BCE, to Ameresco. The transaction is accounted for as the sale of a business and was structured to close in multiple stages that were completed on January 12, 2024. Certain investments and assets that BCE previously held, including the TransCanyon joint venture and holdings in the two Tenaska wind farm investments, were not included in the BCE Sale and were instead transferred to PNW Power, a wholly-owned subsidiary of Pinnacle West. The BCE Sale did not include a $31 million equity bridge loan relating to BCE’s Los Alamitos project, which was paid in full by Pinnacle West on August 4, 2023. Other than these retained investments and the debt instrument, all BCE assets and liabilities were included in the BCE Sale and were transferred to Ameresco.

The total carrying value of net assets transferred to Ameresco as a result of the BCE Sale was $79 million, with total consideration received by Pinnacle West of $108 million, resulting in a total pre-tax gain of $29 million, which was recognized between August 4, 2023 and January 12, 2024. The net assets transferred includes $41 million of liabilities that have been assumed by Ameresco. The consideration received by Pinnacle West includes both cash and interest-bearing promissory notes. The stages of the BCE Sale and timing of net assets transferring to Ameresco and related gain recognition are as follows:

•The first stage of the BCE Sale was completed on August 4, 2023. In the first stage, the net assets transferred to Ameresco totaled $44 million, which included a $36 million construction term loan. The assets and liabilities transferred in the first stage related to the BCE Los Alamitos project and were previously primarily classified as construction work in progress and current maturities of long-term debt, respectively. A gain of $6 million was recognized on our Consolidated Statements of Income for the year ended December 31, 2023, relating to the first stage of the BCE Sale.

•The final stage of the BCE Sale was completed on January 12, 2024. In the final stage, the net assets transferred to Ameresco totaled $35 million. The assets transferred in the final stage related primarily to equity method investments in the Kūpono Solar Project and other development stage projects. These assets were previously classified as assets held for sale on our December 31, 2023, Consolidated Balance Sheets. Our Consolidated Statements of Income for the year ended December 31, 2024, include a $23 million gain relating to the final stage of the BCE Sale.

As of January 12, 2024, all stages of the BCE Sale have been completed. As partial consideration for the BCE Sale, Pinnacle West received a $46 million interest-bearing promissory note from Ameresco. The note required Ameresco to make cash payments to Pinnacle West throughout 2024 and Pinnacle West received payment in full of the note receivable during the fourth quarter of 2024. As the note receivable has been paid in full, our December 31, 2024 Consolidated Balance Sheets do not include any amounts relating to the promissory note.

 On January 30, 2024, Pinnacle West entered into a tax credit transfer agreement to purchase from Ameresco $23 million of investment tax credits from the BCE Los Alamitos project for $21 million. See Note 4.
Additionally, Pinnacle West continues to maintain certain guarantees relating to the Kūpono Solar Project sale-leaseback financing, which were not transferred in the BCE Sale transaction. See Note 10.
v3.25.0.1
New Accounting Standards
 12 Months Ended
Dec. 31, 2024
Accounting Standards Update and Change in Accounting Principle [Abstract]  
New Accounting Standards New Accounting Standards
 
ASU 2023-07, Segment Reporting: Improvements to Reportable Segment Disclosures

In November 2023, a new standard was issued that modifies segment reporting disclosure requirements. The disclosure changes include information about a reportable segment’s significant expenses, details relating to the entity’s chief operating decision maker, and other disclosures. We adopted this standard on December 31, 2024, using a retrospective approach. The adoption of the new standard results in changes to our reportable segment disclosures, but does not impact how we identify reportable segments or our financial statement results. See Note 1.

ASU 2023-09, Income Taxes: Improvements to Income Tax Disclosures

In December 2023, a new accounting standard was issued that expands disclosures relating to income taxes. The expanded disclosures include a tabular income tax rate reconciliation, disclosure of specific reconciliation categories and reconciling items, the amount of income taxes paid by jurisdiction, and other disclosures. We will adopt this standard on December 31, 2025, using a prospective approach. The adoption of the new standard will result in changes to our income tax disclosures, but will not impact our accounting for income taxes or our financial statement results.

ASU 2024-03, Income Statement: Expense Disaggregation Disclosures

In November 2024, a new accounting standard was issued that requires specific disclosures related to certain costs and expenses. Companies will be required to disclose the amounts of certain cost and expense categories, such as: purchases of inventory, employee compensation, depreciation, and amortization, among other disclosures. The new disclosures may be provided in the notes to the financial statements, and will not require changes to the face of the income statement. The standard is effective for us on December 31, 2027, using either a prospective or retrospective approach, with early adoption permitted. The adoption of the new standard will result in disclosure changes, but will not impact our accounting for such costs and expenses or our financial statement results.
v3.25.0.1
Schedule I - Condensed Financial Information of Registrant
 12 Months Ended
Dec. 31, 2024
Condensed Financial Information Disclosure [Abstract]  
Schedule I - Condensed Financial Information of Registrant
PINNACLE WEST CAPITAL CORPORATION HOLDING COMPANY
SCHEDULE I — CONDENSED FINANCIAL INFORMATION OF REGISTRANT
CONDENSED STATEMENTS OF COMPREHENSIVE INCOME
(dollars in thousands)
 
 Year Ended December 31,
 202420232022
Operating expenses$9,931 $11,249 $8,850 
Other   
Equity in earnings of subsidiaries643,703 539,962 500,042 
Other income (expense)23,835 2,823 (4,725)
Total667,538 542,785 495,317 
Interest expense65,261 47,251 18,861 
Income before income taxes592,346 484,285 467,606 
Income tax benefit(16,460)(17,272)(15,996)
Net income attributable to common shareholders608,806 501,557 483,602 
Other comprehensive income (loss) — attributable to common shareholders2,202 (1,709)23,426 
Total comprehensive income — attributable to common shareholders$611,008 $499,848 $507,028 
 
See Combined Notes to Consolidated Financial Statements.
PINNACLE WEST CAPITAL CORPORATION HOLDING COMPANY
SCHEDULE I — CONDENSED FINANCIAL INFORMATION OF REGISTRANT
CONDENSED BALANCE SHEETS
(dollars in thousands)
 
 December 31,
 20242023
ASSETS  
Current assets  
Cash and cash equivalents$23 $9 
Accounts receivable163,203 163,829 
Income tax receivable6,673 1,832 
Assets held for sale- investment in subsidiaries— 35,139 
Other current assets434 28,379 
Total current assets170,333 229,188 
Investments and other assets  
Investments in subsidiaries8,435,150 7,369,159 
Deferred income taxes— 15,746 
Other assets21,966 22,839 
Total investments and other assets8,457,116 7,407,744 
TOTAL ASSETS$8,627,449 $7,636,932 
  
LIABILITIES AND EQUITY
Current liabilities  
Accounts payable$3,471 $8,176 
Accrued taxes4,799 4,543 
Common dividends payable106,592 99,813 
Short-term borrowings228,550 76,650 
Current maturities of long-term debt500,000 625,000 
Operating lease liabilities 138 127 
Other current liabilities11,389 11,400 
Total current liabilities854,939 825,709 
Long-term debt less current maturities867,770 498,731 
Deferred income taxes24,536 — 
Pension liabilities4,462 6,487 
Operating lease liabilities1,194 1,332 
Other17,070 19,811 
Total deferred credits and other47,262 27,630 
COMMITMENTS AND CONTINGENCIES
Common stock equity
Common stock3,118,294 2,744,491 
Accumulated other comprehensive loss(30,942)(33,144)
Retained earnings3,666,959 3,466,317 
Total Pinnacle West Shareholders’ equity6,754,311 6,177,664 
Noncontrolling interests103,167 107,198 
Total Equity6,857,478 6,284,862 
TOTAL LIABILITIES AND EQUITY$8,627,449 $7,636,932 
See Combined Notes to Consolidated Financial Statements.
PINNACLE WEST CAPITAL CORPORATION HOLDING COMPANY
SCHEDULE I — CONDENSED FINANCIAL INFORMATION OF REGISTRANT
CONDENSED STATEMENTS OF CASH FLOWS
(dollars in thousands)
 Year Ended December 31,
 202420232022
Cash flows from operating activities   
Net income$608,806 $501,557 $483,602 
Adjustments to reconcile net income to net cash provided by operating activities: 
Equity in earnings of subsidiaries — net(643,703)(539,962)(500,042)
Gain on sale relating to BCE(22,988)(6,423)— 
Depreciation and amortization75 76 76 
Deferred income taxes40,231 (13,955)17,256 
Accounts receivable15,268 (28,273)(8,535)
Accounts payable(4,869)1,839 3,431 
Accrued taxes and income tax receivables — net(4,584)9,505 (25,157)
Dividends received from subsidiaries401,400 393,600 385,800 
Other22,959 (14,201)47,719 
Net cash flow provided by operating activities412,595 303,763 404,150 
Cash flows from investing activities   
Proceeds from sale relating to BCE84,322 23,400 — 
Investments in subsidiaries(827,752)(119,682)(186,630)
Repayments of loans from subsidiaries and other1,132 6,526 14,308 
Advances of loans to subsidiaries(11,336)(59,349)(3,308)
Net cash flow used for investing activities(753,634)(149,105)(175,630)
Cash flows from financing activities   
Issuance of long-term debt867,387 175,000 300,000 
Short-term debt borrowings under revolving credit facility200,000 — — 
Short-term borrowings and (repayments) — net(48,100)60,930 2,420 
Dividends paid on common stock(394,663)(386,486)(378,881)
Repayment of long-term debt(625,000)— (150,000)
Common stock equity issuance and purchases — net341,429 (4,093)(2,653)
Net cash flow used for financing activities341,053 (154,649)(229,114)
Net increase (decrease) in cash and cash equivalents14 9 (594)
Cash and cash equivalents at beginning of year9 — 594 
Cash and cash equivalents at end of year$23 $9 $— 
     
See Combined Notes to Consolidated Financial Statements.
PINNACLE WEST CAPITAL CORPORATION HOLDING COMPANY
NOTES TO FINANCIAL STATEMENTS OF HOLDING COMPANY

The Combined Notes to Consolidated Financial Statements in Part II, Item 8 should be read in conjunction with the Pinnacle West Capital Corporation Holding Company Financial Statements.
The Pinnacle West Capital Corporation Holding Company Financial Statements have been prepared to present the financial position, results of operations and cash flows of Pinnacle West on a stand-alone basis as a holding company. Investments in subsidiaries are accounted for using the equity method.
v3.25.0.1
Insider Trading Arrangements
 3 Months Ended
Dec. 31, 2024
Trading Arrangements, by Individual  
Rule 10b5-1 Arrangement Adopted false
Non-Rule 10b5-1 Arrangement Adopted false
Rule 10b5-1 Arrangement Terminated false
Non-Rule 10b5-1 Arrangement Terminated false
v3.25.0.1
Insider Trading Policies and Procedures
 12 Months Ended
Dec. 31, 2024
Insider Trading Policies and Procedures [Line Items]  
Insider Trading Policies and Procedures Adopted true
v3.25.0.1
Cybersecurity Risk Management and Strategy Disclosure
 12 Months Ended
Dec. 31, 2024
Cybersecurity Risk Management, Strategy, and Governance [Line Items]  
Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block]
In fulfilling its responsibility, the Cybersecurity Group manages formal documented internal processes such as risk management and vulnerability scanning, as well as other processes, such as assessing threat intelligence, that include outside partners. Intelligence sharing comes from industry sources such as the Electricity Information Sharing and Analysis Center, government sources, as well as commercially purchased information sources. The Cybersecurity Group also engages third parties for assessments and audits of its systems periodically and as needed. Such assessments and audits may include, among other things, pre-production evaluation of technologies, overall program assessments, and compliance program assessments including audits by our regulators.

Depending on the products and services provided and the potential for data exchange and technology risk, we may require vendors and service providers to pass APS’s vendor risk management program, which sets forth security and data protection requirements, as a condition to doing or continuing to do business with us. For contracts with vendors that will handle or have access to certain sensitive data, APS requires contractual provisions setting forth cybersecurity controls, vulnerability management, secure development practices, and other security and data protection requirements. A subset of vendors that meet a predetermined risk profile due to strategic relationships, technology risk, or other factors is continually monitored by a third-party risk management service, and the Company annually reviews independent assessments of these vendors.

The Cybersecurity Group also has documented processes for identifying, responding to, and internally escalating cybersecurity incidents to management and the Board of Directors. Once an incident meets certain criteria, the Company’s Cybersecurity Incident Command or, in the most severe cases that
impact the entire Company, the Corporate Emergency Operations Center is activated and formal response procedures are followed to address the incident. The Cybersecurity Group has a formal incident response plan that details response and escalation procedures, including activation of a Cybersecurity Disclosure Committee, consisting of the Chief Financial Officer and the General Counsel, to assess an incident’s materiality with input as needed from the Director of Cybersecurity, Chief Accounting Officer, Chief Information Officer, and others, including outside advisors.

Cybersecurity risk management has been integrated into the Company’s overall enterprise risk management program (the “Enterprise Risk Management Program”) through policies and processes that implement a risk management framework designed to identify, manage, and monitor business unit risks throughout the organization. The Enterprise Risk Management Program is overseen by an executive committee (the “Executive Risk Committee”), which meets at least quarterly and is comprised of members holding executive leadership positions in the Company, including the Chairman and Chief Executive Officer, President, and other Executive and Senior Vice Presidents, and is chaired and sponsored by the Chief Financial Officer. Every year, as a part of the Enterprise Risk Management Program, risks affecting the Company are identified. For 2024, cybersecurity was identified as a risk. The applicable subject matter experts brief the Company’s Board of Directors on the status of all top enterprise risks at least once per year. Finally, the Nuclear and Operating Committee of the Company’s Board of Directors provides ultimate oversight of cybersecurity risk and also receives briefings at least twice per year from the Cybersecurity Group, and notable audit findings relating to cybersecurity are aggregated and provided to the Board of Directors’ Audit Committee.

To date, we do not believe there have been risks from cybersecurity threats, including as a result of any previous cybersecurity incidents, that have materially affected or are reasonably likely to materially affect Pinnacle West or APS. However, there is no assurance that will continue to be the case. If a significant cybersecurity event or incident were to occur, our ability to fulfill our critical business functions and our business strategy, results of operations, and financial condition could all be materially impacted. See the risk factor entitled, “We are subject to cybersecurity risks and risks of unauthorized access to our systems that could adversely affect our business and financial condition” in Item 1A—Risk Factors for more information.
Cybersecurity Risk Management Processes Integrated [Flag] true
Cybersecurity Risk Management Processes Integrated [Text Block] Cybersecurity risk management has been integrated into the Company’s overall enterprise risk management program (the “Enterprise Risk Management Program”) through policies and processes that implement a risk management framework designed to identify, manage, and monitor business unit risks throughout the organization.
Cybersecurity Risk Management Third Party Engaged [Flag] true
Cybersecurity Risk Third Party Oversight and Identification Processes [Flag] true
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag] false
Cybersecurity Risk Board of Directors Oversight [Text Block]
Cybersecurity risk management has been integrated into the Company’s overall enterprise risk management program (the “Enterprise Risk Management Program”) through policies and processes that implement a risk management framework designed to identify, manage, and monitor business unit risks throughout the organization. The Enterprise Risk Management Program is overseen by an executive committee (the “Executive Risk Committee”), which meets at least quarterly and is comprised of members holding executive leadership positions in the Company, including the Chairman and Chief Executive Officer, President, and other Executive and Senior Vice Presidents, and is chaired and sponsored by the Chief Financial Officer. Every year, as a part of the Enterprise Risk Management Program, risks affecting the Company are identified. For 2024, cybersecurity was identified as a risk. The applicable subject matter experts brief the Company’s Board of Directors on the status of all top enterprise risks at least once per year. Finally, the Nuclear and Operating Committee of the Company’s Board of Directors provides ultimate oversight of cybersecurity risk and also receives briefings at least twice per year from the Cybersecurity Group, and notable audit findings relating to cybersecurity are aggregated and provided to the Board of Directors’ Audit Committee.
Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block] The Enterprise Risk Management Program is overseen by an executive committee (the “Executive Risk Committee”), which meets at least quarterly and is comprised of members holding executive leadership positions in the Company, including the Chairman and Chief Executive Officer, President, and other Executive and Senior Vice Presidents, and is chaired and sponsored by the Chief Financial Officer. Every year, as a part of the Enterprise Risk Management Program, risks affecting the Company are identified. For 2024, cybersecurity was identified as a risk. The applicable subject matter experts brief the Company’s Board of Directors on the status of all top enterprise risks at least once per year. Finally, the Nuclear and Operating Committee of the Company’s Board of Directors provides ultimate oversight of cybersecurity risk and also receives briefings at least twice per year from the Cybersecurity Group, and notable audit findings relating to cybersecurity are aggregated and provided to the Board of Directors’ Audit Committee.
Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block] Every year, as a part of the Enterprise Risk Management Program, risks affecting the Company are identified. For 2024, cybersecurity was identified as a risk. The applicable subject matter experts brief the Company’s Board of Directors on the status of all top enterprise risks at least once per year. Finally, the Nuclear and Operating Committee of the Company’s Board of Directors provides ultimate oversight of cybersecurity risk and also receives briefings at least twice per year from the Cybersecurity Group, and notable audit findings relating to cybersecurity are aggregated and provided to the Board of Directors’ Audit Committee.
Cybersecurity Risk Role of Management [Text Block] To that end, the Company implements a robust risk management, strategy, and governance regime aimed at ensuring effective controls are in place to identify, mitigate, remediate, and communicate cyber threats at appropriate levels within the organization.
APS’s cybersecurity group (the “Cybersecurity Group”) is comprised of cybersecurity analysts, engineers, architects, and others, led by the Director of Cybersecurity, who reports to APS’s Vice President, Operations Support. The Director of Cybersecurity has more than twenty years of experience in information technology and cybersecurity roles, with more than ten of those years at the Company. The Director of Cybersecurity also holds cybersecurity certifications from multiple certifying bodies and is active in utility cybersecurity professional organizations. The Cybersecurity Group has day-to-day responsibility for safeguarding the Company’s critical assets and assessing, identifying, and managing material risks from cybersecurity threats.

In fulfilling its responsibility, the Cybersecurity Group manages formal documented internal processes such as risk management and vulnerability scanning, as well as other processes, such as assessing threat intelligence, that include outside partners. Intelligence sharing comes from industry sources such as the Electricity Information Sharing and Analysis Center, government sources, as well as commercially purchased information sources. The Cybersecurity Group also engages third parties for assessments and audits of its systems periodically and as needed. Such assessments and audits may include, among other things, pre-production evaluation of technologies, overall program assessments, and compliance program assessments including audits by our regulators.

Depending on the products and services provided and the potential for data exchange and technology risk, we may require vendors and service providers to pass APS’s vendor risk management program, which sets forth security and data protection requirements, as a condition to doing or continuing to do business with us. For contracts with vendors that will handle or have access to certain sensitive data, APS requires contractual provisions setting forth cybersecurity controls, vulnerability management, secure development practices, and other security and data protection requirements. A subset of vendors that meet a predetermined risk profile due to strategic relationships, technology risk, or other factors is continually monitored by a third-party risk management service, and the Company annually reviews independent assessments of these vendors.

The Cybersecurity Group also has documented processes for identifying, responding to, and internally escalating cybersecurity incidents to management and the Board of Directors. Once an incident meets certain criteria, the Company’s Cybersecurity Incident Command or, in the most severe cases that
impact the entire Company, the Corporate Emergency Operations Center is activated and formal response procedures are followed to address the incident. The Cybersecurity Group has a formal incident response plan that details response and escalation procedures, including activation of a Cybersecurity Disclosure Committee, consisting of the Chief Financial Officer and the General Counsel, to assess an incident’s materiality with input as needed from the Director of Cybersecurity, Chief Accounting Officer, Chief Information Officer, and others, including outside advisors.
Cybersecurity Risk Management Positions or Committees Responsible [Flag] true
Cybersecurity Risk Management Positions or Committees Responsible [Text Block] APS’s cybersecurity group (the “Cybersecurity Group”) is comprised of cybersecurity analysts, engineers, architects, and others, led by the Director of Cybersecurity, who reports to APS’s Vice President, Operations Support. The Director of Cybersecurity has more than twenty years of experience in information technology and cybersecurity roles, with more than ten of those years at the Company.
Cybersecurity Risk Management Expertise of Management Responsible [Text Block] The Director of Cybersecurity has more than twenty years of experience in information technology and cybersecurity roles, with more than ten of those years at the Company. The Director of Cybersecurity also holds cybersecurity certifications from multiple certifying bodies and is active in utility cybersecurity professional organizations.
Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block]
The Cybersecurity Group also has documented processes for identifying, responding to, and internally escalating cybersecurity incidents to management and the Board of Directors. Once an incident meets certain criteria, the Company’s Cybersecurity Incident Command or, in the most severe cases that
impact the entire Company, the Corporate Emergency Operations Center is activated and formal response procedures are followed to address the incident. The Cybersecurity Group has a formal incident response plan that details response and escalation procedures, including activation of a Cybersecurity Disclosure Committee, consisting of the Chief Financial Officer and the General Counsel, to assess an incident’s materiality with input as needed from the Director of Cybersecurity, Chief Accounting Officer, Chief Information Officer, and others, including outside advisors.
Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag] true
v3.25.0.1
Summary of Significant Accounting Policies (Policies)
 12 Months Ended
Dec. 31, 2024
Accounting Policies [Abstract]  
Description of Business and Basis of Presentation
Description of Business and Basis of Presentation
 
Pinnacle West is a holding company that conducts business through its subsidiaries, APS, El Dorado and PNW Power. APS, our wholly-owned subsidiary, is a vertically-integrated electric utility that provides either retail or wholesale electric service to substantially all of the state of Arizona, with the major exceptions of about one-half of the Phoenix metropolitan area, the Tucson metropolitan area and Mohave County in northwestern Arizona.  APS accounts for essentially all of our revenues and earnings and is expected to continue to do so.  El Dorado is a wholly-owned subsidiary that invests in energy-related and Arizona community-based ventures. PNW Power is a wholly-owned subsidiary that was created in September 2023 to hold certain investments in wind and transmission joint projects. See Note 20 for more information on PNW Power.
 
BCE was a Pinnacle West subsidiary that was formed in 2014. On August 4, 2023, Pinnacle West entered into a purchase and sale agreement pursuant to which all of our equity interest in BCE was sold. The sale was completed on January 12, 2024. See Note 20 for more information relating to the sale of BCE.

Pinnacle West’s Consolidated Financial Statements include the accounts of Pinnacle West and our subsidiaries, including APS, El Dorado, and PNW Power, as well as our former subsidiary BCE until its sale. Pinnacle West’s Consolidated Financial Statements also include the accounts of a VIE relating to a Captive Insurance Cell (“Captive”). APS’s Consolidated Financial Statements include the accounts of APS and certain VIEs relating to the Palo Verde sale leaseback.  Intercompany accounts and transactions between the consolidated companies have been eliminated.
 
We consolidate Variable Interest Entities (each a “VIE”) for which we are the primary beneficiary.  We determine whether we are the primary beneficiary of a VIE through a qualitative analysis that identifies which variable interest holder has the controlling financial interest in the VIE.  In performing our primary beneficiary analysis, we consider all relevant facts and circumstances, including the design and activities of the VIE, the terms of the contracts the VIE has entered into, and which parties participated significantly in the design or redesign of the entity.  We continually evaluate our primary beneficiary conclusions to determine if changes have occurred which would impact our primary beneficiary assessments.  We have determined that APS is the primary beneficiary of certain VIE lessor trusts relating to the Palo Verde sale leaseback, and therefore APS consolidates these entities. We have also determined that Pinnacle West is the primary beneficiary of a protected captive insurance cell VIE, and therefore Pinnacle West consolidates this insurance cell. See Note 17 for additional information.
Accounting Records and Use of Estimates
Accounting Records and Use of Estimates
 
Our accounting records are maintained in accordance with accounting principles generally accepted in the United States of America (“GAAP”).  The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period.  Actual results could differ from those estimates.
Regulatory Accounting
Regulatory Accounting
 
APS is regulated by the ACC and FERC.  The accompanying financial statements reflect the rate-making policies of these commissions.  As a result, we capitalize certain costs that would be included as expense in the current period by unregulated companies.  Regulatory assets represent incurred costs that have been deferred because they are probable of future recovery in customer rates. Regulatory liabilities generally represent amounts collected in rates to recover costs expected to be incurred in the future or amounts collected in excess of costs incurred and are refundable to customers.
 
Management judgments include continually assessing the likelihood of future recovery of regulatory assets and/or a disallowance of part of the cost of recently completed plant, by considering factors such as applicable regulatory environment changes and recent rate orders to other regulated entities in the same jurisdiction.  This determination reflects the current political and regulatory climate in Arizona and is subject to change in the future.  If future recovery of costs ceases to be probable, the assets would be written off as a charge in current period earnings. Management judgments also include assessing the impact of potential commission-ordered refunds to customers on regulatory liabilities.
Electric Revenues
Electric Revenues
 
Revenues primarily consist of activities that are classified as revenues from contracts with customers. Our electric revenues generally represent a single performance obligation delivered over time. We have elected to apply the practical expedient that allows us to recognize revenue based on the amount to which we have a right to invoice for services performed.

We derive electric revenues primarily from sales of electricity to our regulated retail customers. Revenues related to the sale of electricity are generally recognized when service is rendered or electricity is delivered to customers. Unbilled revenues are estimated by applying an average revenue/kWh by customer class to the number of estimated kWhs delivered but not billed. Differences historically between the actual and estimated unbilled revenues are immaterial. We exclude sales taxes and franchise fees on electric revenues from both revenue and taxes other than income taxes.
 
Revenues from our regulated retail customers and non-derivative instruments are reported on a gross basis on Pinnacle West’s Consolidated Statements of Income. In the electricity business, some contracts to purchase electricity are netted against other contracts to sell electricity. This is called a “book-out” and usually occurs for contracts that have the same terms (quantities, delivery points and delivery periods) and for which power does not flow. We net these book-outs, which reduces both wholesale revenues and fuel and purchased power costs.

Certain cost recovery mechanisms may qualify as alternative revenue programs. For alternative revenue programs that meet specified accounting criteria, we recognize revenues when the specific events permitting billing of the additional revenues have been completed.
Allowance for Doubtful Accounts
Allowance for Doubtful Accounts
 
The allowance for doubtful accounts represents our best estimate of accounts receivable and accrued unbilled revenues that will ultimately be uncollectible due to credit loss risk. The allowance includes a write-off component that is calculated by applying an estimated write-off factor to retail electric revenues. The write-off factor used to estimate uncollectible accounts is based upon consideration of historical collections experience, the current and forecasted economic environment, changes to our collection policies, and management’s best estimate of future collections success.

See Note 2 for additional information.
Property, Plant and Equipment
Property, Plant and Equipment
 
Utility plant is the term we use to describe the business property and equipment that supports electric service, consisting primarily of generation, transmission, and distribution facilities.  We report utility plant at its original cost, which includes:

•material and labor;
•contractor costs;
•capitalized leases;
•construction overhead costs (where applicable); and
•AFUDC.
Property, plant and equipment balances and classes for APS are not materially different than Pinnacle West.

