TENNESSEE VALLEY AUTHORITY, 10-K filed on 11/17/2020
Annual Report
v3.20.2
DEI Document
shares in Millions, $ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
shares
Document Information [Line Items]  
Entity Registrant Name TENNESSEE VALLEY AUTHORITY
Entity Central Index Key 0001376986
Current Fiscal Year End Date --09-30
Entity Filer Category Non-accelerated Filer
Document Type 10-K
Document Period End Date Sep. 30, 2020
Document Fiscal Year Focus 2020
Document Fiscal Period Focus FY
Amendment Flag false
Entity Common Stock, Shares Outstanding | shares 0
Entity Small Business false
Entity Emerging Growth Company false
Entity Shell Company false
Entity Well-known Seasoned Issuer No
Entity Voluntary Filers No
Entity Current Reporting Status Yes
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
v3.20.2
CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Operating revenues      
Electric revenue $ 10,104 $ 11,159 $ 11,075
Other revenue 145 159 158
Revenue from sales of electricity 10,249 11,318 11,233
Operating expenses      
Fuel 1,584 1,896 2,049
Purchased power 880 1,007 973
Operating and maintenance 2,720 3,090 2,598
Depreciation and amortization 1,826 1,973 2,527
Tax equivalents 528 541 518
Total operating expenses 7,538 8,507 8,665
Operating income 2,711 2,811 2,568
Other income (expense), net 36 62 50
Defined Benefit Plan, Other Cost (Credit) 253 258 256
Interest expense      
Interest expense 1,142 1,198 1,243
Net income (loss) 1,352 1,417 1,119
ALABAMA      
Operating revenues      
Electric revenue 1,439 1,593 1,600
GEORGIA      
Operating revenues      
Electric revenue 249 270 267
KENTUCKY      
Operating revenues      
Electric revenue 624 691 696
MISSISSIPPI      
Operating revenues      
Electric revenue 941 1,063 1,052
NORTH CAROLINA      
Operating revenues      
Electric revenue 65 74 66
TENNESSEE      
Operating revenues      
Electric revenue 6,740 7,419 7,350
VIRGINIA      
Operating revenues      
Electric revenue $ 42 $ 45 $ 48
v3.20.2
CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Current assets    
Cash and Cash Equivalents, at Carrying Value $ 500 $ 299
Accounts receivable, net 1,529 1,739
Inventories, net 1,003 999
Regulatory assets 130 156
Other current assets 84 85
Total current assets 3,246 3,278
Property, plant, and equipment    
Completed plant 64,970 62,944
Less accumulated depreciation (33,550) (31,384)
Net completed plant 31,420 31,560
Construction in progress 2,139 1,893
Nuclear fuel 1,504 1,534
Capital leases 516 146
Total property, plant, and equipment, net 35,579 35,133
Long-term Investments 3,198 2,968
Regulatory and other long-term assets    
Regulatory assets 10,245 8,763
Operating Lease, Right-of-Use Asset 232 0
Other long-term assets 325 325
Total regulatory and other long-term assets 10,802 9,088
Total assets 52,825 50,467
Current liabilities    
Accounts payable and accrued liabilities 1,844 1,649
Accrued interest 298 296
Asset Retirement Obligation, Current 345 163
Current portion of leaseback obligations 198 40
Regulatory liabilities 141 150
Short-term debt, net of discounts 57 922
Total Current maturities of power bonds issued at par 1,787 1,030
Current maturities of long-term debt of variable interest entities issued at par 41 39
Current maturities of notes payable 0 23
Total current liabilities 4,711 4,312
Other liabilities    
Post-retirement and post-employment benefit obligations 6,617 6,181
Asset retirement obligations 6,440 5,453
Finance Lease, Liability 525 182
Other long-term liabilities 2,548 2,308
Leaseback obligations 25 223
Non-current regulatory liabilities 23 0
Total other liabilities 16,178 14,347
Long-term debt, net    
Long-term power bonds, net 17,956 19,094
Long-term debt of variable interest entities, net 1,048 1,089
Total long-term debt, net 19,004 20,183
Total liabilities 39,893 38,842
Proprietary capital    
Power program appropriation investment 258 258
Power program retained earnings 12,177 10,823
Total power program proprietary capital 12,435 11,081
Nonpower programs appropriation investment, net 548 556
Accumulated other comprehensive income (loss) (51) (12)
Total proprietary capital 12,932 11,625
Total liabilities and proprietary capital $ 52,825 $ 50,467
v3.20.2
CONSOLIDATED STATEMENTS OF CASH FLOWS
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Regulatory asset amount expensed $ (23) $ (261) $ (2)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents 521 322 322
Cash flows from operating activities      
Net income (loss) 1,352 1,417 1,119
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) 1,848 1,993 2,554
Amortization of nuclear fuel cost 388 379 382
Non-cash retirement benefit expense 324 314 324
Prepayment credits applied to revenue 0 (10) (100)
Changes in current assets and liabilities      
Accounts receivable, net 259 (40) (68)
Inventories and other current assets, net (12) (87) 65
Accounts payable and accrued liabilities (38) (155) 143
Accrued interest 1 (8) (36)
Pension contributions (305) (307) (304)
Settlements of asset retirement obligations (114) (89) (106)
Other, net (44) 52 (37)
Net cash provided by operating activities 3,636 3,720 3,938
Cash flows from investing activities      
Construction expenditures (1,643) (1,700) (1,759)
Nuclear fuel expenditures (342) (474) (457)
Purchases of investments (49) (48) (49)
Loans and other receivables      
Advances (8) (10) (12)
Repayments 7 11 4
Other, net 20 (22) 4
Net cash used in investing activities (2,015) (2,243) (2,269)
Long-term debt      
Issues of power bonds 997 0 998
Redemptions and repurchases of power bonds (1,427) (1,035) (1,731)
Redemptions of notes payable (23) (46) (53)
Payments on debt of variable interest entities (39) (38) (36)
Short-term debt issues (redemptions), net (865) (294) (782)
Payments on leases and leasebacks (55) (43) (42)
Financing costs, net (4) 0 (3)
Other, net (6) (21) (9)
Net cash (used in) provided by financing activities (1,422) (1,477) (1,658)
Net change in cash and cash equivalents 199 0 $ 11
Cash and cash equivalents at beginning of the year 299    
Cash and cash equivalents at end of the year $ 500 $ 299  
v3.20.2
CONSOLIDATED STATEMENTS OF CHANGES IN PROPRIETARY CAPITAL - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Sep. 30, 2020
Dec. 31, 2019
Sep. 30, 2019
Dec. 31, 2018
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Balance at beginning of year   $ 11,625   $ 10,283 $ 11,625 $ 10,283 $ 9,133
Net income (loss) $ 700 192 $ 588 423 1,352 1,417 1,119
Total other comprehensive income (loss)         (39) (69) 36
Return on power program appropriation investment         (6) (6) (5)
Balance at end of year 12,932   11,625   12,932 11,625 10,283
Power Program Appropriation Investment              
Balance at beginning of year   258   258 258 258 258
Net income (loss)         0 0 0
Total other comprehensive income (loss)         0 0 0
Return on power program appropriation investment         0 0 0
Balance at end of year 258   258   258 258 258
Power Program Retained Earnings              
Balance at beginning of year   10,823   9,404 10,823 9,404 8,282
Net income (loss)         1,360 1,425 1,127
Total other comprehensive income (loss)         0 0 0
Return on power program appropriation investment         (6) (6) (5)
Balance at end of year 12,177   10,823   12,177 10,823 9,404
Nonpower Programs Appropriation Investment, Net              
Balance at beginning of year   556   564 556 564 572
Net income (loss)         (8) (8) (8)
Total other comprehensive income (loss)         0 0 0
Return on power program appropriation investment         0 0 0
Balance at end of year 548   556   548 556 564
Accumulated Other Comprehensive Income (Loss) Net Gains (Losses) on Cash Flow Hedges              
Balance at beginning of year   $ (12)   $ 57 (12) 57 21
Net income (loss)         0 0 0
Total other comprehensive income (loss)         (39) (69) 36
Return on power program appropriation investment         0 0 0
Balance at end of year $ (51)   $ (12)   $ (51) $ (12) $ 57
v3.20.2
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) Statement - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Statement of Comprehensive Income [Abstract]      
Net income (loss) $ 1,352 $ 1,417 $ 1,119
Net unrealized gain (loss) on cash flow hedges (1) (114) 10
Reclassification to earnings from cash flow hedges (38) (45) (26)
Total other comprehensive income (loss) (39) (69) 36
Total comprehensive income (loss) $ 1,313 $ 1,348 $ 1,155
v3.20.2
Supplemental Cash Flow Information
 12 Months Ended
Sep. 30, 2020
Supplemental Cash Flow Information [Abstract]  
Supplemental Cash Flow Information Supplemental Cash Flow Information
    Interest paid was $1.1 billion for 2020 and $1.2 billion for both 2019 and 2018. These amounts differ from interest expense in certain years due to the timing of payments. There was no interest capitalized in 2020, 2019, or 2018.

    Construction in progress and Nuclear fuel expenditures included in Accounts payable and accrued liabilities at September 30, 2020, 2019, and 2018 were $398 million, $324 million, and $372 million, respectively, and are excluded from the Statements of Consolidated Cash Flows for the years ended September 30, 2020, 2019, and 2018 as non-cash investing activities. 

    Excluded from the Statements of Consolidated Cash Flows for the years ended September 30, 2020 and 2019, as non-cash financing activities were $394 million related to lease obligations incurred primarily in connection with a PPA and $10 million related to lease obligations incurred for leased equipment, respectively. There were no capital leases incurred during 2018. See Note 7 — Leases for further information regarding TVA's finance leases. Also excluded from the Statement of Consolidated Cash Flows for the year ended September 30, 2020, were $80 million and $73 million as non-cash financing and investing activities, respectively, due to derecognition of the Paradise pipeline financing obligation and asset.

    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.
v3.20.2
Supplemental Cash Flow Information - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Supplemental Cash Flow Information      
Interest paid $ 1,100 $ 1,200  
Capital lease obligations incurred 394 10  
Non-cash financing activities 80    
Non-cash investing activities 73    
Interest Paid, Excluding Capitalized Interest, Operating Activities 1,100 1,200  
Accounts payable and accrued liabilities      
Supplemental Cash Flow Information      
Construction in progress and Nuclear fuel expenditures $ 398 $ 324 $ 372
v3.20.2
Summary of Significant Accounting Policies [Text Block]
 12 Months Ended
Sep. 30, 2020
Accounting Policies [Abstract]  
Summary of Significant Accounting Policies 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.

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 of Directors (the "TVA Board") as authorized by the Tennessee Valley Authority Act of 1933, as amended (the "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 item 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 (2020, 2019, 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 any of the other factors described above cease to be applicable, TVA would no longer be considered to be a regulated entity and would be required to write off these costs.  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, wholly-owned direct subsidiaries, and variable interest entities ("VIE") of which TVA is the primary beneficiary. See Note 10 — 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, including impacts from the COVID-19 pandemic, 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.

Reclassifications

    Certain historical amounts have been reclassified in the accompanying consolidated financial statements to the current presentation. In the Consolidated Balance Sheet at September 30, 2019, TVA reclassified $163 million from Accounts payable and accrued liabilities to Asset retirement obligations in Current liabilities. In addition, as a result of the adoption of the new lease accounting standard effective for TVA October 1, 2019, TVA reclassified $182 million from Other long-term liabilities to Finance lease liabilities in the Consolidated Balance Sheet at September 30, 2019.
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 includes 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 in the Consolidated Balance Sheets and Consolidated Statements of Cash Flows:
Cash, Cash Equivalents, and Restricted Cash
At September 30
 20202019
Cash and cash equivalents$500 $299 
Restricted cash and cash equivalents, included in Other long-term assets21 23 
Total Cash, cash equivalents, and restricted cash$521 $322 

    Due to higher volatility in the financial markets associated with the COVID-19 pandemic, TVA increased its target balance of Cash and cash equivalents beginning in March 2020. TVA continued to hold higher target cash balances at September 30, 2020, and may hold higher balances in future periods due to potential market volatility.

