TENNESSEE VALLEY AUTHORITY, 10-K filed on 11/14/2023
Annual Report
v3.23.3
DEI Document
shares in Millions, $ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
shares
Document Information [Line Items]  
Entity Registrant Name TENNESSEE VALLEY AUTHORITY
Entity Central Index Key 0001376986
Entity Filer Category Non-accelerated Filer
Document Type 10-K
Document Fiscal Year Focus 2023
Document Fiscal Period Focus FY
Amendment Flag false
Entity Common Stock, Shares Outstanding | shares 0
Entity Emerging Growth Company false
Entity Shell Company false
Entity Well-known Seasoned Issuer No
Entity Public Float | $ $ 0
Document Transition Report false
Entity File Number 000-52313
Entity Tax Identification Number 62-0474417
Entity Address, State or Province TN
Entity Address, City or Town Knoxville
Entity Address, Address Line One 400 W. Summit Hill Drive
Local Phone Number 632-2101
City Area Code (865)
Entity Address, Postal Zip Code 37902 (Zip Code)
Entity Interactive Data Current Yes
ICFR Auditor Attestation Flag true
Entity Incorporation, State or Country Code X1
Entity Current Reporting Status Yes
Document Annual Report true
Document Period End Date Sep. 30, 2023
Entity Small Business false
Entity Voluntary Filers No
Current Fiscal Year End Date --09-30
Document Financial Statement Error Correction [Flag] false
Auditor Name Ernst & Young LLP
v3.23.3
Audit Information
 12 Months Ended
Sep. 30, 2023
Auditor [Line Items]  
Auditor Name Ernst & Young LLP
Auditor Location Chattanooga, Tennessee
Auditor Firm ID 42
v3.23.3
CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Operating revenues      
Electric revenue $ 11,899 $ 12,371 $ 10,357
Other revenue 155 169 146
Revenue from sales of electricity 12,054 12,540 10,503
Operating expenses      
Fuel 2,549 2,567 1,737
Purchased power 1,633 1,921 984
Operating and maintenance 3,372 2,986 2,890
Depreciation and amortization 2,213 2,054 1,533
Tax equivalents 593 601 514
Total operating expenses 10,360 10,129 7,658
Operating income 1,694 2,411 2,845
Other income (expense), net 61 7 13
Defined Benefit Plan, Other Cost (Credit) 199 258 258
Interest expense      
Interest expense 1,056 1,052 1,088
Net income (loss) 500 1,108 1,512
ALABAMA      
Operating revenues      
Electric revenue 1,731 1,778 1,508
GEORGIA      
Operating revenues      
Electric revenue 284 299 254
KENTUCKY      
Operating revenues      
Electric revenue 773 821 655
MISSISSIPPI      
Operating revenues      
Electric revenue 1,146 1,182 984
NORTH CAROLINA      
Operating revenues      
Electric revenue 89 87 66
TENNESSEE      
Operating revenues      
Electric revenue 7,819 8,137 6,841
VIRGINIA      
Operating revenues      
Electric revenue $ 46 $ 48 $ 42
v3.23.3
CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Current assets    
Cash and Cash Equivalents, at Carrying Value $ 501 $ 500
Accounts receivable, net 1,745 2,007
Inventories, net 1,108 1,072
Regulatory assets 178 138
Other current assets 134 257
Total current assets 3,666 3,974
Property, plant, and equipment    
Completed plant 68,199 66,442
Less accumulated depreciation (35,871) (34,239)
Net completed plant 32,328 32,203
Construction in progress 3,238 2,535
Nuclear fuel 1,344 1,492
Finance Lease, Right-of-Use-Asset, after Accumulated Amortization 572 630
Total property, plant, and equipment, net 37,482 36,860
Long-term Investments 4,123 3,671
Regulatory and other long-term assets    
Regulatory assets 5,566 6,134
Operating Lease, Right-of-Use Asset 177 155
Other long-term assets 330 394
Total regulatory and other long-term assets 6,073 6,683
Total assets 51,344 51,188
Current liabilities    
Accounts payable and accrued liabilities 2,618 2,466
Accrued interest 272 273
Asset Retirement Obligation, Current 272 275
Regulatory liabilities 222 391
Short-term debt, net of discounts 432 1,172
Total Current maturities of power bonds issued at par 1,022 29
Current maturities of long-term debt of variable interest entities issued at par 35 39
Total current liabilities 4,873 4,645
Other liabilities    
Post-retirement and post-employment benefit obligations 2,527 3,072
Asset retirement obligations 7,217 6,887
Other long-term liabilities 1,211 1,485
Non-current regulatory liabilities 107 172
Total other liabilities 11,638 12,244
Long-term debt, net    
Long-term power bonds, net 17,844 17,826
Long-term debt of variable interest entities, net 933 968
Total long-term debt, net 18,777 18,794
Total liabilities 35,288 35,683
Proprietary capital    
Power program appropriation investment 258 258
Power program retained earnings 15,302 14,800
Total power program proprietary capital 15,560 15,058
Nonpower programs appropriation investment, net 525 533
Accumulated other comprehensive income (loss) (29) (86)
Total proprietary capital 16,056 15,505
Total liabilities and proprietary capital 51,344 51,188
Finance Lease, Liability, Noncurrent $ 576 $ 628
v3.23.3
CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents $ 521 $ 520 $ 518
Cash flows from operating activities      
Net income (loss) 500 1,108 1,512
Adjustments to reconcile net income (loss) to net cash provided by operating activities      
Depreciation and amortization (including amortization of debt issuance costs and premiums/discounts) 2,235 2,076 1,555
Amortization of nuclear fuel cost 371 347 383
Non-cash retirement benefit expense 241 328 333
Regulatory asset amount expensed 31 70 72
Changes in current assets and liabilities      
Accounts receivable, net 301 (412) (18)
Inventories and other current assets, net (83) (163) 42
Accounts payable and accrued liabilities (1) 282 178
Accrued interest (1) (7) (18)
Pension contributions (306) (308) (306)
Settlements of asset retirement obligations (327) (291) 242
Other, net (89) (82) (91)
Net cash provided by operating activities 2,872 2,948 3,256
Cash flows from investing activities      
Construction expenditures (2,526) (2,361) (1,963)
Nuclear fuel expenditures (273) (283) (354)
Acquisition of leasehold interests in combustion turbine assets (155) 0 0
Purchases of investments (51) (51) (50)
Loans and other receivables      
Repayments 8 15 9
Other, net 10 26 27
Net cash used in investing activities (2,994) (2,663) (2,338)
Long-term debt      
Issues of power bonds 992 484 500
Redemptions and repurchases of power bonds (29) (1,028) (1,860)
Payments on debt of variable interest entities (39) (43) (41)
Short-term debt issues (redemptions), net (740) 392 723
Finance Lease, Principal Payments 56 85 250
Financing costs, net (4) (3) (2)
Other, net (1) 0 9
Net cash (used in) provided by financing activities 123 (283) (921)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect 1 2 (3)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total 1    
Advances on loans receivable $ (7) $ (9) $ (7)
v3.23.3
CONSOLIDATED STATEMENTS OF CHANGES IN PROPRIETARY CAPITAL - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Balance at beginning of year $ 15,505 $ 14,465 $ 12,932
Net income (loss) 500 1,108 1,512
Total other comprehensive income (loss) 57 (64) 29
Return on power program appropriation investment (6) (4) (4)
Balance at end of year 16,056 15,505 14,465
Power Program Appropriation Investment      
Balance at beginning of year 258 258 258
Net income (loss) 0 0 0
Total other comprehensive income (loss) 0 0 0
Return on power program appropriation investment 0 0 0
New Accounting Standard - CECL     0
Balance at end of year 258 258 258
Power Program Retained Earnings      
Balance at beginning of year 14,800 13,689 12,177
Net income (loss) 508 1,115 1,520
Total other comprehensive income (loss) 0 0 0
Return on power program appropriation investment (6) (4) (4)
New Accounting Standard - CECL     (4)
Balance at end of year 15,302 14,800 13,689
Nonpower Programs Appropriation Investment, Net      
Balance at beginning of year 533 540 548
Net income (loss) (8) (7) (8)
Total other comprehensive income (loss) 0 0 0
Return on power program appropriation investment 0 0 0
New Accounting Standard - CECL     0
Balance at end of year 525 533 540
Accumulated Other Comprehensive Income (Loss) Net Gains (Losses) on Cash Flow Hedges      
Balance at beginning of year (86) (22) (51)
Net income (loss) 0 0 0
Total other comprehensive income (loss) 57 (64) 29
Return on power program appropriation investment 0 0 0
New Accounting Standard - CECL     0
Balance at end of year $ (29) $ (86) $ (22)
v3.23.3
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) Statement - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Statement of Comprehensive Income [Abstract]      
Net income (loss) $ 500 $ 1,108 $ 1,512
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax 99 (157) 126
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax (42) 93 (97)
Total other comprehensive income (loss) 57 (64) 29
Total comprehensive income (loss) $ 557 $ 1,044 $ 1,541
v3.23.3
Supplemental Cash Flow Information
 12 Months Ended
Sep. 30, 2023
Supplemental Cash Flow Information [Abstract]  
Supplemental Cash Flow Information Interest paid was $1.1 billion for each of 2023, 2022, and 2021. These amounts differ from interest expense in certain years due to the timing of payments. There was no interest capitalized in 2023, 2022, or 2021.
    Construction in progress and nuclear fuel expenditures included in Accounts payable and accrued liabilities at September 30, 2023, 2022, and 2021 were $559 million, $510 million, and $539 million, respectively, and are excluded from the Consolidated Statements of Cash Flows for the years ended September 30, 2023, 2022, and 2021 as non-cash investing activities. ARO project accruals included in Accounts payable and accrued liabilities at September 30, 2023, 2022, and 2021 were $71 million, $119 million, and $98 million, respectively, and are excluded from the Consolidated Statements of Cash Flows for the years ended September 30, 2023, 2022, and 2021 as non-cash operating activities.

    There are no material finance leases that were entered into during the years ended September 30, 2023 and 2022. Excluded from the Consolidated Statements of Cash Flows for the year ended September 30, 2021, were non-cash investing and financing activities of $233 million related primarily to an increase in lease assets and liabilities incurred for a finance lease that was amended in March 2021. See Note 8 — Leases for further information regarding TVA's finance leases.

    Cash flows from swap contracts that are accounted for as hedges are classified in the same category as the item being hedged or on a basis consistent with the nature of the instrument.
v3.23.3
Supplemental Cash Flow Information - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Supplemental Cash Flow Information      
Interest Paid, Excluding Capitalized Interest, Operating Activities $ 1,100 $ 1,100 $ 1,100
ARO project accruals included in AP 71 119 98
Lease assets obtained in exchange for lease obligations - finance 3 0 233
Accounts payable and accrued liabilities      
Supplemental Cash Flow Information      
Construction in progress and Nuclear fuel expenditures $ 559 $ 510 $ 539
v3.23.3
Summary of Significant Accounting Policies [Text Block]
 12 Months Ended
Sep. 30, 2023
Accounting Policies [Abstract]  
Summary of Significant Accounting Policies
1.  Summary of Significant Accounting Policies

General

The Tennessee Valley Authority ("TVA") is a corporate agency and instrumentality of the United States ("U.S.") that was created in 1933 by federal legislation in response to a proposal by President Franklin D. Roosevelt.  TVA was created to, among other things, improve navigation on the Tennessee River, reduce the damage from destructive flood waters within the Tennessee River system and downstream on the lower Ohio and Mississippi Rivers, further the economic development of TVA's service area in the southeastern U.S., and sell the electricity generated at the facilities TVA operates. Today, TVA operates the nation's largest public power system and supplies power in most of Tennessee, northern Alabama, northeastern Mississippi, and southwestern Kentucky and in portions of northern Georgia, western North Carolina, and southwestern Virginia to a population of approximately 10 million people.

    TVA also manages the Tennessee River, its tributaries, and certain shorelines to provide, among other things, year-round navigation, flood damage reduction, and affordable and reliable electricity. Consistent with these primary purposes, TVA also manages the river system and public lands to provide recreational opportunities, adequate water supply, improved water quality, cultural and natural resource protection, and economic development. TVA performs these management duties in cooperation with other federal and state agencies that have jurisdiction and authority over certain aspects of the river system. In addition, the TVA Board of Directors ("TVA Board") has established two councils — the Regional Resource Stewardship Council and the Regional Energy Resource Council — to advise TVA on its stewardship activities in the Tennessee Valley and its energy resource activities.

The power program has historically been separate and distinct from the stewardship programs.  It is required to be self-supporting from power revenues and proceeds from power financings, such as proceeds from the issuance of bonds, notes, or other evidences of indebtedness (collectively, "Bonds").  Although TVA does not currently receive Congressional appropriations, it is required to make annual payments to the United States Department of the Treasury ("U.S. Treasury") as a return on the government's appropriation investment in TVA's power facilities (the "Power Program Appropriation Investment").  In the 1998 Energy and Water Development Appropriations Act, Congress directed TVA to fund essential stewardship activities related to its management of the Tennessee River system and nonpower or stewardship properties with power revenues in the event that there were insufficient appropriations or other available funds to pay for such activities in any fiscal year.  Congress has not
provided any appropriations to TVA to fund such activities since 1999.  Consequently, during 2000, TVA began paying for essential stewardship activities primarily with power revenues, with the remainder funded with user fees and other forms of revenues derived in connection with those activities.  The activities related to stewardship properties do not meet the criteria of an operating segment under accounting principles generally accepted in the United States of America ("GAAP").  Accordingly, these assets and properties are included as part of the power program, TVA's only operating segment.

Power rates are established by the TVA Board as authorized by the Tennessee Valley Authority Act of 1933, as amended ("TVA Act").  The TVA Act requires TVA to charge rates for power that will produce gross revenues sufficient to provide funds for operation, maintenance, and administration of its power system; payments to states and counties in lieu of taxes ("tax equivalents"); debt service on outstanding indebtedness; payments to the U.S. Treasury in repayment of and as a return on the Power Program Appropriation Investment; and such additional margin as the TVA Board may consider desirable for investment in power system assets, retirement of outstanding Bonds in advance of maturity, additional reduction of the Power Program Appropriation Investment, and other purposes connected with TVA's power business.  TVA fulfilled its requirement to repay $1.0 billion of the Power Program Appropriation Investment with the 2014 payment; therefore, this repayment obligation is no longer a component of rate setting. In setting TVA's rates, the TVA Board is charged by the TVA Act to have due regard for the primary objectives of the TVA Act, including the objective that power shall be sold at rates as low as are feasible.  Rates set by the TVA Board are not subject to review or approval by any state or other federal regulatory body.

Fiscal Year

TVA's fiscal year ends September 30.  Years (2023, 2022, etc.) refer to TVA's fiscal years unless they are preceded by "CY," in which case the references are to calendar years.

Cost-Based Regulation

Since the TVA Board is authorized by the TVA Act to set rates for power sold to its customers, TVA is self-regulated. Additionally, TVA's regulated rates are designed to recover its costs.  Based on current projections, TVA believes that rates, set at levels that will recover TVA's costs, can be charged and collected.  As a result of these factors, TVA records certain assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for non-regulated entities.   Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates.  Regulatory liabilities generally represent obligations to make refunds to customers for previous collections for costs that are not likely to be incurred or deferral of gains that will be credited to customers in future periods.  TVA assesses whether the regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, potential legislation, and changes in technology.  Based on these assessments, TVA believes the existing regulatory assets are probable of recovery.  This determination reflects the current regulatory and political environment and is subject to change in the future.  If future recovery of regulatory assets ceases to be probable, or TVA is no longer considered to be a regulated entity, then costs would be required to be written off.  All regulatory asset write offs would be required to be recognized in earnings in the period in which future recovery ceases to be probable.

Basis of Presentation

    The accompanying consolidated financial statements, which have been prepared in accordance with GAAP, include the accounts of TVA and variable interest entities ("VIEs") of which TVA is the primary beneficiary. See Note 11 — Variable Interest Entities. Intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements requires TVA to estimate the effects of various matters that are inherently uncertain as of the date of the consolidated financial statements.  Although the consolidated financial statements are prepared in conformity with GAAP, TVA is required to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the amounts of revenues and expenses, reported during the reporting period.  Each of these estimates varies in regard to the level of judgment involved and its potential impact on TVA's financial results.  Estimates are considered critical either when a different estimate could have reasonably been used, or where changes in the estimate are reasonably likely to occur from period to period, and such use or change would materially impact TVA's financial condition, results of operations, or cash flows.

Cash, Cash Equivalents, and Restricted Cash

    Cash includes cash on hand, non-interest bearing cash, and deposit accounts. All highly liquid investments with original maturities of three months or less are considered cash equivalents. Cash and cash equivalents that are restricted, as to withdrawal or use under the terms of certain contractual agreements, are recorded in Other long-term assets on the Consolidated Balance Sheets. Restricted cash and cash equivalents include cash held in trusts that are currently restricted for TVA economic development loans and for certain TVA environmental programs in accordance with agreements related to compliance with certain environmental regulations. See Note 22 — Commitments and Contingencies — Legal Proceedings — Environmental Agreements.
    The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported on the Consolidated Balance Sheets and Consolidated Statements of Cash Flows:
Cash, Cash Equivalents, and Restricted Cash
At September 30
(in millions)
 20232022
Cash and cash equivalents$501 $500 
Restricted cash and cash equivalents included in Other long-term assets20 20 
Total cash, cash equivalents, and restricted cash$521 $520 

Allowance for Uncollectible Accounts

TVA recognizes an allowance that reflects the current estimate for credit losses expected to be incurred over the life of the financial assets based on historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amounts. The appropriateness of the allowance is evaluated at the end of each reporting period.

To determine the allowance for trade receivables, TVA considers historical experience and other currently available information, including events such as customer bankruptcy and/or a customer failing to fulfill payment arrangements by the due date. TVA's corporate credit department also performs an assessment of the financial condition of customers and the credit quality of the receivables. In addition, TVA reviews other reasonable and supportable forecasts to determine if the allowance for uncollectible amounts should be further adjusted in accordance with the accounting guidance for Current Expected Credit Losses.

To determine the allowance for loans receivables, TVA aggregates loans into the appropriate pools based on the existence of similar risk characteristics such as collateral types and internal assessed credit risks. In situations where a loan exhibits unique risk characteristics and is no longer expected to experience similar risks to the rest of its pool, the loan will be evaluated separately. TVA derives an annual loss rate based on historical loss and then adjusts the rate to reflect TVA's consideration of available information on current conditions and reasonable and supportable future forecasts. This information may include economic and business conditions, default trends, and other internal and external factors. For periods beyond the reasonable and supportable forecast period, TVA uses the current calculated long-term average historical loss rate for the remaining life of the loan portfolio.

The allowance for uncollectible accounts was less than $1 million at both September 30, 2023 and 2022, for trade accounts receivable.  Additionally, loans receivable of $104 million and $105 million at September 30, 2023 and 2022, respectively, are included in Accounts receivable, net and Other long-term assets, for the current and long-term portions, respectively. Loans receivables are reported net of allowances for uncollectible accounts of $3 million at both September 30, 2023 and 2022.

Revenues

TVA recognizes revenue from contracts with customers to depict the transfer of goods or services to customers in an amount to which the entity expects to be entitled in exchange for those goods or services. For the generation and transmission of electricity, this is generally at the time the power is delivered to a metered customer delivery point for the customer's consumption or distribution. As a result, revenues from power sales are recorded as electricity is delivered to customers. In addition to power sales invoiced and recorded during the month, TVA accrues estimated unbilled revenues for power sales provided to five customers whose billing date occurs prior to the end of the month.  Exchange power sales are presented in the accompanying Consolidated Statements of Operations as a component of sales of electricity. Exchange power sales are sales of excess power after meeting TVA native load and directly served requirements.  Native load refers to the customers on whose behalf a company, by statute, franchise, regulatory requirement, or contract, has undertaken an obligation to serve. TVA engages in other arrangements in addition to power sales. Certain other revenue from activities related to TVA's overall mission is recorded in Other revenue. Revenues that are not related to the overall mission are recorded in Other income, net.

Inventories

Certain Fuel, Materials, and Supplies.  Materials and supplies inventories are valued using an average unit cost method. A new average cost is computed after each inventory purchase transaction, and inventory issuances are priced at the latest moving weighted average unit cost. Coal, fuel oil, and natural gas inventories are valued using an average cost method. A new weighted average cost is computed monthly, and monthly issues are priced accordingly.

Renewable Energy Certificates. TVA accounts for Renewable Energy Certificates ("RECs") using the specific identification cost method. RECs that are acquired through power purchases are recorded as inventory and charged to purchased power expense when the RECs are subsequently used or sold. TVA assigns a value to the RECs at the inception of
the power purchase arrangement using a relative standalone selling price approach. RECs created through TVA-owned asset generation are recorded at zero cost.

Emission Allowances.  TVA accounts for emission allowances using the specific identification cost method. Allowances that are acquired through third party purchases are recorded as inventory at cost and charged to operating expense based on tons emitted during the respective compliance periods.  

Allowance for Inventory Obsolescence.  TVA reviews materials and supplies inventories by category and usage on a periodic basis.  Each category is assigned a probability of becoming obsolete based on the type of material and historical usage data.  TVA has a fleet-wide inventory management policy for each generation type. Based on the estimated value of the inventory, TVA adjusts its allowance for inventory obsolescence.

Pre-Commercial Plant Operations

As part of the process of completing the construction of a generating unit, the electricity produced is used to serve the demands of the electric system. TVA estimates revenues earned during pre-commercial operations at the fair value of the energy delivered based on TVA's hourly incremental dispatch cost. Pre-commercial plant operations began on Colbert Combustion Turbine Units 9-10 in June 2023 and on Colbert Combustion Turbine Unit 11 in early July 2023. All three units became operational on July 25, 2023. Estimated revenue of $3 million related to this project was capitalized to offset project costs for the year ended September 30, 2023. TVA also capitalized related fuel costs for this project of $3 million for the year ended September 30, 2023.

Property, Plant, and Equipment, and Depreciation

    Property, Plant, and Equipment. Additions to plant are recorded at cost, which includes direct and indirect costs.  The cost of current repairs and minor replacements is charged to operating expense. When property, plant, and equipment is retired, accumulated depreciation is charged for the original cost of the assets. Gains or losses are only recognized upon the sale of land or an entire operating unit. TVA capitalizes certain costs incurred in connection with developing or obtaining internal-use software. Capitalized software costs are included in Property, plant, and equipment on the Consolidated Balance Sheets and are generally amortized over seven years.  

Nuclear Fuel. Nuclear fuel, which is included in Property, plant, and equipment, is valued using the average cost method for raw materials and the specific identification method for nuclear fuel in a reactor.  Amortization of nuclear fuel in a reactor is calculated on a units-of-production basis and is included in fuel expense.

TVA, the U.S. Department of Energy ("DOE"), and certain nuclear fuel contractors have entered into agreements, referred to as the Down-blend Offering for Tritium ("DBOT"), that provide for the production, processing, and storage of low-enriched uranium that is to be made using surplus DOE highly enriched uranium and other uranium.  Low-enriched uranium can be fabricated into fuel for use in a nuclear power plant.  Production of the low-enriched uranium began in 2019 and is contracted to continue through September 2025. Contract activity will consist of storage and flag management.  Flag management ensures that the uranium is of U.S. origin, free from foreign obligations, and unencumbered by policy restrictions, so that it can be used in connection with the production of tritium. Under the terms of the interagency agreement between the DOE and TVA, the DOE will reimburse TVA for a portion of the costs of converting the highly enriched uranium to low-enriched uranium. Since 2019, TVA has received $219 million in reimbursements from the DOE, which is recorded as a reduction in nuclear fuel inventory costs. At September 30, 2023, TVA recorded $11 million in Accounts receivable, net related to this agreement.

    Depreciation. TVA accounts for depreciation of its properties using the composite depreciation convention of accounting.  Under the composite method, assets with similar economic characteristics are grouped and depreciated as one asset. Depreciation is generally computed on a straight-line basis over the estimated service lives of the various classes of assets. The estimation of asset useful lives requires management judgment, supported by external depreciation studies of historical asset retirement experience. Depreciation rates are determined based on external depreciation studies that are updated approximately every five years, with the latest study implemented during the first quarter of 2022.
Depreciation expense for the years ended September 30, 2023, 2022, and 2021 was $1.9 billion, $1.8 billion, and $1.4 billion, respectively. Depreciation expense expressed as a percentage of the average annual depreciable completed plant was 3.14 percent for 2023, 2.98 percent for 2022, and 2.28 percent for 2021.  Average depreciation rates by asset class are as follows:
Property, Plant, and Equipment Depreciation Rates
At September 30
(percent)
202320222021
Asset Class
Nuclear2.73 2.72 2.38 
Coal-fired(1)
4.98 4.27 1.95 
Hydroelectric1.82 1.85 1.60 
Gas and oil-fired3.17 3.38 2.98 
Transmission1.52 1.51 1.34 
Other4.43 3.64 7.12 
Note
(1) The rates include the acceleration of depreciation related to retiring certain coal-fired units and potentially retiring the remainder of the coal-fired fleet by 2035. See Note 7 — Plant Closures.

Reacquired Rights. Property, plant, and equipment includes intangible reacquired rights, net of amortization, of $324 million and $178 million as of September 30, 2023 and 2022, respectively, related to the purchase of residual interests from lease/leaseback agreements of certain combustion turbine units ("CTs"). Reacquired rights are amortized over the estimated useful lives of the underlying CTs which range from 30 to 35 years. Amortization expense was $10 million, $6 million, and $8 million for the years ended September 30, 2023, 2022, and 2021, respectively, and accumulated amortization at September 30, 2023 and 2022 totaled $52 million and $42 million, respectively. At September 30, 2023, the estimated aggregate amortization expense for each of the next five years and thereafter is shown below:

 20242025202620272028Thereafter
Reacquired Rights$11 $12 $11 $12 $11 $267 

Impairment of Assets.  TVA evaluates long-lived assets for impairment when events or changes in circumstances indicate that the carrying value of such assets may not be recoverable.  For long-lived assets, TVA bases its evaluation on impairment indicators such as the nature of the assets, the future economic benefit of the assets, any historical or future profitability measurements, regulatory approval and ability to set rates at levels that allow for recoverability of the assets, and other external market conditions or factors that may be present.  If such impairment indicators are present or other factors exist that indicate that the carrying amount of an asset may not be recoverable, TVA determines whether an impairment has occurred based on an estimate of undiscounted cash flows attributable to the asset as compared with the carrying value of the asset.  If an impairment has occurred, the amount of the impairment recognized is measured as the excess of the asset's carrying value over its fair value.  Additionally, TVA regularly evaluates construction projects.  If the project is canceled or deemed to have no future economic benefit, the project is written off as an asset impairment or, upon TVA Board approval, reclassified as a regulatory asset and amortized over the Board-approved period. See Note 7 — Plant Closures.

Leases

    TVA recognizes a lease asset and lease liability for leases with terms of greater than 12 months. Lease assets represent TVA's right to use an underlying asset for the lease term, and lease liabilities represent TVA's obligation to make lease payments arising from the lease, both of which are recognized based on the present value of the future minimum lease payments over the lease term at the commencement date.  TVA has certain lease agreements that include variable lease payments that are based on energy production levels. These variable lease payments are not included in the measurement of the lease assets or lease liabilities but are recognized in the period in which the expenses are incurred.
    
    While not specifically structured as leases, certain power purchase agreements ("PPAs") are deemed to contain a lease of the underlying generating units when the terms convey the right to control the use of the assets. Amounts recorded for these leases are generally based on the amount of the scheduled capacity payments due over the remaining terms of the PPAs, the terms of which vary. The total lease obligations included in Accounts payable and accrued liabilities, Other long-term liabilities, and Finance lease liabilities related to these agreements were $390 million and $135 million for finance and operating leases, respectively, at September 30, 2023. The total lease obligations included in Accounts payable and accrued liabilities, Other long-term liabilities, and Finance lease liabilities related to these agreements were $425 million and $133 million for finance and operating leases, respectively, at September 30, 2022.
    TVA has agreements with lease and non-lease components and has elected to account for the components separately. Consideration is allocated to lease and non-lease components generally based on relative standalone selling prices.

    TVA has lease agreements which include options for renewal and early termination. The intent to renew a lease varies depending on the lease type and asset. Renewal options that are reasonably certain to be exercised are included in the lease measurements. The decision to terminate a lease early is dependent on various economic factors. No termination options have been included in TVA's lease measurements.
    
    Leases with an initial term of 12 months or less, which do not include an option to extend the initial term of the lease to greater than 12 months that TVA is reasonably certain to exercise, are not recorded on the Consolidated Balance Sheets at September 30, 2023.
    Operating leases are recognized on a straight-line basis over the term of the lease agreement. Rent expense associated with short-term leases and variable leases is recorded in Operating and maintenance expense, Fuel expense, or Purchased power expense on the Consolidated Statements of Operations. Expenses associated with finance leases result in the separate presentation of interest expense on the lease liability and amortization expense of the related lease asset on the Consolidated Statements of Operations.

Decommissioning Costs

    TVA recognizes legal obligations associated with the future retirement of certain tangible long-lived assets.  These obligations relate to fossil fuel-fired generating plants, nuclear generating plants, hydroelectric generating plants/dams, transmission structures, and other property-related assets.  Activities involved with retiring these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site restoration. Revisions to the forecasted costs of decommissioning activities are made whenever factors indicate that the timing or amounts of estimated cash flows have changed materially. Studies are updated for both nuclear and non-nuclear decommissioning costs at least every five years.  Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset.  See Note 10 — Regulatory Assets and Liabilities — Nuclear Decommissioning Costs and Non-Nuclear Decommissioning Costs and Note 13 — Asset Retirement Obligations.

Investment Funds

    Investment funds consist primarily of trust funds designated to fund decommissioning requirements (see Note 22 — Commitments and Contingencies — Contingencies — Decommissioning Costs), the Supplemental Executive Retirement Plan ("SERP") (see Note 20 — Benefit Plans — Overview of Plans and Benefits — Supplemental Executive Retirement Plan), the Deferred Compensation Plan ("DCP"), and the Restoration Plan ("RP"). The Nuclear Decommissioning Trust ("NDT") holds funds primarily for the ultimate decommissioning of TVA's nuclear power plants. The Asset Retirement Trust ("ART") holds funds primarily for the costs related to the future closure and retirement of TVA's other long-lived assets. The NDT, ART, SERP, DCP, and RP funds are invested in portfolios of securities generally designed to achieve a return in line with overall equity and debt market performance. The NDT, ART, SERP, DCP, and RP funds are all classified as trading.

Research and Development Costs

Research and development costs are expensed when incurred.  TVA's research programs include those related to power delivery technologies, emerging technologies (clean energy, renewables, distributed resources, and energy efficiency), technologies related to generation (fossil fuel, nuclear, and hydroelectric), and environmental technologies.

Tax Equivalents

TVA is not subject to federal income taxation. In addition, neither TVA nor its property, franchises, or income is subject to taxation by states or their subdivisions. The TVA Act requires TVA to make payments to states and counties in which TVA conducts its power operations and in which TVA has acquired power properties previously subject to state and local taxation.   The total amount of these payments is five percent of gross revenues from sales of power during the preceding year, excluding sales or deliveries to other federal agencies and off-system sales with other utilities, with a provision for minimum payments under certain circumstances. TVA calculates tax equivalent expense by subtracting the prior year fuel cost-related tax equivalent regulatory asset or liability from the payments made to the states and counties during the current year and adding back the current year fuel cost-related tax equivalent regulatory asset or liability. Fuel cost-related tax equivalent expense is recognized in the same accounting period in which the fuel cost-related revenue is recognized.

Maintenance Costs
TVA records maintenance costs and repairs related to its property, plant, and equipment on the Consolidated Statements of Operations as they are incurred except for the recording of certain regulatory assets for retirement and removal costs.
v3.23.3
Impact of New Accounting Standards and Interpretations
 12 Months Ended
Sep. 30, 2023
Accounting Changes and Error Corrections [Abstract]  
Accounting Standards Update and Change in Accounting Principle [Text Block] Impact of New Accounting Standards and Interpretations
The following accounting standards have been issued but as of September 30, 2023, were not effective and had not been adopted by TVA:

Accounting for Contract Assets and Contract Liabilities from Contracts with Customers
DescriptionThis guidance requires an entity (acquirer) to recognize and measure contract assets and contract
liabilities acquired in a business combination in accordance with revenue with customers. It is
expected that an acquirer will generally recognize and measure acquired contract assets and contract
liabilities in a manner consistent with how the acquiree recognized and measured contract assets and
contract liabilities in the acquiree’s financial statement. The entity should apply the standard prospectively to business combinations occurring on or after the effective date of the standard.
Effective Date for TVAThis new standard is effective for TVA’s interim and annual reporting periods beginning October 1,
2023. TVA adopted the standard on October 1, 2023, on a prospective basis. While early adoption was permitted, TVA did not adopt the standard early.
Effect on the Financial Statements or Other Significant MattersAdoption of this standard did not have a material impact on TVA's financial condition, results of operations, or cash flows.

Troubled Debt Restructurings and Vintage Disclosures
DescriptionThis guidance eliminates the recognition and measurement guidance on troubled debt restructuring for
creditors that have adopted Financial Instruments-Credit Losses and requires enhanced disclosures
about loan modifications for borrowers experiencing financial difficulty. Additionally, the guidance
requires public business entities to present current-period gross write-offs by year of origination in their
vintage disclosures. The entity should apply the standard prospectively except for the transition method related to the recognition and measurement of troubled debt restructuring. For the transition method, an entity has the option to apply a modified retrospective transition method, resulting in a cumulative-effect adjustment to retained earnings in the period of adoption.
Effective Date for TVAThis new standard is effective for TVA’s interim and annual reporting periods beginning October 1,
2023. TVA adopted the standard on October 1, 2023, on a prospective basis. While early adoption was permitted, TVA did not adopt the standard early.
Effect on the Financial Statements or Other Significant MattersAdoption of this standard did not have a material impact on TVA's financial condition, results of operations, or cash flows.
v3.23.3
Accounts Receivable, Net
 12 Months Ended
Sep. 30, 2023
Accounts Receivable, after Allowance for Credit Loss [Abstract]  
Accounts Receivable, Net
3.  Accounts Receivable, Net

Accounts receivable primarily consist of amounts due from customers for power sales.  The table below summarizes the types and amounts of TVA's accounts receivable:
Accounts Receivable, Net
At September 30
(in millions)
 20232022
Power receivables$1,627 $1,899 
Other receivables118 108 
Accounts receivable, net(1)
$1,745 $2,007 
Note
(1) Allowance for uncollectible accounts was less than $1 million at both September 30, 2023 and 2022, and therefore is not represented in the table above.
v3.23.3
Inventories, Net
 12 Months Ended
Sep. 30, 2023
Inventory, Net [Abstract]  
Inventories, Net
4.  Inventories, Net

The table below summarizes the types and amounts of TVA's inventories:
Inventories, Net 
At September 30
(in millions)
 20232022
Materials and supplies inventory$849 $808 
Fuel inventory313 303 
Renewable energy certificates/emissions allowance inventory, net15 18 
Allowance for inventory obsolescence(69)(57)
Inventories, net$1,108 $1,072 
v3.23.3
Deferred Costs, Capitalized, Prepaid, and Other Assets - Text Block
 12 Months Ended
Sep. 30, 2023
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]  
Other Current Assets
5. Other Current Assets

Other current assets consisted of the following:
Other Current Assets 
At September 30
(in millions)
 2023
2022(1)
Inventory work-in-progress$28 $18 
Current portion of prepaid long-term service agreements25 12 
Commodity contract derivative assets21 172 
Prepaid software maintenance18 14 
Prepaid insurance16 16 
Other26 25 
Other current assets$134 $257 
Note
(1) At September 30, 2022, $18 million, $14 million, $16 million, and $12 million previously classified as Other (a component of Other current assets) have been reclassified to Inventory work-in-progress (a component of Other current assets), Prepaid software maintenance (a component of Other current assets), Prepaid insurance (a component of Other current assets), and Current portion of prepaid long-term service agreements (a component of Other current assets), respectively, to conform with current year presentation.

Commodity Contract Derivative Assets. TVA enters into certain derivative contracts for natural gas that require physical
delivery of the contracted quantity of the commodity as well as certain financial derivative contracts to hedge exposure to the price of natural gas. Commodity contract derivative assets classified as current include deliveries or settlements that will occur within 12 months or less. See Note 15 — Risk Management Activities and Derivative Transactions — Derivatives Not Receiving Hedge Accounting Treatment — Commodity Derivatives and — Commodity Derivatives under the FHP for a discussion of TVA's commodity contract derivatives.
v3.23.3
Net Completed Plant
 12 Months Ended
Sep. 30, 2023
Property, Plant and Equipment, Net, by Type [Abstract]  
Property, Plant, and Equipment and Intangible Assets
6. Net Completed Plant

Net completed plant consisted of the following:
Net Completed Plant
At September 30
(in millions)
 20232022
 CostAccumulated Depreciation 
Net		CostAccumulated DepreciationNet
Coal-fired(1)
$18,525 $14,464 $4,061 $18,145 $13,649 $4,496 
Gas and oil-fired6,663 2,057 4,606 6,112 1,957 4,155 
Nuclear26,803 13,557 13,246 26,629 12,928 13,701 
Transmission9,375 3,359 6,016 8,919 3,301 5,618 
Hydroelectric4,109 1,241 2,868 3,987 1,192 2,795 
Other electrical plant1,798 780 1,018 1,724 807 917 
Multipurpose dams900 404 496 900 396 504 
Other stewardship26 9 17 26 9 17 
Total$68,199 $35,871 $32,328 $66,442 $34,239 $32,203 
Note
(1) TVA recognized accelerated depreciation as a result of the decision to idle or retire certain units and the potential retirement of the remainder of the coal-fired fleet by 2035. See Note 7 — Plant Closures.
v3.23.3
Other Long-Term Assets [Text Block]
 12 Months Ended
Sep. 30, 2023
Assets, Noncurrent [Abstract]  
Other Long-Term Assets
9.  Other Long-Term Assets

The table below summarizes the types and amounts of TVA's other long-term assets:
Other Long-Term Assets 
At September 30
(in millions)
 20232022
Loans and other long-term receivables, net$97 $99 
Prepaid long-term service agreements64 74 
EnergyRight® receivables, net
47 49 
Prepaid capital assets28 — 
Commodity contract derivative assets12 102 
Other82 70 
Total other long-term assets$330 $394 

Loans and Other Long-Term Receivables. TVA's loans and other long-term receivables primarily consist of economic development loans for qualifying organizations and a receivable for reimbursements to recover the cost of providing long-term, on-site storage for spent nuclear fuel. The current and long-term portions of the loans receivable are reported in Accounts receivable, net and Other long-term assets, respectively, on TVA's Consolidated Balance Sheets. At September 30, 2023 and 2022, the carrying amount of the loans receivable, net of discount, reported in Accounts receivable, net was $7 million and $6 million, respectively.    

EnergyRight® Receivables. In association with the EnergyRight® program, TVA's local power company customers ("LPCs") offer financing to end-use customers for the purchase of energy-efficient equipment. Depending on the nature of the energy-efficiency project, loans may have a maximum term of five years or 10 years. TVA purchases the resulting loans receivable from its LPCs. The loans receivable are then transferred to a third-party bank with which TVA has agreed to repay in full any loans receivable that have been in default for 180 days or more or that TVA has determined are uncollectible. Given this continuing involvement, TVA accounts for the transfer of the loans receivable as secured borrowings. The current and long-term portions of the loans receivable are reported in Accounts receivable, net and Other long-term assets, respectively, on TVA's Consolidated Balance Sheets. At September 30, 2023 and 2022, the carrying amount of the loans receivable, net of discount, reported in Accounts receivable, net was $12 million and $13 million, respectively. See Note 12 — Other Long-Term Liabilities for information regarding the associated financing obligation.

Allowance for Loan Losses. The allowance for loan loss is an estimate of expected credit losses, measured over the estimated life of the loan receivables, that considers reasonable and supportable forecasts of future economic conditions in addition to information about historical experience and current conditions. See Note 1 — Summary of Significant Accounting Policies — Allowance for Uncollectible Accounts.