We expense the costs of plant outages, major maintenance and routine maintenance as incurred.  We charge retired utility plant to accumulated depreciation.  Liabilities associated with the retirement of tangible long-lived assets are recognized at fair value as incurred and capitalized as part of the related tangible long-lived assets.  Accretion of the liability due to the passage of time is an operating expense, and
the capitalized cost is depreciated over the useful life of the long-lived asset.  See Note 11 for additional information.

APS records a regulatory liability for the excess that has been recovered in regulated rates over the amount calculated in accordance with guidance on accounting for AROs.  APS believes it is probable it will recover in regulated rates, the costs calculated in accordance with this accounting guidance.
 
We record depreciation and amortization on utility plant on a straight-line basis over the remaining useful life of the related assets.  The approximate remaining average useful lives of our utility property at December 31, 2024, were as follows:

•Steam generation — 11 years;
•Nuclear plant — 25 years;
•Other generation — 18 years;
•Transmission — 38 years;
•Distribution — 33 years; and
•General plant — 7 years.
 
Depreciation of utility property, plant and equipment is computed on a straight-line, remaining-life basis.
Asset Retirement Obligations
Asset Retirement Obligations

APS has AROs for its Palo Verde nuclear facilities and certain other generation assets.  The Palo Verde ARO primarily relates to final plant decommissioning.  This obligation is based on the NRC’s requirements for disposal of irradiated property or plant and agreements APS reached with the ACC for final decommissioning of the plant.  The non-nuclear generation AROs primarily relate to requirements for removing portions of those plants at the end of the plant life or lease term and coal ash pond closures. Some of APS’s transmission and distribution assets have AROs because they are subject to right of way and easement agreements that require final removal.  These agreements have a history of uninterrupted renewal that APS expects to continue.  As a result, APS cannot reasonably estimate the fair value of the ARO related to such transmission and distribution assets. Additionally, APS has aquifer protection permits for some of its generation sites that require the closure of certain facilities at those sites.
Allowance for Funds Used During Construction
Allowance for Funds Used During Construction
 
AFUDC represents the approximate net composite interest cost of borrowed funds and an allowed return on the equity funds used for construction of regulated utility plant.  Both the debt and equity components of AFUDC are non-cash amounts within the Consolidated Statements of Income.  Plant construction costs, including AFUDC, are recovered in authorized rates through depreciation when completed projects are placed into commercial operation.
 
AFUDC was calculated by using a composite rate of 6.23% for 2024, 6.29% for 2023, and 5.75% for 2022.  APS compounds AFUDC semi-annually and ceases to accrue AFUDC when construction work is completed and the property is placed in service.

On June 30, 2020, FERC issued an order granting a waiver request related to the existing AFUDC rate calculation beginning March 1, 2020, through February 28, 2021.  On February 23, 2021, this waiver was extended until September 30, 2021. On September 21, 2021, it was further extended until March 31, 2022. The order provided a simplified approach that companies may elect to implement in order to minimize the significant distorted effect on the AFUDC formula resulting from increased short-term debt financing during the COVID-19 pandemic.  APS adopted this simplified approach to computing the AFUDC composite rate by using a simple average of the actual historical short-term debt balances for 2019, instead of current period short-term debt balances, and left all other aspects of the AFUDC formula composite rate calculation unchanged. This change impacted the AFUDC composite rate in 2021 and for the three-month period ended March 31, 2022.  Furthermore, the change in the composite rate calculation did not impact our accounting treatment for these costs. The change did not have a material impact on our financial statements.
Materials and Supplies
Materials and Supplies
 
APS values materials, supplies and fossil fuel inventory using a weighted-average cost method.  APS materials, supplies and fossil fuel inventories are carried at the lower of weighted-average cost or net realizable value, unless evidence indicates that the weighted-average cost (even if in excess of market) will be recovered.
Fair Value Measurements
Fair Value Measurements
 
We apply recurring fair value measurements to cash equivalents, derivative instruments, investments held in the nuclear decommissioning trust and other special use funds. On an annual basis, we apply fair value measurements to plan assets held in our retirement and other benefits plans. Due to the short-term nature of short-term borrowings, the carrying values of these instruments approximate fair value.  Fair value measurements may also be applied on a nonrecurring basis to other assets and liabilities in certain circumstances such as impairments.  We also disclose fair value information for our long-term debt, which is carried at amortized cost. See Note 6 for additional information.
 
Fair value is the price that would be received for an asset or paid to transfer a liability (exit price) in the principal or most advantageous market which we can access for the asset or liability in an orderly transaction between willing market participants on the measurement date.  Inputs to fair value may include observable and unobservable data.  We maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value.
 
We determine fair market value using observable inputs such as actively-quoted prices for identical instruments when available.  When actively-quoted prices are not available for the identical instruments, we use other observable inputs, such as prices for similar instruments, other corroborative market information, or prices provided by other external sources.  For options, long-term contracts, and other contracts for which observable price data are not available, we use models and other valuation methods, which may incorporate unobservable inputs to determine fair market value.
The use of models and other valuation methods to determine fair market value often requires subjective and complex judgment.  Actual results could differ from the results estimated through application of these methods.
Derivative Accounting
Derivative Accounting
 
We are exposed to the impact of market fluctuations in the commodity price and transportation costs of electricity, natural gas, coal and in interest rates.  We manage risks associated with market volatility by utilizing various physical and financial instruments including futures, forwards, options, and swaps.  As part of our overall risk management program, we may use derivative instruments to hedge purchases and sales of electricity and natural gas as well as interest rate risk.  The changes in market value of such contracts have a high correlation to price changes in the hedged transactions.  We also enter into derivative instruments for economic hedging purposes.  Contracts that have the same terms (quantities, delivery points and delivery periods) and for which power does not flow are netted, which reduces both revenues and fuel and purchased power expenses in our Consolidated Statements of Income, but does not impact our financial condition, net income, or cash flows.
 
We account for our derivative contracts in accordance with derivatives and hedging guidance, which requires all derivatives not qualifying for a scope exception to be measured at fair value on the balance sheet as either assets or liabilities.  Transactions with counterparties that have master netting arrangements are reported net on the balance sheet.
Loss Contingencies and Environmental Liabilities
Loss Contingencies and Environmental Liabilities
 
Pinnacle West and APS are involved in certain legal and environmental matters that arise in the normal course of business.  Contingent losses and environmental liabilities are recorded when it is determined that it is probable that a loss has occurred, and the amount of the loss can be reasonably estimated.  When a range of the probable loss exists and no amount within the range is a better estimate than any other amount, Pinnacle West and APS record a loss contingency at the minimum amount in the range.  Unless otherwise required by GAAP, legal fees are expensed as incurred.
 
The Captive’s contingent losses may include an amount for losses incurred but not reported (“IBNR”). A reserve for IBNR is based upon a loss analysis prepared using actuarial assumptions and techniques. Such liabilities are necessarily based on estimates and the ultimate liability may be in excess of or less than the amount provided. The methods for making such estimates and for establishing the resulting liability are continually reviewed, and any adjustments for the review process as well as differences between estimates and ultimate payments are reflected in earnings currently.
Retirement Plans and Other Postretirement Benefits
Retirement Plans and Other Postretirement Benefits
 
Pinnacle West sponsors a qualified defined benefit and account balance pension plan for the employees of Pinnacle West and its subsidiaries, in addition to a non-qualified pension plan.  We also sponsor another postretirement benefit plan for the employees of Pinnacle West and its subsidiaries that provides medical and life insurance benefits to retired employees.  Pension and other postretirement benefit expense are determined by actuarial valuations, based on assumptions that are evaluated annually.
Nuclear Fuel
Nuclear Fuel
 
APS amortizes nuclear fuel by using the unit-of-production method.  The unit-of-production method is based on actual physical usage.  APS divides the cost of the fuel by the estimated number of thermal units it expects to produce with that fuel.  APS then multiplies that rate by the number of thermal units produced within the current period.  This calculation determines the current period nuclear fuel expense.
 
APS also charges nuclear fuel expense for the interim storage and permanent disposal of spent nuclear fuel.  The DOE is responsible for the permanent disposal of spent nuclear fuel and charged APS $0.001 per kWh of nuclear generation through May 2014, at which point the DOE reduced the fee to zero.  In accordance with a settlement agreement with the DOE in August 2014 for interim storage, we accrued a receivable and an offsetting regulatory liability through the settlement period ended December of 2024.
Income Taxes
Income Taxes
 
Income taxes are provided using the asset and liability approach prescribed by guidance relating to accounting for income taxes and are based on currently enacted tax rates.  We file our federal income tax return on a consolidated basis, and we file our state income tax returns on a consolidated or unitary basis.  In accordance with our intercompany tax sharing agreement, federal and state income taxes are allocated to each first-tier subsidiary as though each first-tier subsidiary filed a separate income tax return.  Any difference between that method and the consolidated (and unitary) income tax liability is attributed to the parent company.  The income tax accounts reflect the tax and interest associated with management’s estimate of the largest amount of tax benefit that is greater than 50% likely of being realized upon settlement for all known and measurable tax exposures.
Cash and Cash Equivalents
Cash and Cash Equivalents
     We consider cash equivalents to be highly liquid investments with a remaining maturity of three months or less at acquisition.
Intangible Assets
Intangible Assets
 
We have separately disclosed intangible assets on Pinnacle West’s Consolidated Balance Sheets. The intangible assets relate primarily to APS’s internal-use software. We have no goodwill recorded. The intangible assets are amortized over their finite useful lives.
Investments
Investments
 
El Dorado holds investments in both debt and equity securities.  Investments in debt securities are generally accounted for as held-to-maturity and investments in equity securities are accounted for using either the equity method (if significant influence) or the measurement alternative for investments without readily determinable fair values (if less than 20% ownership and no significant influence).
PNW Power holds investments in equity securities. Investments in equity securities are accounted for using either the equity method (if significant influence) or the measurement alternative for investments without readily determinable fair values (if less than 20% ownership and no significant influence).
 
Our investments in the nuclear decommissioning trusts, and other special use funds, are accounted for in accordance with guidance on accounting for investments in debt and equity securities. See Notes 12 and 18 for more information on these investments.
Leases
Leases

We determine if an agreement is a lease at contract inception. A lease is defined as a contract, or part of a contract, that conveys the right to control the use of an identified asset for a period of time in exchange for consideration. To control the use of an identified asset an entity must have both a right to obtain substantially all of the benefits from the use of the asset and the right to direct the use of the asset. If we determine an agreement is a lease, and we are the lessee, we recognize a right-of-use lease asset and a lease liability at the lease commencement date. Lease liabilities are recognized based on the present value of the fixed lease payments over the lease term. To present value lease liabilities we use the implicit rate in the lease if the information is readily available, otherwise we use our incremental borrowing rate determined at lease commencement. Our incremental borrowing rate is based on the rate of interest we would have to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. When measuring right-of-use assets and lease liabilities we exclude variable lease payments, other than those that depend on an index or rate or are in-substance fixed payments. For short-term leases with terms of 12 months or less, we do not recognize a right-of-use lease asset or lease liability. We recognize operating lease expense using a straight-line pattern over the periods of use.

APS enters into purchased power contracts that may contain leases. This occurs when a purchased power agreement designates a specific power plant or facility, APS obtains substantially all of the economic benefits from the use of the facility and has the right to direct the use of the facility. Purchased power lease contracts may also include energy storage facilities. Lease costs relating to purchased power lease contracts are reported in fuel and purchased power on the Consolidated Statements of Income and are subject to recovery under the PSA or RES. See Note 3. We also may enter into lease agreements related to vehicles, office space, land, and other equipment. See Note 8 for information on our lease agreements.
Business Segments
Business Segments
 
Pinnacle West’s reportable business segment is our regulated electricity segment, which consists of traditional regulated retail and wholesale electricity businesses (primarily electric service to Native Load customers) and related activities and includes electricity generation, transmission, and distribution. Our reportable segment activities are conducted through our wholly-owned subsidiary, APS. All other operating segment activities are insignificant to Pinnacle West.
For segment reporting purposes, Pinnacle West’s Chief Executive Officer performs the function of chief operating decision maker (“CODM”). The CODM uses net income to measure an operating segment’s profitability. When assessing the performance of an operating segment, and making decisions about allocating resources, the CODM evaluates net income actual results compared to budget. Net income is also used when implementing strategic initiatives and selecting projects to meet business objectives. Our reportable segment’s revenue streams are dependent upon regulated rate recovery, which is a primary factor in how we identify operating segments.
For information on our reportable business segment’s revenues, significant expenses, net income, assets, and other reportable segment items, see the APS’s Consolidated Income Statements, APS Consolidated Balance Sheets, and APS Consolidated Statements of Cash Flows.
New Accounting Standards New Accounting Standards
 
ASU 2023-07, Segment Reporting: Improvements to Reportable Segment Disclosures

In November 2023, a new standard was issued that modifies segment reporting disclosure requirements. The disclosure changes include information about a reportable segment’s significant expenses, details relating to the entity’s chief operating decision maker, and other disclosures. We adopted this standard on December 31, 2024, using a retrospective approach. The adoption of the new standard results in changes to our reportable segment disclosures, but does not impact how we identify reportable segments or our financial statement results. See Note 1.

ASU 2023-09, Income Taxes: Improvements to Income Tax Disclosures

In December 2023, a new accounting standard was issued that expands disclosures relating to income taxes. The expanded disclosures include a tabular income tax rate reconciliation, disclosure of specific reconciliation categories and reconciling items, the amount of income taxes paid by jurisdiction, and other disclosures. We will adopt this standard on December 31, 2025, using a prospective approach. The adoption of the new standard will result in changes to our income tax disclosures, but will not impact our accounting for income taxes or our financial statement results.

ASU 2024-03, Income Statement: Expense Disaggregation Disclosures

In November 2024, a new accounting standard was issued that requires specific disclosures related to certain costs and expenses. Companies will be required to disclose the amounts of certain cost and expense categories, such as: purchases of inventory, employee compensation, depreciation, and amortization, among other disclosures. The new disclosures may be provided in the notes to the financial statements, and will not require changes to the face of the income statement. The standard is effective for us on December 31, 2027, using either a prospective or retrospective approach, with early adoption permitted. The adoption of the new standard will result in disclosure changes, but will not impact our accounting for such costs and expenses or our financial statement results.
v3.25.0.1
Summary of Significant Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2024
Accounting Policies [Abstract]  
Schedule of Property, Plant and Equipment
Pinnacle West’s property, plant and equipment included in the December 31, 2024, and 2023 Consolidated Balance Sheets is composed of the following (dollars in thousands):

Property, Plant and Equipment:20242023
Generation$11,111,915 $10,446,291 
Transmission4,135,970 3,773,253 
Distribution9,016,843 8,448,293 
General plant1,596,222 1,543,330 
Plant in service and held for future use25,860,950 24,211,167 
Accumulated depreciation and amortization(9,027,426)(8,408,040)
Net16,833,524 15,803,127 
Construction work in progress1,592,659 1,724,004 
Palo Verde sale leaseback, net of accumulated depreciation82,556 86,426 
Intangible assets, net of accumulated amortization591,310 267,110 
Nuclear fuel, net of accumulated amortization97,850 99,490 
Total property, plant and equipment$19,197,899 $17,980,157 
Schedule of Supplemental Cash Flow Information
The following table summarizes supplemental Pinnacle West cash flow information for each of the last three years (dollars in thousands):
Year Ended December 31,
202420232022
Cash paid during the period for:
Income taxes, net of refunds$133,968 $8,788 $46,227 
Interest, net of amounts capitalized360,349 310,996 245,271 
Significant non-cash investing and financing activities:
Accrued capital expenditures$257,494 $206,269 $114,999 
Dividends accrued but not yet paid106,592 99,813 97,895 
BCE Sale non-cash consideration (Note 20)
— 28,262 — 

The following table summarizes supplemental APS cash flow information for each of the last three years (dollars in thousands):
Year Ended December 31,
202420232022
Cash paid during the period for:
Income taxes, net of refunds$179,013 $21,734 $95,985 
Interest, net of amounts capitalized299,799 267,261 227,159 
Significant non-cash investing and financing activities:
Accrued capital expenditures$257,494 $206,269 $116,533 
Dividends accrued but not yet paid107,200 99,800 97,900 
Schedule Of Reportable Segment’s Revenues, Significant Expenses, Net Income, And Assets The following tables reconcile our reportable segment’s revenues, significant expenses, net income, and assets to the Pinnacle West Consolidated amounts (dollars in millions):
Year Ended December 31,
202420232022
Regulated Electricity SegmentOther Pinnacle West ConsolidatedRegulated Electricity SegmentOther Pinnacle West ConsolidatedRegulated Electricity SegmentOther Pinnacle West Consolidated
Operating Revenues$5,125 $— $5,125 $4,696 $— $4,696 $4,324 $— $4,324 
Fuel & Purchase Power (1,823)— (1,823)(1,793)— (1,793)(1,629)— (1,629)
Operations & Maintenance(1,159)(6)(1,165)(1,044)(15)(1,059)(974)(13)(987)
Depreciation & Amortization (895)— (895)(794)— (794)(753)— (753)
Taxes other than income taxes (227)— (227)(224)— (224)(220)— (220)
Pension and other postretirement non-service credits, net49 — 49 42 (1)41 99 (1)98 
Other income and expenses, net (a)28 22 50 60 — 60 22 (23)(1)
Interest expense and costs(312)(65)(377)(285)(46)(331)(236)(20)(256)
Income Taxes(127)16 (111)(94)17 (77)(91)16 (75)
Less: income related to noncontrolling interest(17)— (17)(17)— (17)(17)— (17)
Net Income (loss) $642 $(33)$609 $547 $(45)$502 $525 $(41)$484 
(a) See Note 16 for additional details regarding other income and other expenses. Other income includes allowance for equity funds used during construction, see the APS Consolidated Income Statements.

December 31, 2024December 31, 2023
Regulated Electricity SegmentOtherPNW ConsolidatedRegulated Electricity SegmentOtherPNW Consolidated
Total Assets$25,988 $115 $26,103 $24,516 $145 $24,661 
v3.25.0.1
Revenue (Tables)
 12 Months Ended
Dec. 31, 2024
Revenue from Contract with Customer [Abstract]  
Schedule of Disaggregation of revenue
The following table provides detail of Pinnacle West’s consolidated revenue disaggregated by revenue sources (dollars in thousands):
Year Ended December 31,
202420232022
Retail Electric Service
Residential$2,562,822 $2,289,196 $2,046,111 
Non-Residential2,334,925 2,048,416 1,767,616 
Wholesale Energy Sales96,857 208,985 383,126 
Transmission Services for Others119,038 138,631 116,628 
Other Sources11,273 10,763 10,904 
Total Operating Revenues$5,124,915 $4,695,991 $4,324,385 
Schedule of allowance for doubtful accounts
The following table provides a rollforward of Pinnacle West’s allowance for doubtful accounts (dollars in thousands):

Year Ended December 31,
202420232022
Balance at beginning of period$22,433 $23,778 $25,354 
Bad debt expense35,799 23,399 17,006 
Actual write-offs(33,383)(24,744)(18,582)
Balance at end of period$24,849 $22,433 $23,778 
v3.25.0.1
Regulatory Matters (Tables)
 12 Months Ended
Dec. 31, 2024
Regulated Operations [Abstract]  
Schedule of Changes in The Deferred Fuel and Purchased Power Regulatory Asset
The following table shows the changes in the deferred fuel and purchased power regulatory asset for 2024 and 2023 (dollars in thousands):
 Year Ended December 31,
 20242023
Balance at beginning of period$463,195 $460,561 
Deferred fuel and purchased power costs250,288 549,877 
Amounts charged to customers
(425,886)(547,243)
Balance at end of period$287,597 $463,195 
Schedule of Regulatory Assets
The detail of regulatory assets is as follows (dollars in thousands):
December 31,
Amortization Through20242023
Pension(a)$750,976 $696,476 
Deferred fuel and purchased power (b) (c)2025287,597 463,195 
Income taxes — AFUDC equity2054192,936 189,058 
Ocotillo deferral2034114,775 128,636 
SCR deferral (e)203883,123 89,477 
Lease incentives(g)70,541 46,615 
Retired power plant costs203368,380 83,536 
Deferred fuel and purchased power — mark-to-market (Note 15)
202742,275 120,214 
FERC Transmission true up202635,159 616 
Income taxes — investment tax credit basis adjustment205634,834 34,230 
Deferred compensation203633,108 33,972 
Deferred property taxes202723,918 32,488 
Palo Verde VIEs (Note 17)
204620,611 20,772 
Power supply adjustor - interest202511,525 19,416 
Active Union Medical Trust(f)9,673 12,747 
Mead-Phoenix transmission line contributions in aid of construction (“CIAC”)20508,384 8,716 
Navajo coal reclamation20267,905 10,883 
Loss on reacquired debt20386,682 7,965 
Tax expense adjustor mechanism (b)20314,534 5,190 
Four Corners cost deferral2024— 7,922 
OtherVarious3,522 3,912 
Total regulatory assets (d)$1,810,458 $2,016,036 
Less: current regulatory assets$420,969 $625,757 
Total non-current regulatory assets$1,389,489 $1,390,279 
(a)This asset represents the future recovery of pension benefit obligations and expense through retail rates.  If these costs are disallowed by the ACC, this regulatory asset would be charged to OCI and result in lower future revenues.  As a result of the 2019 Rate Case decision, the amount authorized for inclusion in rate base was determined using an averaging methodology, which resulted in a reduced return in retail rates. The 2022 Rate Case decision allows for the full return on the pension asset in rate base. See Note 7 for further discussion.
(b)See “Cost Recovery Mechanisms” discussion above.
(c)Subject to a carrying charge.
(d)There are no regulatory assets for which the ACC has allowed recovery of costs, but not allowed a return by exclusion from rate base. FERC rates are set using a formula rate as described in “Transmission Rates, Transmission Cost Adjustor and Other Transmission Matters.”
(e)See “Four Corners SCR Cost Recovery” discussion above.
(f)Collected in retail rates.
(g)Amortization periods vary based on specific terms of lease contract.
Schedule of Regulatory Liabilities
The detail of regulatory liabilities is as follows (dollars in thousands):
December 31,
Amortization Through20242023
Excess deferred income taxes - ACC — Tax Cuts and Jobs Act (a)2046$888,896 $930,344 
Excess deferred income taxes - FERC — Tax Cuts and Jobs Act (a)2058207,400 214,667 
Asset retirement obligations and removal costs(d)358,403 486,751 
Other postretirement benefits(c)238,113 226,726 
Four Corners coal reclamation203877,532 68,521 
Renewable energy standard (b)202568,523 60,667 
Income taxes — deferred investment tax credit205666,327 55,917 
Income taxes — change in rates205359,133 43,251 
Spent nuclear fuel202726,818 33,154 
Demand side management (b)202523,927 14,374 
Sundance maintenance203123,086 19,989 
TCA Balancing Account (b)202614,834 3,425 
Property tax deferral20274,785 10,850 
Tax expense adjustor mechanism (b)20324,343 4,835 
OtherVarious113 2,317 
Total regulatory liabilities$2,062,233 $2,175,788 
Less: current regulatory liabilities$206,955 $209,923 
Total non-current regulatory liabilities$1,855,278 $1,965,865 
(a)For purposes of presentation on the Statement of Cash Flows, amortization of the regulatory liabilities for excess deferred income taxes are reflected as “Deferred income taxes” under Cash Flows From Operating Activities.
(b)See “Cost Recovery Mechanisms” discussion above.
(c)See Note 7.
(d)In accordance with regulatory accounting, APS accrues removal costs for its regulated assets, even if there is no legal obligation for removal.
v3.25.0.1
Income Taxes (Tables)
 12 Months Ended
Dec. 31, 2024
Income Tax Disclosure [Abstract]  
Schedule of Unrecognized Tax Benefits Roll Forward
The following is a tabular reconciliation of the total amounts of unrecognized tax benefits, excluding interest and penalties, at the beginning and end of the year that are included in accrued taxes and unrecognized tax benefits (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 202420232022202420232022
Total unrecognized tax benefits, January 1$44,274 $43,097 $45,086 $44,274 $43,097 $45,086 
Additions for tax positions of the current year1,271 1,473 1,399 1,271 1,473 1,399 
Additions for tax positions of prior years2,031 419 2,069 2,031 419 2,069 
Reductions for tax positions of prior years for:      
Changes in judgment(2,043)661 (3,495)(2,043)661 (3,495)
Settlements with taxing authorities— — — — — — 
Lapses of applicable statute of limitations(1,184)(1,376)(1,962)(1,184)(1,376)(1,962)
Total unrecognized tax benefits, December 31$44,349 $44,274 $43,097 $44,349 $44,274 $43,097 
Schedule of Unrecognized Tax Benefits
Included in the balances of unrecognized tax benefits are the following tax positions that, if recognized, would decrease our effective tax rate (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 202420232022202420232022
Tax positions, that if recognized, would decrease our effective tax rate$27,899 $28,762 $28,246 $27,899 $28,762 $28,246 
The amount of interest expense or benefit recognized related to unrecognized tax benefits are as follows (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 202420232022202420232022
Unrecognized tax benefit interest expense/(benefit) recognized
$2,743 $452 $(139)$2,743 $452 $(139)