Allowance for Uncollectible Accounts

The allowance for uncollectible accounts reflects TVA's estimate of probable losses inherent in its accounts and loans receivable balances excluding the EnergyRight® loans receivable.  TVA determines the allowance based on known accounts, historical experience, and other currently available information including events such as customer bankruptcy and/or a customer failing to fulfill payment arrangements after 90 days.  It also reflects TVA's corporate credit department's assessment of the financial condition of customers and the credit quality of the receivables. TVA continues to monitor the impact of the COVID-19 pandemic on accounts and loans receivable balances to evaluate the allowance for uncollectible accounts.

The allowance for uncollectible accounts was less than $1 million at both September 30, 2020 and 2019, for accounts receivable.  Additionally, loans receivable of $105 million and $131 million at September 30, 2020 and 2019, respectively, are included in Accounts receivable, net and Other long-term assets, for the current and long-term portions, respectively, and are reported net of allowances for uncollectible accounts of less than $1 million at both September 30, 2020 and 2019, respectively.

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 are recorded in Other revenue. Revenues that are not related to the overall mission are recorded in Other income (expense), net.

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 revenue from such pre-commercial generation based on the guidance provided by Federal Energy Regulatory Commission ("FERC") regulations. The Allen Combined Cycle Plant ("Allen CC") began pre-commercial plant operations in September 2017, and began commercial operations in April 2018. Cogeneration capability at Johnsonville Combustion Turbine Unit 20 commenced pre-commercial plant operations in September 2017, and was placed in service during December 2017. Estimated revenue of $11 million related to Allen CC was capitalized to offset project costs for the year ended September 30, 2018. TVA also capitalized related fuel costs for these construction projects of approximately $19 million during the year ended September 30, 2018. No such amounts were capitalized during 2019 or 2020.
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 Credits. 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 fair value approach. RECs created through TVA-owned asset generation are recorded at zero cost.

Emission Allowances.  TVA has emission allowances for sulfur dioxide ("SO2") and nitrogen oxide ("NOx") which are accounted for as inventory.  The cost of specific allowances used each month is charged to operating expense based on tons of SO2 and NOx emitted during the respective compliance periods.  Allowances granted to TVA by the Environmental Protection Agency ("EPA") are recorded at zero cost.

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.  In 2018, TVA started moving from a site-specific inventory management policy to a fleet-wide strategy 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. 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.  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. 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.

    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 the external depreciation studies. These studies will be updated approximately every five years.  Depreciation expense for the years ended September 30, 2020, 2019, and 2018 was $1.6 billion, $1.8 billion, and $1.3 billion, respectively. Depreciation expense expressed as a percentage of the average annual depreciable completed plant was 2.74 percent for 2020, 3.09 percent for 2019, and 2.45 percent for 2018.  Average depreciation rates by asset class are as follows:
Property, Plant, and Equipment Depreciation Rates
At September 30
(percent)
202020192018
Asset Class
Nuclear2.38 2.38 2.64 
Coal-fired(1)
3.62 4.96 2.32 
Hydroelectric1.60 1.61 1.57 
Gas and oil-fired3.04 3.00 2.93 
Transmission1.34 1.34 1.32 
Other7.26 7.16 5.90 
Note
(1) The rates include the acceleration of depreciation related to retiring certain coal-fired units.
    
    Coal-Fired. As a result of TVA's decision to idle or retire certain units since the previous depreciation study, TVA recognized $387 million, $566 million, and $48 million in accelerated depreciation expense related to the units during the years ended September 30, 2020, 2019, and 2018, respectively. Accelerated depreciation is based on the remaining useful life of the asset at the time the decision is made to idle or retire a unit.

Reacquired Rights. Property, plant, and equipment includes intangible reacquired rights, net of amortization, of $192 million and $200 million as of September 30, 2020 and 2019, 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 life of the underlying CTs. Amortization expense was $8 million for all years 2020, 2019, and 2018.

Software Costs.  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.  At September 30, 2020 and 2019, unamortized computer software costs totaled $54 million and $63 million, respectively.  Amortization expense related to capitalized computer software costs was $42 million, $38 million, and $32 million for 2020, 2019, and 2018, respectively.  Software costs that do not meet capitalization criteria are expensed as incurred.

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. See Note 6 — 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 power purchase agreements, the terms of which vary. The total lease obligation included in Accounts payable and accrued liabilities and lease liabilities related to these agreements were $500 million and $174 million for finance and operating leases, respectively, at September 30, 2020.

    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, 2020.
    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.  These other property-related assets include, but are not limited to, easements and coal rights.  Activities involved with retiring these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site restoration.  Revisions to the estimates of asset retirement obligations ("AROs") are made whenever factors indicate that the timing or amounts of estimated cash flows have changed materially.  Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset.  See Note 9 —
Regulatory Assets and Liabilities — Nuclear Decommissioning Costs and Non-Nuclear Decommissioning Costs and Note 12 — Asset Retirement Obligations.

Down-blend Offering for Tritium

TVA, the Department of Energy ("DOE"), and certain nuclear fuel contractors have entered into agreements, referred to as the Down-blend Offering for Tritium, 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 October 2027.  Beginning October 2027, 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 $89 million in reimbursements from the DOE. At September 30, 2020, TVA recorded $6 million in Accounts receivable, net related to this agreement.

Investment Funds

    Investment funds consist primarily of trust funds designated to fund decommissioning requirements (see Note 22 — Commitments and Contingencies — Decommissioning Costs), the Supplemental Executive Retirement Plan ("SERP") (see Note 21 — Benefit Plans — Overview of Plans and Benefits — Supplemental Executive Retirement Plan), and the Deferred Compensation Plan ("DCP"). 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, and DCP 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, and DCP funds are all classified as trading.

Energy Prepayment Obligations

In 2004, TVA and its largest customer, Memphis Light, Gas and Water Division ("MLGW"), entered into an energy prepayment agreement under which MLGW prepaid TVA $1.5 billion for the future costs of electricity to be delivered by TVA to MLGW over a period of 180 months.  TVA accounted for the prepayment as unearned revenue and reported the obligation to deliver power under this arrangement as Energy prepayment obligations.  The arrangement ceased in 2019. Revenue was recognized in each year of the arrangement as electricity was delivered to MLGW based on the ratio of units of kilowatt hours delivered to total units of kilowatt hours under contract.  As of September 30, 2019, $1.5 billion had been recognized as non-cash revenue on a cumulative basis during the life of the agreement, $10 million and $100 million of which was recognized as non-cash revenue during 2019 and 2018, respectively.

Discounts to account for the time value of money, which are recorded as a reduction to electricity sales, amounted to $4 million and $46 million for the years ended September 30, 2019 and 2018, respectively.

Insurance

Although TVA uses private companies to administer its healthcare plans for eligible active and retired employees not covered by Medicare, TVA does not purchase health insurance.  Third-party actuarial specialists assist TVA in determining certain liabilities for self-insured claims.  TVA recovers the costs of claims through power rates and through adjustments to the participants' contributions to their benefit plans.  These liabilities are included in Other liabilities on the Consolidated Balance Sheets.

TVA sponsors an Owner Controlled Insurance Program which provides workers' compensation and liability insurance for a select group of contractors performing maintenance, modifications, outage, and new construction activities at TVA facilities.

The Federal Employees' Compensation Act ("FECA") governs liability to employees for service-connected injuries.  TVA purchases excess workers' compensation insurance above a self-insured retention.

    In addition to excess workers' compensation insurance, TVA purchases the following types of insurance:
•Nuclear liability insurance; nuclear property, decommissioning, and decontamination insurance; and nuclear accidental outage insurance. See Note 22 — Commitments and Contingencies — Nuclear Insurance.

•Excess liability insurance for aviation, auto, marine, and general liability exposures.

•Property insurance for certain conventional (non-nuclear) assets.
    The insurance policies are subject to the terms and conditions of the specific policy, including deductibles or self-insured retentions. To the extent insurance would not provide either a partial or total recovery of the costs associated with a loss, TVA would have to recover any such costs through other means, including through power rates.

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 in the Consolidated Statements of Operations as they are incurred except for the recording of certain regulatory assets for retirement and removal costs.
v3.20.2
Impact of New Accounting Standards and Interpretations
 12 Months Ended
Sep. 30, 2020
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 are accounting standard updates issued by the Financial Accounting Standards Board ("FASB") that TVA adopted during 2020:
Lease Accounting
DescriptionThis guidance changes the provisions of recognition in both the lessee and lessor accounting models. The standard requires entities that lease assets ("lessees") to recognize on the balance sheet the assets and liabilities for the rights and obligations created by leases with terms of more than 12 months, while also refining the definition of a lease. In addition, lessees are required to disclose key information about the amount, timing, and uncertainty of cash flows arising from leasing arrangements. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee primarily depend on its classification as a finance lease (formerly referred to as capital lease) or operating lease. The standard requires both types of leases to be recognized on the balance sheet. Operating leases will result in straight-line expense, while finance leases will result in recognition of interest on the lease liability separate from amortization expense. The accounting rules for the owner of assets leased by the lessee ("lessor accounting") remain relatively unchanged.

The standard allows for certain practical expedients to be elected related to lease term determination, separation of lease and non-lease elements, reassessment of existing leases, and short-term leases. The standard is to be applied using a modified retrospective transition.
Effective Date for TVAOctober 1, 2019
Effect on the Financial Statements or Other Significant Matters
TVA elected the modified retrospective method of adoption effective October 1, 2019. Under the modified retrospective method of adoption, prior year reported results are not restated.

TVA recorded $205 million and $210 million of lease assets and lease liabilities, respectively, for operating leases in effect at the adoption date. The accounting for finance leases remained substantially unchanged. Adoption of the standard did not materially impact results of operations or cash flows.

TVA has elected to apply the following practical expedients:
Practical ExpedientDescription
Package of transition practical expedients (for leases commenced prior to adoption date; expedients must be adopted as a package)Do not need to (1) reassess whether any expired or existing contracts are leases or contain leases, (2) reassess the lease classification for any expired or existing leases, or (3) reassess initial direct costs for any existing leases.
Short-term lease expedient (elect by class of underlying asset)Elect as an accounting policy to not apply the recognition requirements to short-term leases by asset class.
Existing and expired land easements not previously accounted for as leasesElect to not evaluate existing or expired easements under the new guidance and carry forward current accounting treatment.
Comparative reporting requirements for initial adoptionElect to (1) apply transition requirements at adoption date, (2) recognize cumulative effect adjustment to retained earnings in period of adoption, and (3) not apply the new requirements to comparative periods, including disclosures.
Derivatives and Hedging - Improvements to Accounting for Hedging Activities
DescriptionThis guidance better aligns an entity's risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. To meet that objective, the amendments expand and refine hedge accounting for both nonfinancial and financial risk components and align the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements.
Effective Date for TVAOctober 1, 2019
Effect on the Financial Statements or Other Significant MattersTVA has adopted the standard on a prospective basis. The adoption of this standard did not have a material impact on TVA's financial condition, results of operations, or cash flows. TVA only uses hedge accounting under its foreign currency swap arrangements, and the adoption of this standard had no impact on those arrangements.
Customer's Accounting for Implementation Costs in a Cloud Arrangement That Is a Service Contract
DescriptionThis guidance relates to the accounting for a customer's implementation costs in a hosting arrangement that is a service contract. The amendments align the requirements for capitalizing those implementation costs with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software and hosting arrangements that include an internal-use software license. The amendments also provide requirements for the classification of the capitalized costs and related expense and cash flows in the financial statements, the application of impairment guidance to the capitalized costs, and the application of abandonment guidance to the capitalized costs. Entities are required to apply the amendments either retrospectively or prospectively to all implementation costs incurred after the adoption date.
Effective Date for TVAOctober 1, 2019
Effect on the Financial Statements or Other Significant MattersTVA has adopted the standard on a prospective basis. Adoption of this standard did not have a material impact on TVA's financial condition, results of operations, or cash flows. TVA records qualified implementation costs in a cloud arrangement that is a service contract as a prepaid asset and amortizes the prepaid asset to Operating and maintenance expense based on the term of the contract.
    The following accounting standards have been issued but as of September 30, 2020, were not effective and had not been adopted by TVA:

Financial Instruments - Credit Losses
DescriptionThis guidance eliminates the probable initial recognition threshold in current GAAP and, instead, requires an allowance to be recorded for all expected credit losses for certain financial assets that are not measured at fair value. The allowance for credit losses is based on historical information, current conditions, and reasonable and supportable forecasts. The new standard also makes revisions to the other than temporary impairment model for available-for-sale debt securities. Disclosures of credit quality indicators in relation to the amortized cost of financing receivables are further disaggregated by year of origination.
Effective Date for TVAThe new standard is effective for TVA's interim and annual reporting periods beginning October 1, 2020.
Effect on the Financial Statements or Other Significant MattersTVA adopted this standard using the modified retrospective method through a cumulative-effect adjustment to retained earnings on October 1, 2020. TVA will recognize an allowance that reflects the current estimate of credit losses expected to be incurred over the life of the financial assets based on historical experience, current conditions, and reasonable and supportable forecasts. This standard will primarily impact TVA's long-term loans receivable. Adoption of this standard is not expected to have a material impact on TVA's financial condition, results of operations, or cash flows.
Fair Value Measurement Disclosure
DescriptionThe guidance changes certain disclosure requirements for fair value measurements. It removes certain disclosure requirements, such as the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy; the policy for timing of the transfers between levels; and the valuation processes for Level 3 fair value measurements.  Some disclosure requirements are added, such as the change in unrealized gains and losses included in other comprehensive income for recurring Level 3 fair value measurements and the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements.
Effective Date for TVAThe new standard is effective for TVA's interim and annual reporting periods beginning October 1, 2020.
Effect on the Financial Statements or Other Significant MattersTVA does not expect the adoption of this standard to have a material impact on TVA's financial condition, results of operations, or cash flows.
Reference Rate Reform
DescriptionThe guidance provides temporary optional expedients and exceptions to the guidance in GAAP on contract modifications and hedge accounting to ease the financial reporting burdens related to the expected market transition from the London Interbank Offered Rate ("LIBOR") and other interbank offered rates to alternative reference rates, such as the Secured Overnight Financing Rates.
Effective Date for TVAThe new standard is effective for adoption at any time between March 12, 2020, and December 31, 2022. TVA currently plans to adopt the standard by December 31, 2022.
Effect on the Financial Statements or Other Significant MattersTVA continues to review this standard and evaluate the impact of using an alternative reference rate instead of LIBOR in its interest rate swap contracts. TVA expects the adoption of the standard will simplify the accounting for any modifications to its interest rate swap contracts.
v3.20.2
Accounts Receivable, Net
 12 Months Ended
Sep. 30, 2020
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
 20202019
Power receivables$1,401 $1,624 
Other receivables128 115 
Accounts receivable, net(1)
$1,529 $1,739 
Note
(1) Allowance for uncollectible accounts was less than $1 million at September 30, 2020 and 2019, and therefore is not represented in the table above.
In response to the COVID-19 pandemic, the TVA Board approved the Public Power Support and Stabilization program in March 2020, which includes alternative wholesale payment arrangements for LPCs. Through this program, TVA is offering up to $1.0 billion of credit support to LPCs that demonstrate the need for temporary financial relief, through the deferral of a portion of LPCs' wholesale power payments owed to TVA. The program requires LPCs to apply for the deferral, which is subject to approval by TVA. If approved, TVA will establish and approve a repayment schedule with the LPC by December 31, 2020, with a repayment term not to exceed two years. The program is available through CY 2020, and as of November 16, 2020, $1 million of credit support has been approved under the program.
v3.20.2
Inventories, Net
 12 Months Ended
Sep. 30, 2020
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
 20202019
Materials and supplies inventory$770 $742 
Fuel inventory253 294 
RECs inventory, net15 16 
Allowance for inventory obsolescence(35)(53)
Inventories, net$1,003 $999 
v3.20.2
Net Completed Plant
 12 Months Ended
Sep. 30, 2020
Property, Plant and Equipment, Net, by Type [Abstract]  
Property, Plant, and Equipment and Intangible Assets Net Completed Plant
Net completed plant consisted of the following:
Net Completed Plant
At September 30
 20202019
 CostAccumulated Depreciation 
Net		CostAccumulated DepreciationNet
Coal-fired(1)(2)
$18,613 $13,944 $4,669 $17,400 $12,538 $4,862 
Gas and oil-fired6,010 1,696 4,314 6,054 1,562 4,492 
Nuclear25,741 12,141 13,600 25,543 11,656 13,887 
Transmission8,283 3,140 5,143 7,932 3,083 4,849 
Hydroelectric3,410 1,090 2,320 3,163 1,051 2,112 
Other electrical plant1,981 1,146 835 1,920 1,110 810 
Intangible software3 2 1 3 1 2 
Multipurpose dams900 381 519 900 373 527 
Other stewardship29 10 19 29 10 19 
Total$64,970 $33,550 $31,420 $62,944 $31,384 $31,560 
Notes
(1) TVA recognized accelerated depreciation as a result of the decision to idle or retire certain units. See Note 6 — Plant Closures.
(2) In 2020, TVA recorded approximately $1.1 billion in upward revisions to asset retirement costs for coal-fired assets. See Note 12 — Asset Retirement Obligations.
v3.20.2
Other Long-Term Assets [Text Block]
 12 Months Ended
Sep. 30, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]  
Other Long-Term Assets
8.  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
 2020
2019(1)
Loans and other long-term receivables, net$100 $125 
EnergyRight® receivables
69 81 
Prepaid long-term service agreements42 22 
Commodity contract derivative assets23 — 
Restricted cash and cash equivalents21 23 
Prepaid capacity payments11 19 
Other59 55 
Total other long-term assets$325 $325 
Note
(1) At September 30, 2019, $22 million previously classified as Other (a component of Other long-term assets) has been reclassified to Prepaid long-term service agreements (a component of Other long-term assets) to conform with current year presentation.

    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, 2020 and 2019, the carrying amount of the loans receivable, net of discount, reported in Accounts receivable, net was approximately $18 million and $20 million, respectively. See Note 11 — Other Long-Term Liabilities for information regarding the associated financing obligation.

In response to the COVID-19 pandemic, customers experiencing financial hardship can request a deferral of EnergyRight® loan payments for a period of up to six months. This deferral option began April 20, 2020, and is available through October 31, 2020. Deferred loans will not accrue interest during the deferral months. These deferred loans have resulted in a less than $1 million impact to TVA.

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, 2020 and 2019, prepayments of $3 million and $5 million,
respectively, were recorded in Other current assets.
v3.20.2
Regulatory Assets and Liabilities [Text Block]
 12 Months Ended
Sep. 30, 2020
Regulatory Assets and Liabilities Disclosure [Abstract]  
Regulatory Assets and Liabilities Regulatory Assets and 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
 2020
2019(1)
Current regulatory assets  
Unrealized losses on interest rate derivatives$114 $89 
Unrealized losses on commodity derivatives4 39 
Fuel cost adjustment receivable12 28 
Total current regulatory assets130 156 
Non-current regulatory assets  
Deferred pension costs and other post-retirement benefits costs5,193 4,756 
Non-nuclear decommissioning costs2,512 1,741 
Unrealized losses on interest rate derivatives1,506 1,241 
Nuclear decommissioning costs896 868 
Unrealized losses on commodity derivatives— 15 
Other non-current regulatory assets138 142 
Total non-current regulatory assets10,245 8,763 
Total regulatory assets$10,375 $8,919 
Current regulatory liabilities  
Fuel cost adjustment tax equivalents$115 $138 
Unrealized gains on commodity derivatives26 12 
Total current regulatory liabilities141 150 
Non-current regulatory liabilities  
Unrealized gains on commodity derivatives23 — 
Total non-current regulatory liabilities23 — 
Total regulatory liabilities$164 $150 
Note
(1) At September 30, 2019, $12 million previously classified as Environmental agreements (a component of Regulatory assets) has been reclassified to Other non-current regulatory assets (a component of Regulatory assets) to conform with current year presentation.

    In 2017, the TVA Board authorized management to accelerate amortization of certain regulatory assets to the extent actual net income in 2018 exceeded the budgeted amount, up to the aggregate amount of those certain regulatory assets. Assets included in this TVA Board action include: deferred nuclear generating units, environmental cleanup costs related to the Kingston ash spill, and nuclear training costs related to the refurbishing and restarting of Browns Ferry Nuclear Plant ("Browns Ferry") Unit 1 and the construction of Watts Bar Nuclear Plant ("Watts Bar") Unit 2. TVA recorded $857 million of accelerated amortization of the Deferred nuclear generating units and Nuclear training costs regulatory assets in 2018. The TVA Board authorized TVA to use the amount included in the 2019 rate action for these two regulatory assets, to the extent needed, to accelerate amortization of the Environmental cleanup costs - Kingston ash spill regulatory asset in 2019. TVA recorded $266 million of accelerated recovery for the Kingston ash spill regulatory asset in 2019. No accelerated amortization was recorded in 2020.

    Deferred Pension Costs and Other Post-retirement Benefit Costs.  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 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 21 — 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 recent plan design changes, future contributions are expected to exceed the expense calculated under U.S. GAAP. Accordingly, TVA will discontinue this regulatory accounting practice once all such deferred costs have been recovered, at which time it will recognize pension costs in accordance with U.S. GAAP.

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 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 already set aside in the ART, future earnings on those investment funds, and future cash contributions to the ART and future earnings thereon.  For 2020, TVA recovered in rates a portion of its estimated current year non-nuclear decommissioning costs 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. There is not a specified recovery period; therefore, the regulatory asset is classified as long-term consistent with the ART investments and ARO liability.

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 Sheet.

Due to changing interest rates in the financial markets associated with the COVID-19 pandemic, TVA has experienced unrealized losses related to its derivative instruments for the year ended September 30, 2020. 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, future earnings on the investment funds, and future earnings thereon. 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.  There is not a specified recovery period; therefore, the regulatory asset is classified as long-term consistent with the NDT investments and ARO liability.

Unrealized Gains (Losses) on Commodity Derivatives.  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.  During the fourth quarter of 2020, TVA discontinued derivative accounting for forward coal contracts because these contracts no longer meet the criteria of net settlement. As a result, the associated net regulatory assets have been derecognized. 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 2024.  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.

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 Capital Leases and Other Financing Obligations. For certain leases that were determined prior to TVA's adoption of the new lease accounting standard effective October 1, 2019, TVA recognized the initial capital lease liability and asset at inception. However, the annual expense recognized in rates is equal to the annual lease payments, which differs from GAAP treatment. 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 each capital lease. These costs will be amortized over the respective lease as lease 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.
v3.20.2
Asset Acquisitions and Business Combinations (Notes)
 12 Months Ended
Sep. 30, 2020
Business Combinations and Settlement of Preexisting Relationships [Abstract]  
Asset Acquisitions and Business Combinations Disclosure Asset Acquisitions
    On September 20, 2017, TVA acquired 100 percent of the equity interests in two special purpose entities ("SPEs") designed to administer rent payments TVA makes under certain of its lease/leaseback arrangements.  Each entity holds residual interests in four of TVA's peaking combustion turbine units ("CTs").  TVA acquired these entities in order to reacquire the residual interests in eight CTs it had previously granted in the lease/leaseback arrangements.

                TVA acquired the entities for total cash consideration of $36 million.  The fair value of the assets acquired consisted of $110 million of reacquired rights, and the fair value of liabilities assumed consisted of $74 million in notes payable.  Reacquired rights are an intangible asset included in TVA's Completed plant balance and are amortized over the estimated useful life of the underlying CTs.  Notes payable assumed in the transaction were paid in full during 2020. TVA recognized less than $1 million of amortization expense, related to reacquired rights, within TVA's consolidated statements of operations.  Transaction costs were not material.

                TVA determined that its lease/leaseback obligations were preexisting relationships that were effectively settled in the asset acquisitions.  TVA settled the preexisting relationships separately from the asset acquisitions, resulting in a loss on extinguishment of the obligations of $3 million.  The carrying value of lease/leaseback obligations effectively settled was $71 million, including accrued interest, and the reacquisition price was $74 million, paid in cash, at the acquisition date.
v3.20.2
Variable Interest Entities
 12 Months Ended
Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Variable Interest Entities
10.  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 conduct, 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 7.0 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 conduct, 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, 2020 and 2019, as reflected on the Consolidated Balance Sheets, are as follows:
Summary of Impact of VIEs on Consolidated Balance Sheets
At September 30
 20202019
Current liabilities 
Accrued interest$10 $11 
Accounts payable and accrued liabilities3 3 
Current maturities of long-term debt of variable interest entities41 39 
Total current liabilities
54 53 
Other liabilities
Other long-term liabilities23 25 
Long-term debt, net
Long-term debt of variable interest entities, net1,048 1,089 
Total liabilities$1,125 $1,167 

Interest expense of $54 million, $56 million, and $58 million related to debt of VIEs and membership interests of variable interest entity subject to mandatory redemption is included in the Consolidated Statements of Operations for the years ended September 30, 2020, 2019, and 2018, respectively.