The allowance components, which consist of a collective allowance and specific loans allowance, are based on the risk characteristics of TVA's loans. Loans that share similar risk characteristics are evaluated on a collective basis in measuring credit losses, while loans that do not share similar risk characteristics with other loans are evaluated on an individual basis.

Allowance Components
At September 30
(in millions)
20232022
EnergyRight® loan reserve
$1 $1 
Economic development loan collective reserve1 1 
Economic development loan specific loan reserve1 1 
Total allowance for loan losses$3 $3 

Prepaid Long-Term Service Agreements. TVA has entered into various long-term service agreements for major
maintenance activities at certain of its combined cycle plants. TVA uses the direct expense method of accounting for these
arrangements. TVA accrues for parts when it takes ownership and for contractor services when they are rendered. Under
certain of these agreements, payments made exceed the value of parts received and services rendered. The current and long-term portions of the resulting prepayments are reported in Other current assets and Other long-term assets, respectively, on
TVA's Consolidated Balance Sheets. At September 30, 2023 and 2022, prepayments of $25 million and $12 million, respectively, were recorded in Other current assets.
Commodity Contract Derivative Assets. TVA enters into certain derivative contracts for natural gas that require physical delivery of the contracted quantity of the commodity as well as certain financial derivative contracts to hedge exposure to the price of natural gas. See Note 15 — Risk Management Activities and Derivative Transactions — Derivatives Not Receiving Hedge Accounting Treatment — Commodity Derivatives and — Commodity Derivatives under the FHP for a discussion of TVA's commodity contract derivatives.
v3.23.3
Regulatory Assets and Liabilities [Text Block]
 12 Months Ended
Sep. 30, 2023
Regulatory Assets and Liabilities Disclosure [Abstract]  
Regulatory Assets and Liabilities
10.  Regulatory Assets and Liabilities

TVA records certain assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for non-regulated entities. As such, certain items that would generally be reported in earnings or that would impact the Consolidated Statements of Operations are recorded as regulatory assets or regulatory liabilities. Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates.  Regulatory liabilities generally represent obligations to make refunds to customers for previous collections for costs that are not likely to be incurred or deferral of gains that will be credited to customers in future periods. Components of regulatory assets and regulatory liabilities are summarized in the table below. 
Regulatory Assets and Liabilities 
At September 30
(in millions)
 20232022
Current regulatory assets  
Unrealized losses on interest rate derivatives$31 $47 
Unrealized losses on commodity derivatives136 14 
Fuel cost adjustment receivable11 77 
Total current regulatory assets178 138 
Non-current regulatory assets  
Retirement benefit plans deferred costs1,440 1,839 
Non-nuclear decommissioning costs2,922 2,856 
Unrealized losses on interest rate derivatives272 479 
Nuclear decommissioning costs728 821 
Unrealized losses on commodity derivatives52 1 
Other non-current regulatory assets152 138 
Total non-current regulatory assets5,566 6,134 
Total regulatory assets$5,744 $6,272 
Current regulatory liabilities  
Fuel cost adjustment tax equivalents$201 $218 
Unrealized gains on commodity derivatives21 173 
Total current regulatory liabilities222 391 
Non-current regulatory liabilities  
Retirement benefit plans deferred credits95 70 
Unrealized gains on commodity derivatives12 102 
Total non-current regulatory liabilities107 172 
Total regulatory liabilities$329 $563 

    Retirement Benefit Plans Deferred Costs (Credits).  TVA measures the funded status of its pension and post-retirement ("OPEB") benefit plans at each year-end balance sheet date. The funded status is measured as the difference between the fair value of plan assets and the benefit obligations at the measurement date for each plan. The changes in funded status are actuarial gains and losses that are recognized on TVA's Consolidated Balance Sheets by adjusting the recognized pension and OPEB liabilities, with the offset deferred as a regulatory asset or a regulatory liability. In an unregulated environment, these deferred costs (credits) would be recognized as an increase or decrease to accumulated other comprehensive income (loss) ("AOCI").
    "Incurred cost" is a cost arising from cash paid out or an obligation to pay for an acquired asset or service, and a loss from any cause that has been sustained and for which payment has been or must be made. In the cases of pension and OPEB costs, the unfunded obligation represents a projected liability to the employee for services rendered, and thus it meets the definition of an incurred cost. Therefore, amounts that otherwise would be charged to AOCI for these costs are recorded as a regulatory asset or liability since TVA has historically recovered pension and OPEB expense in rates. Through historical and current year expense included in ratemaking, the TVA Board has demonstrated the ability and intent to include pension and OPEB costs in allowable costs and in rates for ratemaking purposes. As a result, it is probable that future revenue will result from inclusion of the pension and OPEB regulatory assets or regulatory liability in allowable costs for ratemaking purposes.

    The regulatory asset and liability are classified as long-term, which is consistent with the pension and OPEB liabilities, and are not amortized to the Consolidated Statements of Operations over a specified recovery period. They are adjusted either upward or downward each year in conjunction with the adjustments to the unfunded pension liability and OPEB liability, as calculated by the actuaries. Ultimately the regulatory asset and liability will be recognized in the Consolidated Statements of Operations in the form of pension and OPEB expense as the actuarial liabilities are eliminated in future periods. See Note 20 — Benefit Plans — Obligations and Funded Status.

    Additionally on October 1, 2014, TVA began recognizing pension costs as a regulatory asset to the extent that the amount calculated under GAAP as pension expense differs from the amount TVA contributes to the pension plan. As a result of previous plan design changes, future contributions are expected to exceed the expense calculated under U.S. GAAP. Accordingly, TVA discontinued this regulatory accounting practice as all such deferred costs were recovered as of September 30, 2023.

Non-Nuclear Decommissioning Costs.  Non-nuclear decommissioning costs include (1) certain deferred charges related to the future closure and decommissioning of TVA's non-nuclear long-lived assets, (2) recognition of changes in the liability, (3) recognition of changes in the value of TVA's ART, and (4) certain other deferred charges under the accounting rules for asset retirement obligations ("AROs").  TVA has established the ART to more effectively segregate, manage, and invest funds to help meet future non-nuclear AROs.  The funds from the ART may be used, among other things, to pay the costs related to the future closure and retirement of non-nuclear long-lived assets under various legal requirements.  These future costs can be funded through a combination of investment funds set aside in the ART, future earnings on those investment funds, and future cash contributions to the ART.  In 2023 and 2022, TVA recovered in rates an amount determined by the average life of debt financed for non-nuclear decommissioning expenditures, assuming a 20-year debt service period, and contributions to the ART. Deferred charges will be recovered in rates based on an analysis of the expected expenditures, contributions, and investment earnings required to recover the decommissioning costs. Recovery of future decommissioning costs is dependent upon the future earnings of the ART, timing of decommissioning activities, and changes in decommissioning estimates. The regulatory asset is classified as long-term as amounts recovered are used to service debt or to contribute to the ART, which is restricted for future decommissioning costs.

Unrealized Losses on Interest Rate Derivatives.  TVA uses regulatory accounting treatment to defer the unrealized gains and losses on certain interest rate derivative contracts. When amounts in these contracts are realized, the resulting gains or losses are included in the ratemaking formula.  The unrealized losses on these interest rate derivatives are recorded on TVA's Consolidated Balance Sheets as current and non-current regulatory assets, and the related realized gains or losses, if any, are recorded on TVA's Consolidated Statements of Operations when the contracts settle. A portion of certain unrealized gains and losses will be amortized into earnings over the remaining lives of the contracts. Gains and losses on interest rate derivatives that are expected to be realized within the next year are included as a current regulatory asset or liability on TVA's Consolidated Balance Sheets.

Due to rising interest rates in the financial markets and net settlement payments made during 2023, TVA experienced a reduction in unrealized losses related to its derivative instruments for the year ended September 30, 2023. TVA does not recognize unrealized gains and losses from the investment portfolios and derivative instruments within earnings but rather defers all such gains and losses within a regulatory liability or asset in accordance with its accounting policy. See Note 15 — Risk Management Activities and Derivative Transactions and Note 16 — Fair Value Measurements.

Nuclear Decommissioning Costs.  Nuclear decommissioning costs include (1) certain deferred charges related to the future closure and decommissioning of TVA's nuclear generating units under the Nuclear Regulatory Commission ("NRC") requirements, (2) recognition of changes in the liability, (3) recognition of changes in the value of TVA's NDT, and (4) certain other deferred charges under the accounting rules for AROs.  These future costs can be funded through a combination of investment funds set aside in the NDT and ART and future earnings on those investment funds. Deferred charges will be recovered in rates based on the analysis of expected expenditures, contributions, and investment earnings required to recover the decommissioning costs.  See Note 1 — Summary of Significant Accounting Policies — Investment Funds.  Recovery of future decommissioning costs is dependent upon the future earnings of the NDT and ART, timing of decommissioning activities, and changes in decommissioning estimates. The regulatory asset is classified as long-term as amounts recovered are contributed to the NDT or the ART, which are restricted for future decommissioning costs.

Nuclear decommissioning costs decreased $93 million for the year ended September 30, 2023 as compared to the same period of the prior year, primarily due to investment gains in the NDT and amortization of regulatory assets into expenses
during 2023 as amounts were collected in rates, and these increases were partially offset by accretion of the related AROs. See Note 13 — Asset Retirement Obligations and Note 16 — Fair Value Measurements.

Unrealized Gains (Losses) on Commodity Derivatives.  TVA enters into certain derivative contracts for natural gas that require the physical delivery of the contracted quantity of the commodity. Unrealized gains (losses) on natural gas purchase contracts, included as part of unrealized gains (losses) on commodity derivatives, relate to the mark-to-market ("MtM") valuation of natural gas purchase contracts.  The natural gas purchase contracts qualify as derivative contracts but do not qualify for cash flow hedge accounting treatment.  As a result, TVA recognizes the changes in the market value of these derivative contracts as a regulatory liability or asset.  This treatment reflects TVA's ability and intent to recover the cost of these commodity contracts on a settlement basis for ratemaking purposes through the fuel cost adjustment. TVA recognizes the actual cost of fuel received under these contracts in fuel expense at the time the fuel is used to generate electricity.  These contracts expire at various times through March 2026.  Unrealized gains and losses on contracts with a maturity of less than one year are included as a current regulatory asset or liability on TVA's Consolidated Balance Sheets.  See Note 15 — Risk Management Activities and Derivative Transactions.

TVA reinstated the FHP in December 2021, and hedging activity began under the program in the second quarter of 2022. Currently, TVA is hedging exposure to the price of natural gas under the FHP. Deferred gains and losses relating to TVA's FHP are included as part of unrealized gains and losses on commodity derivatives. TVA defers all MtM unrealized gains or losses as regulatory liabilities or assets, respectively, and records the realized gains or losses in fuel and purchased power expense as the contracts settle to match the delivery period of the underlying commodity. This accounting treatment reflects TVA's ability and intent to include the realized gains or losses of these commodity contracts in future periods through the fuel cost adjustment. Net unrealized gains and losses for any settlements that occur within 12 months or less are classified as a current regulatory liability or asset. See Note 15 — Risk Management Activities and Derivative Transactions.

Fuel Cost Adjustment Receivable.  The fuel cost adjustment provides a mechanism to alter rates monthly to reflect changing fuel and purchased power costs. There is typically a lag between the occurrence of a change in fuel and purchased power costs and the reflection of the change in fuel rates.  Balances in the fuel cost adjustment regulatory accounts represent over-collected or under-collected revenues that offset fuel and purchased power costs, and the fuel rate is designed to recover or refund the balance in less than one year.

Other Non-Current Regulatory Assets. Other non-current regulatory assets consist of the following:

    Deferred Lease Asset and Other Financing Obligations. For certain leases, TVA recognized the initial finance lease and other financing asset and liability at inception of the lease or other obligation. However, the annual expense recognized in rates is equal to the annual payments, which differs from GAAP treatment for non-regulated entities. This practice results in TVA's asset balances being higher than they otherwise would have been under GAAP, with the difference representing a regulatory asset related to the lease or other financing obligation. These costs will be amortized over the respective lease or other financing obligation terms as payments are made. As the costs associated with this regulatory asset are not currently being considered in rates and the asset is expected to increase over the next year, the regulatory asset has been classified as long-term.

Debt Reacquisition Costs.  Reacquisition expenses, call premiums, and other related costs, such as unamortized debt issue costs associated with redeemed Bond issues, are deferred and amortized (accreted) on a straight-line basis over the weighted average life of TVA's debt portfolio. Because timing of additional reacquisition expenses and changes to the weighted average life of the debt are uncertain, the regulatory asset is classified as long-term.

Retirement Removal Costs.  Retirement removal costs, net of salvage, that are not legally required are recognized as a regulatory asset. Net removal costs are amortized over a one-year period subsequent to completion of the removal activities. TVA treats this regulatory asset as long-term in its entirety primarily because it relates to assets that are long-term in nature.
Fuel Cost Adjustment Tax Equivalents.  The fuel cost adjustment includes a provision related to the current funding of the future payments TVA will make.  As TVA records the fuel cost adjustment, five percent of the calculation that relates to a future asset or liability for tax equivalent payments is recorded as a current regulatory liability and paid or refunded in the following year.
v3.23.3
Variable Interest Entities (Text Block)
 12 Months Ended
Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Variable Interest Entities
11.  Variable Interest Entities

A VIE is an entity that either (i) has insufficient equity to permit the entity to finance its activities without additional subordinated financial support or (ii) has equity investors who lack the characteristics of owning a controlling financial interest. When TVA determines that it has a variable interest in a VIE, a qualitative evaluation is performed to assess which interest holders have the power to direct the activities that most significantly impact the economic performance of the entity and have the obligation to absorb losses or receive benefits that could be significant to the entity. The evaluation considers the purpose and design of the business, the risks that the business was designed to create and pass along to other entities, the activities of the business that can be directed and which party can direct them, and the expected relative impact of those activities on the economic performance of the business through its life. TVA has the power to direct the activities of an entity when it has the
ability to make key operating and financing decisions, including, but not limited to, capital investment and the issuance of debt. Based on the evaluation of these criteria, TVA has determined it is the primary beneficiary of certain entities and as such is required to account for the VIEs on a consolidated basis.

John Sevier VIEs

In 2012, TVA entered into a $1.0 billion construction management agreement and lease financing arrangement with John Sevier Combined Cycle Generation LLC ("JSCCG") for the completion and lease by TVA of the John Sevier Combined Cycle Facility ("John Sevier CCF"). JSCCG is a special single-purpose limited liability company formed in January 2012 to finance the John Sevier CCF through a $900 million secured note issuance (the "JSCCG notes") and the issuance of $100 million of membership interests subject to mandatory redemption.  The membership interests were purchased by John Sevier Holdco LLC ("Holdco").  Holdco is a special single-purpose entity, also formed in January 2012, established to acquire and hold the membership interests in JSCCG.  A non-controlling interest in Holdco is held by a third-party through nominal membership interests, to which none of the income, expenses, and cash flows are allocated. 
 
The membership interests held by Holdco in JSCCG were purchased with proceeds from the issuance of $100 million of secured notes (the "Holdco notes") and are subject to mandatory redemption pursuant to a schedule of amortizing, semi-annual payments due each January 15 and July 15, with a final payment due in January 2042. The payment dates for the mandatorily redeemable membership interests are the same as those of the Holdco notes. The sale of the JSCCG notes, the membership interests in JSCCG, and the Holdco notes closed in January 2012. The JSCCG notes are secured by TVA's lease payments, and the Holdco notes are secured by Holdco's investment in, and amounts receivable from, JSCCG. TVA's lease payments to JSCCG are equal to and payable on the same dates as JSCCG's and Holdco's semi-annual debt service payments. In addition to the lease payments, TVA pays administrative and miscellaneous expenses incurred by JSCCG and Holdco. Certain agreements related to this transaction contain default and acceleration provisions.

    Due to its participation in the design, business activity, and credit and financial support of JSCCG and Holdco, TVA has determined that it has a variable interest in each of these entities. Based on its analysis, TVA has concluded that it is the primary beneficiary of JSCCG and Holdco and, as such, is required to account for the VIEs on a consolidated basis. Holdco's membership interests in JSCCG are eliminated in consolidation.

Southaven VIE

        In 2013, TVA entered into a $400 million lease financing arrangement with Southaven Combined Cycle Generation LLC ("SCCG") for the lease by TVA of the Southaven Combined Cycle Facility ("Southaven CCF"). SCCG is a special single-purpose limited liability company formed in June 2013 to finance the Southaven CCF through a $360 million secured notes issuance (the "SCCG notes") and the issuance of $40 million of membership interests subject to mandatory redemption. The membership interests were purchased by Southaven Holdco LLC ("SHLLC"). SHLLC is a special single-purpose entity, also formed in June 2013, established to acquire and hold the membership interests in SCCG. A non-controlling interest in SHLLC is held by a third-party through nominal membership interests, to which none of the income, expenses, and cash flows of SHLLC are allocated.

The membership interests held by SHLLC were purchased with proceeds from the issuance of $40 million of secured notes (the "SHLLC notes") and are subject to mandatory redemption pursuant to a schedule of amortizing, semi-annual payments due each February 15 and August 15, with a final payment due on August 15, 2033. The payment dates for the mandatorily redeemable membership interests are the same as those of the SHLLC notes, and the payment amounts are sufficient to provide returns on, as well as returns of, capital until the investment has been repaid to SHLLC in full. The rate of return on investment to SHLLC is seven percent, which is reflected as interest expense in the Consolidated Statements of Operations. SHLLC is required to pay a pre-determined portion of the return on investment to Seven States Southaven, LLC ("SSSL") on each lease payment date as agreed in SHLLC's formation documents (the "Seven States Return"). The current and long-term portions of the Membership interests of VIE subject to mandatory redemption are included in Accounts payable and accrued liabilities and Other long-term liabilities, respectively.

The payment dates for the mandatorily redeemable membership interests are the same as those of the SHLLC notes. The SCCG notes are secured by TVA's lease payments, and the SHLLC notes are secured by SHLLC's investment in, and amounts receivable from, SCCG. TVA's lease payments to SCCG are payable on the same dates as SCCG's and SHLLC's semi-annual debt service payments and are equal to the sum of (i) the amount of SCCG's semi-annual debt service payments, (ii) the amount of SHLLC's semi-annual debt service payments, and (iii) the amount of the Seven States Return. In addition to the lease payments, TVA pays administrative and miscellaneous expenses incurred by SCCG and SHLLC. Certain agreements related to this transaction contain default and acceleration provisions.

    In the event that TVA were to choose to exercise an early buy out feature of the Southaven facility lease, in part or in whole, TVA must pay to SCCG amounts sufficient for SCCG to repay or partially repay on a pro rata basis the membership interests held by SHLLC, including any outstanding investment amount plus accrued but unpaid return. TVA also has the right, at any time and without any early redemption of the other portions of the Southaven facility lease payments due to SCCG, to fully repay SHLLC's investment, upon which repayment SHLLC will transfer the membership interests to a designee of TVA.
    TVA participated in the design, business activity, and financial support of SCCG and has determined that it has a direct variable interest in SCCG resulting from risk associated with the value of the Southaven CCF at the end of the lease term. Based on its analysis, TVA has determined that it is the primary beneficiary of SCCG and, as such, is required to account for the VIE on a consolidated basis.

Impact on Consolidated Financial Statements

    The financial statement items attributable to carrying amounts and classifications of JSCCG, Holdco, and SCCG as of September 30, 2023 and 2022, as reflected on the Consolidated Balance Sheets, are as follows:
Summary of Impact of VIEs on Consolidated Balance Sheets
At September 30
(in millions)
 20232022
Current liabilities 
Accrued interest$9 $10 
Accounts payable and accrued liabilities1 2 
Current maturities of long-term debt of variable interest entities35 39 
Total current liabilities
45 51 
Other liabilities
Other long-term liabilities17 18 
Long-term debt, net
Long-term debt of variable interest entities, net933 968 
Total liabilities$995 $1,037 

Interest expense of $48 million, $50 million, and $52 million related to debt of VIEs and membership interests of variable interest entity subject to mandatory redemption is included on the Consolidated Statements of Operations for the years ended September 30, 2023, 2022, and 2021, respectively.

At September 30, 2023, TVA had outstanding debt of VIEs of $968 million and outstanding membership interests subject to mandatory redemption (including current portion) of $18 million issued by one of its VIEs of which it is the primary beneficiary. The following table sets forth TVA's future payments at September 30, 2023:
Maturities Due in the Year Ending September 30
(in millions)
20242025202620272028Thereafter
Long-term debt of VIEs including current maturities(1)
$35 $37 $39 $40 $42 $781 
Membership interests of variable interest entity subject to mandatory redemption1 1 1 1 1 13 
Note
(1) Long-term debt of VIEs does not include non-cash item of unamortized debt issue costs of $6 million.

Creditors of the VIEs do not have any recourse to the general credit of TVA. TVA does not have any obligations to provide financial support to the VIEs other than as prescribed in the terms of the agreements related to these transactions.
v3.23.3
Asset Retirement Obligations
 12 Months Ended
Sep. 30, 2023
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligations
13.  Asset Retirement Obligations

    During the year ended September 30, 2023, TVA's total ARO liability increased $327 million.

    To estimate its decommissioning obligation related to its nuclear generating stations, TVA uses a probability-weighted, discounted cash flow model which, on a unit-by-unit basis, considers multiple outcome scenarios that include significant estimations and assumptions. Those assumptions include (1) estimates of the cost of decommissioning; (2) the method of decommissioning and the timing of the related cash flows; (3) the license period of the nuclear plant, considering the probability of license extensions; (4) cost escalation factors; and (5) the credit adjusted risk free rate to measure the obligation at the present value of the future estimated costs. TVA has ascribed probabilities to two different decommissioning methods related to its nuclear decommissioning obligation estimate: the DECON method and the SAFSTOR method. The DECON method requires radioactive contamination to be removed from a site and safely disposed of or decontaminated to a level that permits the site to be released for unrestricted use shortly after it ceases operation. The SAFSTOR method allows nuclear facilities to be placed and maintained in a condition that allows the facilities to be safely stored and subsequently decontaminated to levels that permit release for unrestricted use.

    TVA also has decommissioning obligations related to its non-nuclear generating sites, ash impoundments, transmission substation and distribution assets, and certain general facilities. To estimate its decommissioning obligation related to these assets, TVA uses estimations and assumptions for the amounts and timing of future expenditures and makes judgments concerning whether or not such costs are considered a legal obligation. Those assumptions include (1) estimates of the costs of decommissioning, (2) the method of decommissioning and the timing of the related cash flows, (3) the expected retirement date of each asset, (4) cost escalation factors, and (5) the credit adjusted risk free rate to measure the obligation at the present value of the future estimated costs. TVA bases its decommissioning estimates for each asset on its identified preferred closure method.

The revisions in non-nuclear estimates increased the liability balance by $362 million for the year ended September 30, 2023. During the year coal combustion residuals ("CCR") closure liabilities at Bull Run, Johnsonville, and Cumberland increased $458 million due to revised cost estimates for final closure activities based on TVA's current approved closure strategies at these sites. Partially offsetting these increases, expected reductions in CCR post-closure costs for long-term monitoring at Gallatin resulted in a decrease of $60 million. In addition, CCR closure liabilities at Cumberland decreased $15 million due to identified changes in the projected timing of certain asset retirement activities, and CCR closure liabilities at Paradise decreased $9 million based on refined project cost estimates.

    The revisions in non-nuclear estimates increased $186 million for the year ended September 30, 2022. During the year, TVA completed an engineering review of its cost estimates for closure of certain areas containing coal fines at Paradise Fossil Plant ("Paradise"), which resulted in an increase of $119 million due to expected cost increases for necessary changes in activities associated with proper completion of the closure. CCR closure liabilities at Paradise and Cumberland increased $82 million due to new vendor bids, modified closure designs, and revised estimates for construction costs. Refined project cost assumptions and scope changes related to TVA's AROs for the closure of certain coal yards at its fossil plants resulted in an increase of $57 million. In addition, effective October 1, 2022, TVA implemented revised depreciation rates applicable to its completed plant due to the results of a new depreciation study. The study included a decline in the service life estimates of TVA's coal-fired plants based on current planning assumptions to potentially retire the remainder of the coal-fired fleet by 2035. As a result of the change in service life estimates reflected in the depreciation study, TVA performed an assessment of the assumptions used in the timing of cash flows related to its non-nuclear AROs. Based on the assessment, TVA increased AROs by $47 million due to identified changes in the projections of timing of certain asset retirement activities. Partially offsetting these increases, expected reductions in CCR post-closure costs for maintenance and monitoring at Paradise, Shawnee, and Colbert Fossil Plant ("Colbert") resulted in a decrease of $53 million. CCR closure liabilities at Gallatin decreased $30 million due to selection of a new vendor bid and changes to anticipated timing of certain asset retirement activities. In addition, CCR closure liabilities at Allen Fossil Plant decreased $15 million as a result of changes in cost estimates and anticipated timing of various retirement activities.

The revisions in nuclear estimates increased the liability balance by $61 million for the year ended September 30, 2022. This was primarily due to approval and implementation of the most recent site-specific cost study in September 2022 resulting in an increase of $58 million.    
    Additionally, during the years ended September 30, 2023 and 2022, both the nuclear and non-nuclear liabilities were increased by periodic accretion, partially offset by settlement projects that were conducted during these periods. The nuclear and non-nuclear accretion amounts were deferred as regulatory assets. During 2023, 2022, and 2021, $188 million, $137 million, and $72 million, respectively, of the related regulatory assets were amortized into expense as these amounts were collected in rates. See Note 10 — Regulatory Assets and Liabilities. TVA maintains investment trusts to help fund its decommissioning obligations. See Note 16 — Fair Value Measurements — Investment Funds and Note 22 — Commitments and Contingencies — Contingencies — Decommissioning Costs for a discussion of the trusts' objectives and the current balances of the trusts.
Asset Retirement Obligation Activity
(in millions)
 NuclearNon-NuclearTotal
Balance at September 30, 2021$3,428 $3,574 $7,002 
Settlements(2)(309)(311)
Revisions in estimate61 186 247 
Accretion (recorded as regulatory asset)156 68 224 
Balance at September 30, 20223,643 3,519 7,162 
(1)
Settlements(8)(271)(279)
Revisions in estimate7 362 369 
Accretion (recorded as regulatory asset)166 71 237 
Balance at September 30, 2023$3,808 $3,681 $7,489 
(1)
Note
(1) Includes $272 million and $275 million at September 30, 2023 and 2022, respectively, in Current liabilities.
v3.23.3
Other Long-Term Liabilities
 12 Months Ended
Sep. 30, 2023
Other Liabilities, Noncurrent [Abstract]  
Other Long-Term Liabilities 12.  Other Long-Term Liabilities
Other long-term liabilities consist primarily of liabilities related to certain derivative agreements as well as liabilities related to operating leases. The table below summarizes the types and amounts of Other long-term liabilities:
Other Long-Term Liabilities
At September 30
(in millions)
 2023
2022(1)
Interest rate swap liabilities$627 $851 
Operating lease liabilities93 93 
Currency swap liabilities131 228 
Commodity contract derivative liabilities52 1 
EnergyRight® financing obligation
55 58 
Long-term deferred compensation41 39 
Advances for construction56 53 
Long-term deferred revenue45 39 
Other111 123 
Total other long-term liabilities$1,211 $1,485 
Note
(1) At September 30, 2022, $1 million previously classified as Other (a component of Other long-term liabilities) has been reclassified to Commodity contract derivative liabilities (a component of Other long-term liabilities) to conform with current year presentation.
Interest Rate Swap Liabilities. TVA uses interest rate swaps to fix variable short-term debt to a fixed rate. The values of these derivatives are included in Other current assets, Accounts payable and accrued liabilities, Accrued interest, and Other long-term liabilities on the Consolidated Balance Sheets. See Note 15 — Risk Management Activities and Derivative Transactions — Overview of Accounting Treatment and Derivatives Not Receiving Hedge Accounting Treatment — Interest Rate Derivatives for information regarding the interest rate swap liabilities.

Operating Lease Liabilities. TVA's operating leases consist primarily of railcars, equipment, real estate/land, and power generating facilities. At September 30, 2023 and 2022, the current portion of TVA's operating leases reported in Accounts payable and accrued liabilities was $71 million and $59 million, respectively. See Note 8 — Leases for more information regarding leases.

Currency Swap Liabilities. To protect against exchange rate risk related to British pound sterling denominated Bond transactions, TVA entered into foreign currency hedges. The values of these derivatives are included in Accounts payable and accrued liabilities and Other long-term liabilities on the Consolidated Balance Sheets. See Note 15 — Risk Management Activities and Derivative Transactions — Overview of Accounting Treatment and Cash Flow Hedging Strategy for Currency Swaps for more information regarding the currency swap liabilities.

Commodity Contract Derivative Liabilities. TVA enters into certain derivative contracts for natural gas that require physical delivery of the contracted quantity of the commodity as well as certain financial derivative contracts to hedge exposure to the price of natural gas. See Note 15 — Risk Management Activities and Derivative Transactions — Derivatives Not Receiving Hedge Accounting Treatment — Commodity Derivatives and — Commodity Derivatives under the FHP for a discussion of TVA's commodity contract derivatives.

    EnergyRight® Financing Obligation. TVA purchases certain loans receivable from its LPCs in association with the EnergyRight® program. The current and long-term portions of the resulting financing obligation are reported in Accounts payable and accrued liabilities and Other long-term liabilities, respectively, on TVA's Consolidated Balance Sheets. At both September 30, 2023 and 2022, the carrying amount of the financing obligation reported in Accounts payable and accrued liabilities was $14 million. See Note 9 — Other Long-Term Assets for information regarding the associated loans receivable.

Long-Term Deferred Compensation. TVA provides compensation arrangements to engage and retain certain employees, both executive and non-executive, which are designed to provide participants with the ability to defer compensation to future periods. The current and long-term portions are recorded in Accounts payable and accrued liabilities and Other long-term liabilities, respectively, on TVA’s Consolidated Balance Sheets. At September 30, 2023 and 2022, the current amount of deferred compensation recorded in Accounts payable and accrued liabilities was $65 million and $53 million, respectively.

Advances for Construction. TVA receives refundable and non-refundable advances for construction that are generally intended to defray all or a portion of the costs of building or extending TVA’s existing power assets. Amounts received are deferred as a liability with the long-term portion representing amounts that will not be recognized within the next 12 months. As projects meet milestones or other contractual obligations, the refundable portion is refunded to the customer and the non-
refundable portion is recognized as contributions in aid of construction and offsets the cost of plant assets. At September 30, 2023 and 2022, the current amount of advances for construction recorded in Accounts payable and accrued liabilities was $39 million and $33 million, respectively.

Long-Term Deferred Revenue. Long-term deferred revenue represents payments received that exceed services rendered resulting in the deferral of revenue. This long-term portion represents amounts that will not be recognized within the next 12 months primarily related to fiber and transmission agreements. The current and long-term portions of the deferral are recorded in Accounts payable and accrued liabilities and Other long-term liabilities, respectively, on TVA’s Consolidated Balance Sheets. At September 30, 2023 and 2022, the current amount of deferred revenue recorded in Accounts payable and accrued liabilities was $21 million and $16 million, respectively.
v3.23.3
Debt and Other Obligations
 12 Months Ended
Sep. 30, 2023
Debt Disclosure [Abstract]  
Debt and Other Obligations
14.  Debt and Other Obligations

General

The TVA Act authorizes TVA to issue Bonds in an amount not to exceed $30.0 billion at any time.  At September 30, 2023, TVA had only two types of Bonds outstanding: power bonds and discount notes.  Power bonds have maturities between one year and 50 years, and discount notes have maturities of less than one year.  Power bonds and discount notes are both issued pursuant to Section 15d of the TVA Act and pursuant to the Basic Tennessee Valley Authority Power Bond Resolution adopted by the TVA Board on October 6, 1960, as amended on September 28, 1976, October 17, 1989, and March 25, 1992 (the "Basic Resolution").  Bonds are not obligations of the U.S., and the U.S. does not guarantee the payments of principal or interest on Bonds.

Power bonds and discount notes rank on parity and have first priority of payment from net power proceeds, which are defined as the remainder of TVA's gross power revenues after deducting the costs of operating, maintaining, and administering its power properties and tax equivalent payments, but before deducting depreciation accruals or other charges representing the amortization of capital expenditures, plus the net proceeds from the sale or other disposition of any power facility or interest therein.

TVA considers its scheduled payments under its lease financing arrangements involving John Sevier CCF and Southaven CCF as costs of operating, maintaining, and administering its power properties. Costs of operating, maintaining, and administering TVA's power properties have priority over TVA's payments on the Bonds.  Once net power proceeds have been applied to payments on power bonds and discount notes as well as any other Bonds that TVA may issue in the future that rank on parity with or subordinate to power bonds and discount notes, Section 2.3 of the Basic Resolution provides that the remaining net power proceeds shall be used only for (1) minimum payments into the U.S. Treasury required by the TVA Act as repayment of, and as a return on, the Power Program Appropriation Investment; (2) investment in power system assets; (3) additional reductions of TVA's capital obligations; and (4) other lawful purposes related to TVA's power business.

The TVA Act and the Basic Resolution each contain two bond tests: the rate test and the bondholder protection test.  Under the rate test, TVA must charge rates for power which will produce gross revenues sufficient to provide funds for, among other things, debt service on outstanding Bonds.  As of September 30, 2023, TVA was in compliance with the rate test. See Note 1 — Summary of Significant Accounting Policies — General.  Under the bondholder protection test, TVA must, in successive five-year periods, use an amount of net power proceeds at least equal to the sum of (1) the depreciation accruals and other charges representing the amortization of capital expenditures and (2) the net proceeds from any disposition of power facilities for either the reduction of its capital obligations (including Bonds and the Power Program Appropriation Investment) or investment in power assets. TVA met the bondholder protection test for the five-year period ended September 30, 2020, and must next meet the bondholder protection test for the five-year period ending September 30, 2025.
Secured Debt of VIEs

On August 9, 2013, SCCG issued secured notes totaling $360 million that bear interest at a rate of 3.846 percent. The SCCG notes require amortizing semi-annual payments on each February 15 and August 15, and mature on August 15, 2033. Also on August 9, 2013, SCCG issued $40 million of membership interests subject to mandatory redemption. The proceeds from the secured notes issuance and the issuance of the membership interests were paid to TVA in accordance with the terms of the Southaven head lease. See Note 11 — Variable Interest Entities — Southaven VIE. TVA used the proceeds from the transaction primarily to fund the acquisition of the Southaven CCF from SSSL.

On January 17, 2012, JSCCG issued secured notes totaling $900 million in aggregate principal amount that bear interest at a rate of 4.626 percent. Also on January 17, 2012, Holdco issued secured notes totaling $100 million that bear interest at a rate of 7.1 percent. The JSCCG notes and the Holdco notes require amortizing semi-annual payments on each January 15 and July 15, and mature on January 15, 2042. The Holdco notes require a $10 million balloon payment upon maturity. See Note 11 — Variable Interest Entities — John Sevier VIEs. TVA used the proceeds from the transaction to meet its requirements under the TVA Act.

Secured debt of VIEs, including current maturities, outstanding at September 30, 2023 and 2022 totaled $968 million and $1.0 billion, respectively.

Short-Term Debt

    The following table provides information regarding TVA's short-term borrowings:
Short-Term Borrowings
At September 30
 20232022
Gross amount outstanding - discount notes (in millions)$432 $1,173 
Weighted average interest rate - discount notes5.29 %2.93 %

Put Options

TVA has two issues of Putable Automatic Rate Reset Securities ("PARRS") outstanding.  After a fixed-rate period of five years, the coupon rate on the PARRS may automatically be reset downward under certain market conditions on an annual basis.  The coupon rate reset on the PARRS is based on a calculation.  For both series of PARRS, the coupon rate will reset downward on the reset date if the rate calculated is below the then-current coupon rate on the Bond.  The calculation dates, potential reset dates, and terms of the calculation are different for each series.  The coupon rate on the 1998 Series D PARRS may be reset on June 1 (annually) if the sum of the five-day average of the 30-Year Constant Maturity Treasury ("CMT") rate for the week ending the last Friday in April, plus 94 basis points, is below the then-current coupon rate.  The coupon rate on the 1999 Series A PARRS may be reset on May 1 (annually) if the sum of the five-day average of the 30-Year CMT rate for the week ending the last Friday in March, plus 84 basis points, is below the then-current coupon rate.  The coupon rates may only be reset downward, but investors may request to redeem their Bonds at par value in conjunction with a coupon rate reset for a limited period of time prior to the reset dates under certain circumstances.

The coupon rate for the 1998 Series D PARRS, which mature in June 2028, has been reset eight times, from an initial rate of 6.750 percent to the current rate of 2.134 percent.  In connection with these resets, $318 million of the Bonds have been redeemed; therefore, $256 million of the Bonds were outstanding at September 30, 2023.  The coupon rate for the 1999 Series A PARRS, which mature in May 2029, has been reset seven times, from an initial rate of 6.50 percent to the current rate of 2.216 percent.  In connection with these resets, $316 million of the Bonds have been redeemed; therefore, $208 million of the Bonds were outstanding at September 30, 2023.

Due to the contingent nature of the put option on the PARRS, TVA determines whether the PARRS should be classified as long-term debt or current maturities of long-term debt by calculating the expected reset rate for the Bonds on the calculation dates, described above.  If the determination date for reset is before the balance sheet date of the reporting period and the expected reset rate is less than the then-current coupon rate on the PARRS, the PARRS are included in current maturities. Otherwise, the PARRS are included in long-term debt.  
Debt Securities Activity

The table below summarizes the long-term debt securities activity for the years ended September 30, 2023 and 2022.
Debt Securities Activity
For the years ended September 30
(in millions)
 20232022
Issues
2022 Series A(1)
$— $500 
2023 Series A(2)
1,000 — 
Discount on debt issues(8)(16)
Total$992 $484 
Redemptions/Maturities(3)
 
2009 Series B $29 $28 
2012 Series A— 1,000 
Total redemptions/maturities of power bonds29 1,028 
Debt of variable interest entities39 43 
Total redemptions/maturities of debt$68 $1,071 
Notes
(1) The 2022 Series A Bonds were issued at 96.786 percent of par.
(2) The 2023 Series A Bonds were issued at 99.187 percent of par.
(3) All redemptions were at 100 percent of par.

Debt Outstanding

    Total debt outstanding at September 30, 2023 and 2022, consisted of the following: 
Short-Term Debt
At September 30
(in millions)
 
CUSIP or Other Identifier
 
Maturity
 
Coupon Rate		20232022
Short-term debt, net of discounts$432 $1,172 
Current maturities of long-term debt of VIEs issued at par35 39 
Current maturities of power bonds issued at par
880591EF512/15/20233.770%1 1 
880591EF56/15/20243.770%21 28 
880591ER99/15/20242.875%1,000 — 
Total current maturities of power bonds issued at par  1,022 29 
Total current debt outstanding, net  $1,489 $1,240 
Long-Term Debt
At September 30
(in millions)
 
CUSIP or Other Identifier
 
Maturity
Coupon
Rate		2023 Par2022 ParStock Exchange Listings
880591ER99/15/20242.875%$— $1,000 New York
880591EW85/15/20250.750%1,000 1,000 New York
880591CJ911/1/20256.750%1,350 1,350 New York, Hong Kong, Luxembourg, Singapore
880591EU22/1/20272.875%1,000 1,000 New York
880591300(3)
6/1/20282.134%256 256 New York
880591409(3)
5/1/20292.216%208 208 New York
880591DM15/1/20307.125%1,000 1,000 New York, Luxembourg
880591EX69/15/20311.500%500 500 New York
880591DP46/7/20326.587%
(2)
305 
(1)
279 
(1)
New York, Luxembourg
880591DV17/15/20334.700%472 472 New York, Luxembourg
880591EF56/15/20343.770%139 160 None
880591DX76/15/20354.650%436 436 New York
880591CK64/1/20365.980%121 121 New York
880591CS94/1/20365.880%1,500 1,500 New York
880591CP51/15/20386.150%1,000 1,000 New York
880591ED06/15/20385.500%500 500 New York
880591EH19/15/20395.250%2,000 2,000 New York
880591EP312/15/20423.500%1,000 1,000 New York
880591DU36/7/20434.962%
(2)
183 
(1)
168 
(1)
New York, Luxembourg
880591EB41/15/20484.875%500 500 New York, Luxembourg
880591DZ24/1/20565.375%1,000 1,000 New York
880591EJ79/15/20604.625%1,000 1,000 New York
880591ES79/15/20654.250%1,000 1,000 New York
880591EY49/15/20524.250%500 500 New York
880591EZ13/15/20283.875%1,000 — New York
Subtotal17,970 17,950  
Unamortized discounts, premiums, issue costs, and other (126)(124) 
Total long-term outstanding power bonds, net 17,844 17,826  
Long-term debt of VIEs, net933 968 
Total long-term debt, net$18,777 $18,794 
Notes
(1)  Includes total net exchange gain from currency transactions of $109 million and $150 million at September 30, 2023 and 2022, respectively.
(2)  The coupon rate represents TVA's effective interest rate.
(3)  TVA PARRS, CUSIP numbers 880591300 and 880591409, may be redeemed under certain conditions.  See Put Options above.