Following are the total amounts of accrued liabilities for interest recognized related to unrecognized benefits that could reverse and decrease our effective tax rate to the extent matters are settled favorably (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 202420232022202420232022
Unrecognized tax benefit interest accrued $4,376 $1,633 $1,181 $4,376 $1,633 $1,181 
Schedule of Components of Income Tax Expense
The components of income tax expense are as follows (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 Year Ended December 31,Year Ended December 31,
 202420232022202420232022
Current:   
Federal$137,342 $21,272 $35,617 $165,653 $26,405 $103,349 
State2,392 2,854 1,950 26,054 1,027 161 
Total current139,734 24,126 37,567 191,707 27,432 103,510 
Deferred:      
Federal(53,228)37,273 23,693 (69,075)44,922 (31,860)
State24,023 15,513 13,567 4,361 21,830 19,150 
Total deferred(29,205)52,786 37,260 (64,714)66,752 (12,710)
Income tax expense/(benefit)$110,529 $76,912 $74,827 $126,993 $94,184 $90,800 
Schedule of Comparison of Pretax Income from Federal Income Tax Rate to Income Tax Expense
The following chart compares pretax income at the 21% statutory federal income tax rate to income tax expense (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 Year Ended December 31,Year Ended December 31,
 202420232022202420232022
Federal income tax expense at statutory rate$154,677 $125,095 $120,887 $165,090 $138,337 $132,920 
Increases (reductions) in tax expense resulting from:      
State income tax net of federal income tax benefit24,218 18,024 17,740 25,639 19,832 19,000 
State income tax credits net of federal income tax benefit(3,349)(3,513)(5,482)(1,611)(1,775)(3,744)
Excess deferred income taxes — Tax Cuts and Jobs Act(36,559)(36,558)(36,241)(36,559)(36,558)(36,241)
Allowance for equity funds used during construction (Note 1)
(2,545)(5,964)(4,629)(2,545)(5,964)(4,629)
Palo Verde VIE noncontrolling interest (Note 17)
(3,617)(3,617)(3,617)(3,617)(3,617)(3,617)
Investment tax credit amortization(9,425)(9,495)(5,608)(9,425)(9,495)(5,608)
   Federal production tax credit(15,206)(8,441)(3,146)(12,110)(5,460)— 
   Other federal income tax credits(3,881)(3,453)(7,721)(1,551)(2,803)(7,721)
Other6,216 4,834 2,644 3,682 1,687 440 
Income tax expense/(benefit)$110,529 $76,912 $74,827 $126,993 $94,184 $90,800 
Schedule of Components of the Net Deferred Income Tax Liability The components of the net deferred income tax liability were as follows (dollars in thousands):
Pinnacle West ConsolidatedAPS Consolidated
 December 31,December 31,
 2024202320242023
DEFERRED TAX ASSETS  
Risk management activities$14,539 $31,411 $14,539 $31,411 
Regulatory liabilities:   
Excess deferred income taxes — Tax Cuts and Jobs Act271,004 283,161 271,004 283,161 
Asset retirement obligation and removal costs81,308 113,312 81,308 113,312 
Unamortized investment tax credits66,327 68,521 66,327 68,521 
Other postretirement benefits58,862 56,070 58,862 56,070 
Other47,671 39,857 47,671 39,857 
Operating lease liabilities400,771 316,067 400,442 315,670 
Pension liabilities39,070 33,294 36,100 29,918 
Coal reclamation liabilities42,391 45,505 42,391 45,505 
Renewable energy incentives14,571 17,261 14,571 17,261 
Credit and loss carryforwards7,682 43,940 — 3,031 
Employee benefit liabilities57,853 49,222 56,561 48,551 
Other44,412 28,643 44,412 29,314 
Total deferred tax assets1,146,461 1,126,264 1,134,188 1,081,582 
DEFERRED TAX LIABILITIES   
Plant-related(2,562,990)(2,572,495)(2,562,990)(2,572,495)
Risk management activities(4,089)(1,682)(4,089)(1,682)
Pension and other postretirement assets(83,401)(78,853)(82,925)(78,297)
Other special use funds(55,146)(56,550)(55,146)(56,550)
Operating lease right-of-use assets(400,771)(316,067)(400,443)(315,670)
Regulatory assets:   
Allowance for equity funds used during construction(47,694)(46,754)(47,694)(46,754)
Deferred fuel and purchased power(84,393)(149,078)(84,393)(149,078)
Pension benefits(185,641)(172,239)(185,641)(172,239)
Ocotillo deferral(28,372)(31,812)(28,372)(31,812)
SCR deferral(20,548)(22,128)(20,548)(22,128)
Retired power plant costs (16,904)(20,659)(16,904)(20,659)
Other(57,602)(38,320)(57,602)(38,320)
Other(43,383)(36,107)(7,378)(7,595)
Total deferred tax liabilities(3,590,934)(3,542,744)(3,554,125)(3,513,279)
Deferred income taxes — net$(2,444,473)$(2,416,480)$(2,419,937)$(2,431,697)
v3.25.0.1
Lines of Credit and Short-Term Borrowings (Tables)
 12 Months Ended
Dec. 31, 2024
Debt Disclosure [Abstract]  
Schedule of Consolidated Credit Facilities and Amounts Available and Outstanding
The table below presents the consolidated credit and term loan facilities and the amounts available and outstanding (dollars in thousands): 
December 31, 2024December 31, 2023
Pinnacle WestAPSTotalPinnacle WestAPSTotal
Commitments under Credit and Term Loan Facilities$400,000 $1,650,000 $2,050,000 $200,000 $1,250,000 $1,450,000 
Outstanding short-term borrowings(228,550)(339,900)(568,450)(76,650)(532,850)(609,500)
Amount of Credit and Term Loan Facilities Available$171,450 $1,310,100 $1,481,550 $123,350 $717,150 $840,500 
Weighted-Average Commitment Fees0.225%0.175%0.170%0.120%
v3.25.0.1
Long-Term Debt and Liquidity Matters (Tables)
 12 Months Ended
Dec. 31, 2024
Debt Disclosure [Abstract]  
Schedule of Components of Long-Term Debt on the Consolidated Balance Sheets The following table presents the components of long-term debt on the Consolidated Balance Sheets outstanding (dollars in thousands):
 MaturityInterestDecember 31,
 Dates (a)Rates20242023
APS    
Pollution control bonds:    
Variable2029(b)$163,975 $163,975 
Total pollution control bonds  163,975 163,975 
Senior unsecured notes2025-2050
2.20%-6.88%
7,380,000 7,180,000 
Unamortized discount  (14,252)(14,197)
Unamortized premium  9,955 11,162 
Unamortized debt issuance cost(48,800)(49,049)
Total APS long-term debt  7,490,878 7,291,891 
Less current maturities 300,000 250,000 
Total APS long-term debt less current maturities  7,190,878 7,041,891 
Pinnacle West    
Senior unsecured notes2025-2027
1.30%-4.75%
1,025,000 500,000 
Floating rate note2026(c)350,000 — 
Term loans2024(d)— 625,000 
Unamortized discount(5)(15)
Unamortized debt issuance cost(7,225)(1,254)
Total Pinnacle West long-term debt1,367,770 1,123,731 
Less current maturities500,000 625,000 
Total Pinnacle West long-term debt less current maturities867,770 498,731 
TOTAL LONG-TERM DEBT LESS CURRENT MATURITIES
$8,058,648 $7,540,622 
(a)    This schedule does not reflect the timing of redemptions that may occur prior to maturities.
(b)    The weighted-average interest rate for the variable rate pollution control bonds was 4.01% at December 31, 2024, and 4.11% at December 31, 2023.
(c)    The weighted-average interest rate was 5.88% at December 31, 2024, and was not applicable at December 31, 2023. See additional details below.
(d)    The weighted-average interest rate was not applicable at December 31, 2024, and was 6.20% at December 31, 2023. See additional details below.
Schedule of Principal Payments Due on Pinnacle West's and APS's Total Long-Term Debt
The following table shows principal payments due on Pinnacle West’s and APS’s total long-term debt (dollars in thousands):
YearPinnacle West ConsolidatedAPS Consolidated
2025$800,000 $300,000 
2026600,000 250,000 
2027825,000 300,000 
2028— — 
2029568,975 568,975 
Thereafter6,125,000 6,125,000 
Total$8,918,975 $7,543,975 
Schedule of Estimated Fair Value of Long-Term Debt, Including Current Maturities The following table represents the estimated fair value of our long-term debt, including current maturities (dollars in thousands):
 As of December 31, 2024As of December 31, 2023
 Carrying
Amount		Fair ValueCarrying
Amount		Fair Value
Pinnacle West$1,367,770 $1,393,744 $1,123,731 $1,095,935 
APS7,490,878 6,525,248 7,291,891 6,459,718 
Total$8,858,648 $7,918,992 $8,415,622 $7,555,653 
v3.25.0.1
Retirement Plans and Other Postretirement Benefits (Tables)
 12 Months Ended
Dec. 31, 2024
Retirement Benefits [Abstract]  
Schedule of Net Periodic Benefit Costs and the Portion of these Costs Charged to Expense (Including Administrative Costs and Excluding Amounts Capitalized as Overhead Construction, Billed to Electric Plant Participants or Charged or Amortized to the Regulatory Asset)
The following table provides details of the plans’ net periodic benefit costs and the portion of these costs charged to expense (including administrative costs and excluding amounts capitalized as overhead construction or billed to electric plant participants) (dollars in thousands):
Pension PlansOther Benefits Plans
 202420232022202420232022
Service cost-benefits earned during the period$43,641 $39,461 $55,473 $9,955 $8,567 $16,470 
Non-service costs (credits):
Interest cost on benefit obligation148,643 153,561 107,492 22,169 22,509 17,491 
Expected return on plan assets(188,651)(182,938)(185,775)(46,834)(43,486)(46,042)
Amortization of:
Prior service credit (a)— — — (37,789)(37,789)(37,789)
Net actuarial loss (gain)
41,915 38,420 17,515 (8,676)(9,614)(12,835)
Net periodic benefit costs (credits)
$45,548 $48,504 $(5,295)$(61,175)$(59,813)$(62,705)
Portion of costs (credits) charged to expense
$23,652 $27,029 $(16,431)$(45,557)$(43,408)$(45,042)
(a)    Prior-service costs or credits reflect the impact of modifications to the pension or postretirement plan benefits. The impact of these modifications is amortized over a period which reflects the demographics of the impacted population. In 2014, Pinnacle West made changes to the postretirement benefits offered to Medicare eligible retirees which resulted in prior-service credits. We have been amortizing these prior-serviced credits since 2015 with the last full-year amortization occurring in 2024.
Schedule of Changes in the Benefit Obligations and Funded Status
The following table shows the plans’ changes in the benefit obligations and funded status (dollars in thousands):
 Pension PlansOther Benefits Plans
 2024202320242023
Change in Benefit Obligation    
Benefit obligation at January 1$2,908,063 $2,809,529 $430,434 $409,461 
Service cost43,641 39,461 9,955 8,567 
Interest cost148,643 153,561 22,169 22,509 
Benefit payments(216,238)(210,737)(30,516)(30,784)
Actuarial (gain) loss(91,800)116,249 (71,952)20,681 
Benefit obligation at December 312,792,309 2,908,063 360,090 430,434 
Change in Plan Assets    
Fair value of plan assets at January 12,835,549 2,829,485 696,494 652,287 
Actual return on plan assets4,518 199,098 32,816 67,317 
Benefit payments(200,205)(193,034)(27,118)(23,110)
Fair value of plan assets at December 312,639,862 2,835,549 702,192 696,494 
Funded (Underfunded) Status at December 31$(152,447)$(72,514)$342,102 $266,060 
Schedule of Projected Benefit Obligation and the Accumulated Benefit Obligation for Pension Plans with an Accumulated Obligation in Excess of Plan Assets
The following table shows information for pension plans with an accumulated obligation in excess of plan assets (dollars in thousands):
As of December 31,
 20242023
Accumulated benefit obligation$113,541 $123,701 
Fair value of plan assets— — 
The following table shows information for pension plans with a projected benefit obligation in excess of plan assets (dollars in thousands):
As of December 31,
 20242023
Projected benefit obligation$2,792,309 $129,891 
Fair value of plan assets2,639,862 — 
Schedule of Amounts Recognized on the Consolidated Balance Sheets
The following table shows the amounts recognized on the Consolidated Balance Sheets (dollars in thousands):
 Pension PlansOther Benefits Plans
 2024202320242023
Noncurrent asset$— $57,378 $342,102 $266,060 
Current liability(13,130)(17,190)— — 
Noncurrent liability(139,317)(112,702)— — 
Net amount recognized (funded status)$(152,447)$(72,514)$342,102 $266,060 
Schedule of Accumulated Other Comprehensive Loss
The following table shows the details related to accumulated other comprehensive loss (gain) as of December 31, 2024, and 2023 (dollars in thousands): 
 Pension PlansOther Benefits Plans
 2024202320242023
Net actuarial loss (gain)$793,421 $743,003 $(237,889)$(188,630)
Prior service credit— — (1,265)(39,054)
APS’s portion recorded as a regulatory (asset) liability(750,976)(696,476)238,113 226,726 
Income tax expense (benefit)(10,354)(11,506)611 691 
Accumulated other comprehensive loss (gain)$32,091 $35,021 $(430)$(267)
Schedule of Weighted-Average Assumptions Used for Both the Pension and Other Benefits to Determine Benefit Obligations and Net Periodic Benefit Costs
The following table shows the weighted-average assumptions used for both the pension and other benefits to determine benefit obligations and net periodic benefit costs:
 Benefit Obligations
As of December 31,		Benefit Costs
Year Ended December 31,
 20242023202420232022
Discount rate – pension plans5.68 %5.21 %5.21 %5.56 %2.92 %
Discount rate – other benefits plans5.71 %5.23 %5.23 %5.58 %2.98 %
Rate of compensation increase4.50 %4.52 %4.52 %4.57 %4.00 %
Expected long-term return on plan assets - pension plansN/AN/A6.90 %6.70 %5.00 %
Expected long-term return on plan assets - other benefit plansN/AN/A6.85 %6.80 %5.35 %
Initial healthcare cost trend rate (pre-65 participants)6.50 %6.25 %6.25 %6.50 %6.00 %
Ultimate healthcare cost trend rate (pre-65 participants)4.50 %4.75 %4.75 %4.75 %4.75 %
Number of years to ultimate trend rate (pre-65 participants)65453
Initial healthcare cost trend rate (post-65 participants)1.00 %2.00 %2.00 %2.00 %2.00 %
Ultimate healthcare cost trend rate (post-65 participants)— %2.00 %2.00 %2.00 %2.00 %
Interest crediting rate – cash balance pension plans4.66 %4.54 %4.54 %4.50 %4.50 %
Schedule of Fair Value of Pension Plan and Other Postretirement Benefit Plan Assets, by Asset Category
Based on the IPS, the target and actual allocation for the pension plan at December 31, 2024, are as follows:
 Target AllocationActual Allocation
Long-term fixed income assets80 %79 %
Return-seeking assets20 %21 %
Total100 %100 %

The permissible range is within +/-5% of the target allocation shown in the above table, and also considers the plan’s funded status.

The following table presents the additional target allocations, as a percent of total pension plan assets, for the return-seeking assets:
Target Allocation
Equities in US and other developed markets12 %
Equities in emerging markets4 %
Alternative investments4 %
Total20 %
The following table presents the actual allocations of the investment for the other postretirement benefit plan at December 31, 2024:
Actual Allocation
Long-term fixed income assets61 %
Return-seeking assets39 %
Total100 %
The fair value of Pinnacle West’s pension plan and other postretirement benefit plan assets at December 31, 2024, by asset category, are as follows (dollars in thousands):
 
 Level 1Level 2Other (a)Total
Pension Plan:   
Cash and cash equivalents$9,055 $— $— $9,055 
Fixed income securities:   
Corporate— 1,325,833 — 1,325,833 
U.S. Treasury561,317 — — 561,317 
Other (b)— 133,254 — 133,254 
Common stock equities (c)74,939 — — 74,939 
Mutual funds (d)102,722 — — 102,722 
Common and collective trusts:
Equities— — 244,734 244,734 
Real estate— — 127,397 127,397 
Other (e)— — 60,611 60,611 
Total$748,033 $1,459,087 $432,742 $2,639,862 
Other Benefits:    
Cash and cash equivalents$840 $— $— $840 
Fixed income securities:   
Corporate— 186,435 — 186,435 
U.S. Treasury204,274 — — 204,274 
Other (b)— 12,585 — 12,585 
Common stock equities (c)89,685 — — 89,685 
Mutual funds (d)23,415 — — 23,415 
Common and collective trusts:   
Equities— — 140,178 140,178 
Real estate— — 19,474 19,474 
Other (e)19,145 — 6,161 25,306 
Total$337,359 $199,020 $165,813 $702,192 
(a)These investments primarily represent assets valued using NAV as a practical expedient and have not been classified in the fair value hierarchy.
(b)This category consists primarily of debt securities issued by municipalities and asset backed securities.
(c)This category primarily consists of U.S. common stock equities.
(d)These funds invest in international common stock equities.
(e)Primarily relates to short-term investment funds and includes plan receivables and payables.
The fair value of Pinnacle West’s pension plan and other postretirement benefit plan assets at December 31, 2023, by asset category, are as follows (dollars in thousands):
 Level 1Level 2Other (a)Total
Pension Plan:   
Fixed income securities:   
Corporate$— $1,415,346 $— $1,415,346 
U.S. Treasury622,273 — — 622,273 
Other (b)— 135,184 — 135,184 
Common stock equities (c)150,657 — — 150,657 
Mutual funds (d)112,791 — — 112,791 
Common and collective trusts:
   Equities— — 192,945 192,945 
   Real estate— — 140,613 140,613 
Other (e)— — 65,740 65,740 
Total $885,721 $1,550,530 $399,298 $2,835,549 
Other Benefits:    
Fixed income securities:   
Corporate$— $189,902 $— $189,902 
U.S. Treasury207,665 — — 207,665 
Other (b)— 8,372 — 8,372 
Common stock equities (c)139,952 — — 139,952 
Mutual funds (d)22,256 — — 22,256 
Common and collective trusts:
   Equities— — 81,724 81,724 
   Real estate— — 20,001 20,001 
Other (e)21,146 — 5,476 26,622 
Total $391,019 $198,274 $107,201 $696,494 
(a)These investments primarily represent assets valued using NAV as a practical expedient and have not been classified in the fair value hierarchy.
(b)This category consists primarily of debt securities issued by municipalities and asset backed securities.
(c)This category primarily consists of U.S. common stock equities.
(d)These funds invest in U.S. and international common stock equities.
(e)
Schedule of Estimated Future Benefit Payments, which Reflect Estimated Future Employee Service, for the Next Five Years and the Succeeding Five Years Thereafter
Benefit payments, which reflect estimated future employee service, for the next five years and the succeeding five years thereafter, are estimated to be as follows (dollars in thousands):
YearPension PlansOther Benefits Plans
2025$241,762 $28,753 
2026223,562 28,747 
2027230,335 28,276 
2028233,617 27,880 
2029232,591 27,645 
Years 2030-20341,147,273 137,301 
v3.25.0.1
Leases (Tables)
 12 Months Ended
Dec. 31, 2024
Leases [Abstract]  
Schedule of Lease Costs
The following table provides information related to our lease costs (dollars in thousands):
Year Ended December 31,
202420232022
Operating Lease Cost - Purchased Power & Energy Storage Lease Contracts$147,313 $126,655 $104,001 
Operating Lease Cost - Land, Property, and Other Equipment20,120 19,235 18,061 
Total Operating Lease Cost167,433 145,890 122,062 
Variable Lease Cost (a)144,108 135,007 122,040 
Short-term Lease Cost20,653 21,530 9,928 
Total Lease Cost$332,194 $302,427 $254,030 
The following tables provide other additional information related to operating lease liabilities (dollars in thousands):
Year Ended December 31,
202420232022
Cash paid for amounts included in the measurement of lease liabilities — operating cash flows:$143,950 $123,472 $118,463 
Right-of-use operating lease assets obtained in exchange for operating lease liabilities:393,702 (a)602,301 (b)16,990 


December 31, 2024December 31, 2023
Weighted average remaining lease term11 years10 years
Weighted average discount rate (c)4.90 %4.53 %

(a)Primarily relates to the three new energy storage operating lease agreements that commenced in 2024.
(b)Primarily relates to the two purchased power operating lease agreements that were modified in January 2023.
(c)Most of our lease agreements do not contain an implicit rate that is readily determinable. For these agreements we use our incremental borrowing rate to measure the present value of lease liabilities. We determine our incremental borrowing rate at lease commencement based on the rate of interest that we would have to pay to borrow, on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. We use the implicit rate when it is readily determinable.
Schedule of Maturities of Operating Lease Labilities
The following table provides information related to the maturity of our operating lease liabilities (dollars in thousands):
December 31, 2024
YearPurchased Power & Energy Storage Lease ContractsLand, Property & Equipment LeasesTotal
2025 $158,363 $16,834 $175,197 
2026172,087 14,830 186,917 
2027198,007 12,249 210,256 
2028201,804 9,591 211,395 
2029205,741 7,465 213,206 
Thereafter1,140,971 61,855 1,202,826 
Total lease commitments2,076,973 122,824 2,199,797 
Less imputed interest536,948 41,605 578,553 
Total lease liabilities$1,540,025 $81,219 $1,621,244 
v3.25.0.1
Jointly-Owned Facilities (Tables)
 12 Months Ended
Dec. 31, 2024
Jointly Owned Utility Plant, Net Ownership Amount [Abstract]  
Schedule Of APS's Interests In Jointly-owned Facilities Recorded On The Consolidated Balance Sheets The following table shows APS’s interests in those jointly-owned facilities recorded on the Consolidated Balance Sheets at December 31, 2024 (dollars in thousands):
 Percent
Owned		 Plant in
Service		Accumulated
Depreciation		Construction
Work in
Progress
Generating facilities:     
Palo Verde Units 1 and 329.1 %$2,010,346 $1,081,321 $20,694 
Palo Verde Unit 2 (a)16.8 %709,414 397,235 9,076 
Palo Verde Common28.0 %(b)898,401 366,027 47,962 
Palo Verde Sale Leaseback (a)351,050 268,494 — 
Four Corners Generating Station 63.0 %1,848,412 705,667 56,226 
Cholla Common Facilities (c)50.5 %301,035 231,170 1,743 
Transmission facilities:     
Arizona Nuclear Power Project 500kV System33.3 %(b)134,713 60,174 7,174 
Navajo Southern System24.7 %(b)88,528 38,797 626 
Palo Verde — Yuma 500kV System25.5 %(b)24,260 8,120 142 
Four Corners Switchyards58.0 %(b)84,367 23,886 309 
Phoenix — Mead System17.1 %(b)39,788 21,173 330 
Palo Verde — Rudd 500kV System50.0 %95,785 34,254 1,808 
Morgan — Pinnacle Peak System63.2 %(b)117,500 29,013 287 
Round Valley System50.0 %548 213 — 
Palo Verde — Morgan System87.5 %(b)266,547 46,327 208 
Hassayampa — North Gila System80.0 %154,330 27,739 — 
Cholla 500kV Switchyard85.7 %8,454 2,859 35 
Saguaro 500kV Switchyard60.0 %29,850 15,768 101 
Kyrene — Knox System50.0 %578 349 — 
Agua Fria Switchyard10.0 %— — 82 
(a)See Note 17.
(b)Weighted-average of interests.
(c)PacifiCorp owns Cholla Unit 4 (see Note 3 for additional information), and APS operated the unit for PacifiCorp.  Cholla Unit 4 was retired on December 24, 2020. The common facilities at Cholla are jointly-owned.
v3.25.0.1
Commitments and Contingencies (Tables)
 12 Months Ended
Dec. 31, 2024
Commitments and Contingencies Disclosure [Abstract]  
Schedule of Estimated Coal Take-or-pay Commitments
The following table summarizes our estimated coal take-or-pay commitments (dollars in thousands):
 
 
Year Ended December 31,
 20252026202720282029Thereafter (b)
Coal take-or-pay commitments (a)$208,984 $214,090 $212,529 $217,820 $223,291 $463,752 
 
(a)Total take-or-pay commitments are approximately $1.5 billion.  The total net present value of these commitments using a 4.81% discount rate is approximately $1.3 billion.
(b)Through 2031.
Schedule of Actual Take-or-pay Commitments The following table summarizes actual amounts purchased under the coal contracts which include take-or-pay provisions for each of the last three years (dollars in thousands):
 
Year Ended December 31,
 202420232022
Total purchases$237,821 $255,219 $305,502 
v3.25.0.1
Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2024
Asset Retirement Obligation Disclosure [Abstract]  
Schedule of Change in Asset Retirement Obligations
The following table shows the change in our asset retirement obligations (dollars in thousands):

 20242023
Asset retirement obligations at the beginning of year
$966,001 $797,762 
Changes attributable to:  
Accretion expense56,143 44,269 
Settlements(18,379)(14,039)
Estimated cash flow revisions142,821 135,323 
Newly incurred obligation— 2,686 
Asset retirement obligations at the end of year
$1,146,586 $966,001 
v3.25.0.1
Fair Value Measurements (Tables)
 12 Months Ended
Dec. 31, 2024
Fair Value Disclosures [Abstract]  
Schedule of Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
The following table presents the fair value at December 31, 2024, of our assets and liabilities that are measured at fair value on a recurring basis (dollars in thousands):

Level 1Level 2Level 3OtherTotal
ASSETS
Cash equivalents$23 $— $— $— $23 
Risk management activities — derivative instruments:
Commodity contracts— 13,152 7,176 (3,770)(a)16,558 
Nuclear decommissioning trusts:
Equity securities11,859 542 — 3,335 (b)15,736 
U.S. commingled equity funds— — — 423,069 (c)423,069 
U.S. Treasury debt367,396 — — — 367,396 
Corporate debt— 203,180 — — 203,180 
Mortgage-backed securities— 208,533 — — 208,533 
Municipal bonds— 37,429 — — 37,429 
Other fixed income— 27,502 — — 27,502 
Subtotal nuclear decommissioning trusts379,255 477,186 — 426,404 1,282,845 
Other special use funds:
Cash equivalents25,000 — — — (d)$25,000 
Equity securities24,962 — — 2,851 (b,d)27,813 
U.S. Treasury debt355,544 — — — 355,544 
Subtotal other special use funds (d)405,506 — — 2,851 408,357 
Total assets$784,784 $490,338 $7,176 $425,485 $1,707,783 
LIABILITIES
Risk management activities — derivative instruments:
Commodity contracts$— $(40,388)$(22,215)$817 (a)$(61,786)
(a)Represents counterparty netting, margin, and collateral. See Note 15.
(b)Represents net pending securities sales and purchases.
(c)Valued using NAV as a practical expedient and, therefore, are not classified in the fair value hierarchy.
(d)All amounts relate to APS, with the exception of $34.2 million related to Pinnacle West’s Captive investments that are classified within Level 1, $25.0 million in cash equivalents and $9.2 million related to equity securities. See Note 17.
 The following table presents the fair value at December 31, 2023, of our assets and liabilities that are measured at fair value on a recurring basis (dollars in thousands):
 
Level 1Level 2Level 3OtherTotal
ASSETS
Cash equivalents$10 $— $— $— $10 
Risk management activities — derivative instruments:
Commodity contracts— 1,881 6,616 (1,689)(a)6,808 
Nuclear decommissioning trusts:
Equity securities11,064 — — (767)(b)10,297 
U.S. commingled equity funds— — — 409,616 (c)409,616 
U.S. Treasury debt319,734 — — — 319,734 
Corporate debt— 188,317 — — 188,317 
Mortgage-backed securities— 208,306 — — 208,306 
Municipal bonds— 59,323 — — 59,323 
Other fixed income— 5,653 — — 5,653 
Subtotal nuclear decommissioning trusts330,798 461,599 — 408,849 1,201,246 
Other special use funds:
Equity securities40,991 — — 2,196 (b)43,187 
U.S. Treasury debt319,594 — — — 319,594 
Subtotal other special use funds360,585 — — 2,196 362,781 
Total assets$691,393 $463,480 $6,616 $409,356 $1,570,845 
LIABILITIES
Risk management activities — derivative instruments:
Commodity contracts$— $(127,016)$(1,695)$4,823 (a)$(123,888)
(a)Represents counterparty netting, margin, and collateral. See Note 15.
(b)Represents net pending securities sales and purchases.
(c)Valued using NAV as a practical expedient and, therefore, are not classified in the fair value hierarchy.
The following table shows the changes in fair value for our risk management activities’ assets and liabilities that are measured at fair value on a recurring basis using Level 3 inputs (dollars in thousands):

 Year Ended December 31,
Commodity Contracts20242023
Balance at beginning of period$4,921 $(4,888)
Total net losses realized/unrealized:
Deferred as a regulatory asset or liability(60,965)(70,214)
Settlements44,156 69,706 
Transfers into Level 3 from Level 2(4,635)(1,289)
Transfers from Level 3 into Level 21,484 11,606 
Balance at end of period$(15,039)$4,921 
Net unrealized gains/losses included in earnings related to instruments still held at end of period$— $— 
Schedule of Fair Value Measurement Inputs and Valuation Techniques
The following tables provide information regarding our significant unobservable inputs used to value our risk management derivative Level 3 instruments at December 31, 2024, and December 31, 2023:

December 31, 2024
 Fair Value (thousands) 		ValuationSignificantWeighted-Average
Commodity ContractsAssetsLiabilitiesTechniqueUnobservable InputRange (b)
Electricity Forward Contracts (a)$708 $21,890 Discounted cash flowsElectricity forward price (per MWh)
$25.25
-
$151.11
$106.06
Natural Gas Forward Contracts (a)6,468 325 Discounted cash flowsNatural gas forward price (per MMBtu)
$(0.89)
-
$1.47
$0.71
Total$7,176 $22,215 
(a)Includes swaps and physical and financial contracts.
(b)Unobservable inputs were weighted by the relative fair value of the instrument.