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.
v3.20.2
Other Long-Term Liabilities
 12 Months Ended
Sep. 30, 2020
Other Liabilities, Noncurrent [Abstract]  
Other Long-Term Liabilities Other Long-Term Liabilities
Other long-term liabilities consist primarily of liabilities related to certain derivative agreements as well as for environmental remediation liabilities and liabilities under agreements related to compliance with certain environmental regulations. See Note 12 — Asset Retirement Obligations, Note 15 — Risk Management Activities and Derivative Transactions — Derivatives Not Receiving Hedge Accounting Treatment — Interest Rate Derivatives, and Note 22 — Commitments and Contingencies — Legal Proceedings — Environmental Agreements. The table below summarizes the types and amounts of Other long-term liabilities:
Other Long-Term Liabilities(1)
At September 30
 20202019
Interest rate swap liabilities$1,927 $1,676 
Operating lease liabilities171 — 
Currency swap liabilities123 193 
EnergyRight® financing obligation78 90 
Paradise pipeline financing obligation— 80 
Accrued long-term service agreements56 66 
Other193 203 
Total other long-term liabilities$2,548 $2,308 
Note
(1) Due to the implementation of the new lease accounting standard effective October 1, 2019, TVA reclassified $182 million of finance leases from Other long-term liabilities to Finance lease liabilities in the Consolidated Balance Sheet for the year ending September 30, 2019.
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 Accounts payable and accrued liabilities, Accrued interest, and Other long-term liabilities on the Consolidated Balance Sheets. As of September 30, 2020 and 2019, the carrying amount of the interest rate swap liabilities reported in Accounts payable and accrued liabilities and Accrued interest was approximately $114 million and $88 million, respectively. See Note 15 — Risk Management Activities and Derivative Transactions — Derivatives Not Receiving Hedge Accounting Treatment — Interest Rate Derivatives for information regarding the interest rate swap liabilities. As of September 30, 2020, Interest rate swap liabilities increased $277 million as compared to September 30, 2019, primarily due to a decrease in interest rates resulting in higher mark-to-market values on future expected net cash flows.
    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. As of September 30, 2020 and 2019, the carrying amount of the financing obligation reported in Accounts payable and accrued liabilities was approximately $19 million and $23 million, respectively. See Note 8 — Other Long-Term Assets for information regarding the associated loans receivable.

In response to the COVID-19 pandemic, customers experiencing financial hardship can request a deferral of EnergyRight® loan payments for a period of up to six months. This deferral option began April 20, 2020, and is available through October 31, 2020. Deferred loans will not accrue interest during the deferral months. These deferred loans have resulted in a less than $1 million impact to TVA.

    Paradise Pipeline Financing Obligation. TVA reserves firm pipeline capacity on an approximately 19-mile pipeline
owned by Texas Gas, which serves TVA's Paradise Combined Cycle Facility. TVA had been accounting for the contract covering this arrangement as a financing transaction due to failed sale-leaseback treatment. The contract was revised during the fourth quarter of 2020 and is no longer deemed to contain a lease component. Accordingly, amounts related to the pipeline asset and financing obligation recorded in connection with this transaction were derecognized as of September 30, 2020. The current and long-term portions of less than $1 million and $80 million, respectively, of the financing obligation are reported in Accounts payable and accrued liabilities and Other long-term liabilities, respectively, on TVA's Consolidated Balance Sheet at September 30, 2019.

    Accrued Long-Term Service Agreement. 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, parts received and services rendered exceed payments made. The current and long-term portions
of the resulting obligation are reported in Accounts payable and accrued liabilities and Other long-term liabilities, respectively, on
TVA's Consolidated Balance Sheets. As of September 30, 2020 and 2019, related liabilities of $15 million and $12 million, respectively, were recorded in Accounts payable and accrued liabilities.
v3.20.2
Asset Retirement Obligations
 12 Months Ended
Sep. 30, 2020
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligations Asset Retirement Obligations
    During the year ended September 30, 2020, TVA's total ARO liability increased $1.2 billion.

    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 bases its nuclear decommissioning estimates on site-specific cost studies. The most recent study was approved and implemented in September 2017. An increase of $250 million was recorded to the nuclear AROs as a result of the updates. Site-specific cost studies are updated for each of TVA's nuclear units at least every five years.

    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.

During 2020, the revisions in non-nuclear estimates increased $1.1 billion for the year ended September 30, 2020. In November 2019, the Tennessee Department of Environment and Conservation ("TDEC") released amendments to its regulations which govern solid waste disposal facilities, including TVA's active CCR facilities covered by a solid waste disposal permit and those which closed pursuant to a TDEC approved closure plan. Such facilities are generally subject to a 30-year post-closure care period during which the owner or operator must undertake certain activities, including monitoring and maintaining the facility. The amendments, among other things, add an additional 50-year period after the end of the post-closure care period, require TVA to submit recommendations as to what activities must be performed during this 50-year period to protect human health and
the environment, and require TVA to submit revised closure plans every 10 years. This regulatory revision resulted in an increase of $129 million, of which $38 million was related to operating CCR facilities and $91 million was related to inactive or closed CCR facilities. In June 2020, based on recent project cost data and estimates, TVA revised its AROs for closure-by-removal of certain CCR facilities at Allen Fossil Plant, resulting in an increase to AROs of $273 million. In September 2020, TVA completed an engineering review of its cost estimates to close the ash pond complex at Gallatin Fossil Plant, resulting in an increase of $173 million due to expected cost increases for excavation, disposal, and other activities required in a closure-by-removal project. Also in September 2020, TVA completed a study of its plant decommissioning obligations and CCR post-closure care and monitoring obligations. TVA increased its plant decommissioning obligations by $19 million, primarily due to asbestos and hazardous material abatement costs. TVA increased its CCR post-closure care and monitoring AROs primarily as a result of expected cost increases to monitor groundwater and maintain CCR areas after closure as well as increases in expected acreage to maintain after closure, totaling $460 million.

    During 2019, the revisions in non-nuclear estimates increased $50 million for the year ended September 30, 2019. As a result of recent experience in completing settlements at certain facilities, costs for asbestos abatement activities across TVA's fossil fleet increased $114 million. TVA changed the preferred closure method for Allen West Impoundment from closure-in-place to closure-by-removal, which resulted in a cost increase of $33 million. Partially offsetting these increases was a $57 million decrease in costs for Paradise closure projects, and a $44 million decrease in costs for the Allen East Impoundment closure project. Additionally, as a result of the decision in TVA's favor by the Sixth Circuit in the lawsuit brought by TSRA and TCWN, as well as the June 2019 consent order filed in the case brought by TDEC, Gallatin discounted cash flows related to CCR closure and post-closure costs of $672 million have been recorded as Asset retirement obligations. The obligation is based upon the assumptions outlined in the consent order, including a new lined facility will be permitted and constructed on the Gallatin site and existing CCR materials in the existing wet ash disposal impoundments at Gallatin will be moved to this new facility over a 20-year period.
    
    Additionally, during the years ended September 30, 2020 and 2019, 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 2020, 2019, and 2018, $169 million, $144 million, and $144 million, respectively, of the related regulatory assets were amortized into expense as these amounts were collected in rates. See Note 9 — 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 — Decommissioning Costs for a discussion of the trusts' objectives and the current balances of the trusts.
Asset Retirement Obligation Activity
 NuclearNon-NuclearTotal
Balance at September 30, 2018$2,989 $1,790 $4,779 
Settlements(7)(82)(89)
Revisions in estimate— 50 50 
Additional obligations18 — 18 
Gallatin CCR— 672 672 
Accretion (recorded as regulatory asset)136 50 186 
Balance at September 30, 20193,136 2,480 5,616 
(1)
Settlements(1)(113)(114)
Revisions in estimate— 1,077 1,077 
Accretion (recorded as regulatory asset)143 63 206 
Balance at September 30, 2020$3,278 $3,507 $6,785 
(1)
Note
(1) Includes $345 million and $163 million at September 30, 2020 and 2019, respectively, in Current liabilities.
v3.20.2
Debt and Other Obligations
 12 Months Ended
Sep. 30, 2020
Debt Disclosure [Abstract]  
Debt and Other Obligations 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, 2020, TVA had only two types of Bonds outstanding: power bonds and discount notes.  Power bonds have maturities between one 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 rent payments under its leaseback transactions, as well as 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, 2020, 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 10 — 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 10 — 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 both September 30, 2020 and 2019 totaled $1.1 billion.

Secured Notes

    On July 20, 2016, TVA acquired two entities, in a business combination, designed to administer rent payments TVA makes under certain of its lease/leaseback arrangements. On September 27, 2000, the entities issued secured notes totaling $255 million that had an interest rate of 7.299 percent and required amortizing semi-annual payments on each March 15 and September 15 with a maturity date of March 15, 2019. In 2016, TVA assumed these secured notes in the acquisition at a fair value of $78 million. The secured notes of the entities were paid in full in 2019.

    On September 20, 2017, TVA acquired two entities, in an asset acquisition, designed to administer rent payments TVA makes under certain of its lease/leaseback arrangements. On November 14, 2001, the entities issued secured notes totaling $272 million that had an interest rate of 5.572 percent and required amortizing semi-annual payments on each May 1 and November 1 with a maturity date of May 1, 2020. In 2017, TVA assumed these secured notes in the acquisition at a fair value of $74 million. The secured notes of the entities, including current maturities, outstanding at September 30, 2019, totaled approximately $23 million, and are included in Notes payable on TVA's Consolidated Balance Sheet. The secured notes of the entities were paid in full in 2020.
Short-Term Debt

    The following table provides information regarding TVA's short-term borrowings:
Short-term Borrowings
At September 30
 202020192018
Gross amount outstanding - discount notes$57 $922 $1,217 
Weighted average interest rate - discount notes0.06 %2.15 %2.05 %

Put and Call Options

At September 30, 2019, bond issues of $357 million held by the public were redeemable in whole or in part, at TVA's option, on call dates through 2020 and at call prices of 100 percent of the principal amount. Nine of these bond issues totaling $217 million, with maturity dates ranging from 2025 to 2043, included a "survivor's option," which allowed for right of redemption upon the death of a beneficial owner in certain specified circumstances. These bonds were classified as long-term at September 30, 2019. TVA subsequently announced in October 2019 that $217 million of callable bonds were redeemed at par on November 15, 2019.

Additionally, 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, 2020.  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, 2020.

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, 2020 and 2019.
Debt Securities Activity
For the years ended September 30
 20202019
Issues
2020 Series A(1)
$1,000 $— 
Discount on debt issues(3)— 
Total$997 $— 
Redemptions/Maturities(2)
  
electronotes®
$219 $5 
2013 Series A1,000 
2009 Series B28 30 
2018 Series A1,000 — 
1999 Series A PARRS (TVE)23 — 
1998 Series D PARRS (TVC)17 — 
1995 Series B140 — 
Total redemptions/maturities of power bonds1,427 1,035 
Notes payable23 46 
Variable interest entities39 38 
Total$1,489 $1,119 
Notes
(1) The 2020 Series A Bonds were issued at 99.7 percent of par.
(2) All redemptions were at 100 percent of par.