 
Maturities Due in the Year Ending September 30
(in millions)
20242025202620272028ThereafterTotal
Long-term power bonds including current maturities(1)
$1,022 $1,022 $1,370 $1,020 $1,272 $13,395 $19,101 
Short-term debt(2)
432 — — — — — 432 
Notes
(1) Long-term power bonds do not include non-cash items of foreign currency exchange gain of $109 million, unamortized debt issue costs of $41 million, or net
discount on sale of Bonds of $85 million.
(2) Short-term debt does not include the non-cash item of discount on issuance of discount notes of less than $1 million.

Credit Facility Agreements

TVA has funding available under four long-term revolving credit facilities totaling $2.7 billion. See the table below for additional information on the four long-term revolving credit facilities. The interest rate on any borrowing under these facilities varies based on market factors and the rating of TVA's senior unsecured, long-term, non-credit-enhanced debt. TVA is required to pay an unused facility fee on the portion of the total $2.7 billion that TVA has not borrowed or committed under letters of credit. This fee, along with letter of credit fees, may fluctuate depending on the rating of TVA's senior unsecured, long-term, non-credit-enhanced debt. At September 30, 2023 and 2022, there were $535 million and $704 million, respectively, of letters of credit outstanding under these facilities, and there were no borrowings outstanding. TVA's letters of credit are primarily posted as collateral under TVA's interest rate swaps. See Note 15 — Risk Management Activities and Derivative Transactions — Other Derivative Instruments — Collateral. TVA may also post collateral for TVA's currency swaps, for commodity derivatives under the Financial Hedging program ("FHP"), or for certain transactions with third parties that require TVA to post letters of credit.

The following table provides additional information regarding TVA's funding available under the four long-term revolving credit facilities:
Summary of Long-Term Credit Facilities
At September 30, 2023
(in millions)
Maturity DateFacility LimitLetters of Credit OutstandingCash BorrowingsAvailability
February 2025$500 $302 $— $198 
March 2026150 38 — 112 
September 20261,000 99 — 901 
March 20271,000 96 — 904 
     Total$2,650 $535 $— $2,115 

TVA and the U.S. Treasury, pursuant to the TVA Act, have entered into a memorandum of understanding under which the U.S. Treasury provides TVA with a $150 million credit facility. This credit facility was renewed for 2024 with a maturity date of September 30, 2024. Access to this credit facility or other similar financing arrangements with the U.S. Treasury has been available to TVA since the 1960s. TVA can borrow under the U.S. Treasury credit facility only if it cannot issue Bonds in the market on reasonable terms, and TVA considers the U.S. Treasury credit facility a secondary source of liquidity. The interest rate on any borrowing under this facility is based on the average rate on outstanding marketable obligations of the U.S. with maturities from date of issue of 12 months or less. There were no outstanding borrowings under the facility at September 30, 2023. The availability of this credit facility may be impacted by how the U.S. government addresses the possibility of approaching its debt limit.

Lease/Leasebacks

    TVA previously entered into leasing transactions to obtain third-party financing for 24 peaking CTs as well as certain qualified technological equipment and software ("QTE"). Due to TVA's continuing involvement with the combustion turbine facilities and the QTE during the leaseback term, TVA accounted for the lease proceeds as financing obligations. There were no outstanding leaseback obligations related to the remaining CTs and QTE at September 30, 2023 and 2022. Prior to 2021, TVA made final rent payments involving 16 CTs and acquired the equity interest related to these transactions. Rent payments under the remaining CT lease/leaseback transactions were made through January 2022. In December 2021, TVA gave notice of its election to acquire the leasehold interests related to the remaining eight CTs for a total of $155 million. One associated acquisition closed in December 2022 for $78 million, and the other acquisition closed in May 2023 for $77 million. As a result, TVA recorded the cash consideration as reacquired rights, which is an intangible asset included in Completed plant on the Consolidated Balance Sheet. The amount will be amortized over the remaining estimated useful life of the underlying CTs. TVA recognized $3 million of amortization expense related to the reacquired rights within the Consolidated Statements of Operations for the year ended September 30, 2023. Transaction costs were not material. The estimated amortization expense will be $5 million annually from 2024 through 2052. The estimated amortization expense will be $2 million in 2053.
v3.23.3
Risk Management Activities and Derivative Transactions
 12 Months Ended
Sep. 30, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Risk Management Activities and Derivative Transactions TVA is exposed to various risks related to commodity prices, investment prices, interest rates, currency exchange rates, and inflation as well as counterparty credit and performance risks.  To help manage certain of these risks, TVA has historically entered into various derivative transactions, principally commodity option contracts, forward contracts, swaps, swaptions, futures, and options on futures.  Other than certain derivative instruments in its trust investment funds, it is TVA's policy to enter into these derivative transactions solely for hedging purposes and not for speculative purposes.
Overview of Accounting Treatment

TVA recognizes certain of its derivative instruments as either assets or liabilities on its Consolidated Balance Sheets at fair value.  The accounting for changes in the fair value of these instruments depends on (1) whether TVA uses regulatory accounting to defer the derivative gains and losses, (2) whether the derivative instrument has been designated and qualifies for hedge accounting treatment, and (3) if so, the type of hedge relationship (for example, cash flow hedge).

The following tables summarize the accounting treatment that certain of TVA's financial derivative transactions receive:
Summary of Derivative Instruments That Receive Hedge Accounting Treatment (part 1) 
Amount of Mark-to-Market Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
For the years ended September 30
(in millions)
Derivatives in Cash Flow Hedging RelationshipObjective of Hedge TransactionAccounting for Derivative
Hedging Instrument		20232022
Currency swapsTo protect against changes in cash flows caused by changes in foreign currency exchange rates (exchange rate risk)Unrealized gains and losses are recorded in AOCI and reclassified to Interest expense to the extent they are offset by gains and losses on the hedged transaction$99 $(157)
Summary of Derivative Instruments That Receive Hedge Accounting Treatment (part 2)(1)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) to Interest Expense
For the years ended September 30
Derivatives in Cash Flow Hedging Relationship20232022
Currency swaps$42 $(93)
Note
(1) There were no amounts excluded from effectiveness testing for any of the periods presented. Based on forecasted foreign currency exchange rates, TVA expects to reclassify approximately $20 million of gains from AOCI to Interest expense within the next 12 months to offset amounts anticipated to be recorded in Interest expense related to the forecasted exchange loss on the debt.
Summary of Derivative Instruments That Do Not Receive Hedge Accounting Treatment
Amount of Gain (Loss) Recognized in Income on Derivatives(1)
For the years ended September 30
(in millions)
 
Derivative TypeObjective of DerivativeAccounting for Derivative Instrument20232022
Interest rate swapsTo fix short-term debt variable rate to a fixed rate (interest rate risk)Mark-to-market gains and losses are recorded as regulatory liabilities and assets, respectively

Realized gains and losses are recognized in Interest expense when incurred during the settlement period and are presented in operating cash flow		$(45)$(103)
Commodity derivatives
under the FHP		To protect against fluctuations in market prices of purchased commodities (price risk)
Mark-to-market gains and losses are recorded as regulatory liabilities and assets, respectively

Realized gains and losses are recognized in Fuel expense or Purchased power expense as the contracts settle to match the delivery period of the underlying commodity(2)
(348)47 
Notes
(1) All of TVA's derivative instruments that do not receive hedge accounting treatment have unrealized gains (losses) that would otherwise be recognized in income but instead are deferred as regulatory liabilities and assets. As such, there were no related gains (losses) recognized in income for these unrealized gains (losses) for the years ended September 30, 2023 and 2022.
(2) Of the amount recognized in 2023, $301 million and $47 million were reported in Fuel expense and Purchased power expense, respectively. Of the amount recognized in 2022, $38 million and $9 million were reported in Fuel expense and Purchased power expense, respectively.
Fair Values of TVA Derivatives
At September 30
(in millions)
 20232022
Derivatives That Receive Hedge Accounting Treatment:
 BalanceBalance Sheet PresentationBalanceBalance Sheet Presentation
Currency swaps    
£250 million Sterling
$(72)
Accounts payable and accrued liabilities $(6); Other long-term liabilities $(66)
$(130)
Accounts payable and accrued liabilities $(7); Other long-term liabilities $(123)
£150 million Sterling
(69)
Accounts payable and accrued liabilities $(4); Other long-term liabilities $(65)
(110)
Accounts payable and accrued liabilities $(5); Other long-term liabilities $(105)
Derivatives That Do Not Receive Hedge Accounting Treatment:
 BalanceBalance Sheet PresentationBalanceBalance Sheet Presentation
Interest rate swaps    
$1.0 billion notional
$(499)
Other current assets $1; Accrued interest $(27); Other long-term liabilities $(473)
$(672)
Accounts payable and
accrued liabilities $(9); Accrued interest $(33);
Other long-term liabilities
$(630)
$476 million notional
(159)
Other current assets $3; Accrued interest $(8); Other long-term liabilities $(154)
(233)
Accounts payable and
accrued liabilities $(3); Accrued interest $(9);
Other long-term liabilities
$(221)
Commodity contract derivatives 31 
Other current assets $21; Other long-term assets $12; Accounts payable and accrued liabilities $(1); Other long-term liabilities $(1)
145 
Other current assets $118; Other long-term assets $34; Accounts payable and accrued liabilities $(6); Other long-term liabilities $(1)
Commodity derivatives under the FHP(186)
Accounts payable and accrued liabilities $(135); Other long-term liabilities $(51)
115 
Accounts receivable, net $1; Other current assets $54; Other long-term assets $68; Accounts payable and accrued liabilities $(8)

Cash Flow Hedging Strategy for Currency Swaps

To protect against exchange rate risk related to British pound sterling denominated Bond transactions, TVA entered into foreign currency hedges at the time the Bond transactions occurred.  TVA had the following currency swaps outstanding at September 30, 2023:
Currency Swaps Outstanding
Effective Date of Currency Swap ContractAssociated TVA Bond Issues Currency ExposureExpiration Date of SwapOverall Effective
Cost to TVA
2001£250 million20326.587%
2003£150 million20434.962%

When the dollar strengthens against the British pound sterling, the exchange gain on the Bond liability and related accrued interest is offset by an equal amount of loss on the swap contract that is reclassified out of AOCI.  Conversely, the exchange loss on the Bond liability and related accrued interest is offset by an equal amount of gain on the swap contract that is reclassified out of AOCI.  All such exchange gains or losses on the Bond liability and related accrued interest are included in Long-term debt, net and Accrued interest, respectively.  The offsetting exchange losses or gains on the swap contracts are recognized in AOCI.  If any gain (loss) were to be incurred as a result of the early termination of the foreign currency swap contract, the resulting income (expense) would be amortized over the remaining life of the associated Bond as a component of Interest expense. The values of the currency swap liabilities are included in Accounts payable and accrued liabilities and Other long-term liabilities on the Consolidated Balance Sheets.
    
Derivatives Not Receiving Hedge Accounting Treatment

Interest Rate Derivatives.  Generally TVA uses interest rate swaps to fix variable short-term debt to a fixed rate, and TVA uses regulatory accounting treatment to defer the MtM gains and losses on its interest rate swaps. The net deferred unrealized gains and losses are classified as regulatory liabilities or assets on TVA's Consolidated Balance Sheets and are included in the ratemaking formula when gains or losses are realized. The values of these derivatives are included in Other current assets, Accounts payable and accrued liabilities, Accrued interest, and Other long-term liabilities on the Consolidated Balance Sheets, and realized gains and losses, if any, are included on TVA's Consolidated Statements of Operations. For the years ended September 30, 2023 and 2022, the changes in fair market value of the interest rate swaps resulted in the reduction in unrealized losses of $240 million and $728 million, respectively.  TVA may hold short-term debt balances lower than the notional amount of the interest rate swaps from time to time due to changes in business conditions and other factors. While actual balances vary, TVA generally plans to maintain average balances of short-term debt equal to or in excess of the combined notional amount of the interest rate swaps.

Commodity Derivatives. TVA enters into certain derivative contracts for natural gas that require physical delivery of the contracted quantity of the commodity. TVA may also enter into short-term PPAs with a term of less than one year that provide an option to financially settle contracted power deliveries. This option creates an embedded derivative in the hosting power purchase agreement. TVA marks to market these contracts and defers the unrealized gains (losses) as regulatory liabilities (assets). At September 30, 2023, TVA's natural gas contract derivatives had terms of up to three years.
Commodity Contract Derivatives 
At September 30
 20232022
 
Number of Contracts
Notional AmountFair Value (MtM)
(in millions)		Number of ContractsNotional Amount
Fair Value (MtM)
(in millions)
Natural gas contract derivatives54318 million mmBtu$31 44296 million mmBtu$145 

Commodity Derivatives under the FHP. In 2022, the FHP was reinstated, and hedging activity began under the program in the second quarter of 2022. Currently, TVA is hedging exposure to the price of natural gas under the FHP. There is no Value at Risk aggregate transaction limit under the current FHP structure, but the TVA Board reviews and authorizes the use of tolerances and measures annually. TVA's FHP policy prohibits trading financial instruments under the FHP for speculative purposes. At September 30, 2023, TVA's natural gas swap contracts under the FHP had remaining terms of up to five years.

Commodity Derivatives under Financial Hedging Program(1)
At September 30
20232022
Number of Contracts
Notional Amount
Fair Value (MtM)
(in millions)
Number of Contracts
Notional Amount
Fair Value (MtM)
(in millions)
Natural gas
Swap contracts221388 million mmBtu$(186)225256 million mmBtu$115 
Note
(1) Fair value amounts presented are based on the net commodity position with the counterparty. Notional amounts disclosed represent the net value of contractual amounts.

TVA defers all FHP unrealized gains (losses) as regulatory liabilities (assets) and records the realized gains or losses in Fuel expense and Purchased power expense to match the delivery period of the underlying commodity. The fair value of commodity derivatives under the FHP decreased $301 million primarily due to a decrease in forward natural gas prices at September 30, 2023 as compared to September 30, 2022.
Offsetting of Derivative Assets and Liabilities

    The amounts of TVA's derivative instruments as reported on the Consolidated Balance Sheets are shown in the table below:
Derivative Assets and Liabilities(1)
At September 30
(in millions)
20232022
Assets
Interest rate swaps$4 $— 
Commodity contract derivatives 33 152 
Commodity derivatives under the FHP(2)
— 123 
Total derivatives subject to master netting or similar arrangement$37 $275 
Liabilities
Currency swaps$141 $240 
Interest rate swaps(3)
662 905 
Commodity contract derivatives2 7 
Commodity derivatives under the FHP(2)
186 8 
Total derivatives subject to master netting or similar arrangement$991 $1,160 
Notes
(1) Offsetting amounts include counterparty netting of derivative contracts. Except as discussed below, there were no other material offsetting amounts on TVA's Consolidated Balance Sheets at either September 30, 2023 or 2022.
(2) At September 30, 2023, the gross derivative asset and gross derivative liability was $26 million and $212 million, respectively, with offsetting amounts for each totaling $26 million.
(3) Letters of credit of approximately $509 million and $704 million were posted as collateral at September 30, 2023 and 2022, respectively, to partially secure the liability positions of one of the interest rate swaps in accordance with the collateral requirements for this derivative.

Other Derivative Instruments

Investment Fund Derivatives.  Investment funds consist primarily of funds held in the NDT, ART, SERP, DCP, and RP.  See Note 16 — Fair Value Measurements — Investment Funds for a discussion of the trusts, plans, and types of investments.  The NDT and ART may invest in derivative instruments which may include swaps, futures, options, forwards, and other instruments.   At September 30, 2023 and 2022, the NDT held investments in forward contracts to purchase debt securities. The fair values of these derivatives were in net asset positions totaling $11 million and $4 million at September 30, 2023 and 2022, respectively.

Collateral.  TVA's interest rate swaps, currency swaps, and commodity derivatives under the FHP contain contract provisions that require a party to post collateral (in a form such as cash or a letter of credit) when the party's liability balance under the agreement exceeds a certain threshold.  At September 30, 2023, the aggregate fair value of all derivative instruments with credit-risk related contingent features that were in a liability position was $987 million.  TVA's collateral obligations at September 30, 2023, under these arrangements were $429 million, for which TVA had posted $509 million in letters of credit.  These letters of credit reduce the available balance under the related credit facilities.  TVA's assessment of the risk of its nonperformance includes a reduction in its exposure under the interest rate swap contracts as a result of this posted collateral.

For all of its derivative instruments with credit-risk related contingent features:
    
•If TVA remains a majority-owned U.S. government entity but Standard & Poor's Financial Services, LLC ("S&P") or Moody's Investors Service, Inc. ("Moody's") downgrades TVA's credit rating to AA or Aa2, respectively, TVA's collateral obligations would likely increase by $22 million, and

•If TVA ceases to be majority-owned by the U.S. government, TVA's credit rating would likely be downgraded and TVA would be required to post additional collateral.

Counterparty Risk

    TVA may be exposed to certain risks when a counterparty has the potential to fail to meet its obligations in accordance with agreed terms. These risks may be related to credit, operational, or nonperformance matters. To mitigate certain counterparty risk, TVA analyzes the counterparty's financial condition prior to entering into an agreement, establishes credit limits, monitors the appropriateness of those limits, as well as any changes in the creditworthiness of the counterparty, on an ongoing basis, and when required, employs credit mitigation measures, such as collateral or prepayment arrangements and master purchase and sale agreements.
Customers.  TVA is exposed to counterparty credit risk associated with trade accounts receivable from delivered power sales to LPCs, and from industries and federal agencies directly served, all located in the Tennessee Valley region. Of the $1.6 billion and $1.9 billion of receivables from power sales outstanding at September 30, 2023 and 2022, respectively, nearly all counterparties were rated investment grade. The obligations of customers that are not investment grade are secured by collateral. TVA is also exposed to risk from exchange power arrangements with a small number of investor-owned regional utilities related to either delivered power or the replacement of open positions of longer-term purchased power or fuel agreements. TVA believes its policies and procedures for counterparty performance risk reviews have generally protected TVA against significant exposure related to market and economic conditions. See Note 1 — Summary of Significant Accounting Policies — Allowance for Uncollectible Accounts, Note 3 — Accounts Receivable, Net, and Note 9 — Other Long-Term Assets.
TVA had revenue from two LPCs that collectively accounted for 17 percent of total operating revenues for both the years ended September 30, 2023 and 2022.

Suppliers.  TVA assesses potential supplier performance risks, including procurement of fuel, parts, and services. If suppliers are unable to perform under TVA's existing contracts or if TVA is unable to obtain similar services or supplies from other vendors, TVA could experience delays, disruptions, additional costs, or other operational outcomes that may impact generation, maintenance, and capital programs. If certain fuel or purchased power suppliers fail to perform under the terms of their contract with TVA, TVA might lose the money that it paid to the supplier under the contract and have to purchase replacement fuel or power on the spot market, perhaps at a significantly higher price than TVA was entitled to pay under the contract. In addition, TVA might not be able to acquire replacement fuel or power in a timely manner and thus might be unable to satisfy its own obligations to deliver power. TVA continues evaluating potential supplier performance risks and supplier impact but cannot determine or predict the duration of such risks/impacts or the extent to which such risks/impacts could affect TVA's business, operations, and financial results or cause potential business disruptions.

TVA continues to experience impacts due to inflation, supply chain material challenges, and labor availability. This has led to project delays, limited availability, and/or price increases for supplies and labor. TVA has been able to manage these challenges with limited business disruptions at this time; however, should pressures continue long term, TVA could experience more significant disruptions and pressure to increase power rates.

Natural Gas and Fuel Oil. TVA purchases a significant amount of its natural gas requirements through contracts with a variety of suppliers and purchases substantially all of its fuel oil requirements on the spot market. TVA delivers to its gas fleet under firm and non-firm transportation contracts on multiple interstate natural gas pipelines. TVA contracts for storage capacity that allows for operational flexibility and increased supply during peak gas demand scenarios or supply disruptions. TVA plans to continue using contracts of various lengths and terms to meet the projected natural gas needs of its natural gas fleet. TVA also maintains on-site, fuel oil backup to operate at the majority of the combustion turbine sites in the event of major supply disruptions. In the event suppliers are unable to perform under existing contracts, TVA can utilize its storage portfolio or other suppliers to help secure replacement natural gas volumes.

    Coal. To help ensure a reliable supply of coal, TVA had coal contracts with multiple suppliers at September 30, 2023. The contracted supply of coal is sourced from several geographic regions of the U.S. and is delivered via barge and rail. As a result of emerging technologies, environmental regulations, industry trends, and natural gas market volatility over the past few years, coal suppliers are facing increased financial pressure, which has led to relatively poor credit ratings and bankruptcies, restructuring, mine closures, or other scenarios. A long-term continued decline in demand for coal could result in more consolidations, additional bankruptcies, restructuring, mine closures, or other scenarios.

    Nuclear Fuel. Nuclear fuel is obtained predominantly through long-term uranium concentrate supply contracts, contracted conversion services, contracted enrichment services, or a combination thereof, and contracted fuel fabrication services. The supply markets for uranium concentrates and certain nuclear fuel services are subject to price fluctuations and availability restrictions. Supply market conditions may make procurement contracts subject to credit risk related to the potential nonperformance of counterparties. In the event of nonperformance by these or other suppliers, TVA believes that replacement uranium concentrate and nuclear fuel services can be obtained, although at prices that may be unfavorable when compared to the prices under the current supply agreements.

As a result of Russia’s invasion of Ukraine, new contracts for Russian origin nuclear fuel have been limited by Executive Order 14066, and further restrictions on the purchase or use of Russian origin fuel may be forthcoming. TVA should have no direct impact from existing or future restrictions since TVA has no Russian origin nuclear fuel in inventory for use in its reactors and it is not contracted to purchase any Russian origin nuclear fuel. TVA could be impacted by higher market prices as a result of general market impacts associated with supply restrictions; however, at this time TVA's nuclear fuel is obtained predominantly through long-term contracts.

    Purchased Power. TVA acquires power from a variety of power producers through long-term and short-term PPAs as well as through spot market purchases. Because of the long-term nature and reliability of purchased power, TVA requires that the PPAs contain certain counterparty performance assurance requirements to help insure counterparty performance during the term of the agreements.
Other Suppliers. Mounting solar supply chain constraints, commodity price increases, and the recent trade policy investigation into solar panel imports have created challenges for the U.S. solar industry. Both TVA's Self-Directed Solar project and TVA's existing solar PPA portfolio are not immune from these challenges. Similar to the experience of the rest of the industry, the majority of TVA's contracted PPAs from previous requests for proposals ("RFPs") that are not yet online have been impacted by project delays and price increases, and TVA terminated one PPA because of counterparty default.Derivative Counterparties.  TVA has entered into physical and financial contracts that are classified as derivatives for hedging purposes, and TVA's NDT, ART, and qualified defined benefit plan ("pension plan") have entered into derivative contracts for investment purposes. If a counterparty to one of the physical or financial derivative transactions defaults, TVA might incur costs in connection with entering into a replacement transaction. If a counterparty to the derivative contracts into which the NDT, the ART, or the pension plan have entered for investment purposes defaults, the value of the investment could decline significantly or perhaps become worthless. TVA has concentrations of credit risk from the banking, coal, and gas industries because multiple companies in these industries serve as counterparties to TVA in various derivative transactions. At September 30, 2023, all of TVA's commodity derivatives under the FHP, currency swaps, interest rate swaps, and PPAs with option to settle were with counterparties whose Moody's credit ratings were A2 or higher. TVA classifies forward natural gas contracts as derivatives. At September 30, 2023, the forward natural gas contracts were with counterparties whose ratings ranged from B1 to A1.
v3.23.3
Fair Value Measurements
 12 Months Ended
Sep. 30, 2023
Fair Value Disclosures [Abstract]  
Fair Value Measurements
16.  Fair Value Measurements

Fair value is determined based on the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the asset or liability's principal market, or in the absence of a principal market, the most advantageous market for the asset or liability in an orderly transaction between market participants. TVA uses market or observable inputs as the preferred source of values, followed by assumptions based on hypothetical transactions in the absence of market inputs.

Valuation Techniques

The measurement of fair value results in classification into a hierarchy by the inputs used to determine the fair value as follows:
Level 1—
 		Unadjusted quoted prices in active markets accessible by the reporting entity for identical assets or liabilities.  Active markets are those in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing.
Level 2
 		—
 		Pricing inputs other than quoted market prices included in Level 1 that are based on observable market data and that are directly or indirectly observable for substantially the full term of the asset or liability.  These include quoted market prices for similar assets or liabilities, quoted market prices for identical or similar assets in markets that are not active, adjusted quoted market prices, inputs from observable data such as interest rate and yield curves, volatilities and default rates observable at commonly quoted intervals, and inputs derived from observable market data by correlation or other means.
Level 3—
 
Pricing inputs that are unobservable, or less observable, from objective sources.  Unobservable inputs are only to be used to the extent observable inputs are not available.  These inputs maintain the concept of an exit price from the perspective of a market participant and should reflect assumptions of other market participants.  An entity should consider all market participant assumptions that are available without unreasonable cost and effort.  These are given the lowest priority and are generally used in internally developed methodologies to generate management's best estimate of the fair value when no observable market data is available.

A financial instrument's level within the fair value hierarchy (where Level 1 is the highest and Level 3 is the lowest) is based on the lowest level of input significant to the fair value measurement.

The following sections describe the valuation methodologies TVA uses to measure different financial instruments at fair value. Except for gains and losses on SERP, DCP, and RP assets, all changes in fair value of these assets and liabilities have been recorded as changes in regulatory assets, regulatory liabilities, or AOCI on TVA's Consolidated Balance Sheets and Consolidated Statements of Comprehensive Income (Loss). Except for gains and losses on SERP and DCP assets, there has been no impact to the Consolidated Statements of Operations or the Consolidated Statements of Cash Flows related to these fair value measurements.

Investment Funds

    At September 30, 2023, Investment funds were comprised of $4.1 billion of equity securities and debt securities classified as trading measured at fair value. Equity and trading debt securities are held in the NDT, ART, SERP, DCP, and RP. The NDT holds funds for the ultimate decommissioning of TVA's nuclear power plants. The ART holds funds primarily for the costs related to the future closure and retirement of TVA's other long-lived assets. The balances in the NDT and ART were $2.8 billion and $1.2 billion, respectively, at September 30, 2023.
TVA established a SERP to provide benefits to selected employees of TVA which are comparable to those provided by competing organizations. The DCP is designed to provide participants with the ability to defer compensation to future periods. The RP is a non-qualified excess 401(K) plan designed to allow certain eligible employees whose contributions to the 401(k) plan are limited by Internal Revenue Service ("IRS") rules to save additional amounts for retirement and receive non-elective and matching employer contributions. The NDT, ART, SERP, DCP, and RP funds are invested in portfolios of securities generally designed to achieve a return in line with overall equity and debt market performance.

The NDT, ART, SERP, DCP, and RP are composed of multiple types of investments and are managed by external institutional investment managers. Most U.S. and international equities, U.S. Treasury inflation-protected securities ("TIPS"), real estate investment trust securities, and cash securities and certain derivative instruments are measured based on quoted exchange prices in active markets and are classified as Level 1 valuations. Fixed-income investments, high-yield fixed-income investments, currencies, and most derivative instruments are non-exchange traded and are classified as Level 2 valuations. These measurements are based on market and income approaches with observable market inputs.

    Private equity limited partnerships, private real asset investments, and private credit investments may include holdings of investments in private real estate, venture capital, buyout, mezzanine or subordinated debt, restructuring or distressed debt, and special situations through funds managed by third-party investment managers. These investments generally involve a three-to-four-year period where the investor contributes capital, followed by a period of distribution, typically over several years. The investment period is generally, at a minimum, 10 years or longer. The NDT had unfunded commitments related to private equity limited partnerships of $237 million, private real assets of $123 million, and private credit of $81 million at September 30, 2023. The ART had unfunded commitments related to limited partnerships in private equity of $124 million, private real assets of $60 million, and private credit of $43 million at September 30, 2023. These investments have no redemption or limited redemption options and may also impose restrictions on the NDT's and ART's ability to liquidate their investments. There are no readily available quoted exchange prices for these investments. The fair value of these investments is based on information provided by the investment managers. These investments are valued on a quarterly basis. TVA's private equity limited partnerships, private real asset investments, and private credit investments are valued at net asset values ("NAV") as a practical expedient for fair value. TVA classifies its interest in these types of investments as investments measured at NAV in the fair value hierarchy.

Commingled funds represent investment funds comprising multiple individual financial instruments. The commingled funds held by the NDT, ART, SERP, DCP, and RP consist of either a single class of securities, such as equity, debt, or foreign currency securities, or multiple classes of securities. All underlying positions in these commingled funds are either exchange traded or measured using observable inputs for similar instruments. The fair value of commingled funds is based on NAV per fund share (the unit of account), derived from the prices of the underlying securities in the funds. These commingled funds can be redeemed at the measurement date NAV and are classified as Commingled funds measured at NAV in the fair value hierarchy.

     Realized and unrealized gains and losses on equity and trading debt securities are recognized in current earnings and are based on average cost. The gains and losses of the NDT and ART are subsequently reclassified to a regulatory asset or liability account in accordance with TVA's regulatory accounting policy. See Note 1 — Summary of Significant Accounting Policies — Cost-Based Regulation and Note 10 — Regulatory Assets and Liabilities. TVA recorded unrealized gains and losses related to its equity and trading debt securities held during each period as follows:
Unrealized Investment Gains (Losses)(1)
For the years ended September 30
(in millions)
FundFinancial Statement Presentation20232022
NDT
Regulatory assets(2)
$162 $(396)
ART
Regulatory assets(3)
96 (190)
SERPOther income (expense)6 (19)
DCPOther income (expense)1 (5)
Notes
(1) Employee contributions to the RP began in the second quarter of 2023. As of September 30, 2023, the unrealized losses for the RP were less than $1 million, and therefore were not represented in the table above.
(2) Includes $27 million of unrealized gains and $138 million of unrealized losses related to NDT equity securities (excluding commingled funds) for the years ended September 30, 2023 and 2022, respectively.
(3) Includes $13 million of unrealized gains and $44 million of unrealized losses related to ART equity securities (excluding commingled funds) for the years ended September 30, 2023 and 2022, respectively.

Currency and Interest Rate Swap Derivatives

See Note 15 — Risk Management Activities and Derivative Transactions — Cash Flow Hedging Strategy for Currency Swaps and Derivatives Not Receiving Hedge Accounting Treatment for a discussion of the nature, purpose, and contingent features of TVA's currency swaps and interest rate swaps. These swaps are classified as Level 2 valuations and are valued based on income approaches using observable market inputs for similar instruments.
Commodity Contract Derivatives and Commodity Derivatives under the FHP

Commodity Contract Derivatives. Most of these derivative contracts are valued based on market approaches, which utilize short-term and mid-term market-quoted prices from an external industry brokerage service. These contracts are classified as Level 2 valuations.

Commodity Derivatives under the FHP. Swap contracts are valued using a pricing model based on New York Mercantile Exchange inputs and are subject to nonperformance risk outside of the exit price. These contracts are classified as Level 2 valuations.

See Note 15 — Risk Management Activities and Derivative Transactions — Derivatives Not Receiving Hedge Accounting Treatment — Commodity Derivatives and — Commodity Derivatives under the FHP.

Nonperformance Risk

The assessment of nonperformance risk, which includes credit risk, considers changes in current market conditions, readily available information on nonperformance risk, letters of credit, collateral, other arrangements available, and the nature of master netting arrangements. TVA is a counterparty to currency swaps, interest rate swaps, commodity contracts, and other derivatives which subject TVA to nonperformance risk. Nonperformance risk on the majority of investments and certain exchange-traded instruments held by TVA is incorporated into the exit price that is derived from quoted market data that is used to mark the investment to market.

Nonperformance risk for most of TVA's derivative instruments is an adjustment to the initial asset/liability fair value. TVA adjusts for nonperformance risk, both of TVA (for liabilities) and the counterparty (for assets), by applying credit valuation adjustments ("CVAs"). TVA determines an appropriate CVA for each applicable financial instrument based on the term of the instrument and TVA's or the counterparty's credit rating as obtained from Moody's. For companies that do not have an observable credit rating, TVA uses internal analysis to assign a comparable rating to the counterparty. TVA discounts each financial instrument using the historical default rate (as reported by Moody's for CY 1983 to CY 2022) for companies with a similar credit rating over a time period consistent with the remaining term of the contract. The application of CVAs resulted in a $1 million decrease in the fair value of assets and a $1 million decrease in the fair value of liabilities at September 30, 2023.

Fair Value Measurements

The following tables set forth by level, within the fair value hierarchy, TVA's financial assets and liabilities that were measured at fair value on a recurring basis at September 30, 2023 and 2022. Financial assets and liabilities have been classified in their entirety based on the lowest level of input that is significant to the fair value measurement. TVA's assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the determination of the fair value of the assets and liabilities and their classification in the fair value hierarchy levels.
Fair Value Measurements
At September 30, 2023
(in millions)
Quoted Prices in Active
 Markets for
Identical Assets
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)		Total
Assets
Investments    
Equity securities$608 $— $— $608 
Government debt securities(1)(2)
287 60 — 347 
Corporate debt securities(3)
— 300 — 300 
Mortgage and asset-backed securities— 36 — 36 
Institutional mutual funds288 — — 288 
Forward debt securities contracts— 11 — 11 
Cash equivalents and other short-term investments(2)
104 166 — 270 
Private equity funds measured at net asset value(4)
— — — 583 
Private real asset funds measured at net asset value(4)
— — — 387 
Private credit funds measured at net asset value(4)
— — — 158 
Commingled funds measured at net asset value(4)
— — — 1,135 
Total investments1,287 573 — 4,123 
Interest rate swaps— 4 — 4 
Commodity contract derivatives— 33 — 33 
Total$1,287 $610 $— $4,160 
Quoted Prices in Active Markets for Identical Liabilities
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)		Total
Liabilities
Currency swaps(5)
$— $141 $— $141 
Interest rate swaps— 662 — 662 
Commodity contract derivatives— 2 — 2 
Commodity derivatives under the FHP— 186 — 186 
Total$— $991 $— $991 
Notes
(1) Includes securities of government-sponsored entities.
(2) There are $287 million of U.S. Treasury Securities in Level 1 Government debt securities and $104 million of U.S. Treasury Securities in Level 1 Cash equivalents and other short-term investments for a total of $391 million of U.S. Treasury securities within Level 1 of the fair value hierarchy.
(3) Includes both U.S. and foreign debt.
(4) Certain investments that are measured at fair value using the NAV or its equivalent ("alternative investments") have not been categorized in the fair value hierarchy. The inputs to these fair value measurements include underlying NAVs, discounted cash flow valuations, comparable market valuations, and adjustments for currency, credit, liquidity, and other risks. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented on the Consolidated Balance Sheets.
(5) TVA records currency swaps net of cash collateral received from or paid to the counterparty, to the extent such amount is not recorded in Accounts payable and accrued liabilities. See Note 15 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.
Fair Value Measurements
At September 30, 2022
(in millions)
Quoted Prices in Active
 Markets for
Identical Assets
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)		Total
Assets
Investments    
Equity securities$534 $— $— $534 
Government debt securities(1)(2)(3)
297 35 — 332 
Corporate debt securities(3)(4)
— 282 — 282 
Mortgage and asset-backed securities— 52 — 52 
Institutional mutual funds242 — — 242 
Forward debt securities contracts— 4 — 4 
Cash equivalents and other short-term investments(2)(3)
61 118 — 179 
Private equity funds measured at net asset value(5)
— — — 487 
Private real asset funds measured at net asset value(5)
— — — 369 
    Private credit funds measured at net asset value(5)
— — — 103 
Commingled funds measured at net asset value(3)(5)
— — — 1,087 
Total investments1,134 491 — 3,671 
Commodity contract derivatives— 152 — 152 
Commodity derivatives under the FHP— 123 — 123 
Total$1,134 $766 $— $3,946 
Quoted Prices in Active Markets for Identical Liabilities
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)		Total
Liabilities
Currency swaps(6)
$— $240 $— $240 
Interest rate swaps— 905 — 905 
Commodity contract derivatives— 7 — 7 
Commodity derivatives under the FHP— 8 — 8 
Total$— $1,160 $— $1,160 
Notes
(1) Includes securities of government-sponsored entities.
(2) There are $297 million of U.S. Treasury Securities in Level 1 Government debt securities and $61 million of U.S. Treasury Securities in Level 1 Cash equivalents and other short-term investments for a total of $358 million of U.S. Treasury securities within Level 1 of the fair value hierarchy.
(3) At September 30, 2022, $61 million of the Level 1 Government debt securities have been reclassified to Level 1 Cash equivalents and other short-term investments. At September 30, 2022, $1 million of the Level 2 Government debt securities, $1 million of the Level 2 Corporate debt securities, and $116 million of the Commingled funds measured at net asset value have been reclassified to Level 2 Cash equivalents and other short-term investments.
(4) Includes both U.S. and foreign debt.
(5) Certain investments that are measured at fair value using the NAV or its equivalent ("alternative investments") have not been categorized in the fair value hierarchy. The inputs to these fair value measurements include underlying NAVs, discounted cash flow valuations, comparable market valuations, and adjustments for currency, credit, liquidity, and other risks. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented on the Consolidated Balance Sheets.
(6) TVA records currency swaps net of cash collateral received from or paid to the counterparty, to the extent such amount is not recorded in Accounts payable and accrued liabilities. See Note 15 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.



Other Financial Instruments Not Recorded at Fair Value

TVA uses the methods and assumptions described below to estimate the fair value of each significant class of financial instruments. The fair value of the financial instruments held at September 30, 2023 and 2022, may not be representative of the actual gains or losses that will be recorded when these instruments mature or are called or presented for early redemption. The estimated values of TVA's financial instruments not recorded at fair value at September 30, 2023 and 2022, were as follows:
Estimated Values of Financial Instruments Not Recorded at Fair Value
(in millions)
 At September 30, 2023At September 30, 2022
 Valuation ClassificationCarrying
Amount		Fair
Value		Carrying
Amount		Fair
Value
EnergyRight® receivables, net (including current portion)
Level 2$59 $55 $62 $62 
Loans and other long-term receivables, net (including current portion)Level 2104 96 105 96 
EnergyRight® financing obligations (including current portion)
Level 269 81 72 81 
Unfunded loan commitmentsLevel 2— 1 — — 
Membership interests of VIEs subject to mandatory redemption (including current portion)Level 218 19 20 22 
Long-term outstanding power bonds, net (including current maturities)Level 218,866 17,963 17,856 18,070 
Long-term debt of VIEs, net (including current maturities)Level 2968 927 1,007 989 

The carrying value of Cash and cash equivalents, Restricted cash and cash equivalents, Accounts receivable, net, and Short-term debt, net approximate their fair values.