December 31, 2023
 Fair Value (thousands) 		ValuationSignificantWeighted-Average
Commodity ContractsAssetsLiabilitiesTechniqueUnobservable InputRange(b)
Electricity Forward Contracts (a)$6,587 $658 Discounted cash flowsElectricity forward price (per MWh)$37.79 -$259.04$158.08
Natural Gas Forward Contracts (a)29 1,037 Discounted cash flowsNatural gas forward price (per MMBtu)$0.00-$0.08$0.03
Total$6,616 $1,695 
(a)Includes swaps and physical and financial contracts.
(b)Unobservable inputs were weighted by the relative fair value of the instrument.
v3.25.0.1
Common Stock Equity and Earnings Per Share (Tables)
 12 Months Ended
Dec. 31, 2024
Earnings Per Share [Abstract]  
Schedule of Earnings Per Weighted Average Common Share Outstanding
The following table presents the calculation of Pinnacle West’s basic and diluted EPS (in thousands, except per share amounts):
 202420232022
Net income attributable to common shareholders$608,806 $501,557 $483,602 
Weighted average common shares outstanding — basic113,846 113,442 113,196 
Net effect of dilutive securities:   
Contingently issuable performance shares and restricted stock units480 362 220 
Dilutive shares related to equity forward sale agreements (a)1,906 — — 
Total contingently issuable shares2,386 362 220 
Weighted average common shares outstanding — diluted116,232 113,804 113,416 
Earnings per weighted-average common share outstanding
Net income attributable to common shareholders — basic$5.35 $4.42 $4.27 
Net income attributable to common shareholders — diluted$5.24 $4.41 $4.26 
(a)    For the years ended December 31, 2024, 2023 and 2022, diluted weighted average common shares excludes 1,038,463, 0 and 0 shares, respectively, relating to the Convertible Notes and the ATM equity forward. These potentially issuable shares were excluded from the calculation of diluted shares as their inclusion would have been antidilutive.
v3.25.0.1
Stock-Based Compensation (Tables)
 12 Months Ended
Dec. 31, 2024
Share-Based Payment Arrangement [Abstract]  
Schedule of Restricted Stock Units, Stock Grants and Stock Units
The following table is a summary of awards granted and the weighted-average grant date fair value for each of the last three years:
Restricted Stock Units, Stock Grants, and Stock Units (a)Performance Shares (b)
 202420232022202420232022
Units granted261,808 192,295 174,791 225,516 202,562 208,736 
Weighted-average grant date fair value$71.10 $74.32 $69.66 $72.89 $79.61 $77.63 
(a)The Units granted does not include awards that will be cash settled in 2024, 2023 or 2022. See below for additional information on restricted stock unit grants.
(b)Reflects the target payout level.
Schedule of Nonvested Performance Shares
The following table shows the change of nonvested awards:

Restricted Stock Units, Stock Grants, and Stock UnitsPerformance Shares
SharesWeighted-Average
Grant Date
Fair Value		Shares (b)Weighted-Average
Grant Date
Fair Value
Nonvested at December 31, 2023
374,367 $73.29 347,283 $77.29 
Granted261,808 71.10 225,516 72.89 
Vested(155,345)74.54 (165,194)76.55 
Forfeited (c)(20,039)71.32 (17,054)75.69 
Nonvested at December 31, 2024
460,791 (a)71.72 390,551 77.29 
Vested Awards Outstanding at December 31, 2024
70,851 165,194 
(a)Includes 11,750 of awards that will be cash settled.
(b)The performance shares are reflected at target payout level. 
(c)We account for forfeitures as they occur.
v3.25.0.1
Derivative Accounting (Tables)
 12 Months Ended
Dec. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Schedule of Outstanding Gross Notional Amount of Derivatives, which Represents Both Purchases and Sales (Does Not Reflect Net Position)
The following table shows the outstanding gross notional volume of energy derivatives, which represent both purchases and sales (does not reflect net position):
Quantity
CommodityUnit of MeasureDecember 31, 2024December 31, 2023
PowerGWh1,051 1,212 
GasBillion cubic feet235 200 
Schedule of Gains and Losses from Derivative Instruments Not Designated as Accounting Hedges Instruments The following table provides information about gains and losses from energy derivative instruments not designated as accounting hedging instruments (dollars in thousands):
Financial Statement Year Ended December 31,
Commodity ContractsLocation202420232022
Net Gain (Loss) Recognized in Income
Fuel and purchased power (a)(88,522)(370,145)307,287 
(a)Amounts are before the effect of PSA deferrals.
Schedule of the Entity's Fair Value of Risk Management Activities Reported on a Gross Basis and the Impacts on Offsetting Liabilities
The following tables provide information about the fair value of APS’s risk management activities reported on a gross basis and the impacts of offsetting.  These amounts relate to commodity contracts and are located in the assets and liabilities from risk management activities lines of APS’s Consolidated Balance Sheets.
As of December 31, 2024:
 (dollars in thousands) 		Gross 
Recognized 
Derivatives
 (a)		Amounts 
Offset
(b)		Net
 Recognized
 Derivatives		Other
 (c)		Amounts 
Reported on 
Balance Sheets
Current assets$13,718 $(3,158)$10,560 $18 $10,578 
Investments and other assets6,610 (630)5,980 — 5,980 
Total assets20,328 (3,788)16,540 18 16,558 
Current liabilities(52,527)3,158 (49,369)(2,971)(52,340)
Deferred credits and other(10,076)630 (9,446)— (9,446)
Total liabilities(62,603)3,788 (58,815)(2,971)(61,786)
Total$(42,275)$— $(42,275)$(2,953)$(45,228)
(a)All of our gross recognized derivative instruments were subject to master netting arrangements.
(b)No cash collateral has been provided to counterparties, or received from counterparties, that is subject to offsetting.
(c)Represents cash collateral and cash margin that is not subject to offsetting. Amounts relate to non-derivative instruments, derivatives qualifying for scope exceptions, or collateral and margin posted in excess of the recognized derivative instrument.  Includes cash collateral received from counterparties of $2,971 thousand and cash margin provided to counterparties of $18 thousand.
As of December 31, 2023:
 (dollars in thousands) 		Gross
 Recognized
 Derivatives
 (a)		Amounts
Offset 
(b)		Net
 Recognized
 Derivatives		Other
 (c)		Amounts
 Reported on
 Balance Sheets
Current assets$8,497 $(1,694)$6,803 $5 $6,808 
Investments and other assets— — — — — 
Total assets8,497 (1,694)6,803 5 6,808 
Current liabilities(85,736)10,894 (74,842)(6,071)(80,913)
Deferred credits and other(42,975)— (42,975)— (42,975)
Total liabilities(128,711)10,894 (117,817)(6,071)(123,888)
Total$(120,214)$9,200 $(111,014)$(6,066)$(117,080)
(a)All of our gross recognized derivative instruments were subject to master netting arrangements.
(b)Includes cash collateral provided to counterparties of $9,200 thousand that is subject to offsetting.
(c)Represents cash collateral and cash margin that is not subject to offsetting.  Amounts relate to non-derivative instruments, derivatives qualifying for scope exceptions, or collateral and margin posted in excess of the recognized derivative instrument.  Includes cash collateral received from counterparties of $6,071 thousand and cash margin provided to counterparties of $5 thousand.
Schedule of the Entity's Fair Value of Risk Management Activities Reported on a Gross Basis and the Impacts on Offsetting Assets
The following tables provide information about the fair value of APS’s risk management activities reported on a gross basis and the impacts of offsetting.  These amounts relate to commodity contracts and are located in the assets and liabilities from risk management activities lines of APS’s Consolidated Balance Sheets.
As of December 31, 2024:
 (dollars in thousands) 		Gross 
Recognized 
Derivatives
 (a)		Amounts 
Offset
(b)		Net
 Recognized
 Derivatives		Other
 (c)		Amounts 
Reported on 
Balance Sheets
Current assets$13,718 $(3,158)$10,560 $18 $10,578 
Investments and other assets6,610 (630)5,980 — 5,980 
Total assets20,328 (3,788)16,540 18 16,558 
Current liabilities(52,527)3,158 (49,369)(2,971)(52,340)
Deferred credits and other(10,076)630 (9,446)— (9,446)
Total liabilities(62,603)3,788 (58,815)(2,971)(61,786)
Total$(42,275)$— $(42,275)$(2,953)$(45,228)
(a)All of our gross recognized derivative instruments were subject to master netting arrangements.
(b)No cash collateral has been provided to counterparties, or received from counterparties, that is subject to offsetting.
(c)Represents cash collateral and cash margin that is not subject to offsetting. Amounts relate to non-derivative instruments, derivatives qualifying for scope exceptions, or collateral and margin posted in excess of the recognized derivative instrument.  Includes cash collateral received from counterparties of $2,971 thousand and cash margin provided to counterparties of $18 thousand.
As of December 31, 2023:
 (dollars in thousands) 		Gross
 Recognized
 Derivatives
 (a)		Amounts
Offset 
(b)		Net
 Recognized
 Derivatives		Other
 (c)		Amounts
 Reported on
 Balance Sheets
Current assets$8,497 $(1,694)$6,803 $5 $6,808 
Investments and other assets— — — — — 
Total assets8,497 (1,694)6,803 5 6,808 
Current liabilities(85,736)10,894 (74,842)(6,071)(80,913)
Deferred credits and other(42,975)— (42,975)— (42,975)
Total liabilities(128,711)10,894 (117,817)(6,071)(123,888)
Total$(120,214)$9,200 $(111,014)$(6,066)$(117,080)
(a)All of our gross recognized derivative instruments were subject to master netting arrangements.
(b)Includes cash collateral provided to counterparties of $9,200 thousand that is subject to offsetting.
(c)Represents cash collateral and cash margin that is not subject to offsetting.  Amounts relate to non-derivative instruments, derivatives qualifying for scope exceptions, or collateral and margin posted in excess of the recognized derivative instrument.  Includes cash collateral received from counterparties of $6,071 thousand and cash margin provided to counterparties of $5 thousand.
Schedule of Information about Derivative Instruments that have Credit-Risk-Related Contingent Features
The following table provides information about our energy derivative instruments that have credit-risk-related contingent features (dollars in thousands):
 December 31, 2024
Aggregate fair value of derivative instruments in a net liability position$62,603 
Additional collateral in the event credit-risk related contingent features were fully triggered (a)32,728 
(a)This amount is after counterparty netting and includes those contracts which qualify for scope exceptions, which are excluded from the derivative details above.
v3.25.0.1
Other Income and Other Expense (Tables)
 12 Months Ended
Dec. 31, 2024
Other Income and Expenses [Abstract]  
Schedule of other income and other expense
The following table provides detail of Pinnacle West’s Consolidated other income and other expense for 2024, 2023, and 2022 (dollars in thousands):
 202420232022
Other income:   
Interest income$24,322 (a)$27,242 (a)$7,326 
Gain on sale of BCE (Note 20)
22,988 6,205 — 
Miscellaneous1,304 219 590 
Total other income$48,614 $33,666 $7,916 
Other expense:
Non-operating costs$(27,370)(b)$(15,260)$(18,619)
Investment losses — net(1,418)(3,402)(20,537)(c)
Miscellaneous(5,348)(6,394)(13,229)
Total other expense$(34,136)$(25,056)$(52,385)
(a)The 2023 and 2024 Interest income is primarily related to PSA Interest. See Note 3.
(b)The 2024 Non-operating cost is primarily related to corporate giving.
(c)The 2022 investment loss is primarily related to an impairment of PNW Power’s Clear Creek wind farm investment.
The following table provides detail of APS’s other income and other expense for 2024, 2023, and 2022 (dollars in thousands):
 202420232022
Other income:   
Interest income (a)$21,088 (a)$26,853 (a)$5,332 
Miscellaneous6 219 556 
 Total other income$21,094 $27,072 $5,888 
Other expense:
Non-operating costs$(26,588)(b)$(14,070)$(15,579)
Miscellaneous(3,110)(4,194)(10,529)
Total other expense$(29,698)$(18,264)$(26,108)
(a)The 2023 and 2024 Interest income is primarily related to PSA Interest. See Note 3.
(b)The 2024 Non-operating cost is primarily related to corporate giving.
v3.25.0.1
Variable Interest Entities (Tables)
 12 Months Ended
Dec. 31, 2024
Variable Interest Entities [Abstract]  
Schedule of Amounts Relating to the VIEs Included in Consolidated Balance Sheets
Our Consolidated Balance Sheets include the following amounts relating to these VIEs (dollars in thousands):
 December 31, 2024December 31, 2023
Palo Verde sale leaseback property, plant and equipment, net of accumulated depreciation$82,556 $86,426 
Equity — Noncontrolling interests103,167 107,198 
v3.25.0.1
Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Tables)
 12 Months Ended
Dec. 31, 2024
Investments, Debt and Equity Securities [Abstract]  
Schedule of Fair Value of APS's Nuclear Decommissioning Trust Fund Assets
The following tables present the unrealized gains and losses based on the original cost of the investment and summarizes the fair value of the nuclear decommissioning trusts and other special use fund assets (dollars in thousands): 
December 31, 2024
 Fair ValueTotal
Unrealized
Gains		Total
Unrealized
Losses
Investment Type:Nuclear Decommissioning TrustsOther Special Use FundsTotal
Equity securities$435,470 $24,962 $460,432 $359,127 $(176)
Available for sale-fixed income securities844,040 355,544 1,199,584 (a)7,717 (31,960)
Other3,335 27,851 31,186 (b)— — 
Total$1,282,845 $408,357 $1,691,202 (c)$366,844 $(32,136)
(a)As of December 31, 2024, the amortized cost basis of these available-for-sale investments is $1,224 million.
(b)Represents net pending securities sales and purchases.
(c)All amounts pertain to APS, with the exception of $34 million of Other Special Use Fund investments in equity securities relating to the Captive.

December 31, 2023
 Fair ValueTotal
Unrealized
Gains		Total
Unrealized
Losses
Investment Type:Nuclear Decommissioning TrustsOther Special Use FundsTotal
Equity securities$420,680 $40,991 $461,671 $336,555 $— 
Available for sale-fixed income securities781,333 319,594 1,100,927 (a)21,518 (40,868)
Other(767)2,196 1,429 (b)39 — 
Total$1,201,246 $362,781 $1,564,027 (c)$358,112 $(40,868)
(a)As of December 31, 2023, the amortized cost basis of these available-for-sale investments is $1,120 million.
(b)Represents net pending securities sales and purchases.
(c)All amounts pertain to APS.
Schedule of Realized Gains and Losses and Proceeds from the Sale of Securities by the Nuclear Decommissioning Trust Funds
 Year Ended December 31,
 Nuclear Decommissioning TrustsOther Special Use FundsTotal
2024
Realized gains$75,690 $372 $76,062 
Realized losses$(21,966)$— $(21,966)
Proceeds from the sale of securities (a)$1,330,940 $355,154 $1,686,094 
2023
Realized gains$111,922 $172 $112,094 
Realized losses$(41,212)$(568)$(41,780)
Proceeds from the sale of securities (a)$1,324,978 $354,744 $1,679,722 
2022
Realized gains$9,017 $420 $9,437 
Realized losses$(40,239)$— $(40,239)
Proceeds from the sale of securities (a)$979,639 $227,558 $1,207,197 
(a)Proceeds are reinvested in the nuclear decommissioning trusts and other special use funds, excluding amounts reimbursed to the Company for active union employee medical claims from the active union employee medical account.
Schedule of Fair Value of Fixed Income Securities, Summarized by Contractual Maturities
The fair value of APS’s fixed income securities, summarized by contractual maturities, at December 31, 2024, is as follows (dollars in thousands):
 