Debt Outstanding

    Total debt outstanding at September 30, 2020 and 2019, consisted of the following: 
Short-Term Debt
At September 30
 
CUSIP or Other Identifier
 
Maturity
 Call/(Put) Date 
Coupon Rate		20202019
Short-term debt, net of discounts$57 $922 
Current maturities of long-term debt of VIEs issued at par41 39 
Current maturities of notes payable— 23 
Current maturities of power bonds issued at par
880591EF5
12/15/20193.770%— 1 
880591EF56/15/20203.770%— 27 
880591EF512/15/20203.770%1 — 
880591EF56/15/20213.770%28 — 
88059TEL111/15/20192.650%— 1 
88059TEL15/15/20202.650%— 1 
880591EV03/15/20202.250%— 1,000 
880591EL22/15/20213.875%1,500 — 
880591DC36/7/20215.805%258 
(1)
— 
Total current maturities of power bonds issued at par   1,787 1,030 
Total current debt outstanding, net   $1,885 $2,014 
Note
(1) Includes net exchange gain from currency transactions of $73 million at September 30, 2020.
Long-Term Debt
At September 30
 
CUSIP or Other Identifier
 
Maturity
Coupon
Rate		Effective Call Date2020 Par2019 ParStock Exchange Listings
electronotes®(2)
5/15/2020 - 2/15/20432.375% - 3.625%
2/15/2015 - 2/15/2018 (5)
$— $217 None
880591EL22/15/20213.875%— 1,500 New York
880591DC36/7/20215.805%
(3)
— 

246 
(1)
New York, Luxembourg
880591EN88/15/20221.875%1,000 1,000 New York
880591ER99/15/20242.875%1,000 1,000 New York
880591EW85/15/20250.750%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(4)
6/1/20282.134%256 273 New York
880591409(4)
5/1/20292.216%208 232 New York
880591DM15/1/20307.125%1,000 1,000 New York, Luxembourg
880591DP46/7/20326.587%
(3)
323 
(1)
307 
(1)
New York, Luxembourg
880591DV17/15/20334.700%472 472 New York, Luxembourg
880591EF56/15/20343.770%218 246 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%
(3)
194 
(1)
185 
(1)
New York, Luxembourg
880591CF77/15/20456.235%7/15/2020— 140 New York
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
Subtotal 18,078 19,225  
Unamortized discounts, premiums, issue costs, and other  (122)(131) 
Total long-term outstanding power bonds, net  17,956 19,094  
Long-term debt of VIEs, net1,048 1,089 
Total long-term debt, net$19,004 $20,183 
Notes
(1)  Includes net exchange gain from currency transactions of $80 million and $191 million at September 30, 2020 and 2019, respectively.
(2)  Includes one electronotes® issue with partial maturities of principal for each required annual payment.
(3)  The coupon rate represents TVA's effective interest rate.
(4)  TVA PARRS, CUSIP numbers 880591300 and 880591409, may be redeemed under certain conditions.  See Put and Call Options above.
(5)  The bonds were callable on or after the dates shown.
 
Maturities Due in the Year Ending September 30
 20212022202320242025ThereafterTotal
Long-term power bonds, long-term debt of VIEs, and notes payable including current maturities(1)
$1,901 $1,071 $69 $1,058 $1,059 $15,957 $21,115 
Short-term debt, net of discounts57 — — — — — 57 
Note
(1) Long-term power bonds does not include non-cash items of foreign currency exchange gain of $153 million, unamortized debt issue costs of $45 million, and net discount on sale of Bonds of $77 million. Long-term debt of VIE does not include non-cash item of unamortized debt issue costs of $8 million.

Credit Facility Agreements

TVA has funding available under four long-term revolving credit facilities totaling $2.7 billion: a $150 million credit facility that matures on December 11, 2021, a $1.0 billion credit facility that matures on June 13, 2023, a $1.0 billion credit facility that matures on September 28, 2023, and a $500 million credit facility that matures on February 1, 2025. 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, 2020 and 2019, there were $1.5 billion and $1.3 billion, respectively, of letters of credit outstanding under these facilities, and there were no borrowings outstanding. See Note 15 — Risk Management Activities and Derivative Transactions — Other Derivative Instruments — Collateral.

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, 2020
Maturity DateFacility LimitLetters of Credit OutstandingCash BorrowingsAvailability
December 2021$150 $38 $— $112 
June 20231,000 432 — 568 
September 20231,000 487 — 513 
February 2025500 500 — — 
     Total$2,650 $1,457 $— $1,193 

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 2021 with a maturity date of September 30, 2021. 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 one year or less. There were no outstanding borrowings under the facility at September 30, 2020. 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. On September 30, 2020 and 2019, the outstanding leaseback obligations related to the remaining CTs and QTE were $223 million and $263 million, respectively. In March 2019, TVA made final rent payments under lease/leaseback transactions involving eight CTs, and TVA had previously acquired the equity interests related to these transactions. These transactions were terminated in July 2019. In May 2020, TVA made final rent payments under lease/leaseback transactions involving eight additional CTs, and TVA had previously acquired the equity interest related to these transactions. Rent payments under the remaining CT lease/leaseback transactions are scheduled to be made through January 2022. TVA does have the option to acquire the equity interests related to transactions involving the remaining eight CTs for additional amounts. In addition, on October 30, 2019, TVA provided notice of its intent to purchase the ownership interest in certain QTE. Repurchase payments are expected to be paid through a series of installments in 2021 and 2022, after which the associated leases will be terminated.
v3.20.2
Accumulated Other Comprehensive Income (Loss)
 12 Months Ended
Sep. 30, 2020
Equity [Abstract]  
Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss)
    AOCI represents market valuation adjustments related to TVA's currency swaps. The currency swaps are cash flow hedges and are the only derivatives in TVA's portfolio that have been designated and qualify for hedge accounting treatment. TVA records exchange rate gains and losses on its foreign currency-denominated debt and any related accrued interest in net income and marks its currency swap assets and liabilities to market through other comprehensive income (loss) ("OCI"). TVA then reclassifies an amount out of AOCI into net income, offsetting the exchange gain/loss recorded on the debt. For the years ended September 30, 2020 and 2019, TVA reclassified $38 million of gains and $45 million of losses, respectively, related to its cash flow hedges from AOCI to Interest expense. See Note 15 — Risk Management Activities and Derivative Transactions.

    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 AOCI or that would impact the statements of operations are recorded as regulatory assets or regulatory liabilities. See Note 9 — Regulatory Assets and Liabilities for a schedule of regulatory assets and liabilities.  See Note 15 — Risk Management Activities and Derivative Transactions for a discussion of the recognition in AOCI of gains and losses associated with certain derivative contracts. See Note 16 — Fair Value Measurements for a discussion of the recognition of certain investment fund gains and losses as regulatory assets and liabilities.  See Note 21 — Benefit Plans for a discussion of the regulatory accounting related to components of TVA's benefit plans.
v3.20.2
Risk Management Activities and Derivative Transactions
 12 Months Ended
Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Risk Management Activities and Derivative Transactions 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. During the fourth quarter of 2020, TVA discontinued derivative accounting for forward coal contracts because these contracts no longer meet the criteria of net settlement. As a result, the associated $10 million net derivative liabilities have been derecognized. TVA suspended its FTP in 2014 and no longer uses financial instruments to hedge risks related to commodity prices; however, TVA plans to continue to manage fuel price volatility through other methods and is currently reevaluating its suspended FTP program for future use of financial instruments.

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
Derivatives in Cash Flow Hedging RelationshipObjective of Hedge TransactionAccounting for Derivative
Hedging Instrument		20202019
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$(1)$(114)
Summary of Derivative Instruments That Receive Hedge Accounting Treatment (part 2)(1)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income to Interest Expense
For the years ended September 30
Derivatives in Cash Flow Hedging Relationship20202019
Currency swaps$38 $(45)
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 $27 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 exchange gain 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
 
Derivative Type
Objective of Derivative(2)
Accounting for Derivative Instrument20202019
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 assets or liabilities

Realized gains and losses are recognized in Interest expense when incurred during the settlement period and are presented in operating cash flow		$(97)$(79)
Commodity contract derivativesTo protect against fluctuations in market prices of purchased coal or natural gas (price risk)Mark-to-market gains and losses are recorded as regulatory assets or liabilities

Realized gains and losses due to contract settlements are recognized in Fuel expense as incurred		(1)— 
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 assets and liabilities. As such, there were no related gains (losses) recognized in income for these unrealized gains (losses) for the years ended September 30, 2020 and 2019.
(2) During the fourth quarter of 2020, TVA discontinued derivative accounting for forward coal contracts.
Fair Values of TVA Derivatives
At September 30
 20202019
Derivatives That Receive Hedge Accounting Treatment:
 BalanceBalance Sheet PresentationBalanceBalance Sheet Presentation
Currency swaps    
£200 million Sterling
$(78)Accounts payable and accrued liabilities $(78)$(90)Accounts payable and accrued liabilities $(6); Other long-term liabilities $(84)
£250 million Sterling
(63)Accounts payable and accrued liabilities $(5); Other long-term liabilities $(58)(61)Accounts payable and accrued liabilities $(5); Other long-term liabilities $(56)
£150 million Sterling
(68)Accounts payable and accrued liabilities $(3); Other long-term liabilities $(65)(57)Accounts payable and accrued liabilities $(4); Other long-term liabilities $(53)
Derivatives That Do Not Receive Hedge Accounting Treatment:
 BalanceBalance Sheet PresentationBalanceBalance Sheet Presentation
Interest rate swaps    
$1.0 billion notional
$(1,449)Accounts payable and accrued liabilities $(43); Accrued interest $(37); Other long-term liabilities $(1,369)$(1,261)Accounts payable and
accrued liabilities $(29); Accrued interest $(33);
Other long-term liabilities
$(1,199)
$476 million notional
(588)Accounts payable and accrued liabilities $(22); Accrued interest $(10); Other long-term liabilities $(556)(498)Accounts payable and
accrued liabilities $(15); Accrued interest $(9);
Other long-term liabilities
$(474)
$42 million notional(4)Accounts payable and accrued liabilities $(2); Other long-term liabilities $(2)(5)Accounts payable and
accrued liabilities $(1); Accrued interest $(1); Other long-term liabilities $(3)
Commodity contract derivatives46 Other current assets $26; Other long-term assets $23; Accounts payable and accrued liabilities $(3)(41)Other current assets $12; Other long-term liabilities $(16); Accounts payable and accrued liabilities $(37)
Cash Flow Hedging Strategy for Currency Swaps

To protect against exchange rate risk related to three 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, 2020:
Currency Swaps Outstanding
September 30, 2020
Effective Date of Currency Swap ContractAssociated TVA Bond Issues Currency ExposureExpiration Date of SwapOverall Effective
Cost to TVA
1999£200 million20215.81%
2001£250 million20326.59%
2003£150 million20434.96%

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 Accounts payable and accrued liabilities, 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 assets or liabilities 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 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 in TVA's Consolidated Statements of Operations. For the years ended September 30, 2020 and 2019, the changes in fair market value of the interest rate swaps resulted in the deferral of unrealized losses of $272 million and $565 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 commodity contracts for coal and natural gas that require physical delivery of the contracted quantity of the commodity. During the fourth quarter of 2020, TVA discontinued derivative accounting for forward coal contracts. TVA marks to market natural gas contracts and defers the fair market values as regulatory assets or liabilities on a gross basis. At September 30, 2020, TVA's natural gas contract derivatives had terms of up to four years.
Commodity Contract Derivatives 
At September 30
 20202019
 
Number of Contracts
Notional AmountFair Value (MtM)Number of ContractsNotional Amount
Fair Value (MtM)
Coal contract derivatives—— million tons$— 89 million tons$(4)
Natural gas contract derivatives42302 million mmBtu$46 65330 million mmBtu$(37)
Offsetting of Derivative Assets and Liabilities

    The amounts of TVA's derivative instruments as reported on the Consolidated Balance Sheets at September 30, 2020 and 2019, are shown in the table below.
Derivative Assets and Liabilities(1)
(in millions)
At September 30, 2020
At September 30, 2019
Assets
Commodity derivatives not subject to master netting or similar arrangement$49 $12 
Liabilities
Currency swaps(2)
$209 $208 
Interest rate swaps(2)
2,041 1,764 
Total derivatives subject to master netting or similar arrangement2,250 1,972 
Commodity derivatives not subject to master netting or similar arrangement3 53 
Total liabilities$2,253 $2,025 
Notes
(1) Offsetting amounts primarily include counterparty netting of derivative contracts, margin account deposits for futures commission merchants transactions, and cash collateral received or paid in accordance with the accounting guidance for derivatives and hedging transactions. There were no offsetting amounts on TVA's Consolidated Balance Sheets at either September 30, 2020 or 2019.
(2) Letters of credit of approximately $1.5 billion and $1.3 billion were posted as collateral at September 30, 2020 and 2019, respectively, to partially secure the liability positions of one of the currency swaps and one of the interest rate swaps in accordance with the collateral requirements for these derivatives.