The fair value for loans and other long-term receivables is estimated by determining the present value of future cash flows using a discount rate equal to lending rates for similar loans made to borrowers with similar credit ratings and for similar remaining maturities, where applicable. The fair value of long-term debt and membership interests of VIEs subject to mandatory redemption is estimated by determining the present value of future cash flows using current market rates for similar obligations, giving effect to credit ratings and remaining maturities.
v3.23.3
Other Income (Expense), Net
 12 Months Ended
Sep. 30, 2023
Other Income and Expenses [Abstract]  
Other Income (Expense), Net
18.  Other Income, Net

Income and expenses not related to TVA's operating activities are summarized in the following table:
Other Income, Net
For the years ended September 30
(in millions)
 202320222021
Bellefonte$— $— $(28)
Interest income34 15 12 
External services15 16 13 
Gains (losses) on investments13 (17)16 
Miscellaneous(1)(7)— 
Total other income, net$61 $7 $13 
v3.23.3
Commitments and Contingencies
 12 Months Ended
Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies
22. Commitments and Contingencies

Commitments

    Power Purchase Obligations.  TVA has contracted with various independent power producers and LPCs for additional capacity to be made available to TVA. Several of these agreements have contractual minimum payments and are accounted for as either finance or operating leases.  In total, these agreements provide 4,487 megawatts ("MW") of summer net capability.  The remaining terms of the agreements range up to 12 years.  Additionally, TVA has contracted with regional transmission organizations to reserve 2,792 MW of transmission service to support purchases from the market and wind PPAs. The remaining terms of these agreements range up to four years. Excluding lease-related costs, TVA incurred $301 million, $318 million, and $202 million of expense under these power purchase and transmission service agreements during 2023, 2022, and 2021, respectively.
TVA has one power purchase agreement that meets the definition of an unconditional purchase obligation. At September 30, 2023, the non-lease portion of the commitment for each of the next five years and thereafter is shown below:
 20242025202620272028Thereafter
Unconditional purchase obligation$155 $155 $155 $155 $154 $541 

Under federal law, TVA is obligated to purchase power from qualifying facilities (cogenerators and small power producers).  As of September 30, 2023, there was a combined qualifying facility capacity of 285 MW from 955 different generation sources, from which TVA purchased power under this law.  

Unfunded Loan Commitments. At September 30, 2023, TVA's commitments under unfunded loan commitments were $1 million for 2024. TVA has no commitments under unfunded loan commitments for 2025 through 2028.

Other Commitments. See Note 8 — Leases, Note 11 — Variable Interest Entities, Note 14 — Debt and Other Obligations, and Note 20 — Benefit Plans for the obligations and commitments attributable to leases, VIEs and membership interests of VIEs subject to mandatory redemption, leaseback obligations, and the retirement plan, respectively.

Contingencies

Nuclear Insurance. Section 170 of the Atomic Energy Act, commonly known as the Price-Anderson Act, provides a layered framework of financial protection to compensate for liability claims of members of the public for personal injury and property damages arising from a nuclear incident in the U.S. This financial protection consists of two layers of coverage. The primary level is private insurance underwritten by American Nuclear Insurers and provides public liability insurance coverage of $450 million for each nuclear power plant licensed to operate. If this amount is not sufficient to cover claims arising from a nuclear incident, the second level, Secondary Financial Protection, applies. Within the Secondary Financial Protection level, the licensee of each nuclear reactor has a contingent obligation to pay a retrospective premium, equal to its proportionate share of the loss in excess of the primary level, regardless of proximity to the incident of fault, up to a maximum of $138 million per reactor per incident. With TVA's seven reactors, the maximum total contingent obligation per incident is $963 million. This retrospective premium is payable at a maximum rate currently set at $20 million per year per nuclear incident per reactor. Currently, 97 reactors are participating in the Secondary Financial Protection program.

In the event that a nuclear incident results in public liability claims, the primary level provided by American Nuclear Insurers combined with the Secondary Financial Protection should provide up to $13.8 billion in coverage.

Federal law requires that each NRC power reactor licensee obtain property insurance from private sources to cover the cost of stabilizing and decontaminating a reactor and its station site after an accident. TVA carries property, decommissioning liability, and decontamination liability insurance from Nuclear Electric Insurance Limited ("NEIL") and European Mutual Association for Nuclear Insurance. The limits available for a loss are up to $2.1 billion for two of TVA's nuclear sites and up to $2.8 billion for the remaining site. Some of this insurance may require the payment of retrospective premiums up to a maximum of $114 million.

TVA purchases accidental outage (business interruption) insurance for TVA's nuclear sites from NEIL.  In the event that an accident covered by this policy takes a nuclear unit offline or keeps a nuclear unit offline, NEIL will pay TVA, after a waiting period, an indemnity (a set dollar amount per week) with a maximum indemnity of $490 million per unit.  This insurance policy may require the payment of retrospective premiums up to a maximum of $44 million, but only to the extent the retrospective premium is deemed necessary by the NEIL Board of Directors to pay losses unable to be covered by NEIL's surplus.

Decommissioning Costs.  TVA recognizes legal obligations associated with the future retirement of certain tangible long-lived assets related primarily to nuclear generating plants, coal-fired generating plants, hydroelectric generating plants/dams, transmission structures, and other property-related assets. See Note 13 — Asset Retirement Obligations.

Nuclear Decommissioning.  Provision for decommissioning costs of nuclear generating units is based on options prescribed by the NRC procedures to dismantle and decontaminate the facilities to meet the NRC criteria for license termination. At September 30, 2023, $3.8 billion, representing the discounted value of future estimated nuclear decommissioning costs, was included in nuclear AROs.  The actual decommissioning costs may vary from the derived estimates because of, among other things, changes in current assumptions, such as the assumed dates of decommissioning, changes in regulatory requirements, changes in technology, and changes in the cost of labor, materials, and equipment.  Utilities that own and operate nuclear plants are required to use different procedures in calculating nuclear decommissioning costs under GAAP than those that are used in calculating nuclear decommissioning costs when reporting to the NRC.  The two sets of procedures produce different estimates for the costs of decommissioning primarily because of differences in the underlying assumptions. TVA bases its nuclear decommissioning estimates on site-specific cost studies. The most recent study was approved and implemented in September 2022. Site-specific cost studies are updated for each of TVA's nuclear units at least every five years.
TVA maintains an NDT to provide funding for the ultimate decommissioning of its nuclear power plants.  See Note 16 — Fair Value Measurements — Investment Funds. TVA monitors the value of its NDT and believes that, over the long term and before cessation of nuclear plant operations and commencement of decommissioning activities, adequate funds from investments and additional contributions, if necessary, will be available to support decommissioning.  TVA's operating nuclear power units are licensed through various dates between 2033 - 2055, depending on the unit.  It may be possible to extend the operating life of some of the units with approval from the NRC.  See Note 10 — Regulatory Assets and Liabilities — Nuclear Decommissioning Costs and Note 13 — Asset Retirement Obligations.

Non-Nuclear Decommissioning.  At September 30, 2023, $3.7 billion, representing the discounted value of future estimated non-nuclear decommissioning costs, was included in non-nuclear AROs.  This decommissioning cost estimate involves estimating the amount and timing of future expenditures and making judgments concerning whether or not such costs are considered a legal obligation.  Estimating the amount and timing of future expenditures includes, among other things, making projections of the timing and duration of the asset retirement process and how costs will escalate with inflation.  The actual decommissioning costs may vary from the derived estimates because of changes in current assumptions, such as the assumed dates of decommissioning, changes in regulatory requirements, changes in technology, and changes in the cost of labor, materials, and equipment. TVA updates its underlying assumptions for non-nuclear decommissioning AROs at least every five years. However, material changes in underlying assumptions that impact the amount and timing of undiscounted cash flows are continuously monitored and incorporated into ARO balances in the period identified.

TVA maintains an ART to help fund the ultimate decommissioning of its non-nuclear power assets.  See Note 16 — Fair Value Measurements — Investment Funds. Estimates involved in determining if additional funding will be made to the ART include inflation rate, rate of return projections on the fund investments, and the planned use of other sources to fund decommissioning costs.  See Note 10 — Regulatory Assets and Liabilities — Non-Nuclear Decommissioning Costs and Note 13 — Asset Retirement Obligations.

Environmental Matters. TVA's generation activities, like those across the utility industry and in other industrial sectors, are subject to federal, state, and local environmental laws and regulations.  Major areas of regulation affecting TVA's activities include air quality control, greenhouse gas ("GHG") emissions, water quality control, and management and disposal of solid and hazardous wastes.  Regulations in these major areas continue to become more stringent and have, and will continue to have, a particular emphasis on climate change, renewable generation, and energy efficiency.

TVA has incurred, and expects to continue to incur, substantial capital and operating and maintenance costs to comply with evolving environmental requirements primarily associated with, but not limited to, the operation of TVA's coal-fired and natural gas-fired generating units in general and emissions of pollutants from those units.  Environmental requirements placed on the operation of coal-fired and other generating units using fossil fuels such as oil and natural gas will likely continue to become more restrictive over time.  Failure to comply with environmental and safety requirements can result in enforcement actions and litigation, which can lead to the imposition of significant civil liability, including fines and penalties, criminal sanctions, and/or temporary or permanent closure of non-compliant facilities. Historical non-compliance can also lead to difficulty in renewing existing permits, as well as difficulty in obtaining permits to bring new generation facilities online. Other obstacles to renewal or permitting of new facilities include a proliferation of non-government organizations seeking to use litigation tools to delay or stop altogether permitting of new fossil fuel facilities in favor of renewable energy projects.

From 1970 to 2023, TVA spent $6.8 billion to reduce emissions from its power plants, including $25 million, $16 million, and $17 million in 2023, 2022, and 2021, respectively, on clean air controls. TVA estimates that compliance with existing Clean Air Act ("CAA") requirements (excluding GHG requirements and new or proposed regulations) could lead to costs of $252 million from 2024 to 2028, which include existing controls capital projects and air operations and maintenance projects. TVA also estimates additional expenditures of $1.6 billion from 2024 to 2028 relating to TVA's CCR Program, as well as expenditures of $190 million from 2024 to 2028 relating to compliance with Clean Water Act ("CWA") requirements. Future costs could differ from these estimates if new environmental laws or regulations become applicable to TVA or the facilities it operates, or if existing environmental laws or regulations are revised or reinterpreted.  There could also be costs that cannot reasonably be predicted at this time, due to uncertainty of actions, that could increase these estimates, and these estimates do not include expenditures expected to be incurred after 2028.

Compliance with the EPA's CCR Rule required implementation of a groundwater monitoring program, additional engineering, and ongoing analysis. As further analyses are performed, including evaluation of monitoring results, there is the potential for additional costs for investigation and/or remediation. These costs cannot reasonably be predicted until a final remedy is selected where required.

Liability for releases, natural resource damages, and required cleanup of hazardous substances is primarily regulated by the federal Comprehensive Environmental Response, Compensation, and Liability Act ("CERCLA"), the Resource Conservation and Recovery Act ("RCRA"), and other federal and parallel state statutes.  In a manner similar to many other governmental entities, industries, and power systems, TVA has generated or used hazardous substances over the years. TVA operations at some facilities have resulted in releases of contaminants that TVA has addressed or is addressing consistent with state and federal requirements.  At September 30, 2023 and 2022, TVA's estimated liability for required cleanup and similar environmental work for those sites for which sufficient information is available to develop a cost estimate was $16 million and $17
million, respectively, on a non-discounted basis, and was included in Accounts payable and accrued liabilities and Other long-term liabilities on the Consolidated Balance Sheets. Additionally, the potential inclusion of new hazardous substances under CERCLA and RCRA jurisdiction could significantly affect TVA's future liability for remediating historical releases.

    Potential Liability Associated with Workers' Exposure to CCR Materials.  In response to the 2008 ash spill at Kingston, TVA hired Jacobs Engineering Group, Inc. ("Jacobs") to oversee aspects of the cleanup.  After the cleanup was completed, Jacobs was sued in the U.S. District Court for the Eastern District of Tennessee ("Eastern District") by employees of a contractor involved in the cleanup and family members of some of the employees.  The plaintiffs alleged that Jacobs failed to take or provide proper health precautions and misled workers about the health risks associated with exposure to coal fly ash, which is a CCR material. The plaintiffs also alleged that exposure to the fly ash caused significant illnesses, including in some cases death. Other contractor employees and family members also filed lawsuits against Jacobs in the Eastern District. In the third quarter of 2023, Jacobs announced that it reached a global settlement that resolved all of these lawsuits. While TVA was not a party to any of these lawsuits, TVA may potentially have an indemnity obligation to reimburse Jacobs in some circumstances. TVA does not expect any potential liability to have a material adverse impact on its results of operations or financial condition.

Legal Proceedings

From time to time, TVA is party to or otherwise involved in lawsuits, claims, proceedings, investigations, and other legal matters ("Legal Proceedings") that have arisen in the ordinary course of conducting TVA's activities, as a result of a catastrophic event or otherwise.  
 
General. At September 30, 2023, TVA had accrued $28 million of probable losses with respect to Legal Proceedings. Of the accrued amount, $10 million is included in Other long-term liabilities and $18 million is included in Accounts payable and accrued liabilities.  No assurance can be given that TVA will not be subject to significant additional claims and liabilities.  If actual liabilities significantly exceed the estimates made, TVA's results of operations, liquidity, and financial condition could be materially adversely affected.
 
Environmental Agreements. On April 14, 2011, TVA entered into two substantively similar agreements, one with the EPA and the other with Alabama, Kentucky, North Carolina, Tennessee, and three environmental advocacy groups (collectively, the "Environmental Agreements"). To resolve alleged New Source Review claims, TVA committed under the Environmental Agreements to, among other things, take now-completed actions regarding coal units and invest $290 million in certain TVA environmental projects. Of this amount, TVA had spent approximately $283 million as of September 30, 2023. Additionally, TVA holds restricted cash in an interest earning trust to fund the remaining project commitments. Any interest earned through the trust must also be spent on agreed upon environmental projects. The total remaining committed costs, including interest earned through the trust, were approximately $8 million as of September 30, 2023.
The liabilities related to the Environmental Agreements are included in Accounts payable and accrued liabilities and Other long-term liabilities on the September 30, 2023, Consolidated Balance Sheets. In conjunction with the approval of the Environmental Agreements, the TVA Board determined that it was appropriate to record TVA's obligations under the Environmental Agreements as regulatory assets, and they are included as such on the September 30, 2023, Consolidated Balance Sheets and will be recovered in rates in future periods.

Case Involving Johnsonville Aeroderivative Combustion Turbine Project. On December 22, 2022, the Southern Environmental Law Center filed a lawsuit in the U.S. District Court for the Middle District of Tennessee on behalf of the Sierra Club, alleging that TVA violated the National Environmental Policy Act ("NEPA") in deciding to build a new aeroderivative combustion turbine project at its Johnsonville facility.

The Sierra Club claims that TVA violated NEPA by failing to adequately analyze the climate consequences of the project, adequately address GHG mitigation in light of EOs to decarbonize the power sector, consider a reasonable range of alternatives to the project, and prepare an environmental impact statement ("EIS").

The Sierra Club requests the federal court to enter a declaratory judgment that TVA's environmental assessment ("EA") violates NEPA and that TVA's decision to issue a finding of no significant impact ("FONSI") was arbitrary, vacate the EA and FONSI, order TVA to prepare an EIS, and prohibit further construction and operation of the combustion turbines until TVA has complied with NEPA. On March 20, 2023, TVA moved to dismiss the case, and that motion remains pending before the court. In addition, on October 23, 2023, TVA and the plaintiffs filed cross-motions for summary judgment. TVA cannot predict the outcome of this litigation.

Case Involving Cumberland Combined Cycle Plant. On June 14, 2023, Appalachian Voices, the Center for Biological Diversity, and the Sierra Club filed a lawsuit in the United States District Court for the Middle District of Tennessee alleging that TVA violated NEPA in deciding to build a 1,450 MW combined cycle plant at its Cumberland facility. The plaintiffs request the court, among other things, to enter a declaratory judgment that the Cumberland EIS violated NEPA and TVA's decision to issue the Cumberland Record of Decision was arbitrary, capricious, and/or not in accordance with law; enter a declaratory judgment that TVA’s failure to supplement the Cumberland EIS violated NEPA and was arbitrary, capricious, and/or not in accordance with law; vacate the Cumberland EIS and the Cumberland Record of Decision; order TVA to prepare a revised draft EIS or
supplemental EIS subject to public comment that corrects the NEPA violations identified by the plaintiffs; and enjoin further construction and operation of the Cumberland combined cycle plant until TVA has complied with NEPA. TVA filed an amended answer on September 14, 2023. TVA cannot predict the outcome of this litigation.
v3.23.3
Related Parties
 12 Months Ended
Sep. 30, 2023
Related Party Transactions [Abstract]  
Related Parties
TVA is a wholly-owned corporate agency of the federal government, and because of this relationship, TVA's revenues and expenses are included as part of the federal budget as a revolving fund.  TVA's purpose and responsibilities as an agency are described under the "Other Agencies" section of the federal budget.

TVA's power program and stewardship (nonpower) programs were originally funded primarily by appropriations from Congress.  In 1959, Congress passed an amendment to the TVA Act that required TVA's power program to be self-financing from power revenues and proceeds from power program financings.  While TVA's power program did not directly receive appropriated funds after it became self-financing, TVA continued to receive appropriations for certain multipurpose and other nonpower mission-related activities as well as for its stewardship activities.  TVA has not received any appropriations from Congress for any activities since 1999, and since that time, TVA has funded stewardship program activities primarily with power revenues.

The 1959 amendment to the TVA Act also required TVA, beginning in 1961, to make annual payments to the U.S. Treasury from net power proceeds as a repayment of and as a return on the Power Program Appropriation Investment until a total of $1.0 billion of the Power Program Appropriation Investment has been repaid in accordance with the 1959 amendment.   TVA fulfilled its requirement to repay $1.0 billion of the Power Program Appropriation Investment in 2014. The TVA Act requires TVA to continue making payments to the U.S. Treasury as a return on the remaining $258 million of the Power Program Appropriation Investment.

TVA paid the U.S. Treasury $6 million, $4 million, and $4 million in 2023, 2022, and 2021, respectively, as a return on the Power Program Appropriation Investment.  The amount of the return on the Power Program Appropriation Investment is based on the Power Program Appropriation Investment balance at the beginning of that year and the computed average interest rate payable by the U.S. Treasury on its total marketable public obligations at the same date.  The interest rates payable by TVA on the Power Program Appropriation Investment were 1.99 percent, 1.47 percent, and 1.64 percent for 2023, 2022, and 2021, respectively.

TVA also has access to a financing arrangement with the U.S. Treasury pursuant to the TVA Act.  TVA and the U.S. Treasury entered into a memorandum of understanding under which the U.S. Treasury provides TVA with a $150 million credit facility.  This credit facility has a maturity date of September 30, 2024, and is typically renewed annually.  Access to this credit facility or other similar financing arrangements has been available to TVA since the 1960s.  See Note 14 — Debt and Other Obligations — Credit Facility Agreements.

In the normal course of business, TVA contracts with other federal agencies for sales of electricity and other services.   Transactions with agencies of the federal government were as follows:
Related Party Transactions
At or for the years ended September 30
(in millions)
 202320222021
Revenue from sales of electricity$120 $134 $109 
Other income282 296 280 
Expenditures
Operating expenses234 228 214 
Additions to property, plant, and equipment8 11 10 
Cash and cash equivalents31 30 30 
Accounts receivable, net87 78 65 
Investment funds391 358 573 
Long-term accounts receivable38 43 31 
Accounts payable and accrued liabilities42 42 15 
Long-term power bonds, net1 1 1 
Return on power program appropriation investment6 4 4 
v3.23.3
Revenue
 12 Months Ended
Sep. 30, 2023
Revenue from Contract with Customer [Abstract]  
Revenue from Contract with Customer
17. Revenue

Revenue from Sales of Electricity

TVA's revenue from contracts with customers is primarily derived from the generation and sale of electricity to its customers and is included in Revenue from sales of electricity on the Consolidated Statements of Operations. Electricity is sold primarily to LPCs for distribution to their end-use customers. In addition, TVA sells electricity to directly served industrial companies, federal agencies, and others.

LPC sales
Approximately 92 percent of TVA's Revenue from sales of electricity for both the years ended September 30, 2023 and 2022, was from LPCs, which then distribute the power to their customers using their own distribution systems. Power is delivered to each LPC at delivery points within the LPC's service territory. TVA recognizes revenue when the customer takes possession of the power at the delivery point. For power sales, the performance obligation to deliver power is satisfied in a series over time because the sales of electricity over the term of the customer contract are a series of distinct goods that are substantially the same and have the same pattern of transfer to the customer. TVA has no continuing performance obligations subsequent to delivery. Using the output method for revenue recognition provides a faithful depiction of the transfer of electricity as customers obtain control of the power and benefit from its use at delivery. Additionally, TVA has an enforceable right to consideration for energy delivered at any discrete point in time and will recognize revenue at an amount that reflects the consideration to which TVA is entitled for the energy delivered.

The amount of revenue is based on contractual prices approved by the TVA Board. Customers are invoiced monthly for power delivered as measured by meters located at the delivery points. The net transaction price is offset by certain credits available to customers that are known at the time of billing. Credits are designed to achieve objectives of the TVA Act and include items such as hydro preference credits for residential customers of LPCs, economic development credits to promote growth in the Tennessee Valley, wholesale bill credits to maintain long-term partnerships with LPCs, pandemic credits created to support LPCs and strengthen the public power response to the COVID-19 pandemic, and demand response credits allowing TVA to reduce industrial customer usage in periods of peak demand to balance system demand. Payments are typically due within approximately one month of invoice issuance.
 
Directly served customersDirectly served customers, including industrial customers, federal agencies, and other customers, take power for their own consumption. Similar to LPCs, power is delivered to a delivery point, at which time the customer takes possession and TVA recognizes revenue. For all power sales, the performance obligation to deliver power is satisfied in a series over time since the sales of electricity over the term of the customer contract are a series of distinct goods that are substantially the same and have the same pattern of transfer to the customer. TVA has no continuing performance obligations subsequent to delivery. Using the output method for revenue recognition provides a faithful depiction of the transfer of electricity as customers obtain control of the power and benefit from its use at delivery. Additionally, TVA has an enforceable right to consideration for energy delivered at any discrete point in time and will recognize revenue at an amount that reflects the consideration to which TVA is entitled for the energy delivered.

The amount of revenue is based on contractual prices approved by the TVA Board. Customers are invoiced monthly for power delivered as measured by meters located at the delivery points. The net transaction price is offset by certain credits available to customers that are known at the time of billing. Examples of credits include items such as economic development credits to promote growth in the Tennessee Valley, pandemic credits created to support directly served customers in response to the COVID-19 pandemic, and demand response credits allowing TVA to reduce industrial customer usage in periods of peak demand to balance system demand. Payments are typically due within approximately one month of invoice issuance.

Other Revenue

Other revenue consists primarily of wheeling and network transmission charges, sales of excess steam that is a by-product of power production, delivery point charges for interconnection points between TVA and the customer, REC sales, and certain other ancillary goods or services.
Disaggregated Revenues

During 2023, revenues generated from TVA's electricity sales were $11.9 billion and accounted for virtually all of TVA's revenues. TVA's operating revenues by state for each of the last three years are detailed in the table below:
Operating Revenues By State
For the years ended September 30
(in millions)
 202320222021
Alabama
$1,731 $1,778 $1,508 
Georgia
284 299 254 
Kentucky
773 821 655 
Mississippi
1,146 1,182 984 
North Carolina
89 87 66 
Tennessee
7,819 8,137 6,841 
Virginia
46 48 42 
Subtotal11,888 12,352 10,350 
Off-system sales14 19 7 
Revenue capitalized during pre-commercial plant operations(1)
(3)— — 
Revenue from sales of electricity11,899 12,371 10,357 
Other revenue155 169 146 
Total operating revenues$12,054 $12,540 $10,503 
Note
(1) Represents revenue capitalized during pre-commercial operations at Colbert Combustion Turbine Units 9-11.

    TVA's operating revenues by customer type for each of the last three years are detailed in the table below:
Operating Revenues by Customer Type
For the years ended September 30
(in millions)
 202320222021
Revenue from sales of electricity  
Local power companies$10,903 $11,291 $9,534 
Industries directly served864 926 707 
Federal agencies and other135 154 116 
Revenue capitalized during pre-commercial plant operations(1)
(3)— — 
Revenue from sales of electricity11,899 12,371 10,357 
Other revenue155 169 146 
Total operating revenues$12,054 $12,540 $10,503 
Note
(1) Represents revenue capitalized during pre-commercial operations at Colbert Combustion Turbine Units 9-11.

    TVA and LPCs continue to work together to meet the changing needs of consumers around the Tennessee Valley. In 2019, the TVA Board approved a Partnership Agreement option that better aligns the length of LPC power contracts with TVA's long-term commitments. Under the partnership arrangement, the LPC power contracts automatically renew each year and have a 20-year termination notice. The partnership arrangements can be terminated under certain circumstances, including TVA's failure to limit rate increases as provided for in the agreements going forward. Participating LPCs receive benefits including a 3.1 percent wholesale bill credit in exchange for their long-term commitment, which enables TVA to recover its long-term financial commitments over a commensurate period. The total wholesale bill credits to LPCs participating in the Partnership Agreement were $199 million, $199 million, and $189 million, respectively, for the years ended September 30, 2023, 2022, and 2021. In 2020, TVA provided participating LPCs a flexibility option, named Generation Flexibility, that allows them to locally generate or purchase up to approximately five percent of their average total hourly energy sales over a certain time period in order to meet their individual customers' needs. Revised flexibility agreements were made available to LPCs in August 2023 which permit projects to be located anywhere in TVA's service area, either connected to the LPC distribution system or TVA's transmission system, and make it easier for LPCs to partner in projects. As of September 30, 2023, 147 LPCs had signed the Partnership Agreement with TVA, and 89 LPCs had signed a Power Supply Flexibility Agreement.

In previous years, the TVA Board approved pandemic credits, which were effective for 2021, 2022, and 2023. These
credits provided an annual 2.5 percent monthly base rate credit and applied to service provided to TVA's LPCs, their large commercial and industrial customers, and TVA directly served customers. For the years ended September 30, 2023, 2022, and 2021, pandemic credits totaled $225 million and $228 million, and $221 million, respectively.

The number of LPCs by contract arrangement, the revenues derived from such arrangements for 2023, and the percentage those revenues comprised of TVA's total operating revenues for 2023, are summarized in the table below:
TVA Local Power Company Contracts
At or for the year ended September 30, 2023
Contract Arrangements(1)
Number of LPCs Revenue from Sales of Electricity to LPCs
(in millions)		Percentage of Total Operating Revenues
20-year termination notice147 $9,367 77.7 %
5-year termination notice6 1,536 12.7 %
Total153 $10,903 90.4 %
Note
(1) Ordinarily, the LPCs and TVA have the same termination notice period; however, in a contract with one of the LPCs with a five-year termination notice, TVA has a 10-year termination notice (which becomes a five-year termination notice if TVA loses its discretionary wholesale rate-setting authority). Certain LPCs have five-year termination notices or a shorter period if any act of Congress, court decision, or regulatory change requires or permits that election.
                                                 
    TVA's two largest LPCs — Memphis Light, Gas and Water Division ("MLGW") and Nashville Electric Service ("NES") — have contracts with a five-year and a 20-year termination notice period, respectively.  Sales to MLGW and NES accounted for nine percent and eight percent, respectively, of TVA's total operating revenues in 2023, 2022, and 2021.

Contract Balances

    Contract assets represent an entity's right to consideration in exchange for goods and services that the entity has transferred to customers. TVA did not have any material contract assets at September 30, 2023.

    Contract liabilities represent an entity's obligations to transfer goods or services to customers for which the entity has received consideration (or an amount of consideration is due) from the customers. These contract liabilities are primarily related to upfront consideration received prior to the satisfaction of the performance obligation. See Economic Development Incentives below and Note 12 — Other Long-Term Liabilities — Long-Term Deferred Revenue.
    Economic Development Incentives. Under certain economic development programs TVA offers incentives to existing and potential power customers in targeted business sectors that make multi-year commitments to invest in the Tennessee Valley. TVA records those incentives as reductions of revenue. Incentives recorded as a reduction to revenue were $330 million, $328 million, and $315 million for 2023, 2022, and 2021, respectively. Incentives that have been approved but have not been paid are recorded in Accounts payable and accrued liabilities and Other long-term liabilities on the Consolidated Balance Sheets. At September 30, 2023 and 2022, the outstanding unpaid incentives were $188 million and $187 million, respectively. Incentives that have been paid out may be subject to claw back if the customer fails to meet certain program requirements.
v3.23.3
Plant Closures (Text Block)
 12 Months Ended
Sep. 30, 2023
Property, Plant and Equipment [Abstract]  
Plant Closures
7. Plant Closures

Background

TVA must continuously evaluate all generating assets to ensure an optimal energy portfolio that provides safe, clean, and reliable power while maintaining flexibility and fiscal responsibility to the people of the Tennessee Valley. Based on results of assessments presented to the TVA Board in 2019, the retirement of Bull Run Fossil Plant ("Bull Run") by December 2023 was approved, and as of September 30, 2023, the facility was retired. In addition, TVA is evaluating the impact of retiring the balance of the coal-fired fleet by 2035, and that evaluation includes environmental reviews, public input, and TVA Board approval. Due to these evaluations, certain planning assumptions were updated, and their financial impacts are discussed below.

In January 2023, TVA issued its Record of Decision to retire the two coal-fired units at Cumberland Fossil Plant ("Cumberland") by the end of CY 2026 and CY 2028.

Financial Impact

TVA's policy is to adjust depreciation rates to reflect the most current assumptions, ensuring units will be fully depreciated by the applicable retirement dates. As a result of TVA's decision to accelerate the retirement of Bull Run, TVA has recognized a cumulative $659 million of accelerated depreciation since the second quarter of 2019. Of this amount, $177 million, $140 million, and $136 million were recognized for the years ended September 30, 2023, 2022, and 2021, respectively. TVA's decision to retire the two units at Cumberland is estimated to result in approximately $16 million of additional depreciation quarterly, which does not include any potential impact from additions or retirements to net completed plant. TVA estimates it has recognized a cumulative $48 million of additional depreciation since January 2023, related to this decision.
TVA also recognized $14 million, $22 million, and $4 million in Operating and maintenance expense related to additional inventory reserves and project write-offs for the coal-fired fleet, including Bull Run
v3.23.3
Leases (Text Block)
 12 Months Ended
Sep. 30, 2023
Leases [Abstract]  
Lessee, Operating Leases
8. Leases

    The following table provides information regarding the presentation of leases on the Consolidated Balance Sheets:
Amounts Recognized on TVA's Consolidated Balance Sheets
At September 30
(in millions)
20232022
Assets
  OperatingOperating lease assets, net of amortization$177 $155 
  FinanceFinance leases572 630 
Total lease assets$749 $785 
Liabilities
Current
  OperatingAccounts payable and accrued liabilities$71 $59 
  FinanceAccounts payable and accrued liabilities56 59 
Non-current
  OperatingOther long-term liabilities93 93 
  FinanceFinance lease liabilities576 628 
Total lease liabilities$796 $839 
    TVA's leases consist primarily of railcars, equipment, real estate/land, power generating facilities, and gas pipelines. TVA's leases have various terms and expiration dates remaining from less than one year to 23 years. The components of lease costs were as follows:
Lease Costs
For the years ended September 30
(in millions)
202320222021
Operating lease costs(1)
$69 $56 $52 
Variable lease costs(1)
134 78 75 
Short-term lease costs(1)
18 26 12 
Finance lease costs
Amortization of lease assets(2)
57 58 51 
Interest on lease liabilities(3)(4)
43 42 39 
Total finance lease costs100 100 90 
     Total lease costs$321 $260 $229 
Notes
(1) Costs are included in Operating and maintenance expense, Fuel expense, Purchased power expense, and Tax equivalents expense on the Consolidated Statements of Operations.
(2) Expense is included in Depreciation and amortization expense on the Consolidated Statements of Operations.
(3) Expense is included in Interest expense on the Consolidated Statements of Operations.
(4) Certain finance leases receive regulatory accounting treatment and are reclassified to Fuel expense and Purchased power expense.

    TVA's variable lease costs are primarily related to renewable energy purchase agreements that require TVA to purchase all output from the underlying facility. Payments under those agreements are solely based on the actual output over the lease term. Certain TVA lease agreements contain renewal options. Those renewal options that are reasonably certain to be exercised are included in the lease measurements.

The following table contains additional information with respect to cash and non-cash activities related to leases:
Amounts Recognized on TVA's Consolidated Statements of Cash Flows
For the years ended September 30
(in millions)
202320222021
Operating cash flows for operating leases$77 $57 $53 
Operating cash flows for finance leases43 42 39 
Financing cash flows for finance leases56 60 52 
Lease assets obtained in exchange for lease obligations (non-cash)
Operating leases(1)
$84 $43 $(22)
Finance leases3 — 233 
Note
(1) Amount for 2021 represents a non-cash reduction due to a lease that was amended during the fiscal year resulting in derecognition of the operating lease asset and obligation upon remeasurement.

TVA has certain finance leases under PPAs under which the present value of the minimum lease payments exceeds the fair value of the related lease asset at the date of measurement.  This resulted in an interest rate that was higher than TVA's incremental borrowing rate. The weighted average remaining lease terms in years and the weighted average discount rate for TVA's operating and financing leases were as follows:
Weighted Averages
At September 30
20232022
Weighted average remaining lease terms
Operating leases3 years3 years
Finance leases10 years11 years
Weighted average discount rate(1)
Operating leases4.1%1.5%
Finance leases21.6%17.8%
Note
(1) The discount rate is calculated using the rate implicit in a lease if it is readily determinable. If the rate used by the lessor is not readily determinable, TVA uses its incremental borrowing rate as permitted by accounting guidance. The incremental borrowing rate is influenced by TVA's credit rating and lease term and as such may differ for individual leases, embedded leases, or portfolios of leased assets.

    The following table presents maturities of lease liabilities and a reconciliation of the undiscounted cash flows to lease liabilities at September 30, 2023:
Future Minimum Lease Payments
Minimum payments outstanding at September 30, 2023
(in millions)
Operating leases
2024$76 
202551 
202624 
20279 
20283 
Thereafter11 
Minimum annual payments174 
Less: present value discount(10)
Operating present value of net minimum lease payments$164 
Finance leases
2024$109 
2025107 
2026106 
2027104 
2028102 
   Thereafter450 
Minimum annual payments978 
Less: amount representing interest(346)
Finance present value of net minimum lease payments$632 

During the fourth quarter of 2023, TVA entered into a PPA with a term of 2 years that commenced in October 2023. Lease payments made over the term are expected to total approximately $43 million.

TVA has entered into three PPAs with renewable resource providers for solar generation and rights to charge and discharge battery energy storage systems. The systems are considered a lease component in these agreements. These PPAs have terms of 20 years, and are expected to commence between April 2024 and April 2025. Total capacity payments related to these batteries over the term of these PPAs are expected to total $394 million.
v3.23.3
Research and Development
 12 Months Ended
Sep. 30, 2023
Research and Development [Abstract]  
Collaborative Arrangement Disclosure
21. Collaborative Arrangement

In December 2022, TVA, Ontario Power Generation, BWRX TCA sp. z.o.o., and GE Hitachi Nuclear Energy ("GEH") entered into a multi-party collaborative arrangement to advance the global deployment of the GEH BWRX-300 small modular reactor ("SMR"). GEH is responsible for standard design development. Under the agreement, TVA will contribute up to $88 million for design costs incurred by GEH through 2026. At the time feasibility is determined, TVA will have the right to use the design and may receive additional economic benefits.
Payments pursuant to the agreement are recorded as research and development expense, which is reflected as Operating and maintenance expense on TVA's Consolidated Statements of Operations in the period incurred. TVA recorded $31 million of expenses related to this agreement for the year ended September 30, 2023. TVA also had a $6 million letter of credit posted under this arrangement at September 30, 2023.
v3.23.3
Pay vs Performance Disclosure - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Pay vs Performance Disclosure      
Net income (loss) $ 500 $ 1,108 $ 1,512
v3.23.3
Insider Trading Arrangements
 3 Months Ended
Sep. 30, 2023
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
v3.23.3
Summary of Significant Accounting Policies [Policy Text Block]
 12 Months Ended
Sep. 30, 2023
Accounting Policies [Abstract]  
General
General

The Tennessee Valley Authority ("TVA") is a corporate agency and instrumentality of the United States ("U.S.") that was created in 1933 by federal legislation in response to a proposal by President Franklin D. Roosevelt.  TVA was created to, among other things, improve navigation on the Tennessee River, reduce the damage from destructive flood waters within the Tennessee River system and downstream on the lower Ohio and Mississippi Rivers, further the economic development of TVA's service area in the southeastern U.S., and sell the electricity generated at the facilities TVA operates. Today, TVA operates the nation's largest public power system and supplies power in most of Tennessee, northern Alabama, northeastern Mississippi, and southwestern Kentucky and in portions of northern Georgia, western North Carolina, and southwestern Virginia to a population of approximately 10 million people.

    TVA also manages the Tennessee River, its tributaries, and certain shorelines to provide, among other things, year-round navigation, flood damage reduction, and affordable and reliable electricity. Consistent with these primary purposes, TVA also manages the river system and public lands to provide recreational opportunities, adequate water supply, improved water quality, cultural and natural resource protection, and economic development. TVA performs these management duties in cooperation with other federal and state agencies that have jurisdiction and authority over certain aspects of the river system. In addition, the TVA Board of Directors ("TVA Board") has established two councils — the Regional Resource Stewardship Council and the Regional Energy Resource Council — to advise TVA on its stewardship activities in the Tennessee Valley and its energy resource activities.

The power program has historically been separate and distinct from the stewardship programs.  It is required to be self-supporting from power revenues and proceeds from power financings, such as proceeds from the issuance of bonds, notes, or other evidences of indebtedness (collectively, "Bonds").  Although TVA does not currently receive Congressional appropriations, it is required to make annual payments to the United States Department of the Treasury ("U.S. Treasury") as a return on the government's appropriation investment in TVA's power facilities (the "Power Program Appropriation Investment").  In the 1998 Energy and Water Development Appropriations Act, Congress directed TVA to fund essential stewardship activities related to its management of the Tennessee River system and nonpower or stewardship properties with power revenues in the event that there were insufficient appropriations or other available funds to pay for such activities in any fiscal year.  Congress has not
provided any appropriations to TVA to fund such activities since 1999.  Consequently, during 2000, TVA began paying for essential stewardship activities primarily with power revenues, with the remainder funded with user fees and other forms of revenues derived in connection with those activities.  The activities related to stewardship properties do not meet the criteria of an operating segment under accounting principles generally accepted in the United States of America ("GAAP").  Accordingly, these assets and properties are included as part of the power program, TVA's only operating segment.