 Nuclear Decommissioning TrustsCoal Reclamation Escrow AccountActive Union Employee Medical AccountTotal
Less than one year$19,868 $87,424 $39,090 $146,382 
1 year – 5 years268,974 58,598 154,768 482,340 
5 years – 10 years198,464 — 15,664 214,128 
Greater than 10 years356,734 — — 356,734 
Total$844,040 $146,022 $209,522 $1,199,584 
v3.25.0.1
Changes in Accumulated Other Comprehensive Loss (Tables)
 12 Months Ended
Dec. 31, 2024
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]  
Schedule of Changes in Accumulated Other Comprehensive Loss Including Reclassification Adjustments, by Component
The following table shows the changes in Pinnacle West’s consolidated accumulated other comprehensive loss, including reclassification adjustments, net of tax, by component (dollars in thousands): 
 Pension and Other Postretirement BenefitsDerivative InstrumentsTotal
Balance at December 31, 2022
$(32,332)$897 $(31,435)
Other comprehensive income/(loss) before reclassifications
(4,420)713 (3,707)
Amounts reclassified from accumulated other comprehensive loss
1,998 (a)— 1,998 
Balance at December 31, 2023
(34,754)1,610 (33,144)
Other comprehensive income/(loss) before reclassifications
1,039 (891)148 
Amounts reclassified from accumulated other comprehensive loss
2,054 (a)— 2,054 
Balance at December 31, 2024
$(31,661)$719 $(30,942)
(a)These amounts primarily represent amortization of actuarial loss and are included in the computation of net periodic pension cost. See Note 7.
The following table shows the changes in APS’s consolidated accumulated other comprehensive loss, including reclassification adjustments, net of tax, by component (dollars in thousands): 
 Pension and Other Postretirement Benefits
Balance at December 31, 2022
$(15,596)
Other comprehensive (loss) before reclassifications
(3,383)
Amounts reclassified from accumulated other comprehensive loss
1,760 (a)
Balance at December 31, 2023
(17,219)
Other comprehensive income before reclassifications
1,255 
Amounts reclassified from accumulated other comprehensive loss
1,848 (a)
Balance at December 31, 2024
$(14,116)
(a)These amounts primarily represent amortization of actuarial loss and are included in the computation of net periodic pension cost. See Note 7.
v3.25.0.1
Summary of Significant Accounting Policies - Schedule of Property, Plant and Equipment (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Utility Plant and Depreciation [Line Items]    
Net $ 16,833,524 $ 15,803,127
Construction work in progress 1,592,659 1,724,004
Intangible assets, net of accumulated amortization 591,310 267,110
Nuclear fuel, net of accumulated amortization 97,850 99,490
Total property, plant and equipment 19,197,899 17,980,157
Electric Service    
Utility Plant and Depreciation [Line Items]    
Generation 11,111,915 10,446,291
Transmission 4,135,970 3,773,253
Distribution 9,016,843 8,448,293
General plant 1,596,222 1,543,330
Plant in service and held for future use 25,860,950 24,211,167
Accumulated depreciation and amortization (9,027,426) (8,408,040)
Net 16,833,524 15,803,127
Construction work in progress 1,592,659 1,724,004
Intangible assets, net of accumulated amortization 591,310 267,110
Nuclear fuel, net of accumulated amortization 97,850 99,490
Total property, plant and equipment 19,197,899 17,980,157
Electric Service | Variable Interest Entity    
Utility Plant and Depreciation [Line Items]    
Total property, plant and equipment $ 82,556 $ 86,426
v3.25.0.1
Summary of Significant Accounting Policies - Additional Information (Details)
$ / shares in Units, $ in Millions
 1 Months Ended 12 Months Ended 36 Months Ended
May 31, 2014
$ / kWh
Dec. 31, 2024
USD ($)
$ / shares
shares
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Dec. 31, 2024
USD ($)
$ / shares
shares
Approximate remaining average useful lives of utility property          
Depreciation   $ 723 $ 669 $ 632  
Depreciation rates (as a percent)   3.13% 2.98% 3.03%  
Allowance for Funds Used During Construction          
Composite rate used to calculate AFUDC (as a percent)   6.23% 6.29% 5.75%  
Income Taxes          
Percent likelihood largest tax benefit amount is realized (greater than)   50.00%      
Intangible Assets          
Amortization expense   $ 136 $ 90 $ 84  
Estimated amortization expense on existing intangible assets over the next five years          
2025   106     $ 106
2026   77     77
2027   43     43
2028   25     25
2029   $ 14     $ 14
Remaining amortization period for intangible assets   5 years     5 years
Pinnacle West          
Preferred Stock          
Preferred stock, shares authorized (in shares) | shares   10,000,000     10,000,000
Preferred stock, shares outstanding (in shares) | shares   0     0
Arizona Public Service Company          
Nuclear Fuel          
Charges for the permanent disposal of spent nuclear fuel (in dollars per kWh) | $ / kWh 0.001        
Preferred Stock          
Preferred stock, shares authorized (in shares) | shares   15,535,000     15,535,000
Preferred stock, shares outstanding (in shares) | shares   0     0
Preferred stock par or stated value per share 1 (in dollars per share) | $ / shares   $ 25     $ 25
Preferred stock par or stated value per share 2 (in dollars per share) | $ / shares   50     50
Preferred stock par or stated value per share 3 (in dollars per share) | $ / shares   $ 100     $ 100
Minimum          
Approximate remaining average useful lives of utility property          
Depreciation rates (as a percent)         1.37%
Maximum          
Approximate remaining average useful lives of utility property          
Depreciation rates (as a percent)         12.15%
Investments          
Ownership percentage for classification as cost method investments by El Dorado   20.00%      
Steam Generation          
Approximate remaining average useful lives of utility property          
Average useful life   11 years     11 years
Nuclear Plant          
Approximate remaining average useful lives of utility property          
Average useful life   25 years     25 years
Transmission          
Approximate remaining average useful lives of utility property          
Average useful life   38 years     38 years
Other Generation          
Approximate remaining average useful lives of utility property          
Average useful life   18 years     18 years
Distribution          
Approximate remaining average useful lives of utility property          
Average useful life   33 years     33 years
General Plant          
Approximate remaining average useful lives of utility property          
Average useful life   7 years     7 years
v3.25.0.1
Summary of Significant Accounting Policies - Schedule of Supplemental Cash Flow Information (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Cash and Cash Equivalents [Line Items]      
Income taxes, net of refunds $ 133,968 $ 8,788 $ 46,227
Interest, net of amounts capitalized 360,349 310,996 245,271
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]      
Accrued capital expenditures 257,494 206,269 114,999
Dividends accrued but not yet paid 106,592 99,813 97,895
BCE Sale non-cash consideration (Note 20) 0 28,262 0
Arizona Public Service Company      
Cash and Cash Equivalents [Line Items]      
Income taxes, net of refunds 179,013 21,734 95,985
Interest, net of amounts capitalized 299,799 267,261 227,159
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]      
Accrued capital expenditures 257,494 206,269 116,533
Dividends accrued but not yet paid $ 107,200 $ 99,800 $ 97,900
v3.25.0.1
Summary of Significant Accounting Policies - Schedule Of Reportable Segment’s Revenues, Significant Expenses, Net Income, And Assets (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Segment Reporting Information [Line Items]      
OPERATING REVENUES (Note 2) $ 5,124,915 $ 4,695,991 $ 4,324,385
Fuel and purchased power 1,822,566 1,792,657 1,629,343
Operations and maintenance 1,165,156 1,058,725 987,072
Depreciation and amortization 895,346 794,043 753,195
Taxes other than income taxes 227,395 224,013 220,370
Pension and other postretirement non-service credits, net 48,870 40,648 98,487
Interest expense and costs 377,472 331,323 255,539
Income Taxes 110,529 76,912 74,827
Less: Net income attributable to noncontrolling interests (Note 17) 17,224 17,224 17,224
Net Income (loss) 608,806 501,557 483,602
TOTAL ASSETS 26,102,760 24,661,153  
Regulated Electricity Segment      
Segment Reporting Information [Line Items]      
OPERATING REVENUES (Note 2) 5,125,000 4,696,000 4,324,000
Fuel and purchased power (1,823,000) (1,793,000) (1,629,000)
Operations and maintenance (1,159,000) (1,044,000) (974,000)
Depreciation and amortization (895,000) (794,000) (753,000)
Taxes other than income taxes (227,000) (224,000) (220,000)
Pension and other postretirement non-service credits, net 49,000 42,000 99,000
Other income (expense), net 28,000 60,000 22,000
Interest expense and costs (312,000) (285,000) (236,000)
Income Taxes (127,000) (94,000) (91,000)
Less: Net income attributable to noncontrolling interests (Note 17) (17,000) (17,000) (17,000)
Net Income (loss) 642,000 547,000 525,000
TOTAL ASSETS 25,988,000 24,516,000  
Other      
Segment Reporting Information [Line Items]      
OPERATING REVENUES (Note 2) 0 0 0
Fuel and purchased power 0 0 0
Operations and maintenance (6,000) (15,000) (13,000)
Depreciation and amortization 0 0 0
Taxes other than income taxes 0 0 0
Pension and other postretirement non-service credits, net 0 (1,000) (1,000)
Other income (expense), net 22,000 0 (23,000)
Interest expense and costs (65,000) (46,000) (20,000)
Income Taxes 16,000 17,000 16,000
Less: Net income attributable to noncontrolling interests (Note 17) 0 0 0
Net Income (loss) (33,000) (45,000) (41,000)
TOTAL ASSETS 115,000 145,000  
Pinnacle West      
Segment Reporting Information [Line Items]      
Other income (expense), net 23,835 2,823 (4,725)
Income Taxes (16,460) (17,272) (15,996)
Net Income (loss) 608,806 501,557 483,602
TOTAL ASSETS 8,627,449 7,636,932  
Pinnacle West | Reportable Segment      
Segment Reporting Information [Line Items]      
OPERATING REVENUES (Note 2) 5,125,000 4,696,000 4,324,000
Fuel and purchased power (1,823,000) (1,793,000) (1,629,000)
Operations and maintenance (1,165,000) (1,059,000) (987,000)
Depreciation and amortization (895,000) (794,000) (753,000)
Taxes other than income taxes (227,000) (224,000) (220,000)
Pension and other postretirement non-service credits, net 49,000 41,000 98,000
Other income (expense), net 50,000 60,000 (1,000)
Interest expense and costs (377,000) (331,000) (256,000)
Income Taxes (111,000) (77,000) (75,000)
Less: Net income attributable to noncontrolling interests (Note 17) (17,000) (17,000) (17,000)
Net Income (loss) 609,000 502,000 $ 484,000
TOTAL ASSETS $ 26,103,000 $ 24,661,000  
v3.25.0.1
Revenue - Schedule of Disaggregation of revenue (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Disaggregation of Revenue [Line Items]      
Total Operating Revenues $ 5,124,915 $ 4,695,991 $ 4,324,385
Retail Electric Service | Residential      
Disaggregation of Revenue [Line Items]      
Total Operating Revenues 2,562,822 2,289,196 2,046,111
Retail Electric Service | Non-Residential      
Disaggregation of Revenue [Line Items]      
Total Operating Revenues 2,334,925 2,048,416 1,767,616
Wholesale Energy Sales      
Disaggregation of Revenue [Line Items]      
Total Operating Revenues 96,857 208,985 383,126
Transmission Services for Others      
Disaggregation of Revenue [Line Items]      
Total Operating Revenues 119,038 138,631 116,628
Other Sources      
Disaggregation of Revenue [Line Items]      
Total Operating Revenues $ 11,273 $ 10,763 $ 10,904
v3.25.0.1
Revenue - Additional Information (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Disaggregation of Revenue [Line Items]      
Operating revenues $ 5,124,915 $ 4,695,991 $ 4,324,385
Regulatory cost recovery revenue 52,000 45,000 22,000
Electric and Transmission Service      
Disaggregation of Revenue [Line Items]      
Operating revenues $ 5,073,000 $ 4,651,000 $ 4,302,000
v3.25.0.1
Revenue - Schedule of allowance for doubtful accounts (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Accounts Receivable, Allowance for Credit Loss [Roll Forward]      
Balance at beginning of period $ 22,433 $ 23,778 $ 25,354
Bad debt expense 35,799 23,399 17,006
Actual write-offs (33,383) (24,744) (18,582)
Balance at end of period $ 24,849 $ 22,433 $ 23,778
v3.25.0.1
Regulatory Matters - Retail Rate Case Filing (Details)
$ in Thousands
Feb. 22, 2024
USD ($)
Jan. 25, 2024
USD ($)
$ / MWh
Jun. 14, 2023
USD ($)
Dec. 17, 2021
USD ($)
Nov. 02, 2021
USD ($)
Mar. 06, 2023
Public Utilities, General Disclosures [Line Items]            
Revenue increase (decrease) $ 491,700 $ 523,100        
ACC            
Public Utilities, General Disclosures [Line Items]            
Recommended return on equity, percentage 9.55% 9.55%        
Increment of fair value rate, percentage 0.25% 0.25%        
ACC | Coal Community Transition Plan | Navajo Nation, Hopi Tribe            
Public Utilities, General Disclosures [Line Items]            
Regulatory matters, amounts recoverable by rates         $ 1,000  
ACC | Coal Community Transition Plan | Navajo Nation            
Public Utilities, General Disclosures [Line Items]            
Regulatory matters, amounts recoverable by rates         10,000  
ACC | Coal Community Transition Plan | Navajo Nation, Hopi Reservation            
Public Utilities, General Disclosures [Line Items]            
Regulatory matters, amounts recoverable by rates         1,250  
ACC | Coal Community Transition Plan | Navajo County Communities            
Public Utilities, General Disclosures [Line Items]            
Regulatory matters, amounts recoverable by rates         500  
ACC | Coal Community Transition Plan | Navajo Nation, Electrification Projects            
Public Utilities, General Disclosures [Line Items]            
Amount funded by shareholders         1,500  
ACC | Coal Community Transition Plan | Navajo County Communities, CCT and Economic Development            
Public Utilities, General Disclosures [Line Items]            
Amount funded by shareholders         1,100  
ACC | Coal Community Transition Plan | Navajo Nation, Hopi Tribe for CCT and Economic Development            
Public Utilities, General Disclosures [Line Items]            
Amount funded by shareholders         $ 1,250  
ACC | Arizona Public Service Company            
Public Utilities, General Disclosures [Line Items]            
Regulatory matters, no of basis penalty point         0.0020 0.0020
Reversal of basis point penalty     0.0020      
ACC | Arizona Public Service Company | Retail Rate Case Filing with Arizona Corporation Commission            
Public Utilities, General Disclosures [Line Items]            
Recommended return on equity, percentage       8.90% 8.70%  
Effective fair value percentage 4.39% 4.36%        
Prepaid pension asset rate (in percent)   5.00%        
Pension and otherpost retirement and post employment benefit plans (in percent)   5.35%        
Retention of REAC   $ 1,900        
Transfer to LFCR   $ 27,100        
Base fuel rate (in dollars per kWh) | $ / MWh   0.006        
Increases in annual revenue $ 253,400          
Increase to the typical residential customer’s bill (in percent) 8.00%          
ACC | Arizona Public Service Company | Retail Rate Case Filing with Arizona Corporation Commission | Coal Community Transition Plan | Navajo Nation, Hopi Tribe            
Public Utilities, General Disclosures [Line Items]            
Amount not recoverable         $ 215,500  
Amount funded by shareholders         $ 1,000  
Amount funded by shareholders, term         60 days  
ACC | Arizona Public Service Company | Retail Rate Case Filing with Arizona Corporation Commission | Coal Community Transition Plan | Navajo Nation            
Public Utilities, General Disclosures [Line Items]            
Amount funded by shareholders         $ 10,000  
Amount funded by shareholders, term         3 years  
ACC | Arizona Public Service Company | Retail Rate Case Filing with Arizona Corporation Commission | Coal Community Transition Plan | Navajo County Communities, Cholla Power Plant Closure            
Public Utilities, General Disclosures [Line Items]            
Amount funded by shareholders         $ 500  
Amount funded by shareholders, term         60 days  
ACC | Arizona Public Service Company | Retail Rate Case Filing with Arizona Corporation Commission | Coal Community Transition Plan | Navajo Nation, Hopi Reservation            
Public Utilities, General Disclosures [Line Items]            
Amount funded by shareholders         $ 1,250  
ACC | Arizona Public Service Company | Retail Rate Case Filing with Arizona Corporation Commission | Coal Community Transition Plan | Navajo Nation Reservation            
Public Utilities, General Disclosures [Line Items]            
Revenue increase (decrease)         $ (4,800)  
Recommended return on equity, percentage     8.70%      
Disallowance of plant investments       $ 215,500    
Requested reversal of rate adjustment     $ 215,500      
Lost revenue recovery     $ 59,600      
v3.25.0.1
Regulatory Matters - Cost Recovery Mechanisms (Details)
 12 Months Ended
Dec. 17, 2024
USD ($)
Nov. 27, 2024
$ / kWh
Jul. 31, 2024
USD ($)
Jun. 01, 2024
USD ($)
MW
May 01, 2024
$ / kWh
Apr. 19, 2024
Nov. 30, 2023
USD ($)
$ / kWh
Oct. 26, 2023
USD ($)
Oct. 25, 2023
USD ($)
Oct. 11, 2023
Jul. 31, 2023
USD ($)
Jul. 01, 2023
USD ($)
$ / KWH_Kilowatt_hour
Jun. 01, 2023
USD ($)
May 01, 2023
$ / kWh
Mar. 10, 2023
USD ($)
Feb. 23, 2023
$ / kWh
Feb. 01, 2023
USD ($)
$ / kWh
Jul. 12, 2022
USD ($)
$ / kWh
Jun. 01, 2022
USD ($)
Feb. 15, 2022
USD ($)
Feb. 01, 2022
$ / kWh
Oct. 01, 2021
$ / kWh
Feb. 15, 2021
USD ($)
Feb. 01, 2020
$ / kWh
Sep. 01, 2017
Dec. 31, 2024
USD ($)
Jul. 01, 2024
USD ($)
Apr. 26, 2024
USD ($)
Oct. 27, 2023
USD ($)
Jun. 30, 2023
USD ($)
May 31, 2023
USD ($)
Nov. 30, 2022
USD ($)
Jul. 01, 2022
USD ($)
Apr. 18, 2022
USD ($)
Dec. 17, 2021
USD ($)
Dec. 09, 2021
USD ($)
Jul. 01, 2021
USD ($)
Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Requested equity contributions limit $ 9,500,000,000                                                       $ 500,000,000                
Annual amount of approved equity infusions               $ 150,000,000                                                          
Public utilities, request to permanently modify permitted yearly equity infusions 2.50%         2.50%                                                              
Public utilities,equity infusions recommended limit by administrative law judge, percentage 2.50%                                                                        
Arizona Public Service Company | Damage from Fire, Explosion or Other Hazard                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Past due balance threshold qualifying for payment extension                                                                   $ 75      
Arizona Renewable Energy Standard and Tariff | ACC | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Plan term                                                   5 years                      
Arizona Renewable Energy Standard and Tariff 2018 | ACC | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Amount of proposed budget                                                     $ 92,700,000     $ 95,100,000     $ 86,200,000     $ 100,500,000 $ 93,100,000
Arizona Renewable Energy Standard and Tariff 2018 | ACC | Arizona Public Service Company | Solar Communities                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Program term                                   3 years                                      
Arizona Renewable Energy Standard and Tariff 2018 | ACC | Arizona Public Service Company | Minimum                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Authorized spending in capital costs                                   $ 20,000,000                                      
Arizona Renewable Energy Standard and Tariff 2018 | ACC | Arizona Public Service Company | Maximum                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Authorized spending in capital costs                                   $ 30,000,000                                      
Demand Side Management Adjustor Charge 2022 | ACC | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Amount of proposed budget                                                                     $ 78,400,000    
Rate matter, increase (decrease) in proposed budget                                                                     $ 14,000,000    
2023 Transportation Electrification Plan | ACC | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Amount of proposed budget                                                               $ 5,000,000          
Demand Side Management Adjustor Charge 2023 | ACC | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Amount of proposed budget                                                             $ 88,000,000 $ 88,000,000          
Demand Side Management Adjustor Charge 2024 | ACC | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Amount of proposed budget             $ 91,500,000                                                            
Rate matter, updated budget                                                       $ 90,900,000                  
Power Supply Adjustor (PSA) | ACC | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
PSA rate (in dollars per kWh) | $ / kWh   0.013977         0.019074                 0.019074 0.006       0.007544                                
Forward component of PSA rate1 (in dollars per kWh) | $ / kWh   (0.000281)         (0.012624)                 (0.005527)         0.004842                                
Historical component of PSA rate1 (in dollars per kWh) | $ / kWh   0.008728         0.013071                 0.013071         0.012386                                
Transition component of PSA rate | $ / kWh   0.005530         0.011530                 0.011530                                          
Period to reduce balancing account                               24 months                                          
Reporting threshold of balancing account             $ 100,000,000                                                            
Overall approved PSA rate1 (in dollars per kWh) | $ / kWh             0.011977                                                            
Power Supply Adjustor (PSA) | ACC | Arizona Public Service Company | Cost Recovery Mechanisms                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Maximum increase decrease in PSA rate (in dollars per kWh) | $ / kWh   0.006                                           0.006                          
PSA rate In prior years1 (in dollars per kWh) | $ / kWh   0.002                                     0.004                                
Environmental Improvement Surcharge | FERC | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Rate matters, increase (decrease) In cost recovery                             $ (10,700,000)   $ 14,700,000                                        
Rate matters, increase (decrease) In cost recovery, excess Of annual amount                             (7,500,000)   $ 3,300,000                                        
Rate matters, environmental surcharge cap rate1 (in dollars per kWh)                             $ 4,000,000                                            
Transmission rates, transmission cost adjustor and other transmission matters | FERC | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Rate matters, increase (decrease) In cost recovery       $ 27,400,000                 $ 34,700,000           $ (33,000,000)                                    
Rate matters, increase (decrease) in cost recovery, wholesale customer rates       16,600,000                 20,700,000           (6,400,000)                                    
Rate matters, increase (decrease) in cost recovery, retail customer rates       10,800,000                 14,000,000           (26,600,000)                                    
Rate matters, increase (decrease) In retail revenue requirements       $ 8,800,000                 $ (10,000,000)           $ (2,400,000)                                    
Rate matters, increase in residential and commercial rates (in MW) | MW       3                                                                  
Rate matters, decrease in commercial rates (in MW) | MW       3                                                                  
Lost Fixed Cost Recovery Mechanism | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Rate matter cap percentage of retail revenue                                                   1.00%                      
Amount of adjustment approved representing prorated sales losses pending approval     $ 49,600,000               $ 68,700,000                 $ 59,100,000                                  
Increase (decrease) In amount of adjustment representing prorated sales losses                                       $ 32,500,000     $ 11,800,000                            
Amount of adjustment representing annual recovery     $ 8,000,000               $ 9,600,000                                                    
Lost Fixed Cost Recovery Mechanism | ACC                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Amount of adjustment approved to transfer                 $ 27,100,000                                                        
Court Resolution Surcharge | ACC | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Court resolution surcharge (in dollars per kWh) | $ / KWH_Kilowatt_hour                       0.00175                                                  
Lost revenue recovery                       $ 59,600,000                                                  
Lost revenue recovery collected                                                   $ 26,200,000                      
Net Metering | ACC | Arizona Public Service Company                                                                          
Public Utilities, General Disclosures [Line Items]                                                                          
Rate matters, cost of service, resource comparison proxy method, maximum annual percentage decrease         10.00%         10.00%       10.00%       10.00%             10.00%                        
Rate matter, request second-year energy price for exported energy1 (in dollars per kwh) | $ / kWh                                   0.0846       0.094                              
Third-year export energy price (in dollars per kWh) | $ / kWh         0.06857                 0.07619                                              
Rate lock period                   10 years                                                      
v3.25.0.1
Regulatory Matters - Schedule of Changes in The Deferred Fuel and Purchased Power Regulatory Asset (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Change in regulatory asset      
Deferred fuel and purchased power costs $ 250,288 $ 549,877 $ 291,992
Amounts charged to customers (425,886) (547,243) (219,579)
Arizona Public Service Company      
Change in regulatory asset      
Deferred fuel and purchased power costs 250,288 549,877 291,992
Amounts charged to customers (425,886) (547,243) (219,579)
Power Supply Adjustor (PSA) | ACC | Arizona Public Service Company      
Change in regulatory asset      
Balance at beginning of period 463,195 460,561  
Deferred fuel and purchased power costs 250,288 549,877  
Amounts charged to customers (425,886) (547,243)  
Balance at end of period $ 287,597 $ 463,195 $ 460,561
v3.25.0.1
Regulatory Matters - Four Corners, Cholla and Navajo Plant (Details) - Arizona Public Service Company - USD ($)
$ in Millions
 1 Months Ended
Nov. 02, 2021
Sep. 30, 2018
Apr. 30, 2018
Dec. 31, 2024
Aug. 02, 2021
Coal Community Transition Plan | Navajo Nation, Economic Development Organization | Retail Rate Case Filing with Arizona Corporation Commission | ACC          
Acquisition          
Disallowance of annual amortization percentage         15.00%
Retired power plant costs          
Acquisition          
Net book value       $ 28.1  
Navajo Plant          
Acquisition          
Net book value       33.4  
Navajo Plant, Coal Reclamation Regulatory Asset          
Acquisition          
Net book value       $ 7.9  
SCE | Four Corners Units 4 and 5          
Acquisition          
Settlement agreement, ACC approved rate adjustment, annualized customer impact   $ 58.5 $ 67.5    
Disallowance of plant investments $ 194.0        
Cost deferrals $ 215.5        
v3.25.0.1
Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Detail of regulatory assets    
Total regulatory assets $ 1,810,458 $ 2,016,036
Less: current regulatory assets 420,969 625,757
Total non-current regulatory assets 1,389,489 1,390,279
Pension    
Detail of regulatory assets    
Total regulatory assets 750,976 696,476
Deferred fuel and purchased power    
Detail of regulatory assets    
Total regulatory assets 287,597 463,195
Income taxes — AFUDC equity    
Detail of regulatory assets    
Total regulatory assets 192,936 189,058
Ocotillo deferral    
Detail of regulatory assets    
Total regulatory assets 114,775 128,636
SCR deferral    
Detail of regulatory assets    
Total regulatory assets 83,123 89,477
Lease incentives    
Detail of regulatory assets    
Total regulatory assets 70,541 46,615
Retired power plant costs    
Detail of regulatory assets    
Total regulatory assets 68,380 83,536
Deferred fuel and purchased power — mark-to-market (Note 15)    
Detail of regulatory assets    
Total regulatory assets 42,275 120,214
FERC Transmission true up    
Detail of regulatory assets    
Total regulatory assets 35,159 616
Income taxes — investment tax credit basis adjustment    
Detail of regulatory assets    
Total regulatory assets 34,834 34,230
Deferred compensation    
Detail of regulatory assets    
Total regulatory assets 33,108 33,972
Deferred property taxes    
Detail of regulatory assets    
Total regulatory assets 23,918 32,488
Palo Verde VIEs (Note 17)    
Detail of regulatory assets    
Total regulatory assets 20,611 20,772
Power supply adjustor - interest    
Detail of regulatory assets    
Total regulatory assets 11,525 19,416
Active Union Medical Trust    
Detail of regulatory assets    
Total regulatory assets 9,673 12,747
Mead-Phoenix transmission line contributions in aid of construction (“CIAC”)    
Detail of regulatory assets    
Total regulatory assets 8,384 8,716
Navajo coal reclamation    
Detail of regulatory assets    
Total regulatory assets 7,905 10,883
Loss on reacquired debt    
Detail of regulatory assets    
Total regulatory assets 6,682 7,965
Tax expense adjustor mechanism    
Detail of regulatory assets    
Total regulatory assets 4,534 5,190
Four Corners cost deferral    
Detail of regulatory assets    
Total regulatory assets 0 7,922
Other    
Detail of regulatory assets    
Total regulatory assets $ 3,522 $ 3,912
v3.25.0.1
Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Detail of regulatory liabilities    
Total regulatory liabilities $ 2,062,233 $ 2,175,788
Less: current regulatory liabilities 206,955 209,923
Total non-current regulatory liabilities 1,855,278 1,965,865
Asset retirement obligations and removal costs    
Detail of regulatory liabilities    
Total regulatory liabilities 358,403 486,751
Other postretirement benefits    
Detail of regulatory liabilities    
Total regulatory liabilities 238,113 226,726
Four Corners coal reclamation    
Detail of regulatory liabilities    
Total regulatory liabilities 77,532 68,521
Renewable energy standard    
Detail of regulatory liabilities    
Total regulatory liabilities 68,523 60,667
Income taxes — deferred investment tax credit    
Detail of regulatory liabilities    
Total regulatory liabilities 66,327 55,917
Income taxes — change in rates    
Detail of regulatory liabilities    
Total regulatory liabilities 59,133 43,251
Spent nuclear fuel    
Detail of regulatory liabilities    
Total regulatory liabilities 26,818 33,154
Demand side management    
Detail of regulatory liabilities    
Total regulatory liabilities 23,927 14,374
Sundance maintenance    
Detail of regulatory liabilities    
Total regulatory liabilities 23,086 19,989
TCA Balancing Account    
Detail of regulatory liabilities    
Total regulatory liabilities 14,834 3,425
Property tax deferral    
Detail of regulatory liabilities    
Total regulatory liabilities 4,785 10,850
Tax expense adjustor mechanism    
Detail of regulatory liabilities    
Total regulatory liabilities 4,343 4,835
Other    
Detail of regulatory liabilities    
Total regulatory liabilities 113 2,317
ACC | Excess deferred income taxes - Tax Cuts and Jobs Act    