Other Derivative Instruments

Investment Fund Derivatives.  Investment funds consist primarily of funds held in the NDT, ART, SERP, and DCP.  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, 2020 and 2019, the NDT held investments in forward contracts to purchase debt securities. The fair values of these derivatives were in net asset positions totaling $13 million and $22 million at September 30, 2020 and 2019, respectively.

Collateral.  TVA's interest rate swaps and currency swaps 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, 2020, the aggregate fair value of all derivative instruments with credit-risk related contingent features that were in a liability position was $2.2 billion.  TVA's collateral obligations at September 30, 2020, under these arrangements, were approximately $1.5 billion, for which TVA had posted approximately $1.5 billion 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 contract 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 $1.4 billion and $1.6 billion of receivables from power sales outstanding at September 30, 2020 and 2019, 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 and Note 3 — Accounts Receivable, Net.

TVA had revenue from two LPCs that collectively accounted for 17 percent of total operating revenue for the years ended both September 30, 2020 and September 30, 2019.

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 from other vendors, TVA could experience delays, disruptions, additional costs, or other operational outcomes that may impact generation, maintenance, and capital programs. If one of TVA's fuel or purchased power suppliers fails to perform under the terms of its 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.

Natural Gas. TVA purchases the majority of its natural gas requirements from a variety of suppliers under primarily short-term contracts. In the event of nonperformance by these suppliers, TVA believes that it can obtain replacement natural gas.

    Coal. To help ensure a reliable supply of coal, TVA had coal contracts with multiple suppliers at September 30, 2020. The contracted supply of coal is sourced from multiple geographic regions of the United States and is to be delivered via various transportation methods (e.g., barge, rail, and truck). Emerging technologies, environmental regulations, and low natural gas prices have contributed to weak demand for coal. As a result, coal suppliers are facing increased financial pressure, which has led to relatively poor credit ratings and bankruptcies. Continued difficulties by coal suppliers, including impacts from the COVID-19 pandemic, could result in consolidations, additional bankruptcies, restructuring, contract renegotiations, 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.

    Purchased Power. TVA has a power purchase agreement that expires on March 31, 2032, with a supplier of electricity for 440 megawatts ("MW") of summer net capability from a lignite-fired generating plant. TVA has determined that the supplier has the equivalent of a non-investment grade credit rating; therefore, the supplier has provided credit assurance to TVA under the terms of the agreement.

Other Suppliers. At this time, TVA has experienced minimal impacts due to force majeure events, with the exception of a manufacturing delay for a major turbine component. A mitigation strategy was developed by TVA and the vendor to reduce projected delays and impacts to TVA's outage schedule. TVA will continue to monitor the supply base and remain in contact with suppliers to identify potential risks.

Derivative Counterparties.  TVA has entered into physical and financial contracts that qualify as derivatives for hedging purposes, and TVA's NDT, ART, and qualified defined benefit 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 substantial costs in connection with entering into a replacement transaction. If a counterparty to the derivative contracts into which the NDT, the ART, and the qualified 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, 2020, all of TVA's currency swaps and interest rate swaps as well as all of the derivatives in the NDT and ART were with banking counterparties whose Moody's credit ratings were A3 or higher.
    TVA classifies qualified forward natural gas contracts as derivatives. See Derivatives Not Receiving Hedge Accounting Treatment above. At September 30, 2020, the natural gas contracts were with counterparties whose ratings ranged from Caa2 to A2. TVA recognizes the slowdown in demand and the impacts on the oil and gas industry as a result of the COVID-19 pandemic. TVA will continue to monitor the impacts and affected credit ratings and enforce contract performance assurance provisions when applicable.
v3.20.2
Fair Value Measurements
 12 Months Ended
Sep. 30, 2020
Fair Value Disclosures [Abstract]  
Fair Value Measurements 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 and DCP 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, 2020, Investment funds were comprised of $3.2 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, and DCP. 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 $2.2 billion and $866 million, respectively, at September 30, 2020.

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 NDT, ART, SERP, and DCP 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, and DCP 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, 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 limited partnerships in private equity of $218 million, private real assets of $67 million, and private credit of $33 million at September 30,
2020. The ART had unfunded commitments related to limited partnerships in private equity of $133 million, private real assets of $54 million, and private credit of $16 million at September 30, 2020. 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, and DCP 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 net asset value 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. TVA recorded unrealized gains and losses related to its equity and trading debt securities held during each period as follows:
Unrealized Investment Gains (Losses)
At or for the years ended September 30
FundFinancial Statement Presentation20202019
NDTRegulatory asset$37 $(112)
ARTRegulatory asset32 (70)
SERPOther income (expense)3 — 
DCPOther income (expense)2 (2)

Due to higher volatility in the financial markets associated with the COVID-19 pandemic, TVA has experienced fluctuations related to its ART and NDT investment portfolio during 2020. The losses experienced during the three months ended March 31, 2020, have been recovered. For the year ended September 30, 2020, the NDT increased in value $123 million compared to the year ended September 30, 2019. Despite this volatility, TVA's NDT funding as of September 30, 2020, continues to be fully funded per the NRC funding requirements.

Currency and Interest Rate 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

See Note 15 — Risk Management Activities and Derivative Transactions — Derivatives Not Receiving Hedge Accounting Treatment. Most of these contracts are valued based on market approaches which utilize short-term and mid-term market-quoted prices from an external industry brokerage service.

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 2019) 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 less than $1 million decrease in the fair value of assets and a $1 million decrease in the fair value of liabilities at September 30, 2020.

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, 2020 and 2019. 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, 2020
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$500 $— $— $500 
Government debt securities(1)
485 40 — 525 
Corporate debt securities(2)
— 356 — 356 
Mortgage and asset-backed securities— 27 — 27 
Institutional mutual funds188 — — 188 
Forward debt securities contracts— 13 — 13 
Private equity funds measured at net asset value(3)
— — — 194 
Private real asset funds measured at net asset value(3)
— — — 168 
Private credit measured at net asset value(3)
— — — 53 
Commingled funds measured at net asset value(3)
— — — 1,174 
Total investments1,173 436 — 3,198 
Commodity contract derivatives— 49 — 49 
Total$1,173 $485 $— $3,247 
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(4)
$— $209 $— $209 
Interest rate swaps— 2,041 — 2,041 
Commodity contract derivatives— 3 — 3 
Total$— $2,253 $— $2,253 
Notes
(1) Includes government-sponsored entities.
(2) Includes both U.S. and foreign debt.
(3) Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been categorized in the fair value hierarchy. 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.
(4) 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, 2019
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$464 $— $— $464 
Government debt securities279 65 — 344 
Corporate debt securities— 417 — 417 
Mortgage and asset-backed securities— 32 — 32 
Institutional mutual funds250 — — 250 
Forward debt securities contracts— 22 — 22 
Private equity funds measured at net asset value(1)
— — — 140 
Private real asset funds measured at net asset value(1)
— — — 135 
    Private credit measured at net asset value(1)
— — — 33 
Commingled funds measured at net asset value(1)
— — — 1,131 
Total investments993 536 — 2,968 
Commodity contract derivatives— 7 5 12 
Total$993 $543 $5 $2,980 
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(2)
$— $208 $— $208 
Interest rate swaps— 1,764 — 1,764 
Commodity contract derivatives— 44 9 53 
Total$— $2,016 $9 $2,025 
Notes
(1) Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been categorized in the fair value hierarchy. 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.
(2) 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.

    During the fourth quarter of 2020, TVA discontinued derivative accounting for forward coal contracts. TVA previously used internal valuation specialists for the calculation of its commodity contract derivatives fair value measurements classified as Level 3. Analytical testing was performed on the change in fair value measurements each period to ensure the valuation is reasonable based on changes in general market assumptions. Significant changes to the estimated data used for unobservable inputs, in isolation or combination, may result in significant variations to the fair value measurement reported.

The following table presents a reconciliation of all commodity contract derivatives measured at fair value on a recurring basis using significant unobservable inputs (Level 3):
Fair Value Measurements Using Significant Unobservable Inputs
 Commodity Contract Derivatives
Balance at October 1, 2018$58 
Change in net unrealized gains (losses) deferred as regulatory assets and liabilities(62)
Balance at September 30, 2019(4)
Settlements(1)
Change in net unrealized gains (losses) deferred as regulatory assets and liabilities5 
Balance at September 30, 2020$— 
The following table presents quantitative information related to the significant unobservable inputs used in the measurement of fair value of TVA's assets and liabilities classified as Level 3 in the fair value hierarchy:
Quantitative Information about Level 3 Fair Value Measurements 
 
Fair Value at September 30, 2019
Valuation Technique(s)Unobservable InputsRange
Assets
Commodity contract derivatives$5 Pricing modelCoal supply and demand0.4 - 0.8 billion tons/year
Long-term market prices$12.10 - $94.51/ton
Liabilities
Commodity contract derivatives$9 Pricing modelCoal supply and demand0.4 - 0.8 billion tons/year
Long-term market prices$12.10 - $94.51/ton
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, 2020 and 2019, 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, 2020 and 2019, were as follows:
Estimated Values of Financial Instruments Not Recorded at Fair Value
 At September 30, 2020At September 30, 2019
 Valuation ClassificationCarrying
Amount		Fair
Value		Carrying
Amount		Fair
Value
EnergyRight® receivables (including current portion)
Level 2$87 $86 $101 $100 
Loans and other long-term receivables, net (including current portion)Level 2$105 $93 $131 $120 
EnergyRight® financing obligations (including current portion)
Level 2$97 $108 $113 $126 
Unfunded loan commitmentsLevel 2$— $2 $— $10 
Membership interests of VIEs subject to mandatory redemption (including current portion)Level 2$26 $35 $28 $37 
Long-term outstanding power bonds (including current maturities), netLevel 2$19,743 $26,630 $20,124 $26,059 
Long-term debt of VIEs (including current maturities), netLevel 2$1,089 $1,419 $1,128 $1,371 
Long-term notes payable (including current maturities)Level 2$— $— $23 $23 

The carrying value of Cash and cash equivalents, Restricted cash and cash equivalents, 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.
v3.20.2
Proprietary Capital (Text Block)
 12 Months Ended
Sep. 30, 2020
Stockholders' Equity Note [Abstract]  
Proprietary Capital Proprietary Capital
Appropriation Investment

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.

The table below summarizes TVA's activities related to appropriated funds and retained earnings.
Summary of Proprietary Capital Activity
At or for the years ended September 30
 20202019
Power ProgramNonpower
 Programs		Power ProgramNonpower
 Programs
Appropriation Investment$258 $4,351 $258 $4,351 
Proprietary Capital    
Balance at beginning of year10,823 (3,795)9,404 (3,787)
Net income (loss) for year1,360 (8)1,425 (8)
Return on power program appropriation investment(6)— (6)— 
Balance at end of year12,177 (3,803)10,823 (3,795)
Net proprietary capital at September 30$12,435 $548 $11,081 $556 

Payments to the U.S. Treasury

TVA paid the U.S. Treasury $6 million, $6 million, and $5 million in 2020, 2019, and 2018, 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 2.44 percent, 2.37 percent, and 2.09 percent for 2020, 2019, and 2018, respectively.