Power rates are established by the TVA Board as authorized by the Tennessee Valley Authority Act of 1933, as amended ("TVA Act").  The TVA Act requires TVA to charge rates for power that will produce gross revenues sufficient to provide funds for operation, maintenance, and administration of its power system; payments to states and counties in lieu of taxes ("tax equivalents"); debt service on outstanding indebtedness; payments to the U.S. Treasury in repayment of and as a return on the Power Program Appropriation Investment; and such additional margin as the TVA Board may consider desirable for investment in power system assets, retirement of outstanding Bonds in advance of maturity, additional reduction of the Power Program Appropriation Investment, and other purposes connected with TVA's power business.  TVA fulfilled its requirement to repay $1.0 billion of the Power Program Appropriation Investment with the 2014 payment; therefore, this repayment obligation is no longer a component of rate setting. In setting TVA's rates, the TVA Board is charged by the TVA Act to have due regard for the primary objectives of the TVA Act, including the objective that power shall be sold at rates as low as are feasible.  Rates set by the TVA Board are not subject to review or approval by any state or other federal regulatory body.
Fiscal Year
Fiscal Year

TVA's fiscal year ends September 30.  Years (2023, 2022, etc.) refer to TVA's fiscal years unless they are preceded by "CY," in which case the references are to calendar years.
Cost-Based Regulation
Cost-Based Regulation

Since the TVA Board is authorized by the TVA Act to set rates for power sold to its customers, TVA is self-regulated. Additionally, TVA's regulated rates are designed to recover its costs.  Based on current projections, TVA believes that rates, set at levels that will recover TVA's costs, can be charged and collected.  As a result of these factors, TVA records certain assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for non-regulated entities.   Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates.  Regulatory liabilities generally represent obligations to make refunds to customers for previous collections for costs that are not likely to be incurred or deferral of gains that will be credited to customers in future periods.  TVA assesses whether the regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, potential legislation, and changes in technology.  Based on these assessments, TVA believes the existing regulatory assets are probable of recovery.  This determination reflects the current regulatory and political environment and is subject to change in the future.  If future recovery of regulatory assets ceases to be probable, or TVA is no longer considered to be a regulated entity, then costs would be required to be written off.  All regulatory asset write offs would be required to be recognized in earnings in the period in which future recovery ceases to be probable.
Basis of Presentation Basis of Presentation    The accompanying consolidated financial statements, which have been prepared in accordance with GAAP, include the accounts of TVA and variable interest entities ("VIEs") of which TVA is the primary beneficiary. See Note 11 — Variable Interest Entities. Intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates
Use of Estimates

The preparation of financial statements requires TVA to estimate the effects of various matters that are inherently uncertain as of the date of the consolidated financial statements.  Although the consolidated financial statements are prepared in conformity with GAAP, TVA is required to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the amounts of revenues and expenses, reported during the reporting period.  Each of these estimates varies in regard to the level of judgment involved and its potential impact on TVA's financial results.  Estimates are considered critical either when a different estimate could have reasonably been used, or where changes in the estimate are reasonably likely to occur from period to period, and such use or change would materially impact TVA's financial condition, results of operations, or cash flows.
Reclassification, Comparability Adjustment
Cash and Cash Equivalents and Restricted Cash and Investments
Cash, Cash Equivalents, and Restricted Cash

    Cash includes cash on hand, non-interest bearing cash, and deposit accounts. All highly liquid investments with original maturities of three months or less are considered cash equivalents. Cash and cash equivalents that are restricted, as to withdrawal or use under the terms of certain contractual agreements, are recorded in Other long-term assets on the Consolidated Balance Sheets. Restricted cash and cash equivalents include cash held in trusts that are currently restricted for TVA economic development loans and for certain TVA environmental programs in accordance with agreements related to compliance with certain environmental regulations. See Note 22 — Commitments and Contingencies — Legal Proceedings — Environmental Agreements.
    The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported on the Consolidated Balance Sheets and Consolidated Statements of Cash Flows:
Cash, Cash Equivalents, and Restricted Cash
At September 30
(in millions)
 20232022
Cash and cash equivalents$501 $500 
Restricted cash and cash equivalents included in Other long-term assets20 20 
Total cash, cash equivalents, and restricted cash$521 $520 
Allowance for Uncollectible Accounts
Allowance for Uncollectible Accounts

TVA recognizes an allowance that reflects the current estimate for credit losses expected to be incurred over the life of the financial assets based on historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amounts. The appropriateness of the allowance is evaluated at the end of each reporting period.

To determine the allowance for trade receivables, TVA considers historical experience and other currently available information, including events such as customer bankruptcy and/or a customer failing to fulfill payment arrangements by the due date. TVA's corporate credit department also performs an assessment of the financial condition of customers and the credit quality of the receivables. In addition, TVA reviews other reasonable and supportable forecasts to determine if the allowance for uncollectible amounts should be further adjusted in accordance with the accounting guidance for Current Expected Credit Losses.

To determine the allowance for loans receivables, TVA aggregates loans into the appropriate pools based on the existence of similar risk characteristics such as collateral types and internal assessed credit risks. In situations where a loan exhibits unique risk characteristics and is no longer expected to experience similar risks to the rest of its pool, the loan will be evaluated separately. TVA derives an annual loss rate based on historical loss and then adjusts the rate to reflect TVA's consideration of available information on current conditions and reasonable and supportable future forecasts. This information may include economic and business conditions, default trends, and other internal and external factors. For periods beyond the reasonable and supportable forecast period, TVA uses the current calculated long-term average historical loss rate for the remaining life of the loan portfolio.
The allowance for uncollectible accounts was less than $1 million at both September 30, 2023 and 2022, for trade accounts receivable.  Additionally, loans receivable of $104 million and $105 million at September 30, 2023 and 2022, respectively, are included in Accounts receivable, net and Other long-term assets, for the current and long-term portions, respectively. Loans receivables are reported net of allowances for uncollectible accounts of $3 million at both September 30, 2023 and 2022.
Revenues
Revenues

TVA recognizes revenue from contracts with customers to depict the transfer of goods or services to customers in an amount to which the entity expects to be entitled in exchange for those goods or services. For the generation and transmission of electricity, this is generally at the time the power is delivered to a metered customer delivery point for the customer's consumption or distribution. As a result, revenues from power sales are recorded as electricity is delivered to customers. In addition to power sales invoiced and recorded during the month, TVA accrues estimated unbilled revenues for power sales provided to five customers whose billing date occurs prior to the end of the month.  Exchange power sales are presented in the accompanying Consolidated Statements of Operations as a component of sales of electricity. Exchange power sales are sales of excess power after meeting TVA native load and directly served requirements.  Native load refers to the customers on whose behalf a company, by statute, franchise, regulatory requirement, or contract, has undertaken an obligation to serve. TVA engages in other arrangements in addition to power sales. Certain other revenue from activities related to TVA's overall mission is recorded in Other revenue. Revenues that are not related to the overall mission are recorded in Other income, net.
Inventories
Inventories

Certain Fuel, Materials, and Supplies.  Materials and supplies inventories are valued using an average unit cost method. A new average cost is computed after each inventory purchase transaction, and inventory issuances are priced at the latest moving weighted average unit cost. Coal, fuel oil, and natural gas inventories are valued using an average cost method. A new weighted average cost is computed monthly, and monthly issues are priced accordingly.

Renewable Energy Certificates. TVA accounts for Renewable Energy Certificates ("RECs") using the specific identification cost method. RECs that are acquired through power purchases are recorded as inventory and charged to purchased power expense when the RECs are subsequently used or sold. TVA assigns a value to the RECs at the inception of
the power purchase arrangement using a relative standalone selling price approach. RECs created through TVA-owned asset generation are recorded at zero cost.

Emission Allowances.  TVA accounts for emission allowances using the specific identification cost method. Allowances that are acquired through third party purchases are recorded as inventory at cost and charged to operating expense based on tons emitted during the respective compliance periods.  

Allowance for Inventory Obsolescence.  TVA reviews materials and supplies inventories by category and usage on a periodic basis.  Each category is assigned a probability of becoming obsolete based on the type of material and historical usage data.  TVA has a fleet-wide inventory management policy for each generation type. Based on the estimated value of the inventory, TVA adjusts its allowance for inventory obsolescence.
Property, Plant, and Equipment, and Depreciation
Property, Plant, and Equipment, and Depreciation

    Property, Plant, and Equipment. Additions to plant are recorded at cost, which includes direct and indirect costs.  The cost of current repairs and minor replacements is charged to operating expense. When property, plant, and equipment is retired, accumulated depreciation is charged for the original cost of the assets. Gains or losses are only recognized upon the sale of land or an entire operating unit. TVA capitalizes certain costs incurred in connection with developing or obtaining internal-use software. Capitalized software costs are included in Property, plant, and equipment on the Consolidated Balance Sheets and are generally amortized over seven years.  

Nuclear Fuel. Nuclear fuel, which is included in Property, plant, and equipment, is valued using the average cost method for raw materials and the specific identification method for nuclear fuel in a reactor.  Amortization of nuclear fuel in a reactor is calculated on a units-of-production basis and is included in fuel expense.

TVA, the U.S. Department of Energy ("DOE"), and certain nuclear fuel contractors have entered into agreements, referred to as the Down-blend Offering for Tritium ("DBOT"), that provide for the production, processing, and storage of low-enriched uranium that is to be made using surplus DOE highly enriched uranium and other uranium.  Low-enriched uranium can be fabricated into fuel for use in a nuclear power plant.  Production of the low-enriched uranium began in 2019 and is contracted to continue through September 2025. Contract activity will consist of storage and flag management.  Flag management ensures that the uranium is of U.S. origin, free from foreign obligations, and unencumbered by policy restrictions, so that it can be used in connection with the production of tritium. Under the terms of the interagency agreement between the DOE and TVA, the DOE will reimburse TVA for a portion of the costs of converting the highly enriched uranium to low-enriched uranium. Since 2019, TVA has received $219 million in reimbursements from the DOE, which is recorded as a reduction in nuclear fuel inventory costs. At September 30, 2023, TVA recorded $11 million in Accounts receivable, net related to this agreement.

    Depreciation. TVA accounts for depreciation of its properties using the composite depreciation convention of accounting.  Under the composite method, assets with similar economic characteristics are grouped and depreciated as one asset. Depreciation is generally computed on a straight-line basis over the estimated service lives of the various classes of assets. The estimation of asset useful lives requires management judgment, supported by external depreciation studies of historical asset retirement experience. Depreciation rates are determined based on external depreciation studies that are updated approximately every five years, with the latest study implemented during the first quarter of 2022.
Depreciation expense for the years ended September 30, 2023, 2022, and 2021 was $1.9 billion, $1.8 billion, and $1.4 billion, respectively. Depreciation expense expressed as a percentage of the average annual depreciable completed plant was 3.14 percent for 2023, 2.98 percent for 2022, and 2.28 percent for 2021.  Average depreciation rates by asset class are as follows:
Property, Plant, and Equipment Depreciation Rates
At September 30
(percent)
202320222021
Asset Class
Nuclear2.73 2.72 2.38 
Coal-fired(1)
4.98 4.27 1.95 
Hydroelectric1.82 1.85 1.60 
Gas and oil-fired3.17 3.38 2.98 
Transmission1.52 1.51 1.34 
Other4.43 3.64 7.12 
Note
(1) The rates include the acceleration of depreciation related to retiring certain coal-fired units and potentially retiring the remainder of the coal-fired fleet by 2035. See Note 7 — Plant Closures.

Reacquired Rights. Property, plant, and equipment includes intangible reacquired rights, net of amortization, of $324 million and $178 million as of September 30, 2023 and 2022, respectively, related to the purchase of residual interests from lease/leaseback agreements of certain combustion turbine units ("CTs"). Reacquired rights are amortized over the estimated useful lives of the underlying CTs which range from 30 to 35 years. Amortization expense was $10 million, $6 million, and $8 million for the years ended September 30, 2023, 2022, and 2021, respectively, and accumulated amortization at September 30, 2023 and 2022 totaled $52 million and $42 million, respectively. At September 30, 2023, the estimated aggregate amortization expense for each of the next five years and thereafter is shown below:

 20242025202620272028Thereafter
Reacquired Rights$11 $12 $11 $12 $11 $267 
Impairment of Assets.  TVA evaluates long-lived assets for impairment when events or changes in circumstances indicate that the carrying value of such assets may not be recoverable.  For long-lived assets, TVA bases its evaluation on impairment indicators such as the nature of the assets, the future economic benefit of the assets, any historical or future profitability measurements, regulatory approval and ability to set rates at levels that allow for recoverability of the assets, and other external market conditions or factors that may be present.  If such impairment indicators are present or other factors exist that indicate that the carrying amount of an asset may not be recoverable, TVA determines whether an impairment has occurred based on an estimate of undiscounted cash flows attributable to the asset as compared with the carrying value of the asset.  If an impairment has occurred, the amount of the impairment recognized is measured as the excess of the asset's carrying value over its fair value.  Additionally, TVA regularly evaluates construction projects.  If the project is canceled or deemed to have no future economic benefit, the project is written off as an asset impairment or, upon TVA Board approval, reclassified as a regulatory asset and amortized over the Board-approved period. See Note 7 — Plant Closures.
Lessee, Leases
Leases

    TVA recognizes a lease asset and lease liability for leases with terms of greater than 12 months. Lease assets represent TVA's right to use an underlying asset for the lease term, and lease liabilities represent TVA's obligation to make lease payments arising from the lease, both of which are recognized based on the present value of the future minimum lease payments over the lease term at the commencement date.  TVA has certain lease agreements that include variable lease payments that are based on energy production levels. These variable lease payments are not included in the measurement of the lease assets or lease liabilities but are recognized in the period in which the expenses are incurred.
    
    While not specifically structured as leases, certain power purchase agreements ("PPAs") are deemed to contain a lease of the underlying generating units when the terms convey the right to control the use of the assets. Amounts recorded for these leases are generally based on the amount of the scheduled capacity payments due over the remaining terms of the PPAs, the terms of which vary. The total lease obligations included in Accounts payable and accrued liabilities, Other long-term liabilities, and Finance lease liabilities related to these agreements were $390 million and $135 million for finance and operating leases, respectively, at September 30, 2023. The total lease obligations included in Accounts payable and accrued liabilities, Other long-term liabilities, and Finance lease liabilities related to these agreements were $425 million and $133 million for finance and operating leases, respectively, at September 30, 2022.
    TVA has agreements with lease and non-lease components and has elected to account for the components separately. Consideration is allocated to lease and non-lease components generally based on relative standalone selling prices.

    TVA has lease agreements which include options for renewal and early termination. The intent to renew a lease varies depending on the lease type and asset. Renewal options that are reasonably certain to be exercised are included in the lease measurements. The decision to terminate a lease early is dependent on various economic factors. No termination options have been included in TVA's lease measurements.
    
    Leases with an initial term of 12 months or less, which do not include an option to extend the initial term of the lease to greater than 12 months that TVA is reasonably certain to exercise, are not recorded on the Consolidated Balance Sheets at September 30, 2023.
    Operating leases are recognized on a straight-line basis over the term of the lease agreement. Rent expense associated with short-term leases and variable leases is recorded in Operating and maintenance expense, Fuel expense, or Purchased power expense on the Consolidated Statements of Operations. Expenses associated with finance leases result in the separate presentation of interest expense on the lease liability and amortization expense of the related lease asset on the Consolidated Statements of Operations.
Decommissioning Costs
Decommissioning Costs

    TVA recognizes legal obligations associated with the future retirement of certain tangible long-lived assets.  These obligations relate to fossil fuel-fired generating plants, nuclear generating plants, hydroelectric generating plants/dams, transmission structures, and other property-related assets.  Activities involved with retiring these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site restoration. Revisions to the forecasted costs of decommissioning activities are made whenever factors indicate that the timing or amounts of estimated cash flows have changed materially. Studies are updated for both nuclear and non-nuclear decommissioning costs at least every five years.  Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset.  See Note 10 — Regulatory Assets and Liabilities — Nuclear Decommissioning Costs and Non-Nuclear Decommissioning Costs and Note 13 — Asset Retirement Obligations.
Investment Funds
Investment Funds

    Investment funds consist primarily of trust funds designated to fund decommissioning requirements (see Note 22 — Commitments and Contingencies — Contingencies — Decommissioning Costs), the Supplemental Executive Retirement Plan ("SERP") (see Note 20 — Benefit Plans — Overview of Plans and Benefits — Supplemental Executive Retirement Plan), the Deferred Compensation Plan ("DCP"), and the Restoration Plan ("RP"). The Nuclear Decommissioning Trust ("NDT") holds funds primarily for the ultimate decommissioning of TVA's nuclear power plants. The Asset Retirement Trust ("ART") holds funds primarily for the costs related to the future closure and retirement of TVA's other long-lived assets. The NDT, ART, SERP, DCP, and RP funds are invested in portfolios of securities generally designed to achieve a return in line with overall equity and debt market performance. The NDT, ART, SERP, DCP, and RP funds are all classified as trading.
Insurance
Research and Development Costs
Research and Development Costs

Research and development costs are expensed when incurred.  TVA's research programs include those related to power delivery technologies, emerging technologies (clean energy, renewables, distributed resources, and energy efficiency), technologies related to generation (fossil fuel, nuclear, and hydroelectric), and environmental technologies.
Tax Equivalents
Tax Equivalents

TVA is not subject to federal income taxation. In addition, neither TVA nor its property, franchises, or income is subject to taxation by states or their subdivisions. The TVA Act requires TVA to make payments to states and counties in which TVA conducts its power operations and in which TVA has acquired power properties previously subject to state and local taxation.   The total amount of these payments is five percent of gross revenues from sales of power during the preceding year, excluding sales or deliveries to other federal agencies and off-system sales with other utilities, with a provision for minimum payments under certain circumstances. TVA calculates tax equivalent expense by subtracting the prior year fuel cost-related tax equivalent regulatory asset or liability from the payments made to the states and counties during the current year and adding back the current year fuel cost-related tax equivalent regulatory asset or liability. Fuel cost-related tax equivalent expense is recognized in the same accounting period in which the fuel cost-related revenue is recognized.
Maintenance Costs Maintenance CostsTVA records maintenance costs and repairs related to its property, plant, and equipment on the Consolidated Statements of Operations as they are incurred except for the recording of certain regulatory assets for retirement and removal costs.
Pre-Commercial Plant Operations
Pre-Commercial Plant Operations

As part of the process of completing the construction of a generating unit, the electricity produced is used to serve the demands of the electric system. TVA estimates revenues earned during pre-commercial operations at the fair value of the energy delivered based on TVA's hourly incremental dispatch cost. Pre-commercial plant operations began on Colbert Combustion Turbine Units 9-10 in June 2023 and on Colbert Combustion Turbine Unit 11 in early July 2023. All three units became operational on July 25, 2023. Estimated revenue of $3 million related to this project was capitalized to offset project costs for the year ended September 30, 2023. TVA also capitalized related fuel costs for this project of $3 million for the year ended September 30, 2023.
v3.23.3
Deferred Costs, Capitalized, Prepaid, and Other Assets (Policies)
 12 Months Ended
Sep. 30, 2023
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]  
Derivatives, Methods of Accounting, Hedging Derivatives Commodity Contract Derivative Assets. TVA enters into certain derivative contracts for natural gas that require physicaldelivery of the contracted quantity of the commodity as well as certain financial derivative contracts to hedge exposure to the price of natural gas. Commodity contract derivative assets classified as current include deliveries or settlements that will occur within 12 months or less. See Note 15 — Risk Management Activities and Derivative Transactions — Derivatives Not Receiving Hedge Accounting Treatment — Commodity Derivatives and — Commodity Derivatives under the FHP for a discussion of TVA's commodity contract derivatives.
v3.23.3
Deferred Costs, Capitalized, Prepaid, and Other Assets (Policies)
 12 Months Ended
Sep. 30, 2023
Assets, Noncurrent [Abstract]  
Financing Receivable Loans and Other Long-Term Receivables. TVA's loans and other long-term receivables primarily consist of economic development loans for qualifying organizations and a receivable for reimbursements to recover the cost of providing long-term, on-site storage for spent nuclear fuel. The current and long-term portions of the loans receivable are reported in Accounts receivable, net and Other long-term assets, respectively, on TVA's Consolidated Balance Sheets. At September 30, 2023 and 2022, the carrying amount of the loans receivable, net of discount, reported in Accounts receivable, net was $7 million and $6 million, respectively.
Transfers and Servicing of Financial Assets, Transfers of Financial Assets, Financings, Policy EnergyRight® Receivables. In association with the EnergyRight® program, TVA's local power company customers ("LPCs") offer financing to end-use customers for the purchase of energy-efficient equipment. Depending on the nature of the energy-efficiency project, loans may have a maximum term of five years or 10 years. TVA purchases the resulting loans receivable from its LPCs. The loans receivable are then transferred to a third-party bank with which TVA has agreed to repay in full any loans receivable that have been in default for 180 days or more or that TVA has determined are uncollectible. Given this continuing involvement, TVA accounts for the transfer of the loans receivable as secured borrowings. The current and long-term portions of the loans receivable are reported in Accounts receivable, net and Other long-term assets, respectively, on TVA's Consolidated Balance Sheets. At September 30, 2023 and 2022, the carrying amount of the loans receivable, net of discount, reported in Accounts receivable, net was $12 million and $13 million, respectively. See Note 12 — Other Long-Term Liabilities for information regarding the associated financing obligation.
Credit Loss, Financial Instrument
Allowance for Loan Losses. The allowance for loan loss is an estimate of expected credit losses, measured over the estimated life of the loan receivables, that considers reasonable and supportable forecasts of future economic conditions in addition to information about historical experience and current conditions. See Note 1 — Summary of Significant Accounting Policies — Allowance for Uncollectible Accounts.

The allowance components, which consist of a collective allowance and specific loans allowance, are based on the risk characteristics of TVA's loans. Loans that share similar risk characteristics are evaluated on a collective basis in measuring credit losses, while loans that do not share similar risk characteristics with other loans are evaluated on an individual basis.

Allowance Components
At September 30
(in millions)
20232022
EnergyRight® loan reserve
$1 $1 
Economic development loan collective reserve1 1 
Economic development loan specific loan reserve1 1 
Total allowance for loan losses$3 $3 
Service Agreements
Prepaid Long-Term Service Agreements. TVA has entered into various long-term service agreements for major
maintenance activities at certain of its combined cycle plants. TVA uses the direct expense method of accounting for these
arrangements. TVA accrues for parts when it takes ownership and for contractor services when they are rendered. Under
certain of these agreements, payments made exceed the value of parts received and services rendered. The current and long-term portions of the resulting prepayments are reported in Other current assets and Other long-term assets, respectively, on
TVA's Consolidated Balance Sheets. At September 30, 2023 and 2022, prepayments of $25 million and $12 million, respectively, were recorded in Other current assets.
Commodity contract derivative asset Commodity Contract Derivative Assets. TVA enters into certain derivative contracts for natural gas that require physical delivery of the contracted quantity of the commodity as well as certain financial derivative contracts to hedge exposure to the price of natural gas. See Note 15 — Risk Management Activities and Derivative Transactions — Derivatives Not Receiving Hedge Accounting Treatment — Commodity Derivatives and — Commodity Derivatives under the FHP for a discussion of TVA's commodity contract derivatives.
v3.23.3
Variable Interest Entities (Policies)
 12 Months Ended
Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Summary of Impact of VIEs on Consolidated Balance Sheets The financial statement items attributable to carrying amounts and classifications of JSCCG, Holdco, and SCCG as of September 30, 2023 and 2022, as reflected on the Consolidated Balance Sheets, are as follows:
Summary of Impact of VIEs on Consolidated Balance Sheets
At September 30
(in millions)
 20232022
Current liabilities 
Accrued interest$9 $10 
Accounts payable and accrued liabilities1 2 
Current maturities of long-term debt of variable interest entities35 39 
Total current liabilities
45 51 
Other liabilities
Other long-term liabilities17 18 
Long-term debt, net
Long-term debt of variable interest entities, net933 968 
Total liabilities$995 $1,037 
Consolidation, Variable Interest Entity, Policy A VIE is an entity that either (i) has insufficient equity to permit the entity to finance its activities without additional subordinated financial support or (ii) has equity investors who lack the characteristics of owning a controlling financial interest. When TVA determines that it has a variable interest in a VIE, a qualitative evaluation is performed to assess which interest holders have the power to direct the activities that most significantly impact the economic performance of the entity and have the obligation to absorb losses or receive benefits that could be significant to the entity. The evaluation considers the purpose and design of the business, the risks that the business was designed to create and pass along to other entities, the activities of the business that can be directed and which party can direct them, and the expected relative impact of those activities on the economic performance of the business through its life. TVA has the power to direct the activities of an entity when it has the ability to make key operating and financing decisions, including, but not limited to, capital investment and the issuance of debt. Based on the evaluation of these criteria, TVA has determined it is the primary beneficiary of certain entities and as such is required to account for the VIEs on a consolidated basis.
v3.23.3
Asset Retirement Obligations Asset Retirement Obligations (Policies)
 12 Months Ended
Sep. 30, 2023
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligations, Policy
Decommissioning Costs

    TVA recognizes legal obligations associated with the future retirement of certain tangible long-lived assets.  These obligations relate to fossil fuel-fired generating plants, nuclear generating plants, hydroelectric generating plants/dams, transmission structures, and other property-related assets.  Activities involved with retiring these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site restoration. Revisions to the forecasted costs of decommissioning activities are made whenever factors indicate that the timing or amounts of estimated cash flows have changed materially. Studies are updated for both nuclear and non-nuclear decommissioning costs at least every five years.  Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset.  See Note 10 — Regulatory Assets and Liabilities — Nuclear Decommissioning Costs and Non-Nuclear Decommissioning Costs and Note 13 — Asset Retirement Obligations.
v3.23.3
Benefit Plans Benefit Plans (Policies)
 12 Months Ended
Sep. 30, 2023
Retirement Benefits [Abstract]  
Benefit Plans
Accounting Mechanisms

Regulatory Accounting.  TVA has classified all amounts related to unrecognized prior service costs/(credits), net actuarial gains or losses, and the funded status as regulatory assets or liabilities as such amounts are probable of collection in future rates. Additionally, TVA recognizes pension costs as regulatory assets or regulatory liabilities to the extent that the amount calculated under U.S. GAAP as pension expense differs from the amount TVA contributes to the pension plan as pension plan contributions. As a result of plan design changes, future contributions are expected to exceed the expense calculated under U.S. GAAP. Accordingly, TVA discontinued this regulatory accounting practice as all such deferred costs were recovered as of September 30, 2023.

Cost Method. TVA uses the projected unit credit cost method to determine the service cost and the projected benefit obligation for retirement, termination, and ancillary benefits.  Under this method, a "projected accrued benefit" is calculated at the beginning of the year and at the end of the year for each benefit that may be payable in the future.  The "projected accrued benefit" is based on the plan's accrual formula and upon service at the beginning or end of the year, but it uses final average compensation, social security benefits, and other relevant factors projected to the age at which the employee is assumed to leave active service.  The projected benefit obligation is the actuarial present value of the "projected accrued benefits" at the beginning of the year for employed participants and is the actuarial present value of all benefits for other participants.  The service cost is the actuarial present value of the difference between the "projected accrued benefits" at the beginning and end of the year.

Amortization of Net Gain or Loss.  TVA utilizes the corridor approach for gain/loss amortization.  Differences between actuarial assumptions and actual plan results are deferred and amortized into periodic cost only when the accumulated differences exceed 10 percent of the greater of the projected benefit obligation or the market-related value of plan assets.  If necessary, the excess is amortized over the average future expected working lifetime of participants expected to receive benefits, which is approximately 11 years for the pension plan and 14 years for the post-retirement plans.

Amortization of Prior Service Cost/(Credit). Amortization of net prior service cost/(credit) resulting from a plan change is included as a component of period expense in the year first recognized and every year thereafter until it is fully amortized.  The increase or decrease in the benefit obligation due to the plan change is amortized over the average remaining service period of participating employees expected to receive benefits under the plan. The pension and post-retirement plans currently have prior service costs/(credits) from plan changes made in 2016, 2018, 2020, and 2021 with remaining amortization periods ranging from one to six years. However, when a plan change reduces the benefit obligation, existing positive prior service costs are reduced or eliminated starting with the earliest established before a new prior service credit base is established.

Asset Method.  TVA's asset method calculates a market-related value of assets ("MRVA") that recognizes realized and unrealized investment gains and losses over a three-year smoothing period to decrease the volatility of annual net periodic pension benefit costs. The MRVA is used to determine the expected return on plan assets, a component of net periodic pension benefit cost. The difference in the expected return on the MRVA and the actual return on the fair value on plan assets is recognized as an actuarial (gain)/loss in the pension benefit obligation at September 30. However, the MRVA has no impact on the fair value of plan assets measured at September 30.
v3.23.3
Revenue (Policies)
 12 Months Ended
Sep. 30, 2023
Revenue from Contract with Customer [Abstract]  
Revenues
Revenues

TVA recognizes revenue from contracts with customers to depict the transfer of goods or services to customers in an amount to which the entity expects to be entitled in exchange for those goods or services. For the generation and transmission of electricity, this is generally at the time the power is delivered to a metered customer delivery point for the customer's consumption or distribution. As a result, revenues from power sales are recorded as electricity is delivered to customers. In addition to power sales invoiced and recorded during the month, TVA accrues estimated unbilled revenues for power sales provided to five customers whose billing date occurs prior to the end of the month.  Exchange power sales are presented in the accompanying Consolidated Statements of Operations as a component of sales of electricity. Exchange power sales are sales of excess power after meeting TVA native load and directly served requirements.  Native load refers to the customers on whose behalf a company, by statute, franchise, regulatory requirement, or contract, has undertaken an obligation to serve. TVA engages in other arrangements in addition to power sales. Certain other revenue from activities related to TVA's overall mission is recorded in Other revenue. Revenues that are not related to the overall mission are recorded in Other income, net.
v3.23.3
Plant Closures (Policies)
 12 Months Ended
Sep. 30, 2023
Plant Closure [Abstract]  
Plant Retirement and Abandonment, Policy [Policy Text Block]
Background

TVA must continuously evaluate all generating assets to ensure an optimal energy portfolio that provides safe, clean, and reliable power while maintaining flexibility and fiscal responsibility to the people of the Tennessee Valley. Based on results of assessments presented to the TVA Board in 2019, the retirement of Bull Run Fossil Plant ("Bull Run") by December 2023 was approved, and as of September 30, 2023, the facility was retired. In addition, TVA is evaluating the impact of retiring the balance of the coal-fired fleet by 2035, and that evaluation includes environmental reviews, public input, and TVA Board approval. Due to these evaluations, certain planning assumptions were updated, and their financial impacts are discussed below.

In January 2023, TVA issued its Record of Decision to retire the two coal-fired units at Cumberland Fossil Plant ("Cumberland") by the end of CY 2026 and CY 2028.

Financial Impact

TVA's policy is to adjust depreciation rates to reflect the most current assumptions, ensuring units will be fully depreciated by the applicable retirement dates. As a result of TVA's decision to accelerate the retirement of Bull Run, TVA has recognized a cumulative $659 million of accelerated depreciation since the second quarter of 2019. Of this amount, $177 million, $140 million, and $136 million were recognized for the years ended September 30, 2023, 2022, and 2021, respectively. TVA's decision to retire the two units at Cumberland is estimated to result in approximately $16 million of additional depreciation quarterly, which does not include any potential impact from additions or retirements to net completed plant. TVA estimates it has recognized a cumulative $48 million of additional depreciation since January 2023, related to this decision.
TVA also recognized $14 million, $22 million, and $4 million in Operating and maintenance expense related to additional inventory reserves and project write-offs for the coal-fired fleet, including Bull Run
v3.23.3
Summary of Significant Accounting Policies [Table Text Block]
 12 Months Ended
Sep. 30, 2023
Accounting Policies [Abstract]  
Property, Plant, and Equipment Depreciation Rates Average depreciation rates by asset class are as follows:
Property, Plant, and Equipment Depreciation Rates
At September 30
(percent)
202320222021
Asset Class
Nuclear2.73 2.72 2.38 
Coal-fired(1)
4.98 4.27 1.95 
Hydroelectric1.82 1.85 1.60 
Gas and oil-fired3.17 3.38 2.98 
Transmission1.52 1.51 1.34 
Other4.43 3.64 7.12 
v3.23.3
Accounts Receivable, Net Accounts Receivable, Net (Tables)
 12 Months Ended
Sep. 30, 2023
Accounts Receivable, after Allowance for Credit Loss [Abstract]  
Accounts Receivable, Net
Accounts receivable primarily consist of amounts due from customers for power sales.  The table below summarizes the types and amounts of TVA's accounts receivable:
Accounts Receivable, Net
At September 30
(in millions)
 20232022
Power receivables$1,627 $1,899 
Other receivables118 108 
Accounts receivable, net(1)
$1,745 $2,007 
Note
(1) Allowance for uncollectible accounts was less than $1 million at both September 30, 2023 and 2022, and therefore is not represented in the table above.
v3.23.3
Inventories, Net Inventories, Net (Tables)
 12 Months Ended
Sep. 30, 2023
Inventory, Net [Abstract]  
Inventories, Net
The table below summarizes the types and amounts of TVA's inventories:
Inventories, Net 
At September 30
(in millions)
 20232022
Materials and supplies inventory$849 $808 
Fuel inventory313 303 
Renewable energy certificates/emissions allowance inventory, net15 18 
Allowance for inventory obsolescence(69)(57)
Inventories, net$1,108 $1,072 
v3.23.3
Deferred Costs, Capitalized, Prepaid, and Other Assets (Tables)
 12 Months Ended
Sep. 30, 2023
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]  
Schedule of Other Current Assets
Other current assets consisted of the following:
Other Current Assets 
At September 30
(in millions)
 2023
2022(1)
Inventory work-in-progress$28 $18 
Current portion of prepaid long-term service agreements25 12 
Commodity contract derivative assets21 172 
Prepaid software maintenance18 14 
Prepaid insurance16 16 
Other26 25 
Other current assets$134 $257 
Note
(1) At September 30, 2022, $18 million, $14 million, $16 million, and $12 million previously classified as Other (a component of Other current assets) have been reclassified to Inventory work-in-progress (a component of Other current assets), Prepaid software maintenance (a component of Other current assets), Prepaid insurance (a component of Other current assets), and Current portion of prepaid long-term service agreements (a component of Other current assets), respectively, to conform with current year presentation.
v3.23.3
Net Completed Plant Net Completed Plant (Tables)
 12 Months Ended
Sep. 30, 2023
Property, Plant and Equipment, Net, by Type [Abstract]  
Net Completed Plant
Net completed plant consisted of the following:
Net Completed Plant
At September 30
(in millions)
 20232022
 CostAccumulated Depreciation 
Net		CostAccumulated DepreciationNet
Coal-fired(1)
$18,525 $14,464 $4,061 $18,145 $13,649 $4,496 
Gas and oil-fired6,663 2,057 4,606 6,112 1,957 4,155 
Nuclear26,803 13,557 13,246 26,629 12,928 13,701 
Transmission9,375 3,359 6,016 8,919 3,301 5,618 
Hydroelectric4,109 1,241 2,868 3,987 1,192 2,795 
Other electrical plant1,798 780 1,018 1,724 807 917 
Multipurpose dams900 404 496 900 396 504 
Other stewardship26 9 17 26 9 17 
Total$68,199 $35,871 $32,328 $66,442 $34,239 $32,203 
Note
(1) TVA recognized accelerated depreciation as a result of the decision to idle or retire certain units and the potential retirement of the remainder of the coal-fired fleet by 2035. See Note 7 — Plant Closures.
v3.23.3
Other Long-Term Assets (Tables)
 12 Months Ended
Sep. 30, 2023
Assets, Noncurrent [Abstract]  
Other Long-Term Assets
The table below summarizes the types and amounts of TVA's other long-term assets:
Other Long-Term Assets 
At September 30
(in millions)
 20232022
Loans and other long-term receivables, net$97 $99 
Prepaid long-term service agreements64 74 
EnergyRight® receivables, net
47 49 
Prepaid capital assets28 — 
Commodity contract derivative assets12 102 
Other82 70 
Total other long-term assets$330 $394 
v3.23.3
Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Tables)
 12 Months Ended
Sep. 30, 2023
Regulatory Assets and Liabilities Disclosure [Abstract]  
Regulatory Assets and Liabilities Components of regulatory assets and regulatory liabilities are summarized in the table below. 
Regulatory Assets and Liabilities 
At September 30
(in millions)
 20232022
Current regulatory assets  
Unrealized losses on interest rate derivatives$31 $47 
Unrealized losses on commodity derivatives136 14 
Fuel cost adjustment receivable11 77 
Total current regulatory assets178 138 
Non-current regulatory assets  
Retirement benefit plans deferred costs1,440 1,839 
Non-nuclear decommissioning costs2,922 2,856 
Unrealized losses on interest rate derivatives272 479 
Nuclear decommissioning costs728 821 
Unrealized losses on commodity derivatives52 1 
Other non-current regulatory assets152 138 
Total non-current regulatory assets5,566 6,134 
Total regulatory assets$5,744 $6,272 
Current regulatory liabilities  
Fuel cost adjustment tax equivalents$201 $218 
Unrealized gains on commodity derivatives21 173 
Total current regulatory liabilities222 391 
Non-current regulatory liabilities  
Retirement benefit plans deferred credits95 70 
Unrealized gains on commodity derivatives12 102 
Total non-current regulatory liabilities107 172 
Total regulatory liabilities$329 $563 
v3.23.3
Asset Retirement Obligations Asset Retirement Obligations (Tables)
 12 Months Ended
Sep. 30, 2023
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligation Activity
Asset Retirement Obligation Activity
(in millions)
 NuclearNon-NuclearTotal
Balance at September 30, 2021$3,428 $3,574 $7,002 
Settlements(2)(309)(311)
Revisions in estimate61 186 247 
Accretion (recorded as regulatory asset)156 68 224 
Balance at September 30, 20223,643 3,519 7,162 
(1)
Settlements(8)(271)(279)
Revisions in estimate7 362 369 
Accretion (recorded as regulatory asset)166 71 237 
Balance at September 30, 2023$3,808 $3,681 $7,489 
(1)
Note
(1) Includes $272 million and $275 million at September 30, 2023 and 2022, respectively, in Current liabilities.
v3.23.3
Other Long-Term Liabilities Other Long-Term Liabilities (Tables)
 12 Months Ended
Sep. 30, 2023
Other Liabilities, Noncurrent [Abstract]  
Other Long-Term Liabilities
Other Long-Term Liabilities
At September 30
(in millions)
 2023
2022(1)
Interest rate swap liabilities$627 $851 
Operating lease liabilities93 93 
Currency swap liabilities131 228 
Commodity contract derivative liabilities52 1 
EnergyRight® financing obligation
55 58 
Long-term deferred compensation41 39 
Advances for construction56 53 
Long-term deferred revenue45 39 
Other111 123 
Total other long-term liabilities$1,211 $1,485 
Note(1) At September 30, 2022, $1 million previously classified as Other (a component of Other long-term liabilities) has been reclassified to Commodity contract derivative liabilities (a component of Other long-term liabilities) to conform with current year presentation.
v3.23.3
Debt and Other Obligations Debt and Other Obligations (Tables)
 12 Months Ended
Sep. 30, 2023
Debt and Other Obligations [Abstract]  
Schedule of short-term borrowings The following table provides information regarding TVA's short-term borrowings:
Short-Term Borrowings
At September 30
 20232022
Gross amount outstanding - discount notes (in millions)$432 $1,173 
Weighted average interest rate - discount notes5.29 %2.93 %
Debt Securities Activity
The table below summarizes the long-term debt securities activity for the years ended September 30, 2023 and 2022.
Debt Securities Activity
For the years ended September 30
(in millions)
 20232022
Issues
2022 Series A(1)
$— $500 
2023 Series A(2)
1,000 — 
Discount on debt issues(8)(16)
Total$992 $484 
Redemptions/Maturities(3)
 
2009 Series B $29 $28 
2012 Series A— 1,000 
Total redemptions/maturities of power bonds29 1,028 
Debt of variable interest entities39 43 
Total redemptions/maturities of debt$68 $1,071 
Notes
(1) The 2022 Series A Bonds were issued at 96.786 percent of par.
(2) The 2023 Series A Bonds were issued at 99.187 percent of par.
(3) All redemptions were at 100 percent of par.
Debt Outstanding Total debt outstanding at September 30, 2023 and 2022, consisted of the following: 
Short-Term Debt
At September 30
(in millions)
 
CUSIP or Other Identifier
 
Maturity
 
Coupon Rate		20232022
Short-term debt, net of discounts$432 $1,172 
Current maturities of long-term debt of VIEs issued at par35 39 
Current maturities of power bonds issued at par
880591EF512/15/20233.770%1 1 
880591EF56/15/20243.770%21 28 
880591ER99/15/20242.875%1,000 — 
Total current maturities of power bonds issued at par  1,022 29 
Total current debt outstanding, net  $1,489 $1,240 
Long-Term Debt
At September 30
(in millions)
 