Detail of regulatory liabilities    
Total regulatory liabilities 888,896 930,344
FERC | Excess deferred income taxes - Tax Cuts and Jobs Act    
Detail of regulatory liabilities    
Total regulatory liabilities $ 207,400 $ 214,667
v3.25.0.1
Income Taxes - Additional Information (Details) - USD ($)
$ in Thousands
 12 Months Ended
Jan. 30, 2024
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Income Taxes        
Interest expense to be received on the underpayment of income taxes   $ 2,100    
Increase (decrease) in deferred income taxes due to regulation adoption   4,000    
Income tax benefits   0    
Income tax benefit   110,529 $ 76,912 $ 74,827
Variable Interest Entity, Not Primary Beneficiary | Palo Verde Sale Leaseback        
Income Taxes        
Income tax benefit   0    
Discontinued Operations, Disposed of by Sale | Bright Canyou Energy Corportion        
Income Taxes        
Investment tax credits $ 23,000      
Payments to acquire investment tax credits $ 21,000      
Arizona Public Service Company        
Income Taxes        
Income tax benefit   126,993 $ 94,184 $ 90,800
Federal        
Income Taxes        
State credit carryforwards net of federal benefit   12,000    
Federal | Arizona Public Service Company        
Income Taxes        
State credit carryforwards net of federal benefit   0    
State        
Income Taxes        
State credit carryforwards net of federal benefit   12,000    
State | Arizona Public Service Company        
Income Taxes        
State credit carryforwards net of federal benefit   $ 0    
v3.25.0.1
Income Taxes - Schedule of Unrecognized Tax Benefits Roll Forward (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Tabular reconciliation of the total amounts of unrecognized tax benefits, excluding interest and penalties, at the beginning and end of the year      
Total unrecognized tax benefits, beginning of the year $ 44,274 $ 43,097 $ 45,086
Additions for tax positions of the current year 1,271 1,473 1,399
Additions for tax positions of prior years 2,031 419 2,069
Reductions for tax positions of prior years for:      
Changes in judgment (2,043) 661 (3,495)
Settlements with taxing authorities 0 0 0
Lapses of applicable statute of limitations (1,184) (1,376) (1,962)
Total unrecognized tax benefits, end of the year 44,349 44,274 43,097
Arizona Public Service Company      
Tabular reconciliation of the total amounts of unrecognized tax benefits, excluding interest and penalties, at the beginning and end of the year      
Total unrecognized tax benefits, beginning of the year 44,274 43,097 45,086
Additions for tax positions of the current year 1,271 1,473 1,399
Additions for tax positions of prior years 2,031 419 2,069
Reductions for tax positions of prior years for:      
Changes in judgment (2,043) 661 (3,495)
Settlements with taxing authorities 0 0 0
Lapses of applicable statute of limitations (1,184) (1,376) (1,962)
Total unrecognized tax benefits, end of the year $ 44,349 $ 44,274 $ 43,097
v3.25.0.1
Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Income Tax [Line Items]      
Tax positions, that if recognized, would decrease our effective tax rate $ 27,899 $ 28,762 $ 28,246
Unrecognized tax benefit interest expense/(benefit) recognized 2,743 452 (139)
Unrecognized tax benefit interest accrued 4,376 1,633 1,181
Arizona Public Service Company      
Income Tax [Line Items]      
Tax positions, that if recognized, would decrease our effective tax rate 27,899 28,762 28,246
Unrecognized tax benefit interest expense/(benefit) recognized 2,743 452 (139)
Unrecognized tax benefit interest accrued $ 4,376 $ 1,633 $ 1,181
v3.25.0.1
Income Taxes - Schedule of Components of Income Tax Expense (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Current:      
Federal $ 137,342 $ 21,272 $ 35,617
State 2,392 2,854 1,950
Total current 139,734 24,126 37,567
Deferred:      
Federal (53,228) 37,273 23,693
State 24,023 15,513 13,567
Total deferred (29,205) 52,786 37,260
Income tax expense/(benefit) 110,529 76,912 74,827
Arizona Public Service Company      
Current:      
Federal 165,653 26,405 103,349
State 26,054 1,027 161
Total current 191,707 27,432 103,510
Deferred:      
Federal (69,075) 44,922 (31,860)
State 4,361 21,830 19,150
Total deferred (64,714) 66,752 (12,710)
Income tax expense/(benefit) $ 126,993 $ 94,184 $ 90,800
v3.25.0.1
Income Taxes - Schedule of Comparison of Pretax Income from Federal Income Tax Rate to Income Tax Expense (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Income Tax Reconciliation Increases Reductions in Tax Expense [Abstract]      
Federal income tax expense at statutory rate $ 154,677 $ 125,095 $ 120,887
State income tax net of federal income tax benefit 24,218 18,024 17,740
State income tax credits net of federal income tax benefit (3,349) (3,513) (5,482)
Excess deferred income taxes — Tax Cuts and Jobs Act (36,559) (36,558) (36,241)
Allowance for equity funds used during construction (Note 1) (2,545) (5,964) (4,629)
Palo Verde VIE noncontrolling interest (Note 17) (3,617) (3,617) (3,617)
Investment tax credit amortization (9,425) (9,495) (5,608)
Federal production tax credit (15,206) (8,441) (3,146)
Other federal income tax credits (3,881) (3,453) (7,721)
Other 6,216 4,834 2,644
Income tax expense/(benefit) 110,529 76,912 74,827
Arizona Public Service Company      
Income Tax Reconciliation Increases Reductions in Tax Expense [Abstract]      
Federal income tax expense at statutory rate 165,090 138,337 132,920
State income tax net of federal income tax benefit 25,639 19,832 19,000
State income tax credits net of federal income tax benefit (1,611) (1,775) (3,744)
Excess deferred income taxes — Tax Cuts and Jobs Act (36,559) (36,558) (36,241)
Allowance for equity funds used during construction (Note 1) (2,545) (5,964) (4,629)
Palo Verde VIE noncontrolling interest (Note 17) (3,617) (3,617) (3,617)
Investment tax credit amortization (9,425) (9,495) (5,608)
Federal production tax credit (12,110) (5,460) 0
Other federal income tax credits (1,551) (2,803) (7,721)
Other 3,682 1,687 440
Income tax expense/(benefit) $ 126,993 $ 94,184 $ 90,800
v3.25.0.1
Income Taxes - Schedule of Components of the Net Deferred Income Tax Liability (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
DEFERRED TAX ASSETS    
Risk management activities $ 14,539 $ 31,411
Regulatory liabilities:    
Excess deferred income taxes — Tax Cuts and Jobs Act 271,004 283,161
Asset retirement obligation and removal costs 81,308 113,312
Unamortized investment tax credits 66,327 68,521
Other postretirement benefits 58,862 56,070
Other 47,671 39,857
Operating lease liabilities 400,771 316,067
Pension liabilities 39,070 33,294
Coal reclamation liabilities 42,391 45,505
Renewable energy incentives 14,571 17,261
Credit and loss carryforwards 7,682 43,940
Employee benefit liabilities 57,853 49,222
Other 44,412 28,643
Total deferred tax assets 1,146,461 1,126,264
DEFERRED TAX LIABILITIES    
Plant-related (2,562,990) (2,572,495)
Risk management activities (4,089) (1,682)
Pension and other postretirement assets (83,401) (78,853)
Other special use funds (55,146) (56,550)
Operating lease right-of-use assets (400,771) (316,067)
Regulatory assets:    
Allowance for equity funds used during construction (47,694) (46,754)
Deferred fuel and purchased power (84,393) (149,078)
Pension benefits (185,641) (172,239)
Retired power plant costs (16,904) (20,659)
Other (57,602) (38,320)
Other (43,383) (36,107)
Total deferred tax liabilities (3,590,934) (3,542,744)
Deferred income taxes — net (2,444,473) (2,416,480)
Ocotillo deferral    
Regulatory assets:    
Defferal (28,372) (31,812)
SCR deferral    
Regulatory assets:    
Defferal (20,548) (22,128)
Arizona Public Service Company    
DEFERRED TAX ASSETS    
Risk management activities 14,539 31,411
Regulatory liabilities:    
Excess deferred income taxes — Tax Cuts and Jobs Act 271,004 283,161
Asset retirement obligation and removal costs 81,308 113,312
Unamortized investment tax credits 66,327 68,521
Other postretirement benefits 58,862 56,070
Other 47,671 39,857
Operating lease liabilities 400,442 315,670
Pension liabilities 36,100 29,918
Coal reclamation liabilities 42,391 45,505
Renewable energy incentives 14,571 17,261
Credit and loss carryforwards 0 3,031
Employee benefit liabilities 56,561 48,551
Other 44,412 29,314
Total deferred tax assets 1,134,188 1,081,582
DEFERRED TAX LIABILITIES    
Plant-related (2,562,990) (2,572,495)
Risk management activities (4,089) (1,682)
Pension and other postretirement assets (82,925) (78,297)
Other special use funds (55,146) (56,550)
Operating lease right-of-use assets (400,443) (315,670)
Regulatory assets:    
Allowance for equity funds used during construction (47,694) (46,754)
Deferred fuel and purchased power (84,393) (149,078)
Pension benefits (185,641) (172,239)
Retired power plant costs (16,904) (20,659)
Other (57,602) (38,320)
Other (7,378) (7,595)
Total deferred tax liabilities (3,554,125) (3,513,279)
Deferred income taxes — net $ (2,419,937) $ (2,431,697)
v3.25.0.1
Lines of Credit and Short-Term Borrowings - Schedule of Consolidated Credit Facilities and Amounts Available and Outstanding (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Pinnacle West    
Lines of Credit and Short-Term Borrowings    
Commitment fees (as a percent) 0.225% 0.17%
Arizona Public Service Company    
Lines of Credit and Short-Term Borrowings    
Commitment fees (as a percent) 0.175% 0.12%
Commercial paper    
Lines of Credit and Short-Term Borrowings    
Commitments under Credit and Term Loan Facilities $ 2,050,000 $ 1,450,000
Outstanding short-term borrowings (568,450) (609,500)
Amount of Credit and Term Loan Facilities Available 1,481,550 840,500
Commercial paper | Pinnacle West    
Lines of Credit and Short-Term Borrowings    
Commitments under Credit and Term Loan Facilities 400,000 200,000
Outstanding short-term borrowings (228,550) (76,650)
Amount of Credit and Term Loan Facilities Available 171,450 123,350
Commercial paper | Arizona Public Service Company    
Lines of Credit and Short-Term Borrowings    
Commitments under Credit and Term Loan Facilities 1,650,000 1,250,000
Outstanding short-term borrowings (339,900) (532,850)
Amount of Credit and Term Loan Facilities Available $ 1,310,100 $ 717,150
v3.25.0.1
Lines of Credit and Short-Term Borrowings - Additional Information (Details) - USD ($)
$ in Thousands
 1 Months Ended
Dec. 20, 2024
Dec. 05, 2024
Feb. 09, 2024
Dec. 12, 2023
Jun. 30, 2024
Dec. 31, 2024
Dec. 17, 2024
Aug. 02, 2024
Dec. 31, 2023
Oct. 27, 2023
Apr. 10, 2023
Apr. 09, 2023
Arizona Public Service Company                        
Lines of Credit and Short-Term Borrowings                        
Requested equity contributions limit             $ 9,500,000     $ 500,000    
Arizona Public Service Company | ACC                        
Lines of Credit and Short-Term Borrowings                        
Percentage of APS's capitalization used in calculation of short-term debt authorization             7.00%          
Required amount to be used in purchases of natural gas and power which is used in calculation of short-term debt authorization             $ 500,000          
Term Loan | Arizona Public Service Company                        
Lines of Credit and Short-Term Borrowings                        
Debt instrument term   364 days   364 days                
Notes issued   $ 400,000   $ 350,000                
Debt instrument, basis spread on variable rate   0.90%   1.00%                
Loan amount drawn     $ 350,000                  
Revolving credit facility | Revolving Credit Facility Maturing April 2029 | Arizona Public Service Company                        
Lines of Credit and Short-Term Borrowings                        
Current borrowing capacity on credit facility               $ 1,250,000        
Accordion feature, increase limit               400,000        
Maximum borrowing capacity on credit facility upon satisfaction of certain conditions and consent of lenders               1,650,000        
Long-term line of credit           $ 0            
Debt, weighted average interest rate           4.62%            
Commercial paper                        
Lines of Credit and Short-Term Borrowings                        
Current borrowing capacity on credit facility           $ 2,050,000     $ 1,450,000      
Long-term line of credit           568,450     609,500      
Commercial paper | Arizona Public Service Company                        
Lines of Credit and Short-Term Borrowings                        
Current borrowing capacity on credit facility           1,650,000     1,250,000      
Maximum commercial paper support available under credit facility                     $ 1,000,000 $ 750,000
Long-term line of credit           339,900     532,850      
Commercial paper | Revolving Credit Facility Maturing April 2029 | Arizona Public Service Company                        
Lines of Credit and Short-Term Borrowings                        
Commercial paper           340,000            
Letter of Credit | Arizona Public Service Company                        
Lines of Credit and Short-Term Borrowings                        
Outstanding letters of credit           18,000            
Letter of Credit | Revolving Credit Facility Maturing April 2029 | Arizona Public Service Company                        
Lines of Credit and Short-Term Borrowings                        
Outstanding letters of credit           0            
Pinnacle West | Term Loan                        
Lines of Credit and Short-Term Borrowings                        
Debt instrument term   364 days                    
Notes issued   $ 200,000                    
Debt instrument, basis spread on variable rate   0.95%                    
Loan amount drawn $ 200,000                      
Pinnacle West | Term Loan | Arizona Public Service Company                        
Lines of Credit and Short-Term Borrowings                        
Debt instrument term         364 days              
Pinnacle West | Revolving credit facility | Revolving Credit Facility Maturing April 2029                        
Lines of Credit and Short-Term Borrowings                        
Current borrowing capacity on credit facility               200,000        
Accordion feature, increase limit               300,000        
Long-term line of credit           0            
Pinnacle West | Commercial paper                        
Lines of Credit and Short-Term Borrowings                        
Current borrowing capacity on credit facility           400,000     200,000      
Long-term line of credit           $ 228,550     $ 76,650      
Pinnacle West | Commercial paper | Revolving Credit Facility Maturing April 2029                        
Lines of Credit and Short-Term Borrowings                        
Commercial paper               $ 29,000        
Debt, weighted average interest rate           4.58%            
Pinnacle West | Letter of Credit | Revolving Credit Facility Maturing April 2029                        
Lines of Credit and Short-Term Borrowings                        
Outstanding letters of credit           $ 0            
v3.25.0.1
Long-Term Debt and Liquidity Matters - Schedule of Components of Long-Term Debt on the Consolidated Balance Sheets (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Long-Term Debt and Liquidity Matters [Line Items]    
Total long-term debt $ 8,858,648 $ 8,415,622
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 6) 8,058,648 7,540,622
Pinnacle West    
Long-Term Debt and Liquidity Matters [Line Items]    
Total 8,918,975  
Unamortized discount (5) (15)
Unamortized debt issuance cost (7,225) (1,254)
Total long-term debt 1,367,770 1,123,731
Less current maturities 500,000 625,000
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 6) 867,770 498,731
Arizona Public Service Company    
Long-Term Debt and Liquidity Matters [Line Items]    
Total 7,543,975  
Unamortized discount (14,252) (14,197)
Unamortized premium 9,955 11,162
Unamortized debt issuance cost (48,800) (49,049)
Total long-term debt 7,490,878 7,291,891
Less current maturities 300,000 250,000
LONG-TERM DEBT LESS CURRENT MATURITIES (Note 6) 7,190,878 7,041,891
Pollution Control Bonds - Variable | Arizona Public Service Company    
Long-Term Debt and Liquidity Matters [Line Items]    
Total $ 163,975 $ 163,975
Weighted-average interest rate (as a percent) 4.01% 4.11%
Total Pollution Control Bonds | Arizona Public Service Company    
Long-Term Debt and Liquidity Matters [Line Items]    
Total $ 163,975 $ 163,975
Senior Unsecured Notes | Pinnacle West    
Long-Term Debt and Liquidity Matters [Line Items]    
Total $ 1,025,000 500,000
Senior Unsecured Notes | Pinnacle West | Minimum    
Long-Term Debt and Liquidity Matters [Line Items]    
Interest rate (as a percent) 1.30%  
Senior Unsecured Notes | Pinnacle West | Maximum    
Long-Term Debt and Liquidity Matters [Line Items]    
Interest rate (as a percent) 4.75%  
Senior Unsecured Notes | Arizona Public Service Company    
Long-Term Debt and Liquidity Matters [Line Items]    
Total $ 7,380,000 7,180,000
Senior Unsecured Notes | Arizona Public Service Company | Minimum    
Long-Term Debt and Liquidity Matters [Line Items]    
Interest rate (as a percent) 2.20%  
Senior Unsecured Notes | Arizona Public Service Company | Maximum    
Long-Term Debt and Liquidity Matters [Line Items]    
Interest rate (as a percent) 6.88%  
Floating Rate Notes Due 2026 | Pinnacle West | Unsecured Debt    
Long-Term Debt and Liquidity Matters [Line Items]    
Total $ 350,000 0
Weighted-average interest rate (as a percent) 5.88%  
Term Loan | Pinnacle West | Secured Debt    
Long-Term Debt and Liquidity Matters [Line Items]    
Total $ 0 $ 625,000
Weighted-average interest rate (as a percent)   6.20%
v3.25.0.1
Long-Term Debt and Liquidity Matters - Schedule of Principal Payments Due on Pinnacle West's and APS's Total Long-Term Debt (Details)
$ in Thousands
Dec. 31, 2024
USD ($)
Arizona Public Service Company  
Principal payments due on long-term debt  
2025 $ 300,000
2026 250,000
2027 300,000
2028 0
2029 568,975
Thereafter 6,125,000
Total 7,543,975
Pinnacle West  
Principal payments due on long-term debt  
2025 800,000
2026 600,000
2027 825,000
2028 0
2029 568,975
Thereafter 6,125,000
Total $ 8,918,975
v3.25.0.1
Long-Term Debt and Liquidity Matters - Schedule of Estimated Fair Value of Long-Term Debt, Including Current Maturities (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Estimated fair value of long-term debt, including current maturities    
Carrying Amount $ 8,858,648 $ 8,415,622
Fair Value 7,918,992 7,555,653
Arizona Public Service Company    
Estimated fair value of long-term debt, including current maturities    
Carrying Amount 7,490,878 7,291,891
Fair Value 6,525,248 6,459,718
Pinnacle West    
Estimated fair value of long-term debt, including current maturities    
Carrying Amount 1,367,770 1,123,731
Fair Value $ 1,393,744 $ 1,095,935
v3.25.0.1
Long-Term Debt and Liquidity Matters - Additional Information (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended 12 Months Ended
Dec. 23, 2024
USD ($)
Dec. 20, 2024
USD ($)
Dec. 17, 2024
USD ($)
Dec. 05, 2024
USD ($)
Jun. 17, 2024
USD ($)
Jun. 12, 2024
USD ($)
Jun. 10, 2024
USD ($)
Jun. 06, 2024
USD ($)
Apr. 19, 2024
USD ($)
Feb. 28, 2024
USD ($)
shares
Feb. 09, 2024
USD ($)
Dec. 12, 2023
USD ($)
Feb. 11, 2022
USD ($)
MW
Dec. 31, 2024
USD ($)
$ / shares
shares
Jun. 30, 2024
USD ($)
day
Dec. 31, 2024
USD ($)
$ / shares
shares
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
May 09, 2024
USD ($)
Apr. 18, 2024
USD ($)
Oct. 27, 2023
USD ($)
Aug. 04, 2023
USD ($)
Dec. 16, 2022
USD ($)
Long-Term Debt and Liquidity Matters [Line Items]                                              
Short-term debt repayments under term loan facility                               $ 350,000 $ 0 $ 0          
February 2024 Forward Sale Agreements                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Sale of stock, settlement terms (in shares) | shares                   5,377,115                          
Proceeds from issuance of common stock                   $ 345,000                          
Number of shares issued in transaction (in shares) | shares                   11,240,601                          
November 2024 Forward Sale Agreement                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Sale of stock, settlement terms (in shares) | shares                               552,833              
Proceeds from issuance of common stock                               $ 50,000              
Maximum                                              
Debt Provisions                                              
Ratio of consolidated debt to consolidated capitalization (as a percent)                           65.00%   65.00%              
Arizona Public Service Company                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Short-term debt repayments under term loan facility                               $ 350,000 0 $ 0          
Long-term debt                           $ 7,543,975   7,543,975              
Annual amount of approved equity infusions                               $ 150,000              
Requested equity contributions limit     $ 9,500,000                                   $ 500,000    
Public utilities, request to permanently modify permitted yearly equity infusions     2.50%           2.50%                            
Public utilities, number of basis point of approved rate                           0.0050   0.0050              
Equity infusion from Pinnacle West $ 345,000         $ 450,000                                  
Public utility, permitted equity infusions, percentage                 2.50%                            
Debt Provisions                                              
Actual ratio of consolidated debt to total consolidated capitalization required to be maintained as per the debt covenant (as a percent)                           49.00%   49.00%              
Arizona Public Service Company | ACC                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Public utility order long term debt, authorized                 $ 9,500,000                            
Debt Provisions                                              
Long term debt authorization                 $ 9,500,000                     $ 8,000,000      
Bright Canyon Energy Corporation                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Solar plant capacity (in mw) | MW                         31                    
Battery storage capacity (in mwh) | MW                         20                    
Pinnacle West | Forward Sale Agreements                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Number of shares issued in transaction (in shares) | shares                           5,377,115                  
Proceeds from issuance of common stock                           $ 345,000                  
Pinnacle West | February 2024 Forward Sale Agreements                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Sale of stock, settlement terms (in shares) | shares                               5,863,486              
Proceeds from issuance of common stock                               $ 377,000              
Pinnacle West | November 2024 Forward Sale Agreement                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Sale of stock, settlement terms (in shares) | shares                               552,833              
Proceeds from issuance of common stock                               $ 50,000              
Term Loan | Arizona Public Service Company                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Notes issued       $ 400,000               $ 350,000                      
Debt instrument term       364 days               364 days                      
Debt instrument, basis spread on variable rate       0.90%               1.00%                      
Loan amount drawn                     $ 350,000                        
Unsecured Senior Notes Due 2024 | Arizona Public Service Company | Senior Notes                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Notes issued                                     $ 450,000        
Repayments of unsecured debt         $ 250,000                                    
Interest rate (as a percent)         3.35%                           5.70%        
Term Loan | Non-Recourse Construction Term Loan Facility | Bright Canyon Energy Corporation                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Notes issued                         $ 36,000                 $ 36,000  
Bridge Loan | Equity Bridge Loan Facility | Bright Canyon Energy Corporation                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Notes issued                         $ 31,000                 $ 31,000  
Debt Provisions                                              
Term loans                           0   0              
Pinnacle West                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Long-term debt                           $ 8,918,975   $ 8,918,975              
Debt Provisions                                              
Actual ratio of consolidated debt to total consolidated capitalization required to be maintained as per the debt covenant (as a percent)                           59.00%   59.00%              
Pinnacle West | Convertible Notes Due Maturing June 2027 | Convertible Debt                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Notes issued                           $ 525,000 $ 525,000 $ 525,000              
Interest rate (as a percent)                           4.75% 4.75% 4.75%              
Debt instrument, convertible, conversion ratio                               0.108338              
Debt instrument, convertible, conversion price (in usd per share) | $ / shares                           $ 92.30   $ 92.30              
Debt instrument redemption price percentage                               100.00%              
Long-term debt                           $ 525,000   $ 525,000              
Unamortized debt issuance expense                           8,000   8,000              
Convertible debt, fair value                           552,000   552,000              
Pinnacle West | Convertible Notes Due Maturing June 2027 | Convertible Debt | Debt Conversion Terms One                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Debt instrument, convertible, threshold trading days | day                             20                
Debt instrument, convertible, threshold consecutive trading days | day                             30                
Debt instrument, convertible, threshold percentage of stock price trigger                             130.00%                
Pinnacle West | Convertible Notes Due Maturing June 2027 | Convertible Debt | Debt Conversion Terms Two                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Debt instrument, convertible, threshold trading days | day                             5                
Debt instrument, convertible, threshold consecutive trading days | day                             10                
Debt instrument, convertible, threshold percentage of stock price trigger                             98.00%                
Pinnacle West | Term Loan                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Notes issued       $ 200,000                                      
Debt instrument term       364 days                                      
Short-term debt repayments under term loan facility   $ 200,000                                          
Debt instrument, basis spread on variable rate       0.95%                                      
Loan amount drawn   $ 200,000                                          
Pinnacle West | Term Loan | Arizona Public Service Company                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Debt instrument term                             364 days                
Short-term debt repayments under term loan facility                             $ 350,000                
Pinnacle West | Floating Rate Notes Due 2026 | Unsecured Debt                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Notes issued                           350,000   350,000              
Long-term debt                           350,000   350,000 $ 0            
Debt instrument, basis spread on variable rate                             0.82%                
Pinnacle West | 450 Million Term Loan Maturing December 2024                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Notes issued               $ 450,000           450,000   450,000              
Repayments of unsecured debt               $ 250,000                              
Pinnacle West | 175 Million Term Loan Maturing December 2024                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Notes issued                           $ 175,000   $ 175,000              
Repayments of unsecured debt             $ 175,000                                
Pinnacle West | Term Loan                                              
Long-Term Debt and Liquidity Matters [Line Items]                                              
Notes issued                                             $ 175,000
v3.25.0.1
Retirement Plans and Other Postretirement Benefits - Net Periodic Benefit Costs and Portion including Portion Charged to Expense (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Net periodic benefit costs and the portion of these costs charged to expense      
Portion of costs (credits) charged to expense $ (48,870) $ (40,648) $ (98,487)
Pension Plans      
Net periodic benefit costs and the portion of these costs charged to expense      
Service cost-benefits earned during the period 43,641 39,461 55,473
Interest cost on benefit obligation 148,643 153,561 107,492
Expected return on plan assets (188,651) (182,938) (185,775)
Prior service credit (a) 0 0 0
Net actuarial loss (gain) 41,915 38,420 17,515
Net periodic benefit costs (credits) 45,548 48,504 (5,295)
Portion of costs (credits) charged to expense 23,652 27,029 (16,431)
Other Benefits Plans      
Net periodic benefit costs and the portion of these costs charged to expense      
Service cost-benefits earned during the period 9,955 8,567 16,470
Interest cost on benefit obligation 22,169 22,509 17,491
Expected return on plan assets (46,834) (43,486) (46,042)
Prior service credit (a) (37,789) (37,789) (37,789)
Net actuarial loss (gain) (8,676) (9,614) (12,835)
Net periodic benefit costs (credits) (61,175) (59,813) (62,705)
Portion of costs (credits) charged to expense $ (45,557) $ (43,408) $ (45,042)
v3.25.0.1
Retirement Plans and Other Postretirement Benefits - Changes Benefit Obligations and Funded Status (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Pension Plans      
Change in Benefit Obligation      
Benefit obligation at the beginning of the period $ 2,908,063 $ 2,809,529  
Service cost 43,641 39,461 $ 55,473
Interest cost 148,643 153,561 107,492
Benefit payments (216,238) (210,737)  
Actuarial (gain) loss (91,800) 116,249  
Benefit obligation at the end of the period 2,792,309 2,908,063 2,809,529
Change in Plan Assets      
Balance at the beginning of the period 2,835,549 2,829,485  
Actual return on plan assets 4,518 199,098  
Benefit payments (200,205) (193,034)  
Balance at the end of the period 2,639,862 2,835,549 2,829,485
Funded/(Underfunded) Status at the end of the period (152,447) (72,514)  
Other Benefits Plans      
Change in Benefit Obligation      
Benefit obligation at the beginning of the period 430,434 409,461  
Service cost 9,955 8,567 16,470
Interest cost 22,169 22,509 17,491
Benefit payments (30,516) (30,784)  
Actuarial (gain) loss (71,952) 20,681  
Benefit obligation at the end of the period 360,090 430,434 409,461
Change in Plan Assets      
Balance at the beginning of the period 696,494 652,287  
Actual return on plan assets 32,816 67,317  
Benefit payments (27,118) (23,110)  
Balance at the end of the period 702,192 696,494 $ 652,287
Funded/(Underfunded) Status at the end of the period $ 342,102 $ 266,060  
v3.25.0.1
Retirement Plans and Other Postretirement Benefits - Projected Benefit Obligation for Pension Plans (Details) - Pension Plans - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Projected benefit obligation and the accumulated benefit obligation for pension plans with an accumulated obligation in excess of plan assets    
Accumulated benefit obligation $ 113,541 $ 123,701
Fair value of plan assets 0 0
Projected benefit obligation 2,792,309 129,891
Fair value of plan assets $ 2,639,862 $ 0
v3.25.0.1
Retirement Plans and Other Postretirement Benefits - Additional Information (Details) - USD ($)
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]      
Funded percentage 99.00% 102.00%  