Accumulated Other Comprehensive Income (Loss)

The items included in AOCI consist of market valuation adjustments for certain derivative instruments.  See Note 15 — Risk Management Activities and Derivative Transactions.
TVA records exchange rate gains and losses on debt and related accrued interest in net income and marks its currency swap assets and liabilities to market through OCI.  TVA recognized unrealized gains (losses) of $(1) million and $(114) million in 2020 and 2019, respectively, into AOCI on the mark-to-market of currency swaps. TVA then reclassified an amount out of AOCI into net income, offsetting the gain/loss from recording the exchange gain/loss on the debt and related accrued interest.  The amounts reclassified from OCI into net income resulted in increases (decreases) to net income of $38 million, $(45) million, and $(26) million in 2020, 2019, and 2018, respectively.  These reclassifications, coupled with the recording of the exchange gain/loss on the debt and related accrued interest, did not have an impact on net income in 2020, 2019, and 2018.  Based on forecasted foreign currency exchange rates, TVA expects to reclassify approximately $27 million of gains from AOCI to interest expense within the next 12 months to offset amounts anticipated to be recorded in interest expense related to exchange gain on the debt and related accrued interest.
v3.20.2
Other Income (Expense), Net
 12 Months Ended
Sep. 30, 2020
Other Income and Expenses [Abstract]  
Other Income (Expense), Net Other Income (Expense), Net
Income and expenses not related to TVA's operating activities are summarized in the following table:
Other Income (Expense), Net
For the years ended September 30
 202020192018
Bellefonte deposit$— $21 $— 
Interest income18 25 23 
External services12 13 14 
Gains (losses) on investments9 3 6 
Miscellaneous(3)— 7 
Total other income (expense), net$36 $62 $50 

During 2020, Other income (expense), net decreased $26 million, primarily driven by $21 million of other income in 2019 related to a deposit liability received by TVA as a down payment on the sale of Bellefonte. The purchaser, Nuclear Development, LLC, failed to fulfill the requirements of the sales contract with respect to obtaining NRC approval of the transfer of required nuclear licenses and payment of the remainder of the selling price before the November 30, 2018 closing date. Additionally, Interest income decreased $7 million primarily as a result of lower interest rates. See Note 22 — Commitments and Contingencies — Legal Proceedings for a discussion of the lawsuit filed by Nuclear Development, LLC.
v3.20.2
Related Parties
 12 Months Ended
Sep. 30, 2020
Related Party Transactions [Abstract]  
Related Parties 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 currently receives no appropriations from Congress and funds its business using power system revenues, power financings, and other revenues.  TVA is a source of cash to the federal government.  TVA will indefinitely continue to pay the U.S. Treasury a return on the outstanding $258 million of the government's appropriation investment in TVA's power facilities (the "Power Program Appropriation Investment").  See Note 18 — Proprietary Capital — Appropriation Investment.

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, 2021, 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 13 — 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
For the years ended, or at, September 30
 202020192018
Revenue from sales of electricity$105 $118 $122 
Other income260 258 240 
Expenditures
Operating expenses224 222 220 
Additions to property, plant, and equipment9 10 8 
Cash and cash equivalents31 45 46 
Accounts receivable, net94 76 60 
Investment funds485 279 199 
Long-term accounts receivable27 53 46 
Accounts payable and accrued liabilities39 69 69 
Long-term power bonds, net1 — — 
Return on power program appropriation investment6 6 5 
v3.20.2
Unaudited Quarterly Financial Information
 12 Months Ended
Sep. 30, 2020
Quarterly Financial Information Disclosure [Abstract]  
Unaudited Quarterly Financial Information
24. Unaudited Quarterly Financial Information

A summary of the unaudited quarterly results of operations for the years 2020 and 2019 follows.  This summary should be read in conjunction with the audited consolidated financial statements appearing herein.  Results for interim periods may fluctuate as a result of seasonal weather conditions, changes in rates, and other factors.
Unaudited Quarterly Financial Information
2020
 FirstSecondThirdFourthTotal
Operating revenues$2,578 $2,521 $2,251 $2,899 $10,249 
Operating expenses2,046 1,914 1,716 1,862 7,538 
Operating income532 607 535 1,037 2,711 
Net income (loss)192 255 205 700 1,352 
Unaudited Quarterly Financial Information
2019
 FirstSecondThirdFourthTotal
Operating revenues$2,725 $2,750 $2,604 $3,239 $11,318 
Operating expenses1,960 2,158 2,088 2,301 8,507 
Operating income765 592 516 938 2,811 
Net income (loss)423 241 165 588 1,417 
v3.20.2
Revenue
 12 Months Ended
Sep. 30, 2020
Revenue from Contract with Customer [Abstract]  
Revenue from Contract with Customer Revenue     TVA adopted Revenue from Contracts with Customers effective October 1, 2018, using the modified retrospective method of adoption, which does not require restatement of prior year reported results. As a result of the adoption of this standard, no cumulative effect adjustment was recorded. Additionally, comparative disclosures for 2018 operating results with
the previous revenue recognition rules are not applicable as TVA's revenue recognition has not materially changed as a result of the new standard.

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 93 percent of TVA's revenue from sales of electricity is to 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, 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 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, and certain other ancillary goods or services.
Disaggregated Revenue

In 2020, the revenues generated from TVA's electricity sales were $10.1 billion and accounted for virtually all of TVA's revenues. TVA's 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)
 202020192018
Alabama
$1,439 $1,593 $1,600 
Georgia
249 270 267 
Kentucky
624 691 696 
Mississippi
941 1,063 1,052 
North Carolina
65 74 66 
Tennessee
6,740 7,419 7,350 
Virginia
42 45 48 
Subtotal10,100 11,155 11,079 
Off-system sales4 4 7 
Revenue capitalized during pre-commercial plant operations(1)
— — (11)
Revenue from sales of electricity10,104 11,159 11,075 
Other revenue145 159 158 
Total operating revenues$10,249 $11,318 $11,233 
Note
(1) Represents revenue capitalized during pre-commercial operations of $11 million at Allen CC in 2018. See Note 1 — Summary of Significant Accounting Policies — Pre-Commercial Plant Operations.

    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)
 202020192018
Revenue from sales of electricity  
Local power companies(1)
$9,406 $10,351 $10,262 
Industries directly served588 686 695 
Federal agencies and other110 122 129 
Revenue capitalized during pre-commercial plant operations(2)
— — (11)
Revenue from sales of electricity10,104 11,159 11,075 
Other revenue145 159 158 
Total operating revenues$10,249 $11,318 $11,233 
Notes
(1) The amount for the years ended September 30, 2020 and 2019, is net of $163 million and $14 million, respectively, of wholesale bill credits to LPCs participating in the long-term Partnership Agreement. There were no such credits in 2018.
(2) Represents revenue capitalized during pre-commercial operations of $11 million at Allen CC in 2018. See Note 1 — Summary of Significant Accounting Policies — Pre-Commercial Plant Operations.

    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 20-year Partnership Agreement option that better aligns the length of LPC contracts with TVA's long-term commitments. These agreements are automatically extended each year after their initial effective date, contingent upon certain circumstances, including limited rate increases going forward. Participating LPCs will 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. In June 2020, TVA provided participating LPCs a flexibility option that allows them to locally generate up to approximately five percent of average total hourly energy sales over the prior five years in order to meet their individual customers' needs. As of November 16, 2020, 142 LPCs had signed the 20-year Partnership Agreement with TVA, and 64 LPCs had signed a Flexibility Agreement.

In August 2020, the TVA Board approved a $200 million Pandemic Relief Credit. The 2.5 percent base rate credit will be applied beginning in October 2020 and will remain in effect through the end of 2021. The credit will apply to service provided to TVA's local power company customers, their large commercial and industrial customers, and TVA directly served customers.
    The number of LPCs with the contract arrangements described below, the revenues derived from such arrangements during 2020, and the percentage of TVA's total operating revenues during 2020 represented by these revenues are summarized in the tables below:
TVA Local Power Company Contracts
At or for the year ended September 30, 2020
Contract Arrangements(1)
Number of LPCs Revenue from Sales of Electricity to LPCs
(in millions)		Percentage of Total Operating Revenues
20-year termination notice142 $7,666 74.8 %
5-year termination notice11 1,740 17.0 %
Total(2)
153 $9,406 91.8 %
Notes
(1) Ordinarily, the LPCs and TVA have the same termination notice period; however, in contracts with two of the LPCs with five-year termination notices, 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.
(2) TVA wholesale power contracts decreased to 153 in 2020 due to a merger between two LPCs in July 2020.
                                                 
    TVA's two largest LPCs — MLGW and 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 2020. In May 2020, MLGW published a draft IRP to guide energy choices in the future, and in July 2020, TVA made a proposal to MLGW that highlights the benefits of remaining a TVA customer. In August 2020, MLGW published a final IRP and announced its plan to issue requests for proposal to validate the cost estimates included in the IRP. In addition, certain other LPCs are evaluating options for future energy choices.

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 does not have any material contract assets as of September 30, 2020.

    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.

    Energy Prepayment Obligations. In 2004, TVA and its largest customer, MLGW, entered into an energy prepayment agreement under which MLGW prepaid TVA $1.5 billion for the future costs of electricity to be delivered by TVA to MLGW over a period of 15 years.  TVA accounted for the prepayment as unearned revenue and reported the obligation to deliver power under this arrangement as Energy prepayment obligations.  The arrangement ceased in 2019. TVA recognized approximately $100 million of noncash revenue in each year of the arrangement as electricity was delivered to MLGW based on the ratio of units of kilowatt hours delivered to total units of kilowatt hours under contract. As of September 30, 2019, $1.5 billion had been recognized as noncash revenue on a cumulative basis during the life of the agreement, $100 million of which was recognized as noncash revenue and a corresponding reduction in the balance of Energy prepayment obligations during 2018. During 2019, $10 million was recognized as noncash revenue and a corresponding reduction in the balance of Energy prepayment obligations. Discounts to account for the time value of money, which were recorded as a reduction to electricity sales, amounted to $4 million and $46 million during 2019 and 2018, respectively.

    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. In 2020 and 2019, TVA recorded a total of $318 million and $310 million, respectively, in incentives as a reduction of revenue. 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, 2020 and 2019, the outstanding unpaid incentives were $172 million and $157 million, respectively. Incentives that have been paid out may be subject to claw back if the customer fails to meet certain program requirements. Additionally, in May 2020, TVA established flexibility provisions to support the continued operations and recovery of participating customers experiencing financial and operational hardships as a result of the COVID-19 pandemic and corresponding economic downturn. These provisions have not had a material impact to TVA.
v3.20.2
Plant Closures [Text Block]
 12 Months Ended
Sep. 30, 2020
Property, Plant and Equipment [Abstract]  
Plant Closures
6. 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 Paradise Fossil Plant ("Paradise") Unit 3 by December 2020 and Bull Run Fossil Plant ("Bull Run") by December 2023 was approved. Subsequent to the TVA Board approval, TVA determined that Paradise would not be restarted after January 2020 due to the plant's material condition. Paradise Unit 3 was taken offline on February 1, 2020, effectively retiring the plant.

Financial Impact

As a result of TVA's decision to accelerate the retirements of Paradise and Bull Run, certain construction projects at these locations were identified as probable of abandonment or were no longer expected to be in service for greater than one year prior to the plants' retirement dates. The write-off of these projects resulted in $11 million and $151 million of Operating and maintenance expense during the years ended September 30, 2020 and 2019, respectively. TVA also recognized losses of $2 million and $19 million in Operating and maintenance expense related to additional materials and supplies inventory reserves and write-offs identified at Paradise during the years ended September 30, 2020 and 2019, respectively.

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 Paradise and Bull Run, TVA recognized an additional $387 million and $566 million of accelerated depreciation for the years ended September 30, 2020 and 2019, respectively.
v3.20.2
Leases (Text Block)
 12 Months Ended
Sep. 30, 2020
Leases [Abstract]  
Leases of Lessee Disclosure
7. Leases

    As described in Note 2 — Impact of New Accounting Standards and Interpretations, TVA elected the modified retrospective method of adoption for the new lease accounting standard effective October 1, 2019. Under the modified retrospective method of adoption, prior year reported results are not restated.

    TVA recorded $205 million and $210 million of lease assets and lease liabilities, respectively, for operating leases in effect at the adoption date. The accounting for finance leases remained substantially unchanged. Adoption of the standard did not materially impact results of operations or cash flows.