CUSIP or Other Identifier
 
Maturity
Coupon
Rate		2023 Par2022 ParStock Exchange Listings
880591ER99/15/20242.875%$— $1,000 New York
880591EW85/15/20250.750%1,000 1,000 New York
880591CJ911/1/20256.750%1,350 1,350 New York, Hong Kong, Luxembourg, Singapore
880591EU22/1/20272.875%1,000 1,000 New York
880591300(3)
6/1/20282.134%256 256 New York
880591409(3)
5/1/20292.216%208 208 New York
880591DM15/1/20307.125%1,000 1,000 New York, Luxembourg
880591EX69/15/20311.500%500 500 New York
880591DP46/7/20326.587%
(2)
305 
(1)
279 
(1)
New York, Luxembourg
880591DV17/15/20334.700%472 472 New York, Luxembourg
880591EF56/15/20343.770%139 160 None
880591DX76/15/20354.650%436 436 New York
880591CK64/1/20365.980%121 121 New York
880591CS94/1/20365.880%1,500 1,500 New York
880591CP51/15/20386.150%1,000 1,000 New York
880591ED06/15/20385.500%500 500 New York
880591EH19/15/20395.250%2,000 2,000 New York
880591EP312/15/20423.500%1,000 1,000 New York
880591DU36/7/20434.962%
(2)
183 
(1)
168 
(1)
New York, Luxembourg
880591EB41/15/20484.875%500 500 New York, Luxembourg
880591DZ24/1/20565.375%1,000 1,000 New York
880591EJ79/15/20604.625%1,000 1,000 New York
880591ES79/15/20654.250%1,000 1,000 New York
880591EY49/15/20524.250%500 500 New York
880591EZ13/15/20283.875%1,000 — New York
Subtotal17,970 17,950  
Unamortized discounts, premiums, issue costs, and other (126)(124) 
Total long-term outstanding power bonds, net 17,844 17,826  
Long-term debt of VIEs, net933 968 
Total long-term debt, net$18,777 $18,794 
Notes
(1)  Includes total net exchange gain from currency transactions of $109 million and $150 million at September 30, 2023 and 2022, respectively.
(2)  The coupon rate represents TVA's effective interest rate.
(3)  TVA PARRS, CUSIP numbers 880591300 and 880591409, may be redeemed under certain conditions.  See Put Options above.
Maturities Due in the Year Ending September 30
Maturities Due in the Year Ending September 30
(in millions)
20242025202620272028ThereafterTotal
Long-term power bonds including current maturities(1)
$1,022 $1,022 $1,370 $1,020 $1,272 $13,395 $19,101 
Short-term debt(2)
432 — — — — — 432 
Notes
(1) Long-term power bonds do not include non-cash items of foreign currency exchange gain of $109 million, unamortized debt issue costs of $41 million, or net
discount on sale of Bonds of $85 million.
(2) Short-term debt does not include the non-cash item of discount on issuance of discount notes of less than $1 million.
Summary of Long-Term Credit Facilities The following table provides additional information regarding TVA's funding available under the four long-term revolving credit facilities:
Summary of Long-Term Credit Facilities
At September 30, 2023
(in millions)
Maturity DateFacility LimitLetters of Credit OutstandingCash BorrowingsAvailability
February 2025$500 $302 $— $198 
March 2026150 38 — 112 
September 20261,000 99 — 901 
March 20271,000 96 — 904 
     Total$2,650 $535 $— $2,115 
v3.23.3
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions (Tables)
 12 Months Ended
Sep. 30, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Summary of Derivative Instruments That Receive Hedge Accounting Treatment
The following tables summarize the accounting treatment that certain of TVA's financial derivative transactions receive:
Summary of Derivative Instruments That Receive Hedge Accounting Treatment (part 1) 
Amount of Mark-to-Market Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
For the years ended September 30
(in millions)
Derivatives in Cash Flow Hedging RelationshipObjective of Hedge TransactionAccounting for Derivative
Hedging Instrument		20232022
Currency swapsTo protect against changes in cash flows caused by changes in foreign currency exchange rates (exchange rate risk)Unrealized gains and losses are recorded in AOCI and reclassified to Interest expense to the extent they are offset by gains and losses on the hedged transaction$99 $(157)
Summary of Derivative Instruments That Receive Hedge Accounting Treatment (part 2)(1)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) to Interest Expense
For the years ended September 30
Derivatives in Cash Flow Hedging Relationship20232022
Currency swaps$42 $(93)
Note
(1) There were no amounts excluded from effectiveness testing for any of the periods presented. Based on forecasted foreign currency exchange rates, TVA expects to reclassify approximately $20 million of gains from AOCI to Interest expense within the next 12 months to offset amounts anticipated to be recorded in Interest expense related to the forecasted exchange loss on the debt.
Summary of Derivative Instruments That Do Not Receive Hedge Accounting Treatment
Summary of Derivative Instruments That Do Not Receive Hedge Accounting Treatment
Amount of Gain (Loss) Recognized in Income on Derivatives(1)
For the years ended September 30
(in millions)
 
Derivative TypeObjective of DerivativeAccounting for Derivative Instrument20232022
Interest rate swapsTo fix short-term debt variable rate to a fixed rate (interest rate risk)Mark-to-market gains and losses are recorded as regulatory liabilities and assets, respectively

Realized gains and losses are recognized in Interest expense when incurred during the settlement period and are presented in operating cash flow		$(45)$(103)
Commodity derivatives
under the FHP		To protect against fluctuations in market prices of purchased commodities (price risk)
Mark-to-market gains and losses are recorded as regulatory liabilities and assets, respectively

Realized gains and losses are recognized in Fuel expense or Purchased power expense as the contracts settle to match the delivery period of the underlying commodity(2)
(348)47 
Notes
(1) All of TVA's derivative instruments that do not receive hedge accounting treatment have unrealized gains (losses) that would otherwise be recognized in income but instead are deferred as regulatory liabilities and assets. As such, there were no related gains (losses) recognized in income for these unrealized gains (losses) for the years ended September 30, 2023 and 2022.
(2) Of the amount recognized in 2023, $301 million and $47 million were reported in Fuel expense and Purchased power expense, respectively. Of the amount recognized in 2022, $38 million and $9 million were reported in Fuel expense and Purchased power expense, respectively.
Fair Values of TVA Derivatives
Fair Values of TVA Derivatives
At September 30
(in millions)
 20232022
Derivatives That Receive Hedge Accounting Treatment:
 BalanceBalance Sheet PresentationBalanceBalance Sheet Presentation
Currency swaps    
£250 million Sterling
$(72)
Accounts payable and accrued liabilities $(6); Other long-term liabilities $(66)
$(130)
Accounts payable and accrued liabilities $(7); Other long-term liabilities $(123)
£150 million Sterling
(69)
Accounts payable and accrued liabilities $(4); Other long-term liabilities $(65)
(110)
Accounts payable and accrued liabilities $(5); Other long-term liabilities $(105)
Derivatives That Do Not Receive Hedge Accounting Treatment:
 BalanceBalance Sheet PresentationBalanceBalance Sheet Presentation
Interest rate swaps    
$1.0 billion notional
$(499)
Other current assets $1; Accrued interest $(27); Other long-term liabilities $(473)
$(672)
Accounts payable and
accrued liabilities $(9); Accrued interest $(33);
Other long-term liabilities
$(630)
$476 million notional
(159)
Other current assets $3; Accrued interest $(8); Other long-term liabilities $(154)
(233)
Accounts payable and
accrued liabilities $(3); Accrued interest $(9);
Other long-term liabilities
$(221)
Commodity contract derivatives 31 
Other current assets $21; Other long-term assets $12; Accounts payable and accrued liabilities $(1); Other long-term liabilities $(1)
145 
Other current assets $118; Other long-term assets $34; Accounts payable and accrued liabilities $(6); Other long-term liabilities $(1)
Commodity derivatives under the FHP(186)
Accounts payable and accrued liabilities $(135); Other long-term liabilities $(51)
115 
Accounts receivable, net $1; Other current assets $54; Other long-term assets $68; Accounts payable and accrued liabilities $(8)
Currency Swaps Outstanding TVA had the following currency swaps outstanding at September 30, 2023:
Currency Swaps Outstanding
Effective Date of Currency Swap ContractAssociated TVA Bond Issues Currency ExposureExpiration Date of SwapOverall Effective
Cost to TVA
2001£250 million20326.587%
2003£150 million20434.962%
Commodity Contract Derivatives
Commodity Contract Derivatives 
At September 30
 20232022
 
Number of Contracts
Notional AmountFair Value (MtM)
(in millions)		Number of ContractsNotional Amount
Fair Value (MtM)
(in millions)
Natural gas contract derivatives54318 million mmBtu$31 44296 million mmBtu$145 
Offsetting Assets and Liabilities The amounts of TVA's derivative instruments as reported on the Consolidated Balance Sheets are shown in the table below:
Derivative Assets and Liabilities(1)
At September 30
(in millions)
20232022
Assets
Interest rate swaps$4 $— 
Commodity contract derivatives 33 152 
Commodity derivatives under the FHP(2)
— 123 
Total derivatives subject to master netting or similar arrangement$37 $275 
Liabilities
Currency swaps$141 $240 
Interest rate swaps(3)
662 905 
Commodity contract derivatives2 7 
Commodity derivatives under the FHP(2)
186 8 
Total derivatives subject to master netting or similar arrangement$991 $1,160 
Notes
(1) Offsetting amounts include counterparty netting of derivative contracts. Except as discussed below, there were no other material offsetting amounts on TVA's Consolidated Balance Sheets at either September 30, 2023 or 2022.
(2) At September 30, 2023, the gross derivative asset and gross derivative liability was $26 million and $212 million, respectively, with offsetting amounts for each totaling $26 million.
(3) Letters of credit of approximately $509 million and $704 million were posted as collateral at September 30, 2023 and 2022, respectively, to partially secure the liability positions of one of the interest rate swaps in accordance with the collateral requirements for this derivative.
Schedule of Derivative Instruments Commodity Contracts under FHP
Commodity Derivatives under Financial Hedging Program(1)
At September 30
20232022
Number of Contracts
Notional Amount
Fair Value (MtM)
(in millions)
Number of Contracts
Notional Amount
Fair Value (MtM)
(in millions)
Natural gas
Swap contracts221388 million mmBtu$(186)225256 million mmBtu$115 
Note
(1) Fair value amounts presented are based on the net commodity position with the counterparty. Notional amounts disclosed represent the net value of contractual amounts.
v3.23.3
Fair Value Measurements (Tables)
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Fair Value Disclosures [Abstract]    
Valuation Techniques
The measurement of fair value results in classification into a hierarchy by the inputs used to determine the fair value as follows:
Level 1—
 		Unadjusted quoted prices in active markets accessible by the reporting entity for identical assets or liabilities.  Active markets are those in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing.
Level 2
 		—
 		Pricing inputs other than quoted market prices included in Level 1 that are based on observable market data and that are directly or indirectly observable for substantially the full term of the asset or liability.  These include quoted market prices for similar assets or liabilities, quoted market prices for identical or similar assets in markets that are not active, adjusted quoted market prices, inputs from observable data such as interest rate and yield curves, volatilities and default rates observable at commonly quoted intervals, and inputs derived from observable market data by correlation or other means.
Level 3—
 
Pricing inputs that are unobservable, or less observable, from objective sources.  Unobservable inputs are only to be used to the extent observable inputs are not available.  These inputs maintain the concept of an exit price from the perspective of a market participant and should reflect assumptions of other market participants.  An entity should consider all market participant assumptions that are available without unreasonable cost and effort.  These are given the lowest priority and are generally used in internally developed methodologies to generate management's best estimate of the fair value when no observable market data is available.
  
Unrealized Investment Gains (Losses) TVA recorded unrealized gains and losses related to its equity and trading debt securities held during each period as follows:
Unrealized Investment Gains (Losses)(1)
For the years ended September 30
(in millions)
FundFinancial Statement Presentation20232022
NDT
Regulatory assets(2)
$162 $(396)
ART
Regulatory assets(3)
96 (190)
SERPOther income (expense)6 (19)
DCPOther income (expense)1 (5)
Notes
(1) Employee contributions to the RP began in the second quarter of 2023. As of September 30, 2023, the unrealized losses for the RP were less than $1 million, and therefore were not represented in the table above.
(2) Includes $27 million of unrealized gains and $138 million of unrealized losses related to NDT equity securities (excluding commingled funds) for the years ended September 30, 2023 and 2022, respectively.
(3) Includes $13 million of unrealized gains and $44 million of unrealized losses related to ART equity securities (excluding commingled funds) for the years ended September 30, 2023 and 2022, respectively. 		 
Fair Value Measurements  
Fair Value Measurements
At September 30, 2023
(in millions)
Quoted Prices in Active
 Markets for
Identical Assets
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)		Total
Assets
Investments    
Equity securities$608 $— $— $608 
Government debt securities(1)(2)
287 60 — 347 
Corporate debt securities(3)
— 300 — 300 
Mortgage and asset-backed securities— 36 — 36 
Institutional mutual funds288 — — 288 
Forward debt securities contracts— 11 — 11 
Cash equivalents and other short-term investments(2)
104 166 — 270 
Private equity funds measured at net asset value(4)
— — — 583 
Private real asset funds measured at net asset value(4)
— — — 387 
Private credit funds measured at net asset value(4)
— — — 158 
Commingled funds measured at net asset value(4)
— — — 1,135 
Total investments1,287 573 — 4,123 
Interest rate swaps— 4 — 4 
Commodity contract derivatives— 33 — 33 
Total$1,287 $610 $— $4,160 
Quoted Prices in Active Markets for Identical Liabilities
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)		Total
Liabilities
Currency swaps(5)
$— $141 $— $141 
Interest rate swaps— 662 — 662 
Commodity contract derivatives— 2 — 2 
Commodity derivatives under the FHP— 186 — 186 
Total$— $991 $— $991 
Notes
(1) Includes securities of government-sponsored entities.
(2) There are $287 million of U.S. Treasury Securities in Level 1 Government debt securities and $104 million of U.S. Treasury Securities in Level 1 Cash equivalents and other short-term investments for a total of $391 million of U.S. Treasury securities within Level 1 of the fair value hierarchy.
(3) Includes both U.S. and foreign debt.
(4) Certain investments that are measured at fair value using the NAV or its equivalent ("alternative investments") have not been categorized in the fair value hierarchy. The inputs to these fair value measurements include underlying NAVs, discounted cash flow valuations, comparable market valuations, and adjustments for currency, credit, liquidity, and other risks. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented on the Consolidated Balance Sheets.
(5) TVA records currency swaps net of cash collateral received from or paid to the counterparty, to the extent such amount is not recorded in Accounts payable and accrued liabilities. See Note 15 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.
Fair Value Measurements
At September 30, 2022
(in millions)
Quoted Prices in Active
 Markets for
Identical Assets
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)		Total
Assets
Investments    
Equity securities$534 $— $— $534 
Government debt securities(1)(2)(3)
297 35 — 332 
Corporate debt securities(3)(4)
— 282 — 282 
Mortgage and asset-backed securities— 52 — 52 
Institutional mutual funds242 — — 242 
Forward debt securities contracts— 4 — 4 
Cash equivalents and other short-term investments(2)(3)
61 118 — 179 
Private equity funds measured at net asset value(5)
— — — 487 
Private real asset funds measured at net asset value(5)
— — — 369 
    Private credit funds measured at net asset value(5)
— — — 103 
Commingled funds measured at net asset value(3)(5)
— — — 1,087 
Total investments1,134 491 — 3,671 
Commodity contract derivatives— 152 — 152 
Commodity derivatives under the FHP— 123 — 123 
Total$1,134 $766 $— $3,946 
Quoted Prices in Active Markets for Identical Liabilities
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)		Total
Liabilities
Currency swaps(6)
$— $240 $— $240 
Interest rate swaps— 905 — 905 
Commodity contract derivatives— 7 — 7 
Commodity derivatives under the FHP— 8 — 8 
Total$— $1,160 $— $1,160 
Notes
(1) Includes securities of government-sponsored entities.
(2) There are $297 million of U.S. Treasury Securities in Level 1 Government debt securities and $61 million of U.S. Treasury Securities in Level 1 Cash equivalents and other short-term investments for a total of $358 million of U.S. Treasury securities within Level 1 of the fair value hierarchy.
(3) At September 30, 2022, $61 million of the Level 1 Government debt securities have been reclassified to Level 1 Cash equivalents and other short-term investments. At September 30, 2022, $1 million of the Level 2 Government debt securities, $1 million of the Level 2 Corporate debt securities, and $116 million of the Commingled funds measured at net asset value have been reclassified to Level 2 Cash equivalents and other short-term investments.
(4) Includes both U.S. and foreign debt.
(5) Certain investments that are measured at fair value using the NAV or its equivalent ("alternative investments") have not been categorized in the fair value hierarchy. The inputs to these fair value measurements include underlying NAVs, discounted cash flow valuations, comparable market valuations, and adjustments for currency, credit, liquidity, and other risks. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented on the Consolidated Balance Sheets.
(6) TVA records currency swaps net of cash collateral received from or paid to the counterparty, to the extent such amount is not recorded in Accounts payable and accrued liabilities. See Note 15 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.
Estimated Values of Financial Instruments Not Recorded at Fair Value The estimated values of TVA's financial instruments not recorded at fair value at September 30, 2023 and 2022, were as follows:
Estimated Values of Financial Instruments Not Recorded at Fair Value
(in millions)
 At September 30, 2023At September 30, 2022
 Valuation ClassificationCarrying
Amount		Fair
Value		Carrying
Amount		Fair
Value
EnergyRight® receivables, net (including current portion)
Level 2$59 $55 $62 $62 
Loans and other long-term receivables, net (including current portion)Level 2104 96 105 96 
EnergyRight® financing obligations (including current portion)
Level 269 81 72 81 
Unfunded loan commitmentsLevel 2— 1 — — 
Membership interests of VIEs subject to mandatory redemption (including current portion)Level 218 19 20 22 
Long-term outstanding power bonds, net (including current maturities)Level 218,866 17,963 17,856 18,070 
Long-term debt of VIEs, net (including current maturities)Level 2968 927 1,007 989 
  
v3.23.3
Other Income (Expense), Net Other Income (Expense), Net (Tables)
 12 Months Ended
Sep. 30, 2023
Other Income and Expenses [Abstract]  
Other Income (Expense), Net
Income and expenses not related to TVA's operating activities are summarized in the following table:
Other Income, Net
For the years ended September 30
(in millions)
 202320222021
Bellefonte$— $— $(28)
Interest income34 15 12 
External services15 16 13 
Gains (losses) on investments13 (17)16 
Miscellaneous(1)(7)— 
Total other income, net$61 $7 $13 
v3.23.3
Benefit Plans Benefit Plans (Tables)
 12 Months Ended
Sep. 30, 2023
Retirement Benefits [Abstract]  
Obligations and Funded Status
The changes in plan obligations, assets, and funded status for the years ended September 30, 2023 and 2022, were as follows:
Obligations and Funded Status
For the years ended September 30
(in millions)
812,900,000 Pension BenefitsOther Post-Retirement Benefits
809,400,000 2023202220232022
Change in benefit obligation    
Benefit obligation at beginning of year$10,536 $13,348 $388 $498 
Service cost32 53 10 17 
Interest cost568 378 18 15 
Plan participants' contributions4 5 — — 
Collections(1)
— — 13 15 
Actuarial (gain) loss (284)(2,509)(44)(114)
Net transfers (to) from variable fund/401(k) plan4 11 — — 
Expenses paid(7)(6)— — 
Benefits paid(754)(744)(38)(43)
Benefit obligation at end of year10,099 10,536 347 388 
Change in plan assets    
Fair value of net plan assets at beginning of year8,094 9,110 — — 
Actual return on plan assets482 (590)— — 
Plan participants' contributions4 5 — — 
Collections(1)
— — 13 15 
Net transfers (to) from variable fund/401(k) plan4 11 — — 
Employer contributions306 308 25 28 
Expenses paid(7)(6)— — 
Benefits paid(754)(744)(38)(43)
Fair value of net plan assets at end of year8,129 8,094 — — 
Funded status$(1,970)$(2,442)$(347)$(388)
Note
(1) Collections include retiree contributions as well as provider discounts and rebates.
Amounts Recognized on TVA's Consolidated Balance Sheets
Amounts related to these benefit plans recognized on TVA's Consolidated Balance Sheets consist of regulatory assets and liabilities that have not been recognized as components of net periodic benefit cost at September 30, 2023 and 2022, and the funded status of TVA's benefit plans, which are included in Accounts payable and accrued liabilities and Post-retirement and post-employment benefit obligations:
Amounts Recognized on TVA's Consolidated Balance Sheets
At September 30
(in millions)
 Pension BenefitsOther Post-Retirement Benefits
 2023202220232022
Regulatory assets (liabilities)$1,440 $1,839 $(95)$(70)
Accounts payable and accrued liabilities(6)(6)(21)(22)
Pension and post-retirement benefit obligations(1)
(1,964)(2,436)(326)(366)
Note
(1) The table above excludes $237 million and $270 million of post-employment benefit costs that are recorded in Post-retirement and post-employment benefit obligations on the Consolidated Balance Sheets at September 30, 2023 and 2022, respectively.
Post-Retirement Benefit Costs Deferred as Regulatory Assets
Unrecognized amounts included in regulatory assets or liabilities yet to be recognized as components of accrued benefit cost at September 30, 2023 and 2022, consisted of the following:
Post-Retirement Benefit Costs Deferred as Regulatory Assets (Liabilities)
At September 30
(in millions)
 Pension BenefitsOther Post-Retirement Benefits
 2023202220232022
Unrecognized prior service credit$(336)$(424)$(59)$(76)
Unrecognized net loss (gain)1,776 2,186 (36)6 
Amount capitalized due to actions of regulator— 77 — — 
Total regulatory assets (liabilities)$1,440 $1,839 $(95)$(70)
Projected Benefit Obligations and Accumulated Benefit Obligations in Excess of Plan Assets
Information for the pension projected benefit obligation ("PBO") in excess of plan assets and other post-retirement accumulated postretirement benefit obligation ("APBO") has been disclosed in the Obligations and Funded Status table above. The following table provides the pension plan accumulated benefit obligation ("ABO") in excess of plan assets. The other post-retirement plans are unfunded or have no plan assets.
Accumulated Benefit Obligations in Excess of Plan Assets
At September 30
(in millions)
 20232022
Accumulated benefit obligation$10,069 $10,508 
Fair value of net plan assets8,129 8,094 
Components of Net Periodic Benefit Cost
The components of net periodic benefit cost and other amounts recognized as changes in regulatory assets for the years ended September 30, 2023, 2022, and 2021 were as follows:
Components of Net Periodic Benefit Cost
For the years ended September 30
(in millions)
 Pension BenefitsOther Post-Retirement Benefits
 202320222021202320222021
Service cost$32 $53 $57 $10 $17 $18 
Interest cost568 378 368 18 15 16 
Expected return on plan assets(492)(435)(493)— — — 
Amortization of prior service credit(88)(93)(97)(17)(17)(18)
Recognized net actuarial loss (gain)135 392 452 (2)5 11 
Total net periodic benefit cost as actuarially determined155 295 287 9 20 27 
Amount expensed due to actions of regulator77 13 19 — — — 
Net periodic benefit cost$232 $308 $306 $9 $20 $27 
Sensitivity to Certain Changes in Pension Assumptions The following chart reflects the sensitivity of pension cost to changes in certain actuarial assumptions:
Sensitivity to Certain Changes in Pension Assumptions
 
 
Actuarial Assumption
Change in Assumption
Impact on 2023 Pension Cost
(in millions)
Impact on 2023 Projected Benefit Obligation
(in millions)
Discount rate(0.25)%$12 $236 
Rate of return on plan assets(0.25)%19 N/A
Cost of living adjustments0.25 %24 165 
Asset Holdings and Fair Value Measurements At September 30, 2023 and 2022, the asset holdings of TVARS included the following:
Asset Holdings of TVARS
  Plan Assets at September 30
Asset CategoryTarget Allocation20232022
Growth assets17 %22 %20 %
Defensive growth assets30 %33 %34 %
Defensive assets33 %17 %18 %
Inflation-sensitive assets20 %28 %28 %
Total100 %100 %100 %
Fair Value Measurements

    The following table provides the fair value measurement amounts for assets held by TVARS at September 30, 2023:
TVA Retirement System
At September 30, 2023
(in millions)
 
Total(1)(2)
Quoted Prices in Active Markets for Identical
Assets/Liabilities
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Assets    
Equity securities$732 $731 $— $1 
Preferred securities4 — 4 — 
Debt securities   
Corporate debt securities1,109 — 1,107 2 
Residential mortgage-backed securities330 — 323 7 
    Debt securities issued by U.S. Treasury602 602 — — 
Debt securities issued by foreign governments
12 — 10 2 
Asset-backed securities
173 — 130 43 
Debt securities issued by state/local governments
21 — 21 — 
Commercial mortgage-backed securities
113 — 108 5 
Commingled funds measured at net asset value(3)
Equity360 — — — 
Debt544 — — — 
Blended101 — — — 
Institutional mutual funds363 363 — — 
Cash equivalents and other short-term investments315 51 264 — 
Private credit funds measured at net asset value(3)
694 — — — 
Private equity funds measured at net asset value(3)
1,769 — — — 
Private real asset funds measured at net asset value(3)
1,162 — — — 
Securities lending collateral181 — 181 — 
Derivatives    
Futures
1 1 — — 
Swaps17 — 17 — 
Foreign currency forward receivable2 — 2 — 
Total assets$8,605 $1,748 $2,167 $60 
Liabilities    
Derivatives
Futures$5 $5 $— $— 
Swaps26 — 26 — 
Options1 1 — — 
Securities sold under agreements to repurchase96 — 96 — 
Total liabilities$128 $6 $122 $— 
Notes
(1)  Excludes approximately $167 million in net payables associated with security purchases and sales and various other payables.
(2)  Excludes a $181 million payable for collateral on loaned securities in connection with TVARS's participation in securities lending programs.
(3) In accordance with Subtopic 820-10, certain investments that are measured at fair value using the NAV or its equivalent ("alternative investments") have not been classified in the fair value hierarchy. The inputs to these fair value measurements include underlying NAVs, discounted cash flow valuations, comparable market valuations, and adjustments for currency, credit, liquidity, and other risks.
    The following table provides the fair value measurement amounts for assets held by TVARS at September 30, 2022:
TVA Retirement System
At September 30, 2022
(in millions)
 
Total(1)(2)
Quoted Prices in Active Markets for Identical
Assets/Liabilities
(Level 1)		Significant Other
Observable Inputs
(Level 2)		Significant
Unobservable
Inputs
(Level 3)
Assets    
Equity securities$709 $707 $— $2 
Preferred securities6 1 5 — 
Debt securities   
Corporate debt securities1,087 — 1,087 — 
Residential mortgage-backed securities293 — 289 4 
Debt securities issued by U.S. Treasury616 616 — — 
Debt securities issued by foreign governments130 — 130 — 
Asset-backed securities176 — 136 40 
Debt securities issued by state/local governments23 — 23 — 
Commercial mortgage-backed securities
161 — 145 16 
Commingled funds measured at net asset value(3)
Equity436 — — — 
Debt657 — — — 
Blended111 — — — 
Institutional mutual funds454 454 — — 
Cash equivalents and other short-term investments431 133 298 — 
Private credit funds measured at net asset value(3)
522 — — — 
Private equity funds measured at net asset value(3)
1,454 — — — 
Private real asset funds measured at net asset value(3)
1,080 — — — 
Securities lending collateral196 — 196 — 
Derivatives
Futures
5 5 — — 
Swaps
17 — 17 — 
Foreign currency forward receivable2 — 2 — 
Total assets$8,566 $1,916 $2,328 $62 
Liabilities    
Derivatives
Futures$10 $10 $— $— 
Foreign currency forward payable1 — 1 — 
Swaps54 — 54 — 
Securities sold under agreements to repurchase111 — 111 — 
Total liabilities$176 $10 $166 $— 
Notes
(1)  Excludes approximately $100 million in net payables associated with security purchases and sales and various other payables.
(2)  Excludes a $196 million payable for collateral on loaned securities in connection with TVARS's participation in securities lending programs.
(3) In accordance with Subtopic 820-10, certain investments that are measured at fair value using the NAV or its equivalent ("alternative investments") have not been classified in the fair value hierarchy. The inputs to these fair value measurements include underlying NAVs, discounted cash flow valuations, comparable market valuations, and adjustments for currency, credit, liquidity, and other risks.
Fair Value Measurements Using Significant Unobservable Inputs
The following table provides a reconciliation of beginning and ending balances of pension plan assets measured at fair value on a recurring basis where the determination of fair value includes significant unobservable inputs (Level 3):
Fair Value Measurements Using Significant Unobservable Inputs
(in millions)
 Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Balance at September 30, 2021
$74 
Net realized/unrealized gains (losses)(4)
Purchases, sales, issuances, and settlements (net)2 
Transfers in and/or out of Level 3(10)
Balance at September 30, 2022
62 
Net realized/unrealized gains (losses)1 
Purchases, sales, issuances, and settlements (net)2 
Transfers in and/or out of Level 3(5)
Balance at September 30, 2023
$60 
Estimated Future Benefit Payments
Cash Flows

Estimated Future Benefit Payments.  The following table sets forth the estimated future benefit payments under the benefit plans.
Estimated Future Benefits Payments
At September 30, 2023
(in millions)
 
Pension
Benefits(1)
Other Post-Retirement Benefits
2024$809 $22 
2025814 21 
2026812 21 
2027812 21 
2028809 21 
2029 - 20333,918 119 
Note
(1) Participants are assumed to receive the Fixed Fund in a lump sum in lieu of available annuity options allowed for certain grandfathered participants resulting in higher estimated pension benefits payments.
Amounts recognized on Consolidated Balance Sheets
Amounts Recognized on TVA's Consolidated Balance Sheets
At September 30
(in millions)
 20232022
Accounts payable and accrued liabilities$29 $29 
Post-retirement and post-employment benefit obligations237 270 
v3.23.3
Commitments and Contingencies (Tables)
 12 Months Ended
Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]  
Unfunded loan commitments At September 30, 2023, TVA's commitments under unfunded loan commitments were $1 million for 2024. TVA has no commitments under unfunded loan commitments for 2025 through 2028.
v3.23.3
Related Parties Related Parties (Tables)
 12 Months Ended
Sep. 30, 2023
Related Party Transactions [Abstract]  
Related Party Transactions Transactions with agencies of the federal government were as follows:
Related Party Transactions
At or for the years ended September 30
(in millions)
 202320222021
Revenue from sales of electricity$120 $134 $109 
Other income282 296 280 
Expenditures
Operating expenses234 228 214 
Additions to property, plant, and equipment8 11 10 
Cash and cash equivalents31 30 30 
Accounts receivable, net87 78 65 
Investment funds391 358 573 
Long-term accounts receivable38 43 31 
Accounts payable and accrued liabilities42 42 15 
Long-term power bonds, net1 1 1 
Return on power program appropriation investment6 4 4 
v3.23.3
Revenue (Tables)
 12 Months Ended
Sep. 30, 2023
Revenue from Contract with Customer [Abstract]  
Revenues
Revenues