Partnership funding commitments, contribution amount (up to) $ 50,000,000    
Partnership funding commitments, funded amount $ 38,000,000    
Arizona Public Service Company      
Defined Benefit Plan Disclosure [Line Items]      
APS's employees share of total cost of the plans (as a percent) 99.00%    
Other Benefits Plans      
Defined Benefit Plan Disclosure [Line Items]      
Expected long-term return on plan assets for next fiscal year (as a percent) 7.15%    
Retiree medical cost reimbursement $ 27,000,000 $ 23,000,000 $ 26,000,000
Pension Plans      
Defined Benefit Plan Disclosure [Line Items]      
Expected long-term return on plan assets for next fiscal year (as a percent) 7.05%    
Minimum contributions under MAP-21 $ 0    
Pinnacle West      
Defined Benefit Plan Disclosure [Line Items]      
Expenses recorded for the defined contribution savings plan $ 14,000,000 $ 12,000,000 $ 12,000,000
v3.25.0.1
Retirement Plans and Other Postretirement Benefits - Amounts Recognized on the Consolidated Balance Sheets (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Amounts recognized on the Consolidated Balance Sheets    
Noncurrent asset $ 342,102 $ 323,438
Pension Plans    
Amounts recognized on the Consolidated Balance Sheets    
Noncurrent asset 0 57,378
Current liability (13,130) (17,190)
Noncurrent liability (139,317) (112,702)
Net amount recognized (funded status) (152,447) (72,514)
Other Benefits Plans    
Amounts recognized on the Consolidated Balance Sheets    
Noncurrent asset 342,102 266,060
Current liability 0 0
Noncurrent liability 0 0
Net amount recognized (funded status) $ 342,102 $ 266,060
v3.25.0.1
Retirement Plans and Other Postretirement Benefits - Impact to Accumulated Other Comprehensive Loss (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Pension Plans    
Details related to accumulated other comprehensive loss    
Net actuarial loss (gain) $ 793,421 $ 743,003
Prior service credit 0 0
APS’s portion recorded as a regulatory (asset) liability (750,976) (696,476)
Income tax expense (benefit) (10,354) (11,506)
Accumulated other comprehensive loss (gain) 32,091 35,021
Other Benefits Plans    
Details related to accumulated other comprehensive loss    
Net actuarial loss (gain) (237,889) (188,630)
Prior service credit (1,265) (39,054)
APS’s portion recorded as a regulatory (asset) liability 238,113 226,726
Income tax expense (benefit) 611 691
Accumulated other comprehensive loss (gain) $ (430) $ (267)
v3.25.0.1
Retirement Plans and Other Postretirement Benefits - Weighted-Average Assumptions for Pensions and Other Benefits (Details)
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Weighted-average assumptions used to determine benefit obligations      
Rate of compensation increase 4.50% 4.52%  
Initial healthcare cost trend rate (pre-65 participants) 6.50% 6.25%  
Ultimate healthcare cost trend rate (pre-65 participants) 4.50% 4.75%  
Number of years to ultimate trend rate (pre-65 participants) 6 years 5 years  
Initial healthcare cost trend rate (post-65 participants) 1.00% 2.00%  
Ultimate healthcare cost trend rate (post-65 participants) 0.00% 2.00%  
Interest crediting rate – cash balance pension plans 4.66% 4.54%  
Weighted-average assumptions used to determine net periodic benefit costs      
Initial healthcare cost trend rate (pre-65 participants) 6.25% 6.50% 6.00%
Ultimate healthcare cost trend rate (pre-65 participants) 4.75% 4.75% 4.75%
Number of years to ultimate trend rate (pre-65 participants) 4 years 5 years 3 years
Initial healthcare cost trend rate (post-65 participants) 2.00% 2.00% 2.00%
Ultimate healthcare cost trend rate (post-65 participants) 2.00% 2.00% 2.00%
Interest crediting rate – cash balance pension plans 4.54% 4.50% 4.50%
Pension Plans      
Weighted-average assumptions used to determine benefit obligations      
Discount rate (as a percent) 5.68% 5.21%  
Weighted-average assumptions used to determine net periodic benefit costs      
Discount rate (as a percent) 5.21% 5.56% 2.92%
Rate of compensation increase 4.52% 4.57% 4.00%
Expected long-term return on plan assets (as a percent) 6.90% 6.70% 5.00%
Other Benefits Plans      
Weighted-average assumptions used to determine benefit obligations      
Discount rate (as a percent) 5.71% 5.23%  
Weighted-average assumptions used to determine net periodic benefit costs      
Discount rate (as a percent) 5.23% 5.58% 2.98%
Expected long-term return on plan assets (as a percent) 6.85% 6.80% 5.35%
v3.25.0.1
Retirement Plans and Other Postretirement Benefits - Asset Allocation (Details)
Dec. 31, 2024
Pension Plans  
Defined Benefit Plan Disclosure [Line Items]  
Target Allocation 100.00%
Actual Allocation 100.00%
Pension Plans | Long-term fixed income assets  
Defined Benefit Plan Disclosure [Line Items]  
Target Allocation 80.00%
Actual Allocation 79.00%
Pension Plans | Return-seeking assets  
Defined Benefit Plan Disclosure [Line Items]  
Target Allocation 20.00%
Actual Allocation 21.00%
Target Allocation 20.00%
Pension Plans | Equities in US and other developed markets  
Defined Benefit Plan Disclosure [Line Items]  
Target Allocation 12.00%
Pension Plans | Equities in emerging markets  
Defined Benefit Plan Disclosure [Line Items]  
Target Allocation 4.00%
Pension Plans | Alternative investments  
Defined Benefit Plan Disclosure [Line Items]  
Target Allocation 4.00%
Other Benefits Plans  
Defined Benefit Plan Disclosure [Line Items]  
Actual Allocation 100.00%
Other Benefits Plans | Long-term fixed income assets  
Defined Benefit Plan Disclosure [Line Items]  
Actual Allocation 61.00%
Other Benefits Plans | Return-seeking assets  
Defined Benefit Plan Disclosure [Line Items]  
Actual Allocation 39.00%
v3.25.0.1
Retirement Plans and Other Postretirement Benefits - Schedule of Fair Value of Pinnacle West's Pension Plan (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Pension Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other $ 432,742 $ 399,298  
Fair value of plan assets 2,639,862 2,835,549 $ 2,829,485
Pension Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 748,033 885,721  
Pension Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 1,459,087 1,550,530  
Other Benefits Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 165,813 107,201  
Fair value of plan assets 702,192 696,494 $ 652,287
Other Benefits Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 337,359 391,019  
Other Benefits Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 199,020 198,274  
Cash and cash equivalents | Pension Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0    
Fair value of plan assets 9,055    
Cash and cash equivalents | Pension Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 9,055    
Cash and cash equivalents | Pension Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0    
Cash and cash equivalents | Other Benefits Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0    
Fair value of plan assets 840    
Cash and cash equivalents | Other Benefits Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 840    
Cash and cash equivalents | Other Benefits Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0    
Corporate | Pension Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0 0  
Fair value of plan assets 1,325,833 1,415,346  
Corporate | Pension Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Corporate | Pension Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 1,325,833 1,415,346  
Corporate | Other Benefits Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0 0  
Fair value of plan assets 186,435 189,902  
Corporate | Other Benefits Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Corporate | Other Benefits Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 186,435 189,902  
U.S. Treasury | Pension Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0 0  
Fair value of plan assets 561,317 622,273  
U.S. Treasury | Pension Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 561,317 622,273  
U.S. Treasury | Pension Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
U.S. Treasury | Other Benefits Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0 0  
Fair value of plan assets 204,274 207,665  
U.S. Treasury | Other Benefits Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 204,274 207,665  
U.S. Treasury | Other Benefits Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Other | Pension Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0 0  
Fair value of plan assets 133,254 135,184  
Other | Pension Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Other | Pension Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 133,254 135,184  
Other | Other Benefits Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0 0  
Fair value of plan assets 12,585 8,372  
Other | Other Benefits Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Other | Other Benefits Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 12,585 8,372  
Common stock equities | Pension Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0 0  
Fair value of plan assets 74,939 150,657  
Common stock equities | Pension Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 74,939 150,657  
Common stock equities | Pension Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Common stock equities | Other Benefits Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0 0  
Fair value of plan assets 89,685 139,952  
Common stock equities | Other Benefits Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 89,685 139,952  
Common stock equities | Other Benefits Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Mutual funds | Pension Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0 0  
Fair value of plan assets 102,722 112,791  
Mutual funds | Pension Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 102,722 112,791  
Mutual funds | Pension Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Mutual funds | Other Benefits Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 0 0  
Fair value of plan assets 23,415 22,256  
Mutual funds | Other Benefits Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 23,415 22,256  
Mutual funds | Other Benefits Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Equities | Pension Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 244,734 192,945  
Fair value of plan assets 244,734 192,945  
Equities | Pension Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Equities | Pension Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Equities | Other Benefits Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 140,178 81,724  
Fair value of plan assets 140,178 81,724  
Equities | Other Benefits Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Equities | Other Benefits Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Real estate | Pension Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 127,397 140,613  
Fair value of plan assets 127,397 140,613  
Real estate | Pension Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Real estate | Pension Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Real estate | Other Benefits Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 19,474 20,001  
Fair value of plan assets 19,474 20,001  
Real estate | Other Benefits Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Real estate | Other Benefits Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Short-term investments and other | Pension Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 60,611 65,740  
Fair value of plan assets 60,611 65,740  
Short-term investments and other | Pension Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Short-term investments and other | Pension Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Short-term investments and other | Other Benefits Plans      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Other 6,161 5,476  
Fair value of plan assets 25,306 26,622  
Short-term investments and other | Other Benefits Plans | Level 1      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 19,145 21,146  
Short-term investments and other | Other Benefits Plans | Level 2      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets $ 0 $ 0  
v3.25.0.1
Retirement Plans and Other Postretirement Benefits - Schedule of Estimated Future Benefit Payments (Details)
$ in Thousands
Dec. 31, 2024
USD ($)
Pension Plans  
Estimated Future Benefit Payments  
2025 $ 241,762
2026 223,562
2027 230,335
2028 233,617
2029 232,591
Years 2030-2034 1,147,273
Other Benefits Plans  
Estimated Future Benefit Payments  
2025 28,753
2026 28,747
2027 28,276
2028 27,880
2029 27,645
Years 2030-2034 $ 137,301
v3.25.0.1
Leases - Additional information (Details)
$ in Billions
Dec. 31, 2024
USD ($)
lease
Jan. 31, 2023
agreement
Leases [Abstract]    
Number of lease agreements, sell and lease back | lease 3  
Term of contract 20 years  
Lease not yet commenced | $ $ 16.7  
Number of purchase power operating lease agreements | agreement   2
v3.25.0.1
Leases - Schedule of Lease costs (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Operating Leased Assets [Line Items]      
Operating Lease Cost $ 167,433 $ 145,890 $ 122,062
Variable lease cost 144,108 135,007 122,040
Short-term Lease Cost 20,653 21,530 9,928
Purchased Power & Energy Storage Lease Contracts      
Operating Leased Assets [Line Items]      
Operating Lease Cost 147,313 126,655 104,001
Land, Property & Equipment Leases      
Operating Leased Assets [Line Items]      
Operating Lease Cost 20,120 19,235 18,061
Total Lease Cost $ 332,194 $ 302,427 $ 254,030
v3.25.0.1
Leases - Schedule of Maturity of our operating lease liabilities (Details)
$ in Thousands
Dec. 31, 2024
USD ($)
Lessee, Lease, Description [Line Items]  
2025 $ 175,197
2026 186,917
2027 210,256
2028 211,395
2029 213,206
Thereafter 1,202,826
Total lease commitments 2,199,797
Less imputed interest 578,553
Total lease liabilities 1,621,244
Purchased Power & Energy Storage Lease Contracts  
Lessee, Lease, Description [Line Items]  
2025 158,363
2026 172,087
2027 198,007
2028 201,804
2029 205,741
Thereafter 1,140,971
Total lease commitments 2,076,973
Less imputed interest 536,948
Total lease liabilities 1,540,025
Land, Property & Equipment Leases  
Lessee, Lease, Description [Line Items]  
2025 16,834
2026 14,830
2027 12,249
2028 9,591
2029 7,465
Thereafter 61,855
Total lease commitments 122,824
Less imputed interest 41,605
Total lease liabilities $ 81,219
v3.25.0.1
Leases - Other additional information related to operating lease liabilities (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
USD ($)
agreement
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Jan. 31, 2023
agreement
Leases [Abstract]        
Cash paid for amounts included in the measurement of lease liabilities — operating cash flows: | $ $ 143,950 $ 123,472 $ 118,463  
Right-of-use operating lease assets obtained in exchange for operating lease liabilities | $ $ 393,702 $ 602,301 $ 16,990  
Weighted average remaining lease term 11 years 10 years    
Weighted average discount rate (in percent) 4.90% 4.53%    
Number of new energy storage operating lease agreement | agreement 3      
Number of purchase power operating lease agreements | agreement       2
v3.25.0.1
Jointly-Owned Facilities (Details) - Arizona Public Service Company
$ in Thousands
Dec. 31, 2024
USD ($)
Palo Verde Units 1 and 3  
Interests in jointly-owned facilities  
Percent Owned 29.10%
Plant in Service $ 2,010,346
Accumulated Depreciation 1,081,321
Construction Work in Progress $ 20,694
Palo Verde Unit 2  
Interests in jointly-owned facilities  
Percent Owned 16.80%
Plant in Service $ 709,414
Accumulated Depreciation 397,235
Construction Work in Progress $ 9,076
Palo Verde Common  
Interests in jointly-owned facilities  
Percent Owned 28.00%
Plant in Service $ 898,401
Accumulated Depreciation 366,027
Construction Work in Progress 47,962
Palo Verde Sale Leaseback  
Interests in jointly-owned facilities  
Plant in Service 351,050
Accumulated Depreciation 268,494
Construction Work in Progress $ 0
Four Corners Generating Station  
Interests in jointly-owned facilities  
Percent Owned 63.00%
Plant in Service $ 1,848,412
Accumulated Depreciation 705,667
Construction Work in Progress $ 56,226
Cholla Common Facilities  
Interests in jointly-owned facilities  
Percent Owned 50.50%
Plant in Service $ 301,035
Accumulated Depreciation 231,170
Construction Work in Progress $ 1,743
Arizona Nuclear Power Project 500kV System  
Interests in jointly-owned facilities  
Percent Owned 33.30%
Plant in Service $ 134,713
Accumulated Depreciation 60,174
Construction Work in Progress $ 7,174
Navajo Southern System  
Interests in jointly-owned facilities  
Percent Owned 24.70%
Plant in Service $ 88,528
Accumulated Depreciation 38,797
Construction Work in Progress $ 626
Palo Verde — Yuma 500kV System  
Interests in jointly-owned facilities  
Percent Owned 25.50%
Plant in Service $ 24,260
Accumulated Depreciation 8,120
Construction Work in Progress $ 142
Four Corners Switchyards  
Interests in jointly-owned facilities  
Percent Owned 58.00%
Plant in Service $ 84,367
Accumulated Depreciation 23,886
Construction Work in Progress $ 309
Phoenix — Mead System  
Interests in jointly-owned facilities  
Percent Owned 17.10%
Plant in Service $ 39,788
Accumulated Depreciation 21,173
Construction Work in Progress $ 330
Palo Verde — Rudd 500kV System  
Interests in jointly-owned facilities  
Percent Owned 50.00%
Plant in Service $ 95,785
Accumulated Depreciation 34,254
Construction Work in Progress $ 1,808
Morgan — Pinnacle Peak System  
Interests in jointly-owned facilities  
Percent Owned 63.20%
Plant in Service $ 117,500
Accumulated Depreciation 29,013
Construction Work in Progress $ 287
Round Valley System  
Interests in jointly-owned facilities  
Percent Owned 50.00%
Plant in Service $ 548
Accumulated Depreciation 213
Construction Work in Progress $ 0
Palo Verde — Morgan System  
Interests in jointly-owned facilities  
Percent Owned 87.50%
Plant in Service $ 266,547
Accumulated Depreciation 46,327
Construction Work in Progress $ 208
Hassayampa — North Gila System  
Interests in jointly-owned facilities  
Percent Owned 80.00%
Plant in Service $ 154,330
Accumulated Depreciation 27,739
Construction Work in Progress $ 0
Cholla 500kV Switchyard  
Interests in jointly-owned facilities  
Percent Owned 85.70%
Plant in Service $ 8,454
Accumulated Depreciation 2,859
Construction Work in Progress $ 35
Saguaro 500kV Switchyard  
Interests in jointly-owned facilities  
Percent Owned 60.00%
Plant in Service $ 29,850
Accumulated Depreciation 15,768
Construction Work in Progress $ 101
Kyrene — Knox System  
Interests in jointly-owned facilities  
Percent Owned 50.00%
Plant in Service $ 578
Accumulated Depreciation 349
Construction Work in Progress $ 0
Agua Fria Switchyard  
Interests in jointly-owned facilities  
Percent Owned 10.00%
Plant in Service $ 0
Accumulated Depreciation 0
Construction Work in Progress $ 82
v3.25.0.1
Commitments and Contingencies - Additional Information (Details)
$ in Millions
 1 Months Ended 12 Months Ended 148 Months Ended
Oct. 31, 2024
claim
Jan. 01, 2024
USD ($)
trust
Jan. 17, 2023
USD ($)
Sep. 30, 2022
USD ($)
Jul. 03, 2018
Aug. 15, 2014
USD ($)
Feb. 25, 2025
USD ($)
Dec. 31, 2024
USD ($)
trust
timePeriod
MW
Oct. 31, 2023
claim
Dec. 31, 2023
USD ($)
Apr. 18, 2023
USD ($)
Schedule of Commitments and Contingencies [Line Items]                      
Coal mine reclamation               $ 16,700.0      
Production tax credit guarantees               $ 29.0      
Kūpono Solar                      
Schedule of Commitments and Contingencies [Line Items]                      
Non-recourse construction financing agreement                     $ 140.0
Kūpono Solar                      
Schedule of Commitments and Contingencies [Line Items]                      
Project plant capacity (in MW's) | MW               42      
Asset purchase power agreement               20 years      
Arizona Public Service Company                      
Schedule of Commitments and Contingencies [Line Items]                      
Maximum insurance against public liability per occurrence for a nuclear incident   $ 16,300.0                  
Maximum available nuclear liability insurance   500.0                  
Remaining nuclear liability insurance through mandatory industry wide retrospective assessment program   15,800.0                  
Maximum assessment per reactor for each nuclear incident   165.9                  
Annual limit per incident with respect to maximum assessment   $ 24.7                  
Number of VIE lessor trusts | trust   3           3      
Maximum potential retrospective assessment per incident of APS   $ 144.9                  
Annual payment limitation with respect to maximum potential retrospective assessment   $ 21.6                  
Amount of "all risk" (including nuclear hazards) insurance for property damage to, and decontamination of, property at Palo Verde               $ 2,800.0      
Request second-year energy price for exported energy               23.1      
Collateral assurance based on rating triggers               $ 64.1      
Period to provide collateral assurance based on rating triggers               20 days      
2025               $ 1,540.0      
2026               1,742.0      
2027               1,973.0      
2028               2,142.0      
2029               2,115.0      
Thereafter               27,200.0      
Arizona Public Service Company | Surety Bonds Expiring in 2025                      
Schedule of Commitments and Contingencies [Line Items]                      
Surety bonds expiring, amount               23.0      
Arizona Public Service Company | Letter of Credit                      
Schedule of Commitments and Contingencies [Line Items]                      
Outstanding letters of credit               18.0      
Arizona Public Service Company | Contaminated Groundwater Wells                      
Schedule of Commitments and Contingencies [Line Items]                      
Costs related to investigation and study under Superfund site               3.0      
Remedial investigation work     $ 1.7                
Arizona Public Service Company | Contaminated Groundwater Wells | Pending Litigation                      
Schedule of Commitments and Contingencies [Line Items]                      
Settlement amount       $ 8.3              
Arizona Public Service Company | Renewable Energy Credits                      
Schedule of Commitments and Contingencies [Line Items]                      
2025               27.0      
2026               24.0      
2027               21.0      
2028               18.0      
2029               16.0      
Thereafter               36.0      
Arizona Public Service Company | Coal Mine Reclamation Balance Sheet Obligations                      
Schedule of Commitments and Contingencies [Line Items]                      
Coal mine reclamation               171.0   $ 184.0  
Arizona Public Service Company | Coal Mine Reclamation Obligations                      
Schedule of Commitments and Contingencies [Line Items]                      
2025               20.0      
2026               21.0      
2027               22.0      
2028               23.0      
Thereafter               2.0      
NTEC | Four Corners                      
Schedule of Commitments and Contingencies [Line Items]                      
Asset purchase agreement, option to purchase, ownership interest, percentage         7.00%            
Arizona Public Service Company and Palo Verde Owners vs. United States Department of Energy - Spent Nuclear Fuel and Waste Disposal                      
Schedule of Commitments and Contingencies [Line Items]                      
Number of claims submitted | claim 11                    
Settlement amount, awarded to company           $ 18.0   $ 156.7      
Arizona Public Service Company and Palo Verde Owners vs. United States Department of Energy - Spent Nuclear Fuel and Waste Disposal | Subsequent Event                      
Schedule of Commitments and Contingencies [Line Items]                      
Settlement amount, awarded to company             $ 17.6        
Arizona Public Service Company and Palo Verde Owners vs. United States Department of Energy - Spent Nuclear Fuel and Waste Disposal | Arizona Public Service Company                      
Schedule of Commitments and Contingencies [Line Items]                      
Number of claims submitted | claim                 10    
Gain contingency, number of settlement agreement time periods | timePeriod               10      
Settlement amount, awarded to company           $ 5.3   $ 45.6      
v3.25.0.1
Commitments and Contingencies - Estimated Coal Take-or-pay Commitments and Actual Amount Purchased (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Fuel and Purchased Power Commitments and Purchase Obligations [Abstract]      
Lease not yet commenced $ 16,700,000    
Arizona Public Service Company      
Fuel and Purchased Power Commitments and Purchase Obligations [Abstract]      
2025 1,540,000    
2026 1,742,000    
2027 1,973,000    
2028 2,142,000    
2029 2,115,000    
Thereafter 27,200,000    
Arizona Public Service Company | Coal Take-or-Pay Commitments      
Fuel and Purchased Power Commitments and Purchase Obligations [Abstract]      
2025 208,984    
2026 214,090    
2027 212,529    
2028 217,820    
2029 223,291    
Thereafter 463,752    
Lease not yet commenced $ 1,500,000    
Present value of commitments discount rate (in percent) 4.81%    
Present value of commitments $ 1,300,000    
Total purchases $ 237,821 $ 255,219 $ 305,502
v3.25.0.1
Asset Retirement Obligations - Additional information (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Schedule of Asset Retirement Obligations [Line Items]      
Palo Verde sale leaseback property, plant and equipment, net of accumulated depreciation $ 19,197,899 $ 17,980,157  
Decrease in regulatory liability (9,416) (28,495) $ 332,470
Arizona Public Service Company      
Schedule of Asset Retirement Obligations [Line Items]      
Palo Verde sale leaseback property, plant and equipment, net of accumulated depreciation 19,197,743 17,979,860  
Decrease in regulatory liability (9,416) (28,495) $ 332,470
Cholla | Arizona Public Service Company      
Schedule of Asset Retirement Obligations [Line Items]      
Increase (decrease) in asset retirement obligation 63,000 71,000  
Four Corners Coal-Fired Power Plant | Arizona Public Service Company      
Schedule of Asset Retirement Obligations [Line Items]      
Increase (decrease) in asset retirement obligation 82,000 (7,000)  
Navajo Coal-Fired Power Plant | Arizona Public Service Company      
Schedule of Asset Retirement Obligations [Line Items]      
Increase (decrease) in asset retirement obligation 8,000 8,000  
Palo Verde Nuclear Plant | Arizona Public Service Company      
Schedule of Asset Retirement Obligations [Line Items]      
Increase (decrease) in asset retirement obligation 1,000 63,000  
Palo Verde sale leaseback property, plant and equipment, net of accumulated depreciation   59,000  
Decrease in regulatory liability   $ 4,000  
Solar | Arizona Public Service Company      
Schedule of Asset Retirement Obligations [Line Items]      
Increase (decrease) in asset retirement obligation $ (11,000)    
v3.25.0.1
Asset Retirement Obligations - Schedule of Change in Asset Retirement Obligations (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Change in asset retirement obligations    
Asset retirement obligations at the beginning of year $ 966,001 $ 797,762
Changes attributable to:    
Accretion expense 56,143 44,269
Settlements (18,379) (14,039)
Estimated cash flow revisions 142,821 135,323
Newly incurred obligation 0 2,686
Asset retirement obligations at the end of year $ 1,146,586 $ 966,001
v3.25.0.1
Fair Value Measurements - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
ASSETS    
Cash equivalents $ 23 $ 10
Nuclear decommissioning trust 1,282,845 1,201,246
Nuclear decommissioning trust, other 426,404 408,849
Other special use fund 408,357 362,781
Other special use funds, other 2,851 2,196
Total assets 1,707,783 1,570,845
Total assets, other 425,485 409,356
Commodity contracts    
ASSETS    
Commodity contracts, assets 16,558 6,808
Commodity contracts assets, other (3,770) (1,689)
LIABILITIES    
Derivative instruments, other 817 4,823
Derivative instruments, total (61,786) (123,888)
Equity securities    
ASSETS    
Nuclear decommissioning trust 15,736 10,297
Nuclear decommissioning trust, other 3,335 (767)
Other special use fund 27,813 43,187
Other special use funds, other 2,851 2,196
U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trust 423,069 409,616
U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trust 367,396 319,734
Other special use fund 355,544 319,594
Corporate debt    
ASSETS    
Nuclear decommissioning trust 203,180 188,317
Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trust 208,533 208,306
Municipal bonds    
ASSETS    
Nuclear decommissioning trust 37,429 59,323
Other fixed income    
ASSETS    
Nuclear decommissioning trust 27,502 5,653
Cash equivalents    
ASSETS    
Other special use fund 25,000  
Other special use funds, other 0  
Level 1    
ASSETS    
Cash equivalents 23 10
Nuclear decommissioning trust 379,255 330,798
Other special use fund 405,506 360,585
Total assets 784,784 691,393
Level 1 | Pinnacle West Captive Insurance Cell    
ASSETS    
Other special use fund 34,200  
Level 1 | Commodity contracts    
ASSETS    
Commodity contracts, assets 0 0
LIABILITIES    
Derivative instruments 0 0
Level 1 | Equity securities    
ASSETS    
Nuclear decommissioning trust 11,859 11,064
Other special use fund 24,962 40,991
Level 1 | Equity securities | Pinnacle West Captive Insurance Cell    
ASSETS    
Other special use fund 9,200  
Level 1 | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trust 0 0
Level 1 | U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trust 367,396 319,734
Other special use fund 355,544 319,594
Level 1 | Corporate debt    
ASSETS    
Nuclear decommissioning trust 0 0
Level 1 | Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trust 0 0
Level 1 | Municipal bonds    
ASSETS    
Nuclear decommissioning trust 0 0
Level 1 | Other fixed income    
ASSETS    
Nuclear decommissioning trust 0 0
Level 1 | Cash equivalents    
ASSETS    
Other special use fund 25,000  
Level 1 | Cash equivalents | Pinnacle West Captive Insurance Cell    
ASSETS    
Other special use fund 25,000  
Level 2    
ASSETS    
Cash equivalents 0 0
Nuclear decommissioning trust 477,186 461,599
Other special use fund 0 0
Total assets 490,338 463,480
Level 2 | Commodity contracts    
ASSETS    
Commodity contracts, assets 13,152 1,881
LIABILITIES    
Derivative instruments (40,388) (127,016)
Level 2 | Equity securities    
ASSETS    
Nuclear decommissioning trust 542 0
Other special use fund 0 0
Level 2 | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trust 0 0
Level 2 | U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trust 0 0
Other special use fund 0 0
Level 2 | Corporate debt    
ASSETS    
Nuclear decommissioning trust 203,180 188,317
Level 2 | Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trust 208,533 208,306
Level 2 | Municipal bonds    
ASSETS    
Nuclear decommissioning trust 37,429 59,323
Level 2 | Other fixed income    
ASSETS    
Nuclear decommissioning trust 27,502 5,653
Level 2 | Cash equivalents    
ASSETS    
Other special use fund 0  
Level 3    
ASSETS    
Cash equivalents 0 0
Nuclear decommissioning trust 0 0
Other special use fund 0 0
Total assets 7,176 6,616
Level 3 | Commodity contracts    
ASSETS    
Commodity contracts, assets 7,176 6,616
LIABILITIES    
Derivative instruments (22,215) (1,695)
Level 3 | Equity securities    
ASSETS    
Nuclear decommissioning trust 0 0
Other special use fund 0 0
Level 3 | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trust 0 0
Level 3 | U.S. Treasury debt    
ASSETS    
Nuclear decommissioning trust 0 0
Other special use fund 0 0
Level 3 | Corporate debt    
ASSETS    
Nuclear decommissioning trust 0 0
Level 3 | Mortgage-backed securities    
ASSETS    
Nuclear decommissioning trust 0 0
Level 3 | Municipal bonds    
ASSETS    
Nuclear decommissioning trust 0 0
Level 3 | Other fixed income    
ASSETS    
Nuclear decommissioning trust 0 0
Level 3 | Cash equivalents    
ASSETS    
Other special use fund 0  
Fair Value Measured at Net Asset Value Per Share | U.S. commingled equity funds    
ASSETS    
Nuclear decommissioning trust $ 423,069 $ 409,616
v3.25.0.1
Fair Value Measurements - Significant Unobservable Inputs Used to Value Level 3 Instruments (Details 2)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
USD ($)
$ / MWh
$ / MMBTU
Dec. 31, 2023
USD ($)
$ / MWh
$ / MMBTU
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments    
Assets $ 1,707,783 $ 1,570,845
Level 3    
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments    
Assets 7,176 6,616