TVA recognizes revenue from contracts with customers to depict the transfer of goods or services to customers in an amount to which the entity expects to be entitled in exchange for those goods or services. For the generation and transmission of electricity, this is generally at the time the power is delivered to a metered customer delivery point for the customer's consumption or distribution. As a result, revenues from power sales are recorded as electricity is delivered to customers. In addition to power sales invoiced and recorded during the month, TVA accrues estimated unbilled revenues for power sales provided to five customers whose billing date occurs prior to the end of the month.  Exchange power sales are presented in the accompanying Consolidated Statements of Operations as a component of sales of electricity. Exchange power sales are sales of excess power after meeting TVA native load and directly served requirements.  Native load refers to the customers on whose behalf a company, by statute, franchise, regulatory requirement, or contract, has undertaken an obligation to serve. TVA engages in other arrangements in addition to power sales. Certain other revenue from activities related to TVA's overall mission is recorded in Other revenue. Revenues that are not related to the overall mission are recorded in Other income, net.
v3.23.3
Leases (Table Text Block)
 12 Months Ended
Sep. 30, 2023
Leases [Abstract]  
Amounts Recognized on Balance Sheets The following table provides information regarding the presentation of leases on the Consolidated Balance Sheets:
Amounts Recognized on TVA's Consolidated Balance Sheets
At September 30
(in millions)
20232022
Assets
  OperatingOperating lease assets, net of amortization$177 $155 
  FinanceFinance leases572 630 
Total lease assets$749 $785 
Liabilities
Current
  OperatingAccounts payable and accrued liabilities$71 $59 
  FinanceAccounts payable and accrued liabilities56 59 
Non-current
  OperatingOther long-term liabilities93 93 
  FinanceFinance lease liabilities576 628 
Total lease liabilities$796 $839 
Lease Costs TVA's leases consist primarily of railcars, equipment, real estate/land, power generating facilities, and gas pipelines. TVA's leases have various terms and expiration dates remaining from less than one year to 23 years. The components of lease costs were as follows:
Lease Costs
For the years ended September 30
(in millions)
202320222021
Operating lease costs(1)
$69 $56 $52 
Variable lease costs(1)
134 78 75 
Short-term lease costs(1)
18 26 12 
Finance lease costs
Amortization of lease assets(2)
57 58 51 
Interest on lease liabilities(3)(4)
43 42 39 
Total finance lease costs100 100 90 
     Total lease costs$321 $260 $229 
Notes
(1) Costs are included in Operating and maintenance expense, Fuel expense, Purchased power expense, and Tax equivalents expense on the Consolidated Statements of Operations.
(2) Expense is included in Depreciation and amortization expense on the Consolidated Statements of Operations.
(3) Expense is included in Interest expense on the Consolidated Statements of Operations.
(4) Certain finance leases receive regulatory accounting treatment and are reclassified to Fuel expense and Purchased power expense.
Amounts Recognized on Statements of Cash Flows
The following table contains additional information with respect to cash and non-cash activities related to leases:
Amounts Recognized on TVA's Consolidated Statements of Cash Flows
For the years ended September 30
(in millions)
202320222021
Operating cash flows for operating leases$77 $57 $53 
Operating cash flows for finance leases43 42 39 
Financing cash flows for finance leases56 60 52 
Lease assets obtained in exchange for lease obligations (non-cash)
Operating leases(1)
$84 $43 $(22)
Finance leases3 — 233 
Note
(1) Amount for 2021 represents a non-cash reduction due to a lease that was amended during the fiscal year resulting in derecognition of the operating lease asset and obligation upon remeasurement.
Weighted Averages TVA has certain finance leases under PPAs under which the present value of the minimum lease payments exceeds the fair value of the related lease asset at the date of measurement.  This resulted in an interest rate that was higher than TVA's incremental borrowing rate. The weighted average remaining lease terms in years and the weighted average discount rate for TVA's operating and financing leases were as follows:
Weighted Averages
At September 30
20232022
Weighted average remaining lease terms
Operating leases3 years3 years
Finance leases10 years11 years
Weighted average discount rate(1)
Operating leases4.1%1.5%
Finance leases21.6%17.8%
Note
(1) The discount rate is calculated using the rate implicit in a lease if it is readily determinable. If the rate used by the lessor is not readily determinable, TVA uses its incremental borrowing rate as permitted by accounting guidance. The incremental borrowing rate is influenced by TVA's credit rating and lease term and as such may differ for individual leases, embedded leases, or portfolios of leased assets.
Future Minimum Lease Payments The following table presents maturities of lease liabilities and a reconciliation of the undiscounted cash flows to lease liabilities at September 30, 2023:
Future Minimum Lease Payments
Minimum payments outstanding at September 30, 2023
(in millions)
Operating leases
2024$76 
202551 
202624 
20279 
20283 
Thereafter11 
Minimum annual payments174 
Less: present value discount(10)
Operating present value of net minimum lease payments$164 
Finance leases
2024$109 
2025107 
2026106 
2027104 
2028102 
   Thereafter450 
Minimum annual payments978 
Less: amount representing interest(346)
Finance present value of net minimum lease payments$632 
v3.23.3
Summary of Significant Accounting Policies - General (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
People
Sep. 30, 2022
USD ($)
Sep. 30, 2021
USD ($)
Sep. 30, 2020
USD ($)
Sep. 30, 2016
USD ($)
Accounting Policies [Abstract]          
Cash and Cash Equivalents, at Carrying Value $ 501 $ 500      
Reimbursements from DOE 219        
Restricted Cash and Investments, Noncurrent 20 20      
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents 521 520 $ 518 $ 521  
Accounts receivable from DOE 11        
Appropriation-investment power program $ 258 258     $ 1,000
Population of Service Area [Line Items]          
Population of service area | People 10,000,000        
Cash and Cash Equivalents, at Carrying Value $ 501 500      
Restricted Cash and Investments, Noncurrent $ 20 $ 20      
v3.23.3
Summary of Significant Accounting Policies - Reclassificatons (Details)
$ in Millions
Sep. 30, 2023
USD ($)
Reclassifications  
Finance Lease, Liability $ 632
v3.23.3
Summary of Significant Accounting Policies - Allowance for Uncollectible Accounts (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Portion at Other than Fair Value Measurement [Member]    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Financing Receivable, after Allowance for Credit Loss $ 104 $ 105
Financing Receivable, after Allowance for Credit Loss 96 96
Allowance for uncollectible accounts - receivables 1 1
Loans and Leases Receivable, Allowance $ 3 $ 3
v3.23.3
Summary of Significant Accounting Policies - Property, Plant, and Equipment, and Depreciation (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Property, Plant, and Equipment, and Depreciation      
Depreciation $ 1,900 $ 1,800 $ 1,400
Composite depreciation rate for completed plant 3.14% 2.98% 2.28%
Reacquired Rights $ 324 $ 178  
Amortization of Reacquired Rights $ 10 6 $ 8
Capitalized software amortization period 7 years    
Accelerated depreciation $ 177 140 $ 136
Accumulated Amortization of Reacquired Rights 52 $ 42  
Amortization Reacquired Rights, Year 1 11    
Amortization Reacquired Rights, Year 2 12    
Amortization Reacquired Rights, Year 3 11    
Amortization Reacquired Rights, Year 4 12    
Amortization Reacquired Rights, Year 5 11    
Amortization Reacquired Rights, Year Thereafter 267    
Reimbursements from DOE 219    
Accounts receivable from DOE $ 11    
Nuclear      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 2.73% 2.72% 2.38%
Coal-fired      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 4.98% 4.27% 1.95%
Hydroelectric      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 1.82% 1.85% 1.60%
Gas and oil-fired      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 3.17% 3.38% 2.98%
Transmission      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 1.52% 1.51% 1.34%
Other      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 4.43% 3.64% 7.12%
v3.23.3
Summary of Significant Accounting Policies - Energy Prepayment Obligations and Discounts on Sales (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Energy Prepayment Obligations and Discounts on Sales    
Accounts Receivable, Allowance for Credit Loss, Current $ 1 $ 1
v3.23.3
Summary of Significant Accounting Policies - Leases (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Leases      
Finance lease under PPA $ 390 $ 425  
Operating lease under PPA 135 133  
Operating cash flows for operating leases $ 77 $ 57 $ 53
v3.23.3
Summary of Significant Accounting Policies - Pre-commercial Plant Ops (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Revenues from External Customers and Long-Lived Assets [Line Items]      
Revenue capitalized during pre-commercial operations $ 3 $ 0 $ 0
Fuel capitalized during pre-commercial ops $ 3    
v3.23.3
Impact of New Accounting Standards and Interpretations (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Lessee, Lease, Description [Line Items]    
Operating Lease, Right-of-Use Asset $ 177 $ 155
v3.23.3
Accounts Receivable, Net Accounts Receivable, Net (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Power receivables $ 1,627 $ 1,899
Other receivables 118 108
Allowance for uncollectible accounts (1) [1] (1)
Accounts receivable, net $ 1,745 $ 2,007
[1] Allowance for uncollectible accounts was less than $1 million at both September 30, 2023 and 2022, and therefore is not represented in the table above.
v3.23.3
Inventories, Net Inventories, Net (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Inventories, Net    
Materials and supplies inventory $ 849 $ 808
Fuel inventory 313 303
Renewable energy certificates/emissions allowance inventory, net 15 18
Allowance for inventory obsolescence (69) (57)
Inventories, net $ 1,108 $ 1,072
v3.23.3
Deferred Costs, Capitalized, Prepaid, and Other Assets (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]    
Inventory, Work in Process, Gross $ 28 $ 18
Prepaid long-term service agreements, current 25 12
Other current assets 134 257
Prepaid Insurance 16 16
Other Assets, Miscellaneous, Current 26 25
Commodity Contract Asset, Current 21 172
Prepaid software maintenance $ 18 $ 14
v3.23.3
Net Completed Plant Net Completed Plant (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Completed Plant    
Completed plant cost $ 68,199 $ 66,442
Accumulated depreciation 35,871 34,239
Net completed plant 32,328 32,203
Coal-fired    
Completed Plant    
Completed plant cost 18,525 18,145
Accumulated depreciation 14,464 13,649
Net completed plant 4,061 4,496
Gas and oil-fired    
Completed Plant    
Completed plant cost 6,663 6,112
Accumulated depreciation 2,057 1,957
Net completed plant 4,606 4,155
Nuclear    
Completed Plant    
Completed plant cost 26,803 26,629
Accumulated depreciation 13,557 12,928
Net completed plant 13,246 13,701
Transmission    
Completed Plant    
Completed plant cost 9,375 8,919
Accumulated depreciation 3,359 3,301
Net completed plant 6,016 5,618
Hydroelectric    
Completed Plant    
Completed plant cost 4,109 3,987
Accumulated depreciation 1,241 1,192
Net completed plant 2,868 2,795
Other electrical plant    
Completed Plant    
Completed plant cost 1,798 1,724
Accumulated depreciation 780 807
Net completed plant 1,018 917
Multipurpose dams    
Completed Plant    
Completed plant cost 900 900
Accumulated depreciation 404 396
Net completed plant 496 504
Other stewardship    
Completed Plant    
Completed plant cost 26 26
Accumulated depreciation 9 9
Net completed plant $ 17 $ 17
v3.23.3
Other Long-Term Assets (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Assets, Noncurrent [Abstract]    
Financing Receivable, after Allowance for Credit Loss, Noncurrent $ 97 $ 99
Financing Receivable, after Allowance for Credit Loss, Current 7 6
Commodity contract derivative assets 12 102
Prepaid long-term service agreements, noncurrent 64 74
Prepaid capital assets 28 0
Other Assets, Miscellaneous, Noncurrent 82 70
Restricted Cash and Investments, Noncurrent 20 20
Total other long-term assets 330 394
Other Long-Term Assets    
Loans and Leases Receivable, Allowance 3 3
Transfers Accounted for as Secured Borrowings, Assets, Carrying Amount 55 62
Other Assets, Miscellaneous, Current 26 25
Accounts Receivable [Member]    
Other Long-Term Assets    
Transfers Accounted for as Secured Borrowings, Assets, Carrying Amount 12 13
Other Noncurrent Assets [Member]    
Other Long-Term Assets    
Transfers Accounted for as Secured Borrowings, Assets, Carrying Amount 47 49
EnergyRight loan reserve    
Other Long-Term Assets    
Loans and Leases Receivable, Allowance 1 1
Economic development loan collective reserve    
Other Long-Term Assets    
Loans and Leases Receivable, Allowance 1 1
Economic development loan specific loan reserve    
Other Long-Term Assets    
Loans and Leases Receivable, Allowance $ 1 $ 1
Energy Right    
Other Long-Term Assets    
Number of days in default 180 days  
Minimum | Energy Right    
Other Long-Term Assets    
EnergyRight loan terms 5 years  
Maximum | Energy Right    
Other Long-Term Assets    
EnergyRight loan terms 10 years  
v3.23.3
Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Regulatory Assets and Liabilities      
Non-current regulatory liabilities $ 107 $ 172  
Current regulatory assets 178 138  
Regulatory assets 5,566 6,134  
Net unrealized gains (losses) (52) (1)  
Regulatory Assets 5,744 6,272  
Current regulatory liabilities 222 391  
Regulatory asset amount expensed 31 70 $ 72
Regulatory Liabilities 329 563  
Change in nuclear decommissioning costs 93    
Regulatory Asset      
Regulatory Assets and Liabilities      
Regulatory assets 152 138  
Unrealized losses on interest rate derivatives      
Regulatory Assets and Liabilities      
Current regulatory assets 31 47  
Regulatory assets 272 479  
Non-nuclear decommissioning costs      
Regulatory Assets and Liabilities      
Regulatory assets 2,922 2,856  
Pension Costs [Member]      
Regulatory Assets and Liabilities      
Regulatory assets 1,440 1,839  
Unrealized gains/losses on commodity derivatives      
Regulatory Assets and Liabilities      
Current regulatory assets 136 14  
Regulatory assets 52 1  
Deferred Fuel Costs [Member]      
Regulatory Assets and Liabilities      
Current regulatory assets 11 77  
Nuclear decommissioning costs      
Regulatory Assets and Liabilities      
Regulatory assets 728 821  
Unrealized gains/losses on commodity derivatives      
Regulatory Assets and Liabilities      
Non-current regulatory liabilities 12 102  
Current regulatory liabilities 21 173  
Deferred other post-retirement benefits cost      
Regulatory Assets and Liabilities      
Non-current regulatory liabilities 95 70  
Fuel cost adjustment tax equivalents      
Regulatory Assets and Liabilities      
Current regulatory liabilities $ 201 $ 218  
v3.23.3
Variable Interest Entities (Details) - USD ($)
$ in Millions
 12 Months Ended 348 Months Ended
Sep. 30, 2053
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2052
Sep. 30, 2013
Sep. 30, 2012
Liabilities              
Current maturities of long-term debt of variable interest entities issued at par   $ 35 $ 39        
Liabilities, Current   4,873 4,645        
Other long-term liabilities   1,211 1,485        
Long-term debt of variable interest entities, net   933 968        
VIE Financing              
Face Amount   $ 40       $ 360  
Rate of Return SHLLC   7.00%          
Accrued interest   $ 9 10        
Minimum payments on membership interests subject to mandatory redemption, due in next twelve months   1          
Minimum payments on membership interests subject to mandatory redemption, due in year two   1          
Minimum payments on membership interests subject to mandatory redemption, due in year three   1          
Minimum payments on membership interests subject to mandatory redemption, due in year four   1          
Minimum payments on membership interests subject to mandatory redemption, due in year five   1          
Minimum payments on membership interests subject to mandatory redemption, due thereafter   13          
Other Long-term Debt, Maturity, Year One   35          
Other Long-term Debt, Maturity, Year Two   37          
Other Long-term Debt, Maturity, Year Three   39          
Other Long-term Debt, Maturity, Year Four   40          
Other Long-term Debt, Maturity, Year Five   42          
Other Long-term Debt, Maturity, Year Six   781          
Long-term debt of variable interest entities (including current maturities)   927 989        
Amount of letters of credit outstanding   6          
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net   126 124        
Variable Interest Entity, Primary Beneficiary [Member]              
VIE Financing              
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net   6          
Portion at Other than Fair Value Measurement [Member]              
VIE Financing              
Long-term debt of variable interest entities (including current maturities)   968 1,007        
Lagoon Creek [Member]              
VIE Financing              
Amortization of reacquired rights   3          
Lagoon Creek [Member] | Scenario, Forecast              
VIE Financing              
Amortization of reacquired rights $ 2       $ 5    
Letter of Credit              
VIE Financing              
Amount of letters of credit outstanding   535 704        
SCCG              
VIE Financing              
Debt and Lease Obligation           $ 400  
Holdco              
VIE Financing              
Face Amount             $ 100
JSCCG              
VIE Financing              
Face Amount             900
Variable Interest Entity, Primary Beneficiary [Member]              
Liabilities              
Liabilities, Current   45 51        
Other long-term liabilities   17 18        
VIE Financing              
Accounts Payable and Accrued Liabilities   1 2        
Liabilities   995 1,037       $ 1,000
Interest Expense   $ 48 $ 50 $ 52      
v3.23.3
Asset Retirement Obligations Asset Retirement Obligations (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Liabilities Settled [Line Items]      
Increase in ARO liability $ 327    
Change in estimate [1] 369 $ 247  
Balance [1] 7,489 7,162 $ 7,002
Asset Retirement Obligation, Liabilities Settled [1] 279 311  
Accretion (recorded as regulatory asset) [1] 237 224  
Asset Retirement Obligation, Current 272 275  
Amortization and Depreciation of Decontaminating and Decommissioning Assets 188 137 72
Total ARO change due to CCR 458 82  
Change due to cost study   58  
Change in estimate due to coal fines   119  
Change in estimate due to closure of coal yards   57  
Change in estimate due to timing of maintenance   53  
Change in estimate due to timing of asset retirement activities   47  
Change in estimate due to Gallatin CCR closure 60 30  
Change in cost estimates at Allen   15  
Changes in closure liabilities 15    
Increase in Asset Retirement Obligation, Revisions in Estimate 9    
Nuclear      
Liabilities Settled [Line Items]      
Change in estimate 7 61  
Balance 3,808 3,643 3,428
Asset Retirement Obligation, Liabilities Settled 8 2  
Accretion (recorded as regulatory asset) 166 156  
Non-nuclear      
Liabilities Settled [Line Items]      
Change in estimate 362 186  
Balance 3,681 3,519 $ 3,574
Asset Retirement Obligation, Liabilities Settled 271 309  
Accretion (recorded as regulatory asset) $ 71 $ 68  
[1] (1) Includes $272 million and $275 million at September 30, 2023 and 2022, respectively, in Current liabilities.
v3.23.3
Other Long-Term Liabilities Other Long-Term Liabilities (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Portion at Other than Fair Value Measurement [Member]    
Derivative, Fair Value, Net [Abstract]    
EnergyRight financing obligation $ (69) $ (72)
Long-term debt of variable interest entities (including current maturities) 968 1,007
Interest rate swaps 662 905
Currency swap liabilities 141 240 [1]
EnergyRight financing obligation (81) (81)
Deferred Revenue, Noncurrent 45 39
Non-current regulatory liabilities 107 172
Total other long-term liabilities 1,211 $ 1,485
Finance Lease, Liability $ 632  
Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration] Other Liabilities Other Liabilities
Deferred Compensation Liability, Current $ (65) $ (53)
Current portion of energy prepayment obligations 21 16
Fair value 52 1
Long-term debt of variable interest entities (including current maturities) 927 989
Other long-term liabilities    
Other Long-Term Liabilities    
Interest rate swaps 627 851
Currency swap liabilities 131 228
Derivative, Fair Value, Net [Abstract]    
EnergyRight financing obligation (55) (58)
Environmental agreements liability 41 39
Customer Advances for Construction 56 53
Other 111 123
Accounts payable and accrued liabilities    
Derivative, Fair Value, Net [Abstract]    
EnergyRight financing obligation (14) (14)
Customer Advances for Construction $ 39 $ 33
[1] See Note 15 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.
v3.23.3
Debt and Other Obligations Debt and Other Obligations - General (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2013
Jan. 17, 2012
Debt Instrument      
Interest rate     7.10%
Debt ceiling $ 30,000    
Face Amount $ 40 $ 360  
PARRS 1998 Series D Bond      
Debt Instrument      
PARRS interest rate after rate reset 2.134%    
Amount of bonds redeemed $ 318    
Amount of redeemable bond issues outstanding $ 256    
PARRS interest rate after rate reset 2.134%    
PARRS 1999 Series A Bond      
Debt Instrument      
PARRS interest rate after rate reset 2.216%    
Amount of bonds redeemed $ 316    
Amount of redeemable bond issues outstanding $ 208    
PARRS interest rate after rate reset 2.216%    
v3.23.3
Debt and Other Obligations Debt and Other Obligations - Secured Debt of VIEs (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2013
Aug. 09, 2013
Sep. 30, 2012
Jan. 17, 2012
Variable Interest Entities            
Face Amount $ 40   $ 360      
Interest rate           7.10%
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount 19 $ 22        
Long-term debt of variable interest entities (including current maturities) 927 $ 989        
SCCG            
Variable Interest Entities            
Interest rate       3.846%    
JSCCG            
Variable Interest Entities            
Face Amount         $ 900  
Debt Instrument, Interest Rate           4.626%
Holdco            
Variable Interest Entities            
Face Amount         $ 100  
Holdco balloon payment upon maturity $ 10          
v3.23.3
Debt and Other Obligations Debt and Other Obligations - Secured Notes of SPEs (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2013
Jan. 17, 2012
Secured notes      
Secured notes $ 40 $ 360  
Interest rate     7.10%
v3.23.3
Debt and Other Obligations Debt and Other Obligations - Short-Term Debt (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Short-Term Debt, Gross [Line Items]    
Short-Term Debt $ 432 $ 1,172
Short-term Borrowings Gross $ 432 $ 1,173
Weighted average interest rate - discount notes 5.29% 2.93%
Foreign Currency Transaction Gain (Loss), Unrealized $ 109 $ 150
v3.23.3
Debt and Other Obligations Debt and Other Obligations - Put and Call Options (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
PARRS 1998 Series D Bond  
Debt Instrument  
Amount of redeemable bond issues outstanding $ 256
PARRS interest rate prior to rate reset 6.75%
PARRS interest rate after rate reset 2.134%
Amount of bonds redeemed $ 318
PARRS 1999 Series A Bond  
Debt Instrument  
Amount of redeemable bond issues outstanding $ 208
PARRS interest rate prior to rate reset 6.50%
PARRS interest rate after rate reset 2.216%
Amount of bonds redeemed $ 316
v3.23.3
Debt and Other Obligations Debt and Other Obligations - Debt Securities Activity (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2013
Jan. 17, 2012
Debt Instrument          
Face Amount $ 40     $ 360  
Discount on debt issues (8) $ (16)      
Redemptions/Maturities of variable interest entities 39 43 $ 41    
Redemptions/Maturities of power bonds $ 29 $ 1,028 $ 1,860    
Percent of par value 99.187% 96.786%      
Total Current maturities of power bonds issued at par $ 1,022 $ 29      
Interest rate         7.10%
Short-term debt, net of discounts 432 1,172      
Current maturities of long-term debt of variable interest entities issued at par 35 39      
Long-term power bonds, net 17,844 17,826      
880591EF5 (12.15.20)          
Debt Instrument          
Total Current maturities of power bonds issued at par $ 1 1      
Interest rate 3.77%        
Debt Instrument, Maturity Date Dec. 15, 2023        
880591EF5 (6.15.21)          
Debt Instrument          
Total Current maturities of power bonds issued at par $ 21 28      
Interest rate 3.77%        
Debt Instrument, Maturity Date Jun. 15, 2024        
880591ER9          
Debt Instrument          
Total Current maturities of power bonds issued at par $ 1,000 $ 0      
Interest rate 2.875%        
Debt Instrument, Maturity Date Sep. 15, 2024        
Total          
Debt Instrument          
Debt Instrument, Redemption Period, End Date 68 1,071      
Percent of par value 100.00%        
Debt of variable interest entities          
Debt Instrument          
Redemptions/Maturities of variable interest entities $ 39 $ 43      
2009 Series B          
Debt Instrument          
Redemptions/Maturities of power bonds 29 28      
2012 Series A          
Debt Instrument          
Redemptions/Maturities of power bonds 0 1,000      
Total          
Debt Instrument          
Debt Securities Issues 992 484      
880591EY4          
Debt Instrument          
Face Amount $ 0 500      
Interest rate 4.25%        
Debt Instrument, Maturity Date Sep. 15, 2052        
Long-term power bonds, net $ 500 500      
880591EX6          
Debt Instrument          
Interest rate 1.50%        
Debt Instrument, Maturity Date Sep. 15, 2031        
Long-term power bonds, net $ 500 500      
880591EZ1          
Debt Instrument          
Interest rate 3.875%        
Debt Instrument, Maturity Date Mar. 15, 2028        
Long-term power bonds, net $ 1,000 $ 0      
v3.23.3
Debt and Other Obligations Debt and Other Obligations - Debt Outstanding (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Jan. 17, 2012
Short-term debt      
Coupon rate     7.10%
Short-term debt, net of discounts $ 432 $ 1,172  
Current maturities of long-term debt of variable interest entities issued at par 35 39  
Total Current maturities of power bonds issued at par 1,022 29  
Current maturities of power bonds 1,022 29  
Total current debt outstanding, net 1,489 1,240  
Long-term debt      
Long-term power bonds, net 17,844 17,826  
Long-term power bonds [1] 17,970 17,950  
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net (126) (124)  
Long-term debt of variable interest entities, net 933 968  
Total long-term debt, net $ 18,777 18,794  
880591DX7      
Short-term debt      
Coupon rate 4.65%    
Debt Instrument, Maturity Date Jun. 15, 2035    
Long-term debt      
Long-term power bonds, net $ 436 436  
880591EF5      
Short-term debt      
Coupon rate 3.77%    
Debt Instrument, Maturity Date Jun. 15, 2034    
Long-term debt      
Long-term power bonds, net $ 139 160  
880591ER9      
Short-term debt      
Coupon rate 2.875%    
Debt Instrument, Maturity Date Sep. 15, 2024    
Long-term debt      
Long-term power bonds, net $ 0 1,000  
880591CJ9      
Short-term debt      
Coupon rate 6.75%    
Debt Instrument, Maturity Date Nov. 01, 2025    
Long-term debt      
Long-term power bonds, net $ 1,350 1,350  
880591EU2 [Member]      
Short-term debt      
Coupon rate 2.875%    
Debt Instrument, Maturity Date Feb. 01, 2027    
Long-term debt      
Long-term power bonds, net $ 1,000 1,000  
880591300      
Short-term debt      
Coupon rate 2.134%    
Debt Instrument, Maturity Date Jun. 01, 2028    
Long-term debt      
Long-term power bonds, net $ 256 256  
880591409      
Short-term debt      
Coupon rate 2.216%    
Debt Instrument, Maturity Date May 01, 2029    
Long-term debt      
Long-term power bonds, net $ 208 208  
880591DM1      
Short-term debt      
Coupon rate 7.125%    
Debt Instrument, Maturity Date May 01, 2030    
Long-term debt      
Long-term power bonds, net $ 1,000 1,000  
880591DV1      
Short-term debt      
Coupon rate 4.70%    
Debt Instrument, Maturity Date Jul. 15, 2033    
Long-term debt      
Long-term power bonds, net $ 472 472  
880591DP4      
Short-term debt      
Coupon rate 6.587%    
Debt Instrument, Maturity Date Jun. 07, 2032    
Long-term debt      
Long-term power bonds, net $ 305 279  
880591CK6      
Short-term debt      
Coupon rate 5.98%    
Debt Instrument, Maturity Date Apr. 01, 2036    
Long-term debt      
Long-term power bonds, net $ 121 121  
880591CS9      
Short-term debt      
Coupon rate 5.88%    
Debt Instrument, Maturity Date Apr. 01, 2036    
Long-term debt      
Long-term power bonds, net $ 1,500 1,500  
880591CP5      
Short-term debt      
Coupon rate 6.15%    
Debt Instrument, Maturity Date Jan. 15, 2038    
Long-term debt      
Long-term power bonds, net $ 1,000 1,000  
880591ED0      
Short-term debt      
Coupon rate 5.50%    
Debt Instrument, Maturity Date Jun. 15, 2038    
Long-term debt      
Long-term power bonds, net $ 500 500  
880591EH1      
Short-term debt      
Coupon rate 5.25%    
Debt Instrument, Maturity Date Sep. 15, 2039    
Long-term debt      
Long-term power bonds, net $ 2,000 2,000  
880591EP3      
Short-term debt      
Coupon rate 3.50%    
Debt Instrument, Maturity Date Dec. 15, 2042    
Long-term debt      
Long-term power bonds, net $ 1,000 1,000  
880591DU3      
Short-term debt      
Coupon rate 4.962%    
Debt Instrument, Maturity Date Jun. 07, 2043    
Long-term debt      
Long-term power bonds, net $ 183 168  
880591EB4      
Short-term debt      
Coupon rate 4.875%    
Debt Instrument, Maturity Date Jan. 15, 2048    
Long-term debt      
Long-term power bonds, net $ 500 500  
880591DZ2      
Short-term debt      
Coupon rate 5.375%    
Debt Instrument, Maturity Date Apr. 01, 2056    
Long-term debt      
Long-term power bonds, net $ 1,000 1,000  
880591EJ7      
Short-term debt      
Coupon rate 4.625%    
Debt Instrument, Maturity Date Sep. 15, 2060    
Long-term debt      
Long-term power bonds, net $ 1,000 1,000  
880591ES7      
Short-term debt      
Coupon rate 4.25%    
Debt Instrument, Maturity Date Sep. 15, 2065    
Long-term debt      
Long-term power bonds, net $ 1,000 1,000  
880591EW8 [Member]      
Short-term debt      
Coupon rate 0.75%    
Debt Instrument, Maturity Date May 15, 2025    
Long-term debt      
Long-term power bonds, net $ 1,000 1,000  
880591EX6      
Short-term debt      
Coupon rate 1.50%    
Debt Instrument, Maturity Date Sep. 15, 2031    
Long-term debt      
Long-term power bonds, net $ 500 500  
880591EY4      
Short-term debt      
Coupon rate 4.25%    
Debt Instrument, Maturity Date Sep. 15, 2052    
Long-term debt      
Long-term power bonds, net $ 500 500  
880591EZ1      
Short-term debt      
Coupon rate 3.875%    
Debt Instrument, Maturity Date Mar. 15, 2028    
Long-term debt      
Long-term power bonds, net $ 1,000 $ 0  
[1] Includes total net exchange gain from currency transactions of $109 million and $150 million at September 30, 2023 and 2022
v3.23.3
Debt and Other Obligations Debt and Other Obligations - Maturities Due (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2029
Sep. 30, 2028
Sep. 30, 2027
Sep. 30, 2026
Sep. 30, 2025
Debt Instrument              
2018 $ 1,022            
2019 1,022            
2020 1,370            
2021 1,020            
2022 1,272            
Thereafter 13,395            
Total 19,101            
Short-Term Debt 432 $ 1,172          
Net discount on sale of Bonds 85            
Foreign Currency Transaction Gain (Loss), Unrealized 109 150          
Short-term Borrowings Gross 432 $ 1,173          
Short-Term Debt              
Debt Instrument              
Debt issuance costs 1            
Scenario, Forecast              
Debt Instrument              
Short-Term Debt     $ 0 $ 0 $ 0 $ 0 $ 0
Power bonds              
Debt Instrument              
Debt issuance costs $ 41            
v3.23.3
Debt and Other Obligations Debt and Other Obligations - Credit Facility Agreements (Details)
Sep. 30, 2023
USD ($)
Credit_facilities
Sep. 30, 2022
USD ($)
Credit Facility Agreements    
Amount of letters of credit outstanding $ 6,000,000  
Letters of Credit Outstanding, Amount 3 99,000,000  
Letter of Credit Outstanding, Amount 2 96,000,000  
Long-term Line of Credit, Borrowings 3 0  
Long-term Line of Credit, Borrowings 2 0  
Borrowings under U.S. Treasury credit facility 0  
Revolving Credit Facilities    
Credit Facility Agreements    
Current borrowing capacity 2,650,000,000  
Credit facility agreements borrowings outstanding $ 0  
Number of revolving credit facilities | Credit_facilities 4  
Revolving Credit Facility 4 $ 150,000,000  
Revolving credit facility 3 1,000,000,000  
Revolving credit facility 1 500,000,000  
Revolving Credit Facility 2 1,000,000,000  
Long-term Line of Credit, Borrowings 4 0  
Long-term Line of Credit, Borrowings 1 0  
Line of Credit Facility, Remaining Borrowing Capacity 4 904,000,000  
Line of Credit Facility, Remaining Borrowing Capacity 2 112,000,000  
Line of Credit Facility, Remaining Borrowing Capacity 3 198,000,000  
Line of Credit Facility, Remaining Borrowing Capacity 1 901,000,000  
Line of Credit Facility, Remaining Borrowing Capacity 2,115,000,000  
Letter of Credit    
Credit Facility Agreements    
Amount of letters of credit outstanding 535,000,000 $ 704,000,000
Letters of Credit Outstanding, Amount 4 38,000,000  
Letters of Credit Outstanding, Amount 1 $ 302,000,000  
v3.23.3
Debt and Other Obligations Debt and Other Obligations - Lease/Leasebacks (Details) - USD ($)
$ in Millions
 12 Months Ended 348 Months Ended
Sep. 30, 2053
Sep. 30, 2023
Sep. 30, 2052
Lagoon Creek [Member]      
Sale Leaseback Transaction [Line Items]      
Amortization of reacquired rights   $ 3  
Lagoon Creek [Member] | Scenario, Forecast      
Sale Leaseback Transaction [Line Items]      
Amortization of reacquired rights $ 2   $ 5
Kemper/Lagoon Creek Leasehold Interests      
Sale Leaseback Transaction [Line Items]      
Leasehold Interests   155  
Lagoon Creek [Member]      
Sale Leaseback Transaction [Line Items]      
Leasehold Interests   78  
Kemper [Member]      
Sale Leaseback Transaction [Line Items]      
Leasehold Interests   $ 77  
v3.23.3
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Derivative Instruments That Receive Hedge Accounting Treatment (Details) - USD ($)
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Summary of Derivative Instruments That Receive Hedge Accounting Treatment      
Interest rate swaps $ 662,000,000 $ 905,000,000  
Ineffective portion excluded from testing 0    
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred 20,000,000    
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax 42,000,000 (93,000,000) $ 97,000,000
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax $ 99,000,000 $ (157,000,000) $ 126,000,000
v3.23.3
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Derivative Instruments That Do Not Receive Hedge Accounting Treatment (Details)
 12 Months Ended
Sep. 30, 2023
USD ($)
Sep. 30, 2022
USD ($)
Derivative    
Change in Unrealized gains (losses) on Interest Rate Derivatives $ (240,000,000) $ (728,000,000)
Fair value 52,000,000 1,000,000
Interest rate swaps 662,000,000 $ 905,000,000
Unrealized gains/losses on derivatives $ 0  
Commodity Contract Derivatives    
Derivative    
Number of contracts 54 44
Notional amount 318,000,000 296,000,000
Fair value $ 31,000,000 $ 145,000,000
Commodity Contract under FHP    
Derivative    
Number of contracts 221 225
Notional amount 388 256
Fair value $ (186,000,000) $ 115,000,000
Commodity Contract under FHP | Fuel Expense    
Derivative    
Unrealized gains/losses on derivatives 301,000,000 38,000,000
Commodity Contract under FHP | Purchased Power Expense    
Derivative    
Unrealized gains/losses on derivatives 47,000,000 9,000,000
Accounts payable and accrued liabilities | Commodity Contract Derivatives    
Derivative    
Fair value (1,000,000) (6,000,000)
Accounts payable and accrued liabilities | Commodity Contract under FHP    
Derivative    
Fair value (135,000,000) (8,000,000)
Other Regulatory Assets (Liabilities) | Interest Rate Swap    
Derivative    
Unrealized gains/losses on derivatives (45,000,000) (103,000,000)
Other Regulatory Assets (Liabilities) | Commodity Contract under FHP    
Derivative    
Unrealized gains/losses on derivatives $ (348,000,000) $ 47,000,000
v3.23.3
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Mark-to-Market Values of TVA Derivatives (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Derivatives, Fair Value    
Amount of letters of credit outstanding $ 6  
Fair value 52 $ 1
250 million Sterling currency swap    
Derivatives, Fair Value    
Fair value (72) (130)
250 million Sterling currency swap | Other long-term liabilities    
Derivatives, Fair Value    
Fair value (66) (123)
250 million Sterling currency swap | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value (6) (7)
150 million Sterling currency swap    
Derivatives, Fair Value    
Fair value (69) (110)
150 million Sterling currency swap | Other long-term liabilities    
Derivatives, Fair Value    
Fair value (65) (105)
150 million Sterling currency swap | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value (4) (5)
$1.0 billion notional interest rate swap    
Derivatives, Fair Value    
Fair value (499) (672)
$1.0 billion notional interest rate swap | Other long-term liabilities    
Derivatives, Fair Value    
Fair value (473) (630)
$1.0 billion notional interest rate swap | Other current assets    
Derivatives, Fair Value    
Fair value 1  
$1.0 billion notional interest rate swap | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value   (9)
$1.0 billion notional interest rate swap | Interest payable, current    
Derivatives, Fair Value    
Fair value (27) (33)
Commodity contract derivatives    
Derivatives, Fair Value    
Fair value 31 145
Commodity contract derivatives | Other Noncurrent Assets [Member]    
Derivatives, Fair Value    
Fair value 12 34
Commodity contract derivatives | Other long-term liabilities    
Derivatives, Fair Value    
Fair value (1) (1)
Commodity contract derivatives | Other current assets    
Derivatives, Fair Value    
Fair value 21 118
Commodity contract derivatives | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value (1) (6)
$14 million notional    
Derivatives, Fair Value    
Fair value (159) (233)
$14 million notional | Other long-term liabilities    
Derivatives, Fair Value    
Fair value (154) (221)
$14 million notional | Other current assets    
Derivatives, Fair Value    
Fair value 3  
$14 million notional | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value   (3)
$14 million notional | Interest payable, current    
Derivatives, Fair Value    
Fair value (8) (9)
Commodity Contract under FHP    
Derivatives, Fair Value    
Derivative Liability, Fair Value, Gross Liability 212  
Fair value (186) 115
Commodity Contract under FHP | Other Noncurrent Assets [Member]    
Derivatives, Fair Value    
Fair value   68
Commodity Contract under FHP | Other long-term liabilities    
Derivatives, Fair Value    
Fair value (51)  
Commodity Contract under FHP | Other current assets    
Derivatives, Fair Value    
Fair value   54
Commodity Contract under FHP | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value $ (135) (8)
Commodity Contract under FHP | Accounts Receivable [Member]    
Derivatives, Fair Value    
Fair value   $ 1
v3.23.3
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Currency Swaps Outstanding (Details)
£ in Millions
Sep. 30, 2023
GBP (£)
250 million Sterling currency swap  
Derivative  
Effective Date of Currency Swap Contract 2001
Associated TVA bond issues currency exposure £ 250
Expiration Date of Swap 2032
Overall effective cost to TVA 6.587%
150 million Sterling currency swap  
Derivative  
Effective Date of Currency Swap Contract 2003
Associated TVA bond issues currency exposure £ 150
Expiration Date of Swap 2043
Overall effective cost to TVA 4.962%
v3.23.3
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Derivatives Under Financial Trading Program (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Derivative    
Unrealized gains (losses) deferred as regulatory liabilities (assets) $ 52 $ 1
v3.23.3
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Counterparty Credit Risk (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
Customers
Sep. 30, 2022
USD ($)
Derivative    
Receivables from power sales | $ $ 1,627 $ 1,899
Credit of Customers    
Derivative    
Number of customers that represent the percent of sales | Customers 2  
v3.23.3
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Offsetting of Derivative Assets (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Offsetting Assets [Line Items]    
Amount of letters of credit outstanding $ 6  
Letter of Credit    
Offsetting Assets [Line Items]    
Amount of letters of credit outstanding 535 $ 704
Commodity Contract under FHP    
Offsetting Assets [Line Items]    
Gross Amounts of Recognized Assets, subject to master netting or similar arrangements $ 26  
v3.23.3
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Offsetting of Derivative Liabilities (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Offsetting Liabilities [Line Items]    
Gross Amounts Offset in the Balance Sheet $ 26  
Amount of letters of credit outstanding 6  
Derivative Liability, Subject to Master Netting Arrangement, after Offset 991 $ 1,160
Derivative Asset, Subject to Master Netting Arrangement, after Offset 37 275
Commodity contract derivatives 33 152
Currency Swap    
Offsetting Liabilities [Line Items]    
Derivative Liability, Subject to Master Netting Arrangement, after Offset 141 240
Commodity Contract under FHP    
Offsetting Liabilities [Line Items]    
Gross Amounts of Recognized Liabilities, subject to master netting or similar arrangements 212  
Derivative Liability, Subject to Master Netting Arrangement, after Offset 186 8
Derivative Asset, Subject to Master Netting Arrangement, after Offset 0 123
Interest Rate Swap    
Offsetting Liabilities [Line Items]    
Derivative Liability, Subject to Master Netting Arrangement, after Offset 662 905
Derivative Asset, Subject to Master Netting Arrangement, after Offset 4 0
Commodity Contract Derivatives    
Offsetting Liabilities [Line Items]    
Derivative Liability, Subject to Master Netting Arrangement, after Offset 2 7
Derivative Asset, Subject to Master Netting Arrangement, after Offset 33 152
Letter of Credit    
Offsetting Liabilities [Line Items]    
Amount of letters of credit outstanding $ 535 $ 704
v3.23.3
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Other Derivative Instruments (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Derivative    
Forward Contract Derivative Asset, at Fair Value $ 11 $ 4
Derivative Liability, Subject to Master Netting Arrangement, after Offset 991 1,160
Fair Value, Inputs, Level 2    
Derivative    
Forward Contract Derivative Asset, at Fair Value $ 11 $ 4
v3.23.3
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Collateral (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Derivative    
Amount of letters of credit outstanding $ 6  
Likely collateral obligation increase if downgraded 22  
Derivative Liability, Subject to Master Netting Arrangement, after Offset 991 $ 1,160
Collateralized Securities [Member]    
Derivative    
Collateral obligations 429  
Credit Risk    
Derivative    
Derivative Liability, Subject to Master Netting Arrangement, after Offset 987  
Letter of Credit    
Derivative    
Amount of letters of credit outstanding 535 $ 704
Interest swap collateral    
Derivative    
Amount of letters of credit outstanding $ 509  
v3.23.3
Risk Management Activities and Derivative Transactions Counterparty Credit Risk (Details)
 12 Months Ended
Sep. 30, 2023
Derivative  
Two Largest Customer Percentage of Total Operating Revenue 17.00%
Moody's, A1 Rating  
Derivative  
Natural Gas Banking Counterparties Credit Rating A1
Moody's, B1 Rating  
Derivative  
Natural Gas Banking Counterparties Credit Rating B1
Moody's, A2 Rating  
Derivative  
Banking Counterparties Credit Rating A2
v3.23.3
Risk Management Activities and Derivative Transactions (Details) - Commodity Derivatives Under the FHP
$ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Increase (Decrease) in Derivative Assets $ 301
v3.23.3
Fair Value Measurements - Investments (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
Units
Sep. 30, 2022
USD ($)
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Long-term Investments $ 4,123 $ 3,671
Period of time where the investor contributes capital to an investment in a private partnership - minimum | Units 3  
Period of time where the investor contributes capital to an investment in a private partnership - maximum | Units 4  
Minimum investment period 10 years  
Fair value of gross plan assets $ 8,605 8,566
Number of readily available quoted exchange prices for the investments 0  
NDT    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Long-term Investments $ 2,800  
ART    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Long-term Investments 1,200  
LTDCP    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) on investments 1 (5)
SERP    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) on investments 6 (19)
ART    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) on investments 96 (190)
Debt and Equity Securities, Unrealized Gain (Loss) 13 (44)
NDT    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) on investments 162 (396)
Debt and Equity Securities, Unrealized Gain (Loss) 27 $ (138)
Equity Funds [Member] | NDT    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Commitments, Fair Value Disclosure 237  
Real Estate Funds [Member] | NDT    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Commitments, Fair Value Disclosure 123  
Credit [Member] | NDT    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Commitments, Fair Value Disclosure 81  
Defensive growth assets | ART    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Commitments, Fair Value Disclosure 124  
Private real estate funds | ART    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Commitments, Fair Value Disclosure 60  
Private Credit [Member] | ART    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Commitments, Fair Value Disclosure 43  
RP    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Debt and Equity Securities, Unrealized Gain (Loss) $ 1  
v3.23.3
Fair Value Measurements - Nonperformance Risk (Details)
$ in Millions
Sep. 30, 2023
USD ($)
Nonperformance Risk  
Derivative credit valuation adjustment, assets $ 1
Derivative credit valuation adjustment, liabilities $ 1
v3.23.3
Fair Value Measurements - Fair Value Measurements (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value $ 52 $ 1
Investments    
Government debt securities 347 332
Corporate debt securities 300 282
Mortgage and asset-backed securities 36 52
Institutional mutual funds 288 242
Forward debt securities contracts - asset 11 4
Cash, Cash Equivalents, and Short-term Investments 270 179
Private equity funds measured at net asset value 583 487
Private real estate measured at net asset value 387 369
Private credit measured at net asset value 158 103
Commingled funds measured at net asset value 1,135 1,087
Total investments 4,123 3,671
Interest Rate Derivative Assets, at Fair Value 4  
Commodity contract derivatives 33 152
Total 4,160 3,946
Liabilities    
Currency swaps 141 240 [1]
Interest rate swaps 662 905
Commodity contract derivatives 2 7
Total 991 1,160
Equity Securities, FV-NI, Noncurrent 608 534
Derivative Liability, Subject to Master Netting Arrangement, after Offset 991 1,160
Derivative Asset, Subject to Master Netting Arrangement, after Offset 37 275
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Cash, Cash Equivalents, and Short-term Investments 270 179
Government debt securities reclassed   1