Level 3 | Forward Contracts | Commodity Contracts    
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments    
Assets 7,176 6,616
Liabilities $ 22,215 $ 1,695
Level 3 | Forward Contracts | Valuation Technique, Discounted Cash Flow | Commodity Contracts | Minimum    
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments    
Electricity forward price (per MWh) | $ / MWh 25.25 37.79
Natural gas forward price (per MMBtu) | $ / MMBTU 0.89 0.00
Level 3 | Forward Contracts | Valuation Technique, Discounted Cash Flow | Commodity Contracts | Maximum    
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments    
Electricity forward price (per MWh) | $ / MWh 151.11 259.04
Natural gas forward price (per MMBtu) | $ / MMBTU 1.47 0.08
Level 3 | Forward Contracts | Valuation Technique, Discounted Cash Flow | Commodity Contracts | Weighted Average    
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments    
Electricity forward price (per MWh) | $ / MWh 106.06 158.08
Natural gas forward price (per MMBtu) | $ / MMBTU 0.71 0.03
Level 3 | Forward Contracts | Valuation Technique, Discounted Cash Flow | Electricity: | Commodity Contracts    
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments    
Assets $ 708 $ 6,587
Liabilities 21,890 658
Level 3 | Forward Contracts | Valuation Technique, Discounted Cash Flow | Natural Gas: | Commodity Contracts    
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments    
Assets 6,468 29
Liabilities $ 325 $ 1,037
v3.25.0.1
Fair Value Measurements - Fair value for our risk management activities (Details) - Commodity Contracts - Level 3 - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Net derivative balance at beginning of period $ 4,921 $ (4,888)
Deferred as a regulatory asset or liability (60,965) (70,214)
Settlements 44,156 69,706
Transfers into Level 3 from Level 2 (4,635) (1,289)
Transfers from Level 3 into Level 2 1,484 11,606
Net derivative balance at end of period (15,039) 4,921
Net unrealized gains/losses included in earnings related to instruments still held at end of period $ 0 $ 0
v3.25.0.1
Common Stock Equity and Earnings Per Share - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Millions
 12 Months Ended
Feb. 28, 2024
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Nov. 08, 2024
Jun. 30, 2024
Subsidiary or Equity Method Investee [Line Items]            
Antidilutive securities excluded from computation of EPS (in shares)   1,038,463 0 0    
Convertible Notes Due Maturing June 2027 | Convertible Debt | Pinnacle West            
Subsidiary or Equity Method Investee [Line Items]            
Notes issued   $ 525       $ 525
Interest rate (as a percent)   4.75%       4.75%
ATM Program            
Subsidiary or Equity Method Investee [Line Items]            
Shares to be issued under ATM program   $ 850     $ 900  
Shares outstanding under ATM program   $ 50        
November 2024 Forward Sale Agreement            
Subsidiary or Equity Method Investee [Line Items]            
Sale of stock, settlement terms (in shares)   552,833        
Proceeds from issuance of common stock   $ 50        
Sales price per share (in usd per share)         $ 89.73  
February 2024 Forward Sale Agreements            
Subsidiary or Equity Method Investee [Line Items]            
Sale of stock, settlement terms (in shares) 5,377,115          
Proceeds from issuance of common stock $ 345          
Number of shares issued in transaction (in shares) 11,240,601          
Sales price per share (in usd per share) $ 64.51          
v3.25.0.1
Common Stock Equity and Earnings Per Share - Schedule of Earnings Per Weighted Average Common Share Outstanding (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Earnings Per Share [Abstract]      
Net income attributable to common shareholders $ 608,806 $ 501,557 $ 483,602
Weighted average common shares outstanding — basic (in shares) 113,846 113,442 113,196
Net effect of dilutive securities:      
Contingently issuable performance shares and restricted stock units (in shares) 480 362 220
Dilutive shares related to equity forward sale agreements (in shares) 1,906 0 0
Total contingently issuable shares 2,386 362 220
Weighted average common shares outstanding — diluted (in shares) 116,232 113,804 113,416
Earnings per weighted-average common share outstanding      
Net income attributable to common shareholders - basic (in dollars per share) $ 5.35 $ 4.42 $ 4.27
Net Income attributable to common shareholders - diluted (in dollars per share) $ 5.24 $ 4.41 $ 4.26
v3.25.0.1
Stock-Based Compensation - Additional Information (Details)
shares in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2024
USD ($)
program
shares
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Dec. 31, 2021
performance_criteria
Stock-Based Compensation        
Compensation cost that has been charged against income $ 24 $ 17 $ 16  
Total income tax benefit recognized 6 3 2  
Total unrecognized compensation cost related to nonvested share-based compensation arrangements granted $ 38      
Expected weighted-average period of recognition of unrecognized compensation cost 2 years      
Total fair value of shares vested $ 24 24 25  
Performance Share Awards        
Performance period 3 years      
Number of unrelated performance element criteria | program 3      
Number of performance element criteria | performance_criteria       2
Minimum        
Performance Share Awards        
Exact number of shares issued as a percentage of the target award 0.00%     0.00%
Maximum        
Performance Share Awards        
Exact number of shares issued as a percentage of the target award 200.00%     200.00%
Restricted Stock Units        
Stock-Based Compensation        
Share-based liabilities paid $ 8 6 3  
Cash flow effect, cash used to settle awards $ 2 $ 3 $ 3  
Restricted Stock Units, Stock Grants and Stock Units        
Vesting period 4 years      
Percentage of cash that the participant may elect as a dividend for the first option available under the plan       50.00%
Percentage of stock that the participant may elect as dividend under second option of plan       50.00%
Officers and Key Employees | Restricted Stock Units        
Restricted Stock Units, Stock Grants and Stock Units        
Percentage of fully transferable shares of stock that the participant may elect as a deferral for the first option available under the plan       100.00%
Percentage of fully transferable shares of stock in that participant may receive cash       100.00%
Non-Officer Board of Director Member | Restricted Stock Units        
Restricted Stock Units, Stock Grants and Stock Units        
Percentage of fully transferable shares of stock that the participant may elect as a deferral for the first option available under the plan     100.00%  
Percentage of cash that the participant may elect as a dividend for the first option available under the plan     100.00%  
Percentage of stock that the participant may elect as dividend under second option of plan     50.00%  
Percentage of fully transferable shares of stock that the participant may elect as a dividend equivalent deferral for the first option available under the plan     50.00%  
2021 Plan        
Stock-Based Compensation        
Common shares available for grant (in shares) | shares 4.3      
Common shares available for issuance (in shares) | shares 2.9      
v3.25.0.1
Stock-Based Compensation - Schedule of Restricted Stock Units, Stock Grants and Stock Units (Details) - $ / shares
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Restricted Stock Units, Stock Grants, and Stock Units      
Stocks granted and the weighted average fair value      
Units granted (in shares) 261,808 192,295 174,791
Weighted-average grant date fair value (in dollars per share) $ 71.10 $ 74.32 $ 69.66
Performance Shares      
Stocks granted and the weighted average fair value      
Units granted (in shares) 225,516 202,562 208,736
Weighted-average grant date fair value (in dollars per share) $ 72.89 $ 79.61 $ 77.63
v3.25.0.1
Stock-Based Compensation - Schedule of Nonvested Performance Shares (Details) - $ / shares
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Restricted Stock Units, Stock Grants, and Stock Units      
Nonvested shares      
Balance at the beginning of the period (in shares) 374,367    
Granted (in shares) 261,808 192,295 174,791
Vested (in shares) (155,345)    
Forfeited (in shares) (20,039)    
Balance at the end of the period (in shares) 460,791 374,367  
Weighted-Average Grant Date Fair Value      
Balance at the beginning of the period (in dollars per share) $ 73.29    
Granted (in dollars per share) 71.10 $ 74.32 $ 69.66
Vested (in dollars per share) 74.54    
Forfeited (in dollars per share) 71.32    
Balance at the end of the period (in dollars per share) $ 71.72 $ 73.29  
Vested awards outstanding at end of year (in shares) 70,851    
Vested awards outstanding at end of year (in dollars per share)    
Number of nonvested awards to be settled in cash (in shares) 11,750    
Performance Shares      
Nonvested shares      
Balance at the beginning of the period (in shares) 347,283    
Granted (in shares) 225,516 202,562 208,736
Vested (in shares) (165,194)    
Forfeited (in shares) (17,054)    
Balance at the end of the period (in shares) 390,551 347,283  
Weighted-Average Grant Date Fair Value      
Balance at the beginning of the period (in dollars per share) $ 77.29    
Granted (in dollars per share) 72.89 $ 79.61 $ 77.63
Vested (in dollars per share) 76.55    
Forfeited (in dollars per share) 75.69    
Balance at the end of the period (in dollars per share) $ 77.29 $ 77.29  
Vested awards outstanding at end of year (in shares) 165,194    
Vested awards outstanding at end of year (in dollars per share)    
v3.25.0.1
Derivative Accounting - Additional Information (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Commodity Contracts    
Derivative [Line Items]    
Derivative asset $ 16,558 $ 6,808
Additional collateral to counterparties for energy related non-derivative instrument contracts $ 416,000  
One Counterparty | Derivative Concentration | Credit Concentration    
Derivative [Line Items]    
Concentration risk, percentage 26.00%  
Arizona Public Service Company    
Derivative [Line Items]    
Percentage of unrealized gains and losses on certain derivatives deferred for future rate treatment before accounting treatment change 100.00%  
v3.25.0.1
Derivative Accounting - Schedule of Outstanding Gross Notional Amounts Outstanding (Details) - Commodity Contracts
MWh in Thousands
 12 Months Ended
Dec. 31, 2024
MWh
Bcf
Dec. 31, 2023
MWh
Bcf
Outstanding gross notional amount of derivatives    
Power | MWh 1,051 1,212
Gas | Bcf 235,000 200,000
v3.25.0.1
Derivative Accounting - Schedule of Gains and Losses from Derivative Instruments (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Commodity Contracts | Fuel and purchased power | Not Designated as Hedging Instruments      
Derivative Instruments Not Designated as Cash Flows Hedges      
Net Gain (Loss) Recognized in Income $ (88,522) $ (370,145) $ 307,287
v3.25.0.1
Derivative Accounting - Schedule of Derivative Instruments in the Balance Sheet (Details) - Commodity Contracts - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Assets    
Gross Recognized Derivatives $ 20,328 $ 8,497
Amounts Offset (3,788) (1,694)
Net Recognized Derivatives 16,540 6,803
Other 18 5
Amounts  Reported on  Balance Sheets 16,558 6,808
Liabilities    
Gross Recognized Derivatives (62,603) (128,711)
Amounts Offset 3,788 10,894
Net Recognized Derivatives (58,815) (117,817)
Other (2,971) (6,071)
Amounts Reported on Balance Sheets (61,786) (123,888)
Assets and Liabilities    
Gross Recognized Derivatives (42,275) (120,214)
Amounts Offset 0 9,200
Net Recognized Derivatives (42,275) (111,014)
Other (2,953) (6,066)
Amounts  Reported on  Balance Sheets (45,228) (117,080)
Current assets    
Assets    
Gross Recognized Derivatives 13,718 8,497
Amounts Offset (3,158) (1,694)
Net Recognized Derivatives 10,560 6,803
Other 18 5
Amounts  Reported on  Balance Sheets 10,578 6,808
Investments and other assets    
Assets    
Gross Recognized Derivatives 6,610 0
Amounts Offset (630) 0
Net Recognized Derivatives 5,980 0
Other 0 0
Amounts  Reported on  Balance Sheets 5,980 0
Current liabilities    
Liabilities    
Gross Recognized Derivatives (52,527) (85,736)
Amounts Offset 3,158 10,894
Net Recognized Derivatives (49,369) (74,842)
Other (2,971) (6,071)
Amounts Reported on Balance Sheets (52,340) (80,913)
Deferred credits and other    
Liabilities    
Gross Recognized Derivatives (10,076) (42,975)
Amounts Offset 630 0
Net Recognized Derivatives (9,446) (42,975)
Other 0 0
Amounts Reported on Balance Sheets $ (9,446) $ (42,975)
v3.25.0.1
Derivative Accounting - Schedule of Credit Risk and Related Contingent Features (Details) - Commodity Contracts
$ in Thousands
Dec. 31, 2024
USD ($)
Credit Risk and Credit-Related Contingent Features  
Aggregate fair value of derivative instruments in a net liability position $ 62,603
Additional cash collateral in the event credit-risk related contingent features were fully triggered $ 32,728
v3.25.0.1
Other Income and Other Expense (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Other income:      
Interest income $ 24,322 $ 27,242 $ 7,326
Gain on sale of BCE (Note 20) 22,988 6,205 0
Miscellaneous 1,304 219 590
Total other income 48,614 33,666 7,916
Other expense:      
Non-operating costs (27,370) (15,260) (18,619)
Investment losses — net (1,418) (3,402) (20,537)
Miscellaneous (5,348) (6,394) (13,229)
Total other expense (34,136) (25,056) (52,385)
Arizona Public Service Company      
Other income:      
Interest income 21,088 26,853 5,332
Miscellaneous 6 219 556
Total other income 21,094 27,072 5,888
Other expense:      
Non-operating costs (26,588) (14,070) (15,579)
Miscellaneous (3,110) (4,194) (10,529)
Total other expense $ (29,698) $ (18,264) $ (26,108)
v3.25.0.1
Variable Interest Entities - Additional Information (Details)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
USD ($)
lease
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Dec. 31, 1986
numberOfTrust
Palo Verde Sale Leaseback Variable Interest Entities        
Net income attributable to noncontrolling interest $ 17,224 $ 17,224 $ 17,224  
Variable Interest Entity        
Palo Verde Sale Leaseback Variable Interest Entities        
Net income attributable to noncontrolling interest 5,000 0 0  
Variable Interest Entity | Pinnacle West Captive Insurance Cell        
Palo Verde Sale Leaseback Variable Interest Entities        
Special use fund 34,000 5,000    
Arizona Public Service Company        
Palo Verde Sale Leaseback Variable Interest Entities        
Net income attributable to noncontrolling interest 17,224 17,224 17,224  
Arizona Public Service Company | Variable Interest Entity        
Palo Verde Sale Leaseback Variable Interest Entities        
Net income attributable to noncontrolling interest 17,000 $ 17,000 $ 17,000  
Number of Vie lessor trusts | numberOfTrust       3
Initial loss exposure to the VIEs noncontrolling equity participants during lease extension period 345,000      
Arizona Public Service Company | Variable Interest Entity | Maximum        
Palo Verde Sale Leaseback Variable Interest Entities        
Maximum loss exposure to the VIE's noncontrolling equity participants during lease extension period (up to) $ 501,000      
Arizona Public Service Company | Sale Leaseback Transaction Period Through 2033 | Variable Interest Entity        
Palo Verde Sale Leaseback Variable Interest Entities        
Number of leases under which assets are retained | lease 3      
Annual lease payments $ 21,000      
Arizona Public Service Company | Sale Leaseback Transaction Period Through 2033 | Variable Interest Entity | Maximum        
Palo Verde Sale Leaseback Variable Interest Entities        
Lease period (up to) 2 years      
v3.25.0.1
Variable Interest Entities - Schedule of Amounts Relating to the VIEs Included in Consolidated Balance Sheets (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Palo Verde Sale Leaseback Variable Interest Entities    
Palo Verde sale leaseback property, plant and equipment, net of accumulated depreciation $ 19,197,899 $ 17,980,157
Amounts relating to the VIEs included in Condensed Consolidated Balance Sheets    
Equity — Noncontrolling interests 103,167 107,198
Arizona Public Service Company    
Palo Verde Sale Leaseback Variable Interest Entities    
Palo Verde sale leaseback property, plant and equipment, net of accumulated depreciation 19,197,743 17,979,860
Amounts relating to the VIEs included in Condensed Consolidated Balance Sheets    
Equity — Noncontrolling interests 103,167 107,198
Palo Verde VIE | Arizona Public Service Company    
Palo Verde Sale Leaseback Variable Interest Entities    
Palo Verde sale leaseback property, plant and equipment, net of accumulated depreciation 82,556 86,426
Amounts relating to the VIEs included in Condensed Consolidated Balance Sheets    
Equity — Noncontrolling interests $ 103,167 $ 107,198
v3.25.0.1
Investments in Nuclear Decommissioning Trusts and Other Special Use Funds - Additional Information (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Arizona Public Service Company    
Schedule of Equity Method Investments [Line Items]    
Employee medical claims amount $ 14 $ 14
v3.25.0.1
Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Fair value of fixed income securities, summarized by contractual maturities      
Cash equivalents $ 23 $ 10  
Nuclear decommissioning trusts (Notes 12 and 18) 1,282,845 1,201,246  
Variable Interest Entity | Pinnacle West Captive Insurance Cell      
Fair value of fixed income securities, summarized by contractual maturities      
Special use fund 34,000 5,000  
Equity securities      
Fair value of fixed income securities, summarized by contractual maturities      
Nuclear decommissioning trusts (Notes 12 and 18) 15,736 10,297  
Arizona Public Service Company      
Nuclear decommissioning trust fund assets      
Fair Value 1,691,202 1,564,027  
Total Unrealized Gains 366,844 358,112  
Total Unrealized Losses (32,136) (40,868)  
Amortized cost 1,224,000 1,120,000  
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds      
Realized gains 76,062 112,094 $ 9,437
Realized losses (21,966) (41,780) (40,239)
Proceeds from the sale of securities 1,686,094 1,679,722 1,207,197
Fair value of fixed income securities, summarized by contractual maturities      
Nuclear decommissioning trusts (Notes 12 and 18) 1,282,845 1,201,246  
Arizona Public Service Company | Nuclear Decommissioning Trusts      
Nuclear decommissioning trust fund assets      
Fair Value 1,282,845 1,201,246  
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds      
Realized gains 75,690 111,922 9,017
Realized losses (21,966) (41,212) (40,239)
Proceeds from the sale of securities 1,330,940 1,324,978 979,639
Arizona Public Service Company | Other Special Use Funds      
Nuclear decommissioning trust fund assets      
Fair Value 408,357 362,781  
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds      
Realized gains 372 172 420
Realized losses 0 (568) 0
Proceeds from the sale of securities 355,154 354,744 $ 227,558
Arizona Public Service Company | Equity securities      
Nuclear decommissioning trust fund assets      
Equity securities 460,432 461,671  
Total Unrealized Gains 359,127 336,555  
Total Unrealized Losses (176) 0  
Arizona Public Service Company | Equity securities | Nuclear Decommissioning Trusts      
Nuclear decommissioning trust fund assets      
Equity securities 435,470 420,680  
Arizona Public Service Company | Equity securities | Other Special Use Funds      
Nuclear decommissioning trust fund assets      
Equity securities 24,962 40,991  
Arizona Public Service Company | Available for sale-fixed income securities      
Nuclear decommissioning trust fund assets      
Fair Value 1,199,584 1,100,927  
Total Unrealized Gains 7,717 21,518  
Total Unrealized Losses (31,960) (40,868)  
Fair value of fixed income securities, summarized by contractual maturities      
Less than one year 146,382    
1 year – 5 years 482,340    
5 years – 10 years 214,128    
Greater than 10 years 356,734    
Total 1,199,584    
Arizona Public Service Company | Available for sale-fixed income securities | Nuclear Decommissioning Trusts      
Nuclear decommissioning trust fund assets      
Fair Value 844,040 781,333  
Fair value of fixed income securities, summarized by contractual maturities      
Less than one year 19,868    
1 year – 5 years 268,974    
5 years – 10 years 198,464    
Greater than 10 years 356,734    
Total 844,040    
Arizona Public Service Company | Available for sale-fixed income securities | Other Special Use Funds      
Nuclear decommissioning trust fund assets      
Fair Value 355,544 319,594  
Arizona Public Service Company | Available for sale-fixed income securities | Coal Reclamation Escrow Account      
Fair value of fixed income securities, summarized by contractual maturities      
Less than one year 87,424    
1 year – 5 years 58,598    
5 years – 10 years 0    
Greater than 10 years 0    
Total 146,022    
Arizona Public Service Company | Available for sale-fixed income securities | Active Union Employee Medical Account      
Fair value of fixed income securities, summarized by contractual maturities      
Less than one year 39,090    
1 year – 5 years 154,768    
5 years – 10 years 15,664    
Greater than 10 years 0    
Total 209,522    
Arizona Public Service Company | Other      
Nuclear decommissioning trust fund assets      
Fair Value 31,186 1,429  
Total Unrealized Gains 0 39  
Total Unrealized Losses 0 0  
Arizona Public Service Company | Other | Nuclear Decommissioning Trusts      
Nuclear decommissioning trust fund assets      
Fair Value 3,335 (767)  
Arizona Public Service Company | Other | Other Special Use Funds      
Nuclear decommissioning trust fund assets      
Fair Value 27,851 $ 2,196  
Pinnacle West | Variable Interest Entity | Pinnacle West Captive Insurance Cell      
Fair value of fixed income securities, summarized by contractual maturities      
Special use fund $ 34,000    
v3.25.0.1
Changes in Accumulated Other Comprehensive Loss (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance $ 6,284,862 $ 6,159,876
Other comprehensive income/(loss) before reclassifications 148 (3,707)
Amounts reclassified from accumulated other comprehensive loss 2,054 1,998
Ending balance 6,857,478 6,284,862
Accumulated Other Comprehensive Loss    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance (33,144) (31,435)
Ending balance (30,942) (33,144)
Pension and Other Postretirement Benefits    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance (34,754) (32,332)
Other comprehensive income/(loss) before reclassifications 1,039 (4,420)
Amounts reclassified from accumulated other comprehensive loss 2,054 1,998
Ending balance (31,661) (34,754)
Derivative Instruments    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance 1,610 897
Other comprehensive income/(loss) before reclassifications (891) 713
Amounts reclassified from accumulated other comprehensive loss 0 0
Ending balance 719 1,610
Arizona Public Service Company    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance 7,349,136 7,052,955
Ending balance 8,376,332 7,349,136
Arizona Public Service Company | Accumulated Other Comprehensive Loss    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance (17,219) (15,596)
Ending balance (14,116) (17,219)
Arizona Public Service Company | Pension and Other Postretirement Benefits    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance (17,219) (15,596)
Other comprehensive income/(loss) before reclassifications 1,255 (3,383)
Amounts reclassified from accumulated other comprehensive loss 1,848 1,760
Ending balance $ (14,116) $ (17,219)
v3.25.0.1
Sale of Bright Canyon Energy (Details) - USD ($)
$ in Thousands
 5 Months Ended 12 Months Ended
Jan. 30, 2024
Jan. 12, 2024
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Aug. 04, 2023
Feb. 11, 2022
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Gain on sale relating to BCE     $ 22,988 $ 6,423 $ 0    
Bridge Loan | Equity Bridge Loan Facility | Bright Canyon Energy Corporation              
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Debt instrument, face amount           $ 31,000 $ 31,000
Term Loan | Non-Recourse Construction Term Loan Facility | Bright Canyon Energy Corporation              
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Debt instrument, face amount           36,000 $ 36,000
Discontinued Operations, Disposed of by Sale | Bright Canyon Energy Corporation              
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Assets held-for-sale   $ 35,000          
Consideration received   108,000       $ 44,000  
Gain on sale relating to BCE   29,000 $ 23,000 $ 6,000      
Promissory notes received   46,000          
Discontinued Operations, Disposed of by Sale | Bright Canyon Energy Corporation | Ameresco, Inc.              
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Assets held-for-sale   79,000          
Liabilities transferred   $ 41,000          
Discontinued Operations, Disposed of by Sale | Bright Canyou Energy Corportion              
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]              
Investment tax credits $ 23,000            
Payments to acquire investment tax credits $ 21,000            
v3.25.0.1
Schedule I - Condensed Financial Information of Registrant - Comprehensive Income (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
CONDENSED FINANCIAL STATEMENTS      
Operating expenses $ 4,112,852 $ 3,871,351 $ 3,592,474
Other      
Total 101,968 102,376 99,281
Interest expense 425,742 374,887 283,569
Income tax benefit 110,529 76,912 74,827
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS 608,806 501,557 483,602
Other comprehensive income (loss) — attributable to common shareholders 2,202 (1,709) 23,426
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS 611,008 499,848 507,028
Pinnacle West      
CONDENSED FINANCIAL STATEMENTS      
Operating expenses 9,931 11,249 8,850
Other      
Equity in earnings of subsidiaries 643,703 539,962 500,042
Other income (expense) 23,835 2,823 (4,725)
Total 667,538 542,785 495,317
Interest expense 65,261 47,251 18,861
Income before income taxes 592,346 484,285 467,606
Income tax benefit (16,460) (17,272) (15,996)
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS 608,806 501,557 483,602
Other comprehensive income (loss) — attributable to common shareholders 2,202 (1,709) 23,426
COMPREHENSIVE INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS $ 611,008 $ 499,848 $ 507,028
v3.25.0.1
Schedule I - Condensed Financial Information of Registrant - Balance Sheets (Details) - USD ($)
$ in Thousands
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Current assets        
Cash and cash equivalents $ 3,838 $ 4,955    
Accounts receivable 525,608 513,892    
Income tax receivable 0 332    
Assets held for sale- investment in subsidiaries 0 35,139    
Other current assets 74,915 101,417    
Total current assets 1,689,404 1,926,967    
Investments and other assets        
Other assets 115,095 102,845    
Total investments and other assets 1,812,277 1,666,872    
TOTAL ASSETS 26,102,760 24,661,153    
Current liabilities        
Accounts payable 485,426 442,455    
Accrued taxes 175,863 166,833    
Common dividends payable 106,592 99,813    
Short-term borrowings 568,450 609,500    
Operating lease liabilities 100,367 67,883    
Other current liabilities 171,651 193,524    
Total current liabilities 2,843,797 2,889,347    
Deferred credits and other        
Long-term debt less current maturities 8,058,648 7,540,622    
Deferred income taxes (Note 4) 2,444,473 2,416,480    
Operating lease liabilities 1,520,877 1,210,189    
Other 242,320 251,469    
Total deferred credits and other 8,342,837 7,946,322    
COMMITMENTS AND CONTINGENCIES    
Common stock equity        
Common stock 3,121,617 2,752,676    
Accumulated other comprehensive loss (30,942) (33,144)    
Retained earnings 3,666,959 3,466,317    
Total shareholders’ equity 6,754,311 6,177,664    
Noncontrolling interests 103,167 107,198    
Total equity 6,857,478 6,284,862 $ 6,159,876 $ 6,021,460
TOTAL LIABILITIES AND EQUITY 26,102,760 24,661,153    
Pinnacle West        
Current assets        
Cash and cash equivalents 23 9    
Accounts receivable 163,203 163,829    
Income tax receivable 6,673 1,832    
Assets held for sale- investment in subsidiaries 0 35,139    
Other current assets 434 28,379    
Total current assets 170,333 229,188    
Investments and other assets        
Investments in subsidiaries 8,435,150 7,369,159    
Deferred income taxes 0 15,746    
Other assets 21,966 22,839    
Total investments and other assets 8,457,116 7,407,744    
TOTAL ASSETS 8,627,449 7,636,932    
Current liabilities        
Accounts payable 3,471 8,176    
Accrued taxes 4,799 4,543    
Common dividends payable 106,592 99,813    
Short-term borrowings 228,550 76,650    
Current maturities of long-term debt 500,000 625,000    
Operating lease liabilities 138 127    
Other current liabilities 11,389 11,400    
Total current liabilities 854,939 825,709    
Deferred credits and other        
Long-term debt less current maturities 867,770 498,731    
Deferred income taxes (Note 4) 24,536 0    
Pension liabilities 4,462 6,487    
Operating lease liabilities 1,194 1,332    
Other 17,070 19,811    
Total deferred credits and other 47,262 27,630    
COMMITMENTS AND CONTINGENCIES    
Common stock equity        
Common stock 3,118,294 2,744,491    
Accumulated other comprehensive loss (30,942) (33,144)    
Retained earnings 3,666,959 3,466,317    
Total shareholders’ equity 6,754,311 6,177,664    
Noncontrolling interests 103,167 107,198    
Total equity 6,857,478 6,284,862    
TOTAL LIABILITIES AND EQUITY $ 8,627,449 $ 7,636,932    
v3.25.0.1
Schedule I - Condensed Financial Information of Registrant - Cash Flows (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Cash flows from operating activities      
Net Income $ 626,030 $ 518,781 $ 500,826
Adjustments to reconcile net income to net cash provided by operating activities:      
Depreciation and amortization 956,184 854,136 817,814
Deferred income taxes (20,923) (24,310) 43,202
Accounts receivable (12,696) (61,983) (63,869)
Accounts payable (7,214) (75,623) 90,076
Net cash provided by operating activities 1,609,823 1,207,697 1,241,441
Cash flows from investing activities      
Construction work in progress (48,270) (43,564) (28,030)
Proceeds from sale relating to BCE 84,322 23,400 0
Net cash used for investing activities (1,933,630) (1,694,249) (1,618,046)
Cash flows from financing activities      
Short-term borrowings and (repayments) — net (241,050) 241,900 48,720
Dividends paid on common stock (394,663) (386,486) (378,881)
Net cash provided by financing activities 322,690 486,675 371,468
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS (1,117) 123 (5,137)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR 4,955 4,832 9,969
CASH AND CASH EQUIVALENTS AT END OF YEAR 3,838 4,955 4,832
Pinnacle West      
Cash flows from operating activities      
Net Income 608,806 501,557 483,602
Adjustments to reconcile net income to net cash provided by operating activities:      
Equity in earnings of subsidiaries — net (643,703) (539,962) (500,042)
Gain on sale relating to BCE (22,988) (6,423) 0
Depreciation and amortization 75 76 76
Deferred income taxes 40,231 (13,955) 17,256
Accounts receivable 15,268 (28,273) (8,535)
Accounts payable (4,869) 1,839 3,431
Accrued taxes and income tax receivables — net (4,584) 9,505 (25,157)
Dividends received from subsidiaries 401,400 393,600 385,800
Other 22,959 (14,201) 47,719
Net cash provided by operating activities 412,595 303,763 404,150
Cash flows from investing activities      
Proceeds from sale relating to BCE 84,322 23,400 0
Investments in subsidiaries (827,752) (119,682) (186,630)
Repayments of loans from subsidiaries and other 1,132 6,526 14,308
Advances of loans to subsidiaries (11,336) (59,349) (3,308)
Net cash used for investing activities (753,634) (149,105) (175,630)
Cash flows from financing activities      
Issuance of long-term debt 867,387 175,000 300,000
Short-term debt borrowings under revolving credit facility 200,000 0 0
Short-term borrowings and (repayments) — net (48,100) 60,930 2,420
Dividends paid on common stock (394,663) (386,486) (378,881)
Repayment of long-term debt (625,000) 0 (150,000)
Common stock equity issuance and purchases — net 341,429 (4,093) (2,653)
Net cash provided by financing activities 341,053 (154,649) (229,114)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS 14 9 (594)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR 9 0 594
CASH AND CASH EQUIVALENTS AT END OF YEAR $ 23 $ 9 $ 0