Corporate debt securities reclassed   1
Commingled funds reclassed   116
Commodity Contract under FHP    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value (186) 115
Liabilities    
Derivative Liability, Subject to Master Netting Arrangement, after Offset 186 8
Derivative Asset, Subject to Master Netting Arrangement, after Offset 0 123
Fair Value, Inputs, Level 1    
Investments    
Government debt securities 287 297
Corporate debt securities 0 0
Mortgage and asset-backed securities 0 0
Institutional mutual funds 288 242
Forward debt securities contracts - asset 0 0
Cash, Cash Equivalents, and Short-term Investments 104 61
Private equity funds measured at net asset value 0 0
Private real estate measured at net asset value 0 0
Private credit measured at net asset value 0 0
Commingled funds measured at net asset value 0 0
Total investments 1,287 1,134
Interest Rate Derivative Assets, at Fair Value 0  
Commodity contract derivatives 0 0
Total 1,287 1,134
Liabilities    
Currency swaps 0 0
Interest rate swaps 0 0
Commodity contract derivatives 0 0
Total 0 0
Equity Securities, FV-NI, Noncurrent 608 534
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Cash, Cash Equivalents, and Short-term Investments 104 61
Fair Value, Inputs, Level 1 | Commodity Contract under FHP    
Liabilities    
Derivative Liability, Subject to Master Netting Arrangement, after Offset 0 0
Derivative Asset, Subject to Master Netting Arrangement, after Offset   0
Fair Value, Inputs, Level 2    
Investments    
Government debt securities 60 35
Corporate debt securities 300 282
Mortgage and asset-backed securities 36 52
Institutional mutual funds 0 0
Forward debt securities contracts - asset 11 4
Cash, Cash Equivalents, and Short-term Investments 166 118
Private equity funds measured at net asset value 0 0
Private real estate measured at net asset value 0 0
Private credit measured at net asset value 0 0
Commingled funds measured at net asset value 0 0
Total investments 573 491
Interest Rate Derivative Assets, at Fair Value 4  
Commodity contract derivatives 33 152
Total 610 766
Liabilities    
Currency swaps 141 240
Interest rate swaps 662 905
Commodity contract derivatives 2 7
Total 991 1,160
Equity Securities, FV-NI, Noncurrent 0 0
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Cash, Cash Equivalents, and Short-term Investments 166 118
Fair Value, Inputs, Level 2 | Commodity Contract under FHP    
Liabilities    
Derivative Liability, Subject to Master Netting Arrangement, after Offset 186 8
Derivative Asset, Subject to Master Netting Arrangement, after Offset   123
Fair Value, Inputs, Level 3    
Investments    
Government debt securities 0 0
Corporate debt securities 0 0
Mortgage and asset-backed securities 0 0
Institutional mutual funds 0 0
Forward debt securities contracts - asset 0 0
Cash, Cash Equivalents, and Short-term Investments 0 0
Private equity funds measured at net asset value 0 0
Private real estate measured at net asset value 0 0
Private credit measured at net asset value 0 0
Commingled funds measured at net asset value 0 0
Total investments 0 0
Interest Rate Derivative Assets, at Fair Value 0  
Commodity contract derivatives 0 0
Total 0 0
Liabilities    
Currency swaps 0 0
Interest rate swaps 0 0
Commodity contract derivatives 0 0
Total 0 0
Equity Securities, FV-NI, Noncurrent 0 0
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Cash, Cash Equivalents, and Short-term Investments 0 0
Fair Value, Inputs, Level 3 | Commodity Contract under FHP    
Liabilities    
Derivative Liability, Subject to Master Netting Arrangement, after Offset $ 0 0
Derivative Asset, Subject to Master Netting Arrangement, after Offset   $ 0
[1] See Note 15 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.
v3.23.3
Fair Value Measurements - Fair Value Measurements Using Significant Unobservable Inputs (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Fair Value Measurements    
Commodity contract derivatives, assets $ 33 $ 152
Commodity contract derivatives, liabilities 2 7
Fair Value, Inputs, Level 3    
Fair Value Measurements    
Commodity contract derivatives, assets 0 0
Commodity contract derivatives, liabilities $ 0 $ 0
v3.23.3
Fair Value Measurements - Estimated Values of Financial Instruments (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Estimated Values of Financial Instruments (Level 2 Valuation)    
EnergyRight receivables (including current portion) $ 55 $ 62
Financing Receivable, after Allowance for Credit Loss 96 96
EnergyRight® financing obligations (including current portion) 81 81
Unfunded Loan Commitments 1 0
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount 19 22
Long-term outstanding power bonds (including current maturities), net 17,963 18,070
Long-term debt of variable interest entities (including current maturities) 927 989
Portion at Other than Fair Value Measurement [Member]    
Estimated Values of Financial Instruments (Level 2 Valuation)    
EnergyRight receivables (including current portion) 59 62
Financing Receivable, after Allowance for Credit Loss 104 105
EnergyRight® financing obligations (including current portion) 69 72
Unfunded Loan Commitments 0 0
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount 18 20
Long-term outstanding power bonds (including current maturities), net 18,866 17,856
Long-term debt of variable interest entities (including current maturities) $ 968 $ 1,007
v3.23.3
Proprietary Capital (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Appropriation Investment      
Amount of appropriation investment that was repaid $ 1,000    
Balance at beginning of year 15,505 $ 14,465 $ 12,932
Net income (loss) 500 1,108 1,512
Return on power program appropriation investment (6) (4) (4)
Balance at end of year 16,056 15,505 $ 14,465
Net proprietary capital at September 30 $ 16,056 $ 15,505  
Computed average interest rate payable 1.99% 1.47% 1.64%
Power Program Appropriation Investment      
Appropriation Investment      
Balance at beginning of year $ 258 $ 258 $ 258
Net income (loss) 0 0 0
Return on power program appropriation investment 0 0 0
Balance at end of year 258 258 258
New Accounting Standard - CECL     0
Power Program Retained Earnings      
Appropriation Investment      
Balance at beginning of year 14,800 13,689 12,177
Net income (loss) 508 1,115 1,520
Return on power program appropriation investment (6) (4) (4)
Balance at end of year 15,302 14,800 13,689
New Accounting Standard - CECL     (4)
Nonpower Programs Appropriation Investment, Net      
Appropriation Investment      
Balance at beginning of year 533 540 548
Net income (loss) (8) (7) (8)
Return on power program appropriation investment 0 0 0
Balance at end of year 525 533 540
New Accounting Standard - CECL     0
Affiliated Entity      
Appropriation Investment      
Return on power program appropriation investment $ (6) $ (4) $ (4)
v3.23.3
Proprietary Capital - Accumulated Other Comprehensive Income (Loss) (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
Accumulated Other Comprehensive Income (Loss)  
Reclassification to earnings from cash flow hedges in the next twelve months $ (20)
v3.23.3
Other Income (Expense), Net Other Income (Expense), Net (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Other Income (Expense), Net      
Interest income $ 34 $ 15 $ 12
External services 15 16 13
Gain (Loss) on Investments 13 (17) 16
Miscellaneous (1) (7) 0
Other income (expense), net 61 7 13
Sale of Bellefonte $ 0 $ 0 $ (28)
v3.23.3
Benefit Plans Components of Benefit Plans (Details) - USD ($)
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Defined Benefit Plan Disclosure      
Fixed and variable fund annual maximum contribution $ 10,000    
Defined contribution plan contribution amount $ 105,000,000 $ 97,000,000 $ 92,000,000
Minimum      
Defined Benefit Plan Disclosure      
Threshold for Deferral of Actuarial Gain/Loss Under Corridor Approach 10.00%    
v3.23.3
Benefit Plans Obligations and Funded Status (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Pension Benefits      
Change in benefit obligation      
Benefit obligation $ 10,536 $ 13,348  
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation 10,099 10,536  
Service cost 32 53 $ 57
Plan participants' contributions 4 5  
Change in Plan Assets due to Collections 0 0  
Collections [1] 0 0  
Actuarial loss (gain) 284 (2,509)  
Net transfers from variable fund/401(k) plan 4 11  
Expenses paid (7) (6)  
Benefits paid 754 744  
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets 8,129 8,094  
Change in plan assets      
Fair value of net plan assets 8,094 9,110  
Actual return on plan assets 482 (590)  
Employer contributions 306 308  
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]      
Funded status $ (1,970) $ (2,442)  
Discount rate 5.95% 5.60% 2.90%
Amount of defined benefit plan actuarial gain (loss) from discount rate change $ (334) $ (3,500)  
Amount of defined benefit plan actuarial gain (loss) from change in mortality assumption (61) (78)  
Amount of defined benefit plan actuarial gain (loss) from change in demograhic and plan experience 12 527  
Amount of defined benefit plan actuarial gain (loss) from assumption change in elections   411  
Other Post-retirement Benefits      
Change in benefit obligation      
Benefit obligation 347 388  
Postconfirmation, Other Postretirement Obligations 388 498  
Service cost 10 17 $ 18
Plan participants' contributions 0 0  
Change in Plan Assets due to Collections 13 15  
Collections [1] 13 15  
Actuarial loss (gain) 44 114  
Net transfers from variable fund/401(k) plan 0 0  
Expenses paid 0 0  
Benefits paid 38 43  
Actuarial Gain (Loss) from Changes in Discount Rate 17 168  
Actuarial Gain (Loss) Reflecting Plan Experience for Contribution Costs 27    
Actuarial Gain (Loss) from Delaying post-Medicare Trend Rate Assumption   31  
Actuarial Gain (Loss) from pre-Medicare Trend Rate Assumptions   67  
Actuarial Gain (Loss) from Changes in Mortality Assumptions   18  
Change in plan assets      
Fair value of net plan assets 0 0  
Actual return on plan assets 0 0  
Employer contributions 25 28  
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]      
Funded status $ (347) $ (388)  
Discount rate 6.05% 5.65% 305.00%
[1] Collections include retiree contributions as well as provider discounts and rebates.
v3.23.3
Benefit Plans Amounts Recognized on TVA's Consolidated Balance Sheets (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Defined Benefit Plan Disclosure      
Regulatory assets $ (5,566) $ (6,134)  
Non-current regulatory liabilities (107) (172)  
Accounts payable and accrued liabilities (2,618) (2,466)  
Pension and post-retirement benefit obligations (2,527) (3,072)  
Postemployment benefits liability, noncurrent 266 299  
Pension Benefits      
Defined Benefit Plan Disclosure      
Amount capitalized due to actions of regulator 0 77  
Regulatory assets (1,440) (1,839)  
Accounts payable and accrued liabilities (6) (6)  
Pension and post-retirement benefit obligations [1] (1,964) (2,436)  
Other Post-retirement Benefits      
Defined Benefit Plan Disclosure      
Amount capitalized due to actions of regulator 0 0  
Regulatory assets (95) (70)  
Non-current regulatory liabilities (95)    
Accounts payable and accrued liabilities (21) (22)  
Pension and post-retirement benefit obligations [1] (326) (366)  
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent      
Defined Benefit Plan Disclosure      
Postemployment benefits liability, noncurrent $ 237 $ 270 $ 340
[1] The table above excludes $237 million and $270 million of post-employment benefit costs that are recorded in Post-retirement and post-employment benefit obligations on the Consolidated Balance Sheets at September 30, 2023 and 2022, respectively.
v3.23.3
Benefit Plans Postretirement Benefit Costs Deferred as Regulatory Assets (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Defined Benefit Plan Disclosure    
Regulatory assets $ (5,566) $ (6,134)
Non-current regulatory liabilities 107 172
Pension Benefits    
Defined Benefit Plan Disclosure    
Unrecognized prior service cost (credit) (336) (424)
Unrecognized net loss 1,776 2,186
Amount capitalized due to actions of regulator 0 (77)
Regulatory assets (1,440) (1,839)
Other Post-retirement Benefits    
Defined Benefit Plan Disclosure    
Unrecognized prior service cost (credit) (59) (76)
Unrecognized net loss (36) 6
Amount capitalized due to actions of regulator 0 0
Regulatory assets (95) $ (70)
Non-current regulatory liabilities $ 95  
v3.23.3
Benefit Plans Projected Benefit Obligations and Accumulated Benefit Obligations in Exess of Plan Assets (Details) - Pension Benefits - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Defined Benefit Plan Disclosure    
Accumulated benefit obligation $ 10,069 $ 10,508
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets 8,129 8,094
Fair value of net plan assets $ 8,094 $ 9,110
v3.23.3
Benefit Plans Components of Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Pension Benefits      
Defined Benefit Plan Disclosure      
Service cost $ 32 $ 53 $ 57
DefinedBenefitPlanNetPeriodicBenefitCostCreditInterestCostStatementOfIncome 568 378 368
DefinedBenefitPlanNetPeriodicBenefitCostCreditExpectedReturnLossStatementOfIncome (492) (435) (493)
DefinedBenefitPlanNetPeriodicBenefitCostCreditAmortizationOfPriorServiceCostCreditStatementOfIncome (88) (93) (97)
DefinedBenefitPlanNetPeriodicBenefitCostCreditAmortizationOfGainLossStatementOfIncome 135 392 452
Net periodic benefit cost as acutarially determined 155 295 287
Amount expensed due to actions of regulator (77) (13) (19)
Total net period benefit cost 232 308 306
Other Post-retirement Benefits      
Defined Benefit Plan Disclosure      
Service cost 10 17 18
DefinedBenefitPlanNetPeriodicBenefitCostCreditInterestCostStatementOfIncome 18 15 16
Expected return on plan assets 0 0 0
DefinedBenefitPlanNetPeriodicBenefitCostCreditAmortizationOfPriorServiceCostCreditStatementOfIncome (17) (17) (18)
DefinedBenefitPlanNetPeriodicBenefitCostCreditAmortizationOfGainLossStatementOfIncome (2) (5) (11)
Net periodic benefit cost as acutarially determined 9 20 27
Amount expensed due to actions of regulator 0 0 0
Total net period benefit cost $ 9 $ 20 $ 27
v3.23.3
Benefit Plans Actuarial Assumptions (Details) - USD ($)
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2024
Defined Benefit Plan Disclosure        
Defined Benefit Plan, Cost of Living Adjustment Assumption 0.25%      
Pension Benefits        
Defined Benefit Plan Disclosure        
Discount rate 5.60% 2.90% 2.75%  
Discount rate 5.95% 5.60% 2.90%  
Rate of compensation increase 4.05% 3.32%    
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate 5.13% 5.14%    
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Weighted-Average Interest Crediting Rate 5.14% 5.14% 5.15%  
Expected return on plan assets 6.50% 5.75% 6.75%  
Defined Benefit Plan, Cost of Living Adjustment Assumption 2.00% 2.00% 2.00%  
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase   3.32% 3.37%  
COLA percentage increase (decrease) 6.00%      
Actual Return on Plan Assets 6.13% (6.64%) 20.30%  
Other Post-retirement Benefits        
Defined Benefit Plan Disclosure        
Discount rate 5.65% 3.05% 3.05%  
Discount rate 6.05% 5.65% 305.00%  
Defined Benefit Plan, Cost of Living Adjustment Assumption 2.00% 2.00% 2.00%  
Minimum        
Defined Benefit Plan Disclosure        
Rate of compensation increase 3.00%      
Maximum        
Defined Benefit Plan Disclosure        
Rate of compensation increase 5.50%      
Scenario, Forecast | Pension Benefits        
Defined Benefit Plan Disclosure        
Defined Benefit Plan, Cost of Living Adjustment Assumption Next Fiscal Year       4.05%
Post-Medicare Eligible [Member] [Member] | Other Post-retirement Benefits        
Defined Benefit Plan Disclosure        
Current health care cost trend rate 0.00% 0.00% 0.00%  
Ultimate health care cost trend rate 4.00% 4.00% 4.00%  
Year health care cost ultimate trend rate is reached for Net Benefit Cost Assumption 2026 2024 2024  
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate 2026 2026    
Pre-Medicare Eligible per Capita Claim Costs | Other Post-retirement Benefits        
Defined Benefit Plan Disclosure        
Current health care cost trend rate 7.00% 6.25% 6.50%  
Ultimate health care cost trend rate 5.00% 5.00% 5.00%  
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate 2034 2031 2027  
Initial health care cost trend rate $ 0.0750 $ 0.0700    
Defined Benefit Plan, Year ultimate trend rate is reached for net periodic benefit 2031 2027    
Pre-Medicare Eligible per Capita Contributions | Other Post-retirement Benefits        
Defined Benefit Plan Disclosure        
Current health care cost trend rate 5.00% 8.51% 11.93%  
Ultimate health care cost trend rate 5.00% 5.00% 5.00%  
Defined Benefit Plan, Year ultimate trend rate is reached per capita contributions   2027    
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate 2022 2022 2027  
Initial health care cost trend rate $ 0.0500 $ 0.0500    
v3.23.3
Benefit Plans Sensitivity to Certain Changes in Pension Assumptions (Details) - USD ($)
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Defined Benefit Plan Disclosure      
Defined Benefit Plan, Cost of Living Adjustment Assumption 0.25%    
Discount rate      
Defined Benefit Plan Disclosure      
Change in Assumption (0.25%)    
Impact on Pension Cost $ 12,000,000    
Impact on Projected Benefit Obligation $ 236,000,000    
Rate of return on plan assets      
Defined Benefit Plan Disclosure      
Change in Assumption (0.25%)    
Impact on Pension Cost $ 19,000,000    
Cost of Living Adjustments [Domain]      
Defined Benefit Plan Disclosure      
Change in Assumption 0.25%    
Impact on Pension Cost $ 24,000,000    
Impact on Projected Benefit Obligation $ 165,000,000    
Other Post-retirement Benefits      
Defined Benefit Plan Disclosure      
Defined Benefit Plan, Cost of Living Adjustment Assumption 2.00% 2.00% 2.00%
Discount rate 6.05% 5.65% 305.00%
Actuarial assumption COLA $ 0.06 $ 0.035 $ 0.0113
Pension Benefits      
Defined Benefit Plan Disclosure      
Defined Benefit Plan, Cost of Living Adjustment Assumption 2.00% 2.00% 2.00%
COLA percentage increase (decrease) 6.00%    
Discount rate 5.95% 5.60% 2.90%
v3.23.3
Benefit Plans Asset Holdings (Details) - USD ($)
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Defined Benefit Plan Disclosure      
Target Allocation 100.00%    
Plan Asset Allocations 100.00% 100.00%  
Growth Assets      
Defined Benefit Plan Disclosure      
Target Allocation 17.00%    
Plan Asset Allocations 22.00% 20.00%  
Defensive growth assets      
Defined Benefit Plan Disclosure      
Target Allocation 30.00%    
Plan Asset Allocations 33.00% 34.00%  
Defensive Assets      
Defined Benefit Plan Disclosure      
Target Allocation 33.00%    
Plan Asset Allocations 17.00% 18.00%  
Inflation-sensitive Assets      
Defined Benefit Plan Disclosure      
Target Allocation 20.00%    
Plan Asset Allocations 28.00% 28.00%  
Other Post-retirement Benefits      
Defined Benefit Plan Disclosure      
Actuarial assumption COLA $ 0.06 $ 0.035 $ 0.0113
v3.23.3
Benefit Plans Fair Value Measurements (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
Years
Sep. 30, 2022
USD ($)
Oct. 01, 2019
USD ($)
Defined Benefit Plan Disclosure      
Fair value of gross plan assets $ 8,605 $ 8,566  
Derivative liabilities 128 176  
Net payables 167 100  
Payables for collateral on loaned securities $ 181 196  
Voting percentage required to desolve partnership in private equity 80.00%    
Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets $ 1,748 1,916  
Derivative liabilities 6 10  
Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 2,167 2,328  
Derivative liabilities 122 166  
Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 60 62 $ 74
Derivative liabilities 0 0  
Equity securities      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 732 709  
Equity securities | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 731 707  
Equity securities | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Equity securities | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 1 2  
Preferred securities      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 4 6  
Preferred securities | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 1  
Preferred securities | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 4 5  
Preferred securities | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Corporate debt securities      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 1,109 1,087  
Corporate debt securities | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Corporate debt securities | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 1,107 1,087  
Corporate debt securities | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 2 0  
Residential mortgage-backed securities      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 330 293  
Residential mortgage-backed securities | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Residential mortgage-backed securities | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 323 289  
Residential mortgage-backed securities | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 7 4  
Debt securities issued by U.S. Treasury and other U.S. government agencies      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 602 616  
Debt securities issued by U.S. Treasury and other U.S. government agencies | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 602 616  
Debt securities issued by U.S. Treasury and other U.S. government agencies | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Debt securities issued by U.S. Treasury and other U.S. government agencies | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Asset-backed securities      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 173 176  
Asset-backed securities | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Asset-backed securities | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 130 136  
Asset-backed securities | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 43 40  
Debt securities issued by state/local governments      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 21 23  
Debt securities issued by state/local governments | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Debt securities issued by state/local governments | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 21 23  
Debt securities issued by state/local governments | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Debt securities issued by foreign governments      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 12 130  
Debt securities issued by foreign governments | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Debt securities issued by foreign governments | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 10 130  
Debt securities issued by foreign governments | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 2 0  
Commercial mortgage-backed securities      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 113 161  
Commercial mortgage-backed securities | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Commercial mortgage-backed securities | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 108 145  
Commercial mortgage-backed securities | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 5 16  
Equity security commingled funds      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 360 436  
Equity security commingled funds | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Equity security commingled funds | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Equity security commingled funds | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Debt security commingled funds      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 544 657  
Debt security commingled funds | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Debt security commingled funds | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Debt security commingled funds | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Blended security commingled funds      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 101 111  
Blended security commingled funds | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Blended security commingled funds | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Blended security commingled funds | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Institutional mutual funds      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 363 454  
Institutional mutual funds | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 363 454  
Institutional mutual funds | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Institutional mutual funds | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Cash equivalents and other short-term investments      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 315 431  
Cash equivalents and other short-term investments | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 51 133  
Cash equivalents and other short-term investments | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 264 298  
Cash equivalents and other short-term investments | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Private Credit [Member]      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 694 522  
Private Credit [Member] | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Private Credit [Member] | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Private Credit [Member] | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Private equity funds measured at net asset value      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 1,769 1,454  
Private equity funds measured at net asset value | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Private equity funds measured at net asset value | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Private equity funds measured at net asset value | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Private real estate funds      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 1,162 1,080  
Private real estate funds | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Private real estate funds | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Private real estate funds | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Securities lending commingled funds      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 181 196  
Securities lending commingled funds | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Securities lending commingled funds | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 181 196  
Securities lending commingled funds | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Futures      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 1 5  
Derivative liabilities 5 10  
Futures | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 1 5  
Derivative liabilities 5 10  
Futures | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Derivative liabilities 0 0  
Futures | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Derivative liabilities 0 0  
Purchased options      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 17 17  
Purchased options | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Purchased options | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 17 17  
Purchased options | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Interest Rate Swap      
Defined Benefit Plan Disclosure      
Derivative liabilities 26 54  
Interest Rate Swap | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Derivative liabilities 0 0  
Interest Rate Swap | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Derivative liabilities 26 54  
Interest Rate Swap | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Derivative liabilities 0 0  
Foreign currency forward      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 2 2  
Derivative liabilities   1  
Foreign currency forward | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Derivative liabilities   0  
Foreign currency forward | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 2 2  
Derivative liabilities   1  
Foreign currency forward | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Derivative liabilities   0  
Credit default swaps      
Defined Benefit Plan Disclosure      
Derivative liabilities 1    
Credit default swaps | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Derivative liabilities 1    
Credit default swaps | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Derivative liabilities 0    
Credit default swaps | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Derivative liabilities 0    
Securities Sold under Agreements to Repurchase [Member]      
Defined Benefit Plan Disclosure      
Derivative liabilities 96 111  
Securities Sold under Agreements to Repurchase [Member] | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Derivative liabilities 0 0  
Securities Sold under Agreements to Repurchase [Member] | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Derivative liabilities 96 111  
Securities Sold under Agreements to Repurchase [Member] | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Derivative liabilities $ 0 $ 0  
Minimum      
Defined Benefit Plan Disclosure      
Number of years partnerships in private equity generally continue | Years 10    
Number of one year extensions for partnerships in private equity | Years 2    
Maximum      
Defined Benefit Plan Disclosure      
Number of years partnerships in private equity generally continue | Years 14    
Number of one year extensions for partnerships in private equity | Years 3    
v3.23.3
Benefit Plans Fair Value Measurements Using Significant Unobservable Inputs (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Oct. 01, 2019
Defined Benefit Plan Disclosure      
Net payables $ 167 $ 100  
Payables for collateral on loaned securities 181 196  
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]      
Fair value of gross plan assets 8,605 8,566  
Fair Value, Inputs, Level 3      
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]      
Fair value of gross plan assets 60 62 $ 74
Net realized/unrealized gains 1 (4)  
Purchases, sales, issuances, and settlements, net 2 2  
Transfers in and/or out of Level 3 (5) $ (10)  
Fair value of net plan assets $ 60    
v3.23.3
Benefit Plans Estimated Future Benefit Payments (Details)
$ in Millions
Sep. 30, 2023
USD ($)
Pension Benefits  
Defined Benefit Plan Disclosure  
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months $ 809
Defined Benefit Plan, Expected Future Benefit Payments, Year Two 814
Defined Benefit Plan, Expected Future Benefit Payments, Year Three 812
Defined Benefit Plan, Expected Future Benefit Payments, Year Four 812
Defined Benefit Plan, Expected Future Benefit Payments, Year Five 809
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter 3,918
Other Post-retirement Benefits  
Defined Benefit Plan Disclosure  
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months 22
Defined Benefit Plan, Expected Future Benefit Payments, Year Two 21
Defined Benefit Plan, Expected Future Benefit Payments, Year Three 21
Defined Benefit Plan, Expected Future Benefit Payments, Year Four 21
Defined Benefit Plan, Expected Future Benefit Payments, Year Five 21
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter $ 119
v3.23.3
Benefit Plans Contributions (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2024
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Defined Benefit Plan Disclosure        
Defined contribution plan contribution amount   $ 105 $ 97 $ 92
Other postretirement benefit contributions   25 28  
Contribution related to TVARS case   4 4  
Supplemental Employee Retirement Plans, Defined Benefit        
Defined Benefit Plan Disclosure        
Defined Benefit Plan, Related to SERP   6 8  
Other Post-retirement Benefits        
Defined Benefit Plan Disclosure        
Employer contributions   25 28  
Pension Benefits        
Defined Benefit Plan Disclosure        
Employer contributions   306 $ 308  
Other Pension Plans, Defined Benefit        
Defined Benefit Plan Disclosure        
Employer contributions   300    
Minimum | Other Pension Plans, Defined Benefit        
Defined Benefit Plan Disclosure        
Employer contributions   $ 300    
Scenario, Forecast | Other Pension Plans, Defined Benefit        
Defined Benefit Plan Disclosure        
Employer contributions $ 300      
v3.23.3
Benefit Plans Other Postemployment Benefits (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2024
Other Post-Employment Benefits        
Discount rate 4.59% 3.83% 1.52%  
Period expense $ (3) $ (40) $ (20)  
Postemployment benefits liability, noncurrent 266 299    
Accounts Payable and Accrued Liabilities        
Other Post-Employment Benefits        
Postemployment Benefits Liability, Current 29 29    
Accounts Payable and Accrued Liabilities | Scenario, Forecast        
Other Post-Employment Benefits        
Postemployment Benefits Liability, Current       $ 28
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent        
Other Post-Employment Benefits        
Postemployment benefits liability, noncurrent $ 237 $ 270 $ 340  
v3.23.3
Commitments and Contingencies - Table (Details)
$ in Millions
Sep. 30, 2023
USD ($)
megawatts
Sep. 30, 2022
USD ($)
Sep. 30, 2021
USD ($)
Obligations      
Megawatts provided under transmission obligations | megawatts 2,792    
Accrual for Environmental Loss Contingencies, Gross $ 16 $ 17  
Estimated future decommissioning cost [1] 7,489 7,162 $ 7,002
Nuclear      
Obligations      
Estimated future decommissioning cost $ 3,808 $ 3,643 $ 3,428
[1] (1) Includes $272 million and $275 million at September 30, 2023 and 2022, respectively, in Current liabilities.
v3.23.3
Commitments and Contingencies - Membership Interests of VIE Subject to Mandatory Redemption (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Portion at Other than Fair Value Measurement [Member]    
Long-term Purchase Commitment [Line Items]    
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount $ 18 $ 20
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount 19 $ 22
Minimum payments on membership interests subject to mandatory redemption, due in next twelve months 1  
Minimum payments on membership interests subject to mandatory redemption, due in year two 1  
Minimum payments on membership interests subject to mandatory redemption, due in year three 1  
Minimum payments on membership interests subject to mandatory redemption, due in year four 1  
Minimum payments on membership interests subject to mandatory redemption, due in year five $ 1  
v3.23.3
Commitments and Contingencies - Leases (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Leases      
Estimated future decommissioning cost [1] $ 7,489 $ 7,162 $ 7,002
[1] (1) Includes $272 million and $275 million at September 30, 2023 and 2022, respectively, in Current liabilities.
v3.23.3
Commitments and Contingencies - Purchase Obligations (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
Megawatts
megawatts
Sep. 30, 2022
USD ($)
Sep. 30, 2021
USD ($)
Sep. 30, 2029
USD ($)
Sep. 30, 2028
USD ($)
Sep. 30, 2027
USD ($)
Sep. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
Sep. 30, 2024
USD ($)
Obligations                  
Megawatts provided under power purchase obligations | Megawatts 4,487                
Remaining terms of the agreements, high end of range 12 years                
Megawatts provided under transmission obligations | megawatts 2,792                
Power purchased under agreement | $ $ 301 $ 318 $ 202            
2019 | $ $ 1                
Scenario, Forecast                  
Obligations                  
Purchase Obligation | $       $ 541 $ 154 $ 155 $ 155 $ 155 $ 155
Purchase Agreements Required by Federal Law                  
Obligations                  
Megawatts provided under power purchase obligations | Megawatts 285                
Number of generation sources under PPAs | Megawatts 955                
v3.23.3
Commitments and Contingencies - Contingencies (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
reactors
Units
Procedures
Insurance_layers
Sep. 30, 2022
USD ($)
Sep. 30, 2021
USD ($)
Contingencies      
Nuclear liability insurance $ 450    
Assessment from licensees for each licensed reactor $ 138    
Number of licensed reactors in US | reactors 97    
Nuclear accident assessment limitation per year per unit $ 20    
Number of licensed nuclear units | Units 7    
Maximum assessment per nuclear incident $ 963    
Total amount of protection available $ 13,800    
Number of layers until the U.S. Congress is required to take action | Insurance_layers 2    
Amount of insurance available for loss at any one site $ 2,100    
Maximum amount of retrospective premiums 114    
Maximum idemnity if a covered accident tasks or keeps a nuclear unit offline 490    
Maximum amount of retrospective premiums 44    
Estimated future decommissioning cost [1] $ 7,489 $ 7,162 $ 7,002
Number of procedures for determining estimates for the costs of nuclear decommissioning | Procedures 2    
Amount spent to reduce emissions since 1970 $ 6,800    
Amount spent to reduce emissions 25 16 17
Possible additional future costs for compliance with Clean Air Act requirements 252    
Possible additional future costs for compliance with CCR requirements 1,600    
Possible additional future costs for compliance with Clean Water requirements. 190    
Estimated liability for cleanup and similar environmental work on a non-discounted basis 16 17  
Amount of insurance available for loss at any one site, max 2,800    
Nuclear      
Contingencies      
Estimated future decommissioning cost 3,808 3,643 3,428
Non-nuclear      
Contingencies      
Estimated future decommissioning cost $ 3,681 $ 3,519 $ 3,574
[1] (1) Includes $272 million and $275 million at September 30, 2023 and 2022, respectively, in Current liabilities.
v3.23.3
Commitments and Contingencies - Legal Proceedings (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Legal Proceedings    
Possible additional future costs for compliance with CCR requirements $ 1,600  
Contribution related to TVARS case 4 $ 4
Possible additional future costs for compliance with Clean Water requirements. 190  
Amount remaining to be spent under environmental agreements 8  
General    
Legal Proceedings    
Legal loss contingency accrual 28  
Environmental Agreements    
Legal Proceedings    
Amount to be invested in certain environmental projects 290  
Amount invested in certain environmental projects 283  
Other long-term liabilities | General    
Legal Proceedings    
Legal loss contingency accrual 10  
Accounts payable and accrued liabilities | General    
Legal Proceedings    
Legal loss contingency accrual $ 18  
v3.23.3
Commitments and Contingencies Unfunded loan commitments (Details)
$ in Millions
Sep. 30, 2023
USD ($)
Other commitments - unfunded loan commitments [Abstract]  
2019 $ 1
2020 $ 0
v3.23.3
Related Parties Related Parties (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Related Parties      
Revenue from sales of electricity $ 12,054 $ 12,540 $ 10,503
Long-term Investments 4,123 3,671  
Return on power program appropriation investment (6) (4) (4)
Related Party Transactions      
Related Parties      
Revenue from sales of electricity 120 134 109
Other income 282 296 280
Operating expenses 234 228 214
Additions to property, plant, and equipment 8 11 10
Cash and cash equivalents 31 30 30
Receivables from Customers 87 78 65
Long-term Investments 391 358 573
Receivables, Long-term Contracts or Programs 38 43 31
Accounts payable and accrued liabilities 42 42 15
Long-term power bonds, net 1 1 1
Return on power program appropriation investment $ (6) $ (4) $ (4)
v3.23.3
Unaudited Quarterly Financial Information Unaudited Quarterly Financial Information (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Quarterly Financial Information Disclosure [Abstract]      
Revenue from sales of electricity $ 12,054 $ 12,540 $ 10,503
Operating expenses 10,360 10,129 7,658
Operating income 1,694 2,411 2,845
Net income (loss) $ 500 $ 1,108 $ 1,512
v3.23.3
Revenue (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Other revenue $ 155 $ 169 $ 146
Off-system sales 14 19 7
Sales of Electricity (subtotal) 11,888 12,352 10,350
Electric revenue (11,899) (12,371) (10,357)
Revenues 12,054 12,540 10,503
Pandemic Relief Credit $ (225) (228) 221
Revenue from Contract with Customer [Abstract]      
Percent of Pandemic Credit Offered 2.50%    
ALABAMA      
Electric revenue $ (1,731) (1,778) (1,508)
GEORGIA      
Electric revenue (284) (299) (254)
KENTUCKY      
Electric revenue (773) (821) (655)
MISSISSIPPI      
Electric revenue (1,146) (1,182) (984)
NORTH CAROLINA      
Electric revenue (89) (87) (66)
TENNESSEE      
Electric revenue (7,819) (8,137) (6,841)
VIRGINIA      
Electric revenue $ (46) $ (48) $ (42)
v3.23.3
Revenue Customer Type (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
Units
Sep. 30, 2022
USD ($)
Sep. 30, 2021
USD ($)
Electric revenue $ 11,899 $ 12,371 $ 10,357
Other revenue 155 169 146
Revenues 12,054 12,540 10,503
Bill credits for LTA $ (199) (199) 189
Number of LPCs signed LTA | Units 147    
Percentage of total operating revenues 90.40%    
Total number of LPCs | Units 153    
Off-system sales $ 14 19 7
Revenue capitalized during pre-commercial operations $ (3) 0 0
Percent of sales of electricity to LPCs 92.00%    
Pandemic Relief Credit $ (225) $ (228) $ 221
Number of LPCs signed flexibility agreement | Units 89    
MLGW's % of operating revenues 9.00% 9.00% 9.00%
NES's % of operating revenues 8.00% 8.00% 8.00%
20-year contract arrangement [Member]      
Percentage of total operating revenues 77.70%    
5-year contract arrangement [Member]      
Number of LPCs signed LTA | Units 6    
Percentage of total operating revenues 12.70%    
TENNESSEE      
Electric revenue $ 7,819 $ 8,137 $ 6,841
VIRGINIA      
Electric revenue 46 48 42
NORTH CAROLINA      
Electric revenue 89 87 66
MISSISSIPPI      
Electric revenue 1,146 1,182 984
KENTUCKY      
Electric revenue 773 821 655
GEORGIA      
Electric revenue 284 299 254
ALABAMA      
Electric revenue 1,731 1,778 1,508
Federal agencies and other [Member]      
Electric revenue 135 154 116
20-year contract arrangement [Member]      
Electric revenue 9,367    
5-year contract arrangement [Member]      
Electric revenue 1,536    
Local Power Company [Member]      
Electric revenue 10,903 11,291 9,534
Industries Directly Served [Member]      
Electric revenue $ 864 $ 926 $ 707
v3.23.3
Revenue Local Power Company Contracts (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2023
USD ($)
Units
Sep. 30, 2022
USD ($)
Sep. 30, 2021
USD ($)
Number of LPCs signed LTA | Units 147    
Electric revenue $ 11,899 $ 12,371 $ 10,357
Total number of LPCs | Units 153    
Percentage of total operating revenues 90.40%    
Percent of wholesale Credit offered 3.10%    
20-year contract arrangement [Member]      
Electric revenue $ 9,367    
5-year contract arrangement [Member]      
Electric revenue 1,536    
Local Power Company [Member]      
Electric revenue $ 10,903 $ 11,291 $ 9,534
5-year contract arrangement [Member]      
Number of LPCs signed LTA | Units 6    
Percentage of total operating revenues 12.70%    
v3.23.3
Revenue Economic Development Incentives (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Revenue from Contract with Customer [Abstract]      
Revenues $ 330 $ 328 $ 315
Unpaid economic incentives $ (188) $ (187)  
v3.23.3
Subsequent Events (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Sep. 30, 2022
Debt Instrument, Redemption [Line Items]    
Non-current regulatory liabilities $ 107 $ 172
Regulatory assets 5,566 6,134
Unrealized gains/losses on commodity derivatives    
Debt Instrument, Redemption [Line Items]    
Regulatory assets 52 1
Unrealized gains/losses on commodity derivatives    
Debt Instrument, Redemption [Line Items]    
Non-current regulatory liabilities $ 12 $ 102
v3.23.3
Plant Closures (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Sep. 30, 2023
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Property, Plant and Equipment [Abstract]        
Accelerated depreciation   $ 177 $ 140 $ 136
Completed Plant        
Accelerated depreciation   177 140 136
Property, Plant, and Equipment, Owned, Accumulated Depreciation $ 659 659    
Depreciation   1,900 1,800 $ 1,400
Accumulated depreciation 35,871 35,871 $ 34,239  
Cumberland        
Property, Plant and Equipment [Abstract]        
Accelerated depreciation 16 48    
Completed Plant        
Accelerated depreciation $ 16 $ 48    
Property, Plant and Equipment [Member]        
Completed Plant        
Property, Plant and Equipment, Dispositions   14 million 22 million 4 million
v3.23.3
Leases (Details) - USD ($)
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Lessee, Lease, Description [Line Items]      
Operating Lease, Right-of-Use Asset $ 177,000,000 $ 155,000,000  
Finance Lease, Right-of-Use-Asset, after Accumulated Amortization 572,000,000 630,000,000  
Total lease assets 749,000,000 785,000,000  
Operating Lease, Liability, Current 71,000,000    
Operating Lease, Liability, Noncurrent 93,000,000 93,000,000  
Finance Lease, Liability, Noncurrent 576,000,000 628,000,000  
Total lease liabilities 796,000,000 839,000,000  
Operating Lease, Cost 69,000,000 56,000,000 $ 52,000,000
Variable Lease, Cost 134,000,000 78,000,000 75,000,000
Short-term Lease, Cost 18,000,000 26,000,000 12,000,000
Finance Lease, Right-of-Use Asset, Amortization 57,000,000 58,000,000 51,000,000
Finance Lease, Interest Expense 43,000,000 42,000,000 39,000,000
Total finance lease costs 100,000,000 100,000,000 90,000,000
Lease, Cost $ 321,000,000 $ 260,000,000 $ 229,000,000
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration] Accounts Payable and Accrued Liabilities, Current Accounts Payable and Accrued Liabilities, Current  
Operating lease under PPA $ 135,000,000 $ 133,000,000  
Leases      
Finance lease under PPA $ 390,000,000 425,000,000  
Operating lease liability      
Lessee, Lease, Description [Line Items]      
Accounts Payable and Accrued Liabilities   $ 59,000,000  
v3.23.3
Leases, SoCF (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Lessee, Lease, Description [Line Items]      
Operating cash flows for operating leases $ 77 $ 57 $ 53
Operating cash flows for finance leases 43 42 39
Financing cash flows for finance leases 56 60 52
Lease assets obtained in exchange for lease obligations - finance 3 0 233
Lease assets obtained in exchange for lease obligations - operating $ 84 $ 43 $ (22)
v3.23.3
Leases, Weighted Averages (Details)
Sep. 30, 2023
Sep. 30, 2022
Lessee, Lease, Description [Line Items]    
Operating Lease, Weighted Average Remaining Lease Term 3 years 3 years
Finance Lease, Weighted Average Remaining Lease Term 10 years 11 years
Operating Lease, Weighted Average Discount Rate, Percent 4.10% 1.50%
Finance Lease, Weighted Average Discount Rate, Percent 21.60% 17.80%
v3.23.3
Leases, Future Minimum Payments (Details)
$ in Millions
Sep. 30, 2023
USD ($)
Lessee, Lease, Description [Line Items]  
Operating Leases, Future Minimum Payments Due, Next Twelve Months $ 76
Total 174
Operating Leases, Future Minimum Payments, Due in Two Years 51
Present value of future minimum lease payments, operating (10)
Operating present value of net minimum lease payments 164
Finance Lease, Liability, to be Paid, Year One 109
Finance Lease, Liability, to be Paid, Year Two 107
Finance Lease, Liability, to be Paid, Year Three 106
Finance Lease, Liability, to be Paid, Year Four 104
Finance Lease, Liability, to be Paid, Year Five 102
Finance Lease, Liability, to be Paid, after Year Five 450
Finance Lease, Liability, Payment, Due 978
Finance Lease, Liability, Payment Amounts Representing Interest (346)
Finance Lease, Liability 632
Purchased Power Lease 43
Operating Leases, Future Minimum Payments, Due in Three Years 24
Operating Leases, Future Minimum Payments, Due in Four Years 9
Operating Leases, Future Minimum Payments, Due in Five Years 3
Operating Leases, Future Minimum Payments, Due Thereafter 11
New PPAs with battery storage $ 394
v3.23.3
Research and Development (Details) - USD ($)
$ in Millions
 12 Months Ended 48 Months Ended
Sep. 30, 2023
Sep. 30, 2026
Research and Development Arrangement, Contract to Perform for Others [Line Items]    
Research and Development Arrangement, Contract to Perform for Others, Costs Incurred, Gross $ 31  
Amount of letters of credit outstanding $ 6  
Scenario, Forecast    
Research and Development Arrangement, Contract to Perform for Others [Line Items]    
Research and Development Arrangement, Contract to Perform for Others, Costs Incurred, Gross   $ 88