    The following table provides additional information regarding the presentation of leases on the Consolidated Balance Sheets at September 30, 2020:
Amounts Recognized on TVA's Consolidated Balance Sheets
At September 30, 2020
Assets
  OperatingOperating lease assets, net of amortization$232 
  FinanceFinance leases516 
Total lease assets$748 
Liabilities
Current
  OperatingAccounts payable and accrued liabilities$63 
  FinanceAccounts payable and accrued liabilities41 
Non-current
  OperatingOther long-term liabilities171 
  FinanceFinance lease liabilities525 
Total lease liabilities$800 

    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 26 years. The components of lease costs for the year September 30, 2020, were as follows:
Lease Costs
For the year ended September 30, 2020
Operating lease costs(1)
$84 
Variable lease costs(1)
75 
Short-term lease costs(1)
7 
Finance lease costs
Amortization of lease assets(2)
15 
Interest on lease liabilities(3)(4)
33 
Total finance lease costs48 
     Total lease costs$214 
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. TVA's rental expense for operating leases was approximately $97 million and $92 million for the years ended September 30, 2019 and 2018, respectively.
(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 Year Ended September 30, 2020
Operating cash flows for operating leases$85 
Operating cash flows for finance leases33 
Financing cash flows for finance leases15 
Lease assets obtained in exchange for lease obligations (non-cash)
Operating leases(1)
$110 
Finance leases394 
Note
(1) Amount excludes operating lease assets recorded as a result of the adoption of the new lease standard.
    
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. At September 30, 2020, the weighted average remaining lease term in years and the weighted average discount rate for TVA's operating and financing leases were as follows:
Weighted Averages
At September 30, 2020
Weighted average remaining lease terms
Operating leases5 years
Finance leases12 years
Weighted average discount rate(1)
Operating leases1.6%
Finance leases21.8%
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, 2020:
Future Minimum Lease Payments
Minimum Payments Due at September 30, 2020
Operating leases
2021$66 
202251 
202339 
202437 
202534 
Thereafter16 
Minimum annual payments243 
Less: present value discount(9)
Operating present value of net minimum lease payments$234 
Finance leases
2021$92 
202293 
202392 
202487 
202586 
   Thereafter592 
Minimum annual payments1,042 
Less: amount representing interest(476)
Finance present value of net minimum lease payments$566 
    The following table presents the future minimum lease payments under operating leases and the finance lease maturities as reported under the previous lease standard at September 30, 2019:
Future Minimum Lease Payments
Minimum Payments Due at September 30, 2019
Operating leases
2020$76 
202175 
202260 
202312 
20243 
   Thereafter2 
Minimum annual payments228 
Less: present value discount— 
Operating present value of net minimum lease payments$228 
Finance leases
2020$53 
202153 
202253 
202355 
202451 
   Thereafter418 
Minimum annual payments683 
Less: amount representing interest(495)
Finance present value of net minimum lease payments$188 

    TVA entered into a PPA with a renewable resource provider for solar generation and rights to charge and discharge a battery energy storage system. The system is considered a lease component in this agreement. This lease has a term of 20 years, and is expected to commence on October 1, 2022. Payments made over the term of this lease are expected to total approximately $89 million.
v3.20.2
Summary of Significant Accounting Policies [Policy Text Block]
 12 Months Ended
Sep. 30, 2020
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.

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 of Directors (the "TVA Board") as authorized by the Tennessee Valley Authority Act of 1933, as amended (the "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 item 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 (2020, 2019, 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 any of the other factors described above cease to be applicable, TVA would no longer be considered to be a regulated entity and would be required to write off these costs.  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, wholly-owned direct subsidiaries, and variable interest entities ("VIE") of which TVA is the primary beneficiary. See Note 10 — 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, including impacts from the COVID-19 pandemic, 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 Reclassifications    Certain historical amounts have been reclassified in the accompanying consolidated financial statements to the current presentation. In the Consolidated Balance Sheet at September 30, 2019, TVA reclassified $163 million from Accounts payable and accrued liabilities to Asset retirement obligations in Current liabilities. In addition, as a result of the adoption of the new lease accounting standard effective for TVA October 1, 2019, TVA reclassified $182 million from Other long-term liabilities to Finance lease liabilities in the Consolidated Balance Sheet at September 30, 2019.
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 includes 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 in the Consolidated Balance Sheets and Consolidated Statements of Cash Flows:
Cash, Cash Equivalents, and Restricted Cash
At September 30
 20202019
Cash and cash equivalents$500 $299 
Restricted cash and cash equivalents, included in Other long-term assets21 23 
Total Cash, cash equivalents, and restricted cash$521 $322 
Allowance for Uncollectible Accounts
Allowance for Uncollectible Accounts

The allowance for uncollectible accounts reflects TVA's estimate of probable losses inherent in its accounts and loans receivable balances excluding the EnergyRight® loans receivable.  TVA determines the allowance based on known accounts, historical experience, and other currently available information including events such as customer bankruptcy and/or a customer failing to fulfill payment arrangements after 90 days.  It also reflects TVA's corporate credit department's assessment of the financial condition of customers and the credit quality of the receivables. TVA continues to monitor the impact of the COVID-19 pandemic on accounts and loans receivable balances to evaluate the allowance for uncollectible accounts.

The allowance for uncollectible accounts was less than $1 million at both September 30, 2020 and 2019, for accounts receivable.  Additionally, loans receivable of $105 million and $131 million at September 30, 2020 and 2019, respectively, are included in Accounts receivable, net and Other long-term assets, for the current and long-term portions, respectively, and are reported net of allowances for uncollectible accounts of less than $1 million at both September 30, 2020 and 2019, respectively.
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 are recorded in Other revenue. Revenues that are not related to the overall mission are recorded in Other income (expense), net.
Energy Prepayment Obligations

In 2004, TVA and its largest customer, Memphis Light, Gas and Water Division ("MLGW"), entered into an energy prepayment agreement under which MLGW prepaid TVA $1.5 billion for the future costs of electricity to be delivered by TVA to MLGW over a period of 180 months.  TVA accounted for the prepayment as unearned revenue and reported the obligation to deliver power under this arrangement as Energy prepayment obligations.  The arrangement ceased in 2019. Revenue was recognized in each year of the arrangement as electricity was delivered to MLGW based on the ratio of units of kilowatt hours delivered to total units of kilowatt hours under contract.  As of September 30, 2019, $1.5 billion had been recognized as non-cash revenue on a cumulative basis during the life of the agreement, $10 million and $100 million of which was recognized as non-cash revenue during 2019 and 2018, respectively.

Discounts to account for the time value of money, which are recorded as a reduction to electricity sales, amounted to $4 million and $46 million for the years ended September 30, 2019 and 2018, respectively.
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 revenue from such pre-commercial generation based on the guidance provided by Federal Energy Regulatory Commission ("FERC") regulations. The Allen Combined Cycle Plant ("Allen CC") began pre-commercial plant operations in September 2017, and began commercial operations in April 2018. Cogeneration capability at Johnsonville Combustion Turbine Unit 20 commenced pre-commercial plant operations in September 2017, and was placed in service during December 2017. Estimated revenue of $11 million related to Allen CC was capitalized to offset project costs for the year ended September 30, 2018. TVA also capitalized related fuel costs for these construction projects of approximately $19 million during the year ended September 30, 2018. No such amounts were capitalized during 2019 or 2020.
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 Credits. 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 fair value approach. RECs created through TVA-owned asset generation are recorded at zero cost.

Emission Allowances.  TVA has emission allowances for sulfur dioxide ("SO2") and nitrogen oxide ("NOx") which are accounted for as inventory.  The cost of specific allowances used each month is charged to operating expense based on tons of SO2 and NOx emitted during the respective compliance periods.  Allowances granted to TVA by the Environmental Protection Agency ("EPA") are recorded at zero cost.

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.  In 2018, TVA started moving from a site-specific inventory management policy to a fleet-wide strategy 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.  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. 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.

    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 the external depreciation studies. These studies will be updated approximately every five years.  Depreciation expense for the years ended September 30, 2020, 2019, and 2018 was $1.6 billion, $1.8 billion, and $1.3 billion, respectively. Depreciation expense expressed as a percentage of the average annual depreciable completed plant was 2.74 percent for 2020, 3.09 percent for 2019, and 2.45 percent for 2018.  Average depreciation rates by asset class are as follows:
Property, Plant, and Equipment Depreciation Rates
At September 30
(percent)
202020192018
Asset Class
Nuclear2.38 2.38 2.64 
Coal-fired(1)
3.62 4.96 2.32 
Hydroelectric1.60 1.61 1.57 
Gas and oil-fired3.04 3.00 2.93 
Transmission1.34 1.34 1.32 
Other7.26 7.16 5.90 
Note
(1) The rates include the acceleration of depreciation related to retiring certain coal-fired units.
    
    Coal-Fired. As a result of TVA's decision to idle or retire certain units since the previous depreciation study, TVA recognized $387 million, $566 million, and $48 million in accelerated depreciation expense related to the units during the years ended September 30, 2020, 2019, and 2018, respectively. Accelerated depreciation is based on the remaining useful life of the asset at the time the decision is made to idle or retire a unit.

Reacquired Rights. Property, plant, and equipment includes intangible reacquired rights, net of amortization, of $192 million and $200 million as of September 30, 2020 and 2019, 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 life of the underlying CTs. Amortization expense was $8 million for all years 2020, 2019, and 2018.

Software Costs.  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.  At September 30, 2020 and 2019, unamortized computer software costs totaled $54 million and $63 million, respectively.  Amortization expense related to capitalized computer software costs was $42 million, $38 million, and $32 million for 2020, 2019, and 2018, respectively.  Software costs that do not meet capitalization criteria are expensed as incurred.
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. See Note 6 — 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 power purchase agreements, the terms of which vary. The total lease obligation included in Accounts payable and accrued liabilities and lease liabilities related to these agreements were $500 million and $174 million for finance and operating leases, respectively, at September 30, 2020.

    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, 2020.
    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.  These other property-related assets include, but are not limited to, easements and coal rights.  Activities involved with retiring these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site restoration.  Revisions to the estimates of asset retirement obligations ("AROs") are made whenever factors indicate that the timing or amounts of estimated cash flows have changed materially.  Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset.  See Note 9 —
Regulatory Assets and Liabilities — Nuclear Decommissioning Costs and Non-Nuclear Decommissioning Costs and Note 12 — Asset Retirement Obligations.
Down-blend Offering for Tritium
Down-blend Offering for Tritium

TVA, the Department of Energy ("DOE"), and certain nuclear fuel contractors have entered into agreements, referred to as the Down-blend Offering for Tritium, 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 October 2027.  Beginning October 2027, 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 $89 million in reimbursements from the DOE. At September 30, 2020, TVA recorded $6 million in Accounts receivable, net related to this agreement.
Investment Funds
Investment Funds

    Investment funds consist primarily of trust funds designated to fund decommissioning requirements (see Note 22 — Commitments and Contingencies — Decommissioning Costs), the Supplemental Executive Retirement Plan ("SERP") (see Note 21 — Benefit Plans — Overview of Plans and Benefits — Supplemental Executive Retirement Plan), and the Deferred Compensation Plan ("DCP"). 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, and DCP 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, and DCP funds are all classified as trading.
Insurance
Insurance

Although TVA uses private companies to administer its healthcare plans for eligible active and retired employees not covered by Medicare, TVA does not purchase health insurance.  Third-party actuarial specialists assist TVA in determining certain liabilities for self-insured claims.  TVA recovers the costs of claims through power rates and through adjustments to the participants' contributions to their benefit plans.  These liabilities are included in Other liabilities on the Consolidated Balance Sheets.

TVA sponsors an Owner Controlled Insurance Program which provides workers' compensation and liability insurance for a select group of contractors performing maintenance, modifications, outage, and new construction activities at TVA facilities.

The Federal Employees' Compensation Act ("FECA") governs liability to employees for service-connected injuries.  TVA purchases excess workers' compensation insurance above a self-insured retention.

    In addition to excess workers' compensation insurance, TVA purchases the following types of insurance:
•Nuclear liability insurance; nuclear property, decommissioning, and decontamination insurance; and nuclear accidental outage insurance. See Note 22 — Commitments and Contingencies — Nuclear Insurance.

•Excess liability insurance for aviation, auto, marine, and general liability exposures.

•Property insurance for certain conventional (non-nuclear) assets.
    The insurance policies are subject to the terms and conditions of the specific policy, including deductibles or self-insured retentions. To the extent insurance would not provide either a partial or total recovery of the costs associated with a loss, TVA would have to recover any such costs through other means, including through power rates.
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 in the Consolidated Statements of Operations as they are incurred except for the recording of certain regulatory assets for retirement and removal costs.
v3.20.2
Variable Interest Entities (Policies)
 12 Months Ended
Sep. 30, 2020
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, 2020 and 2019, as reflected on the Consolidated Balance Sheets, are as follows:
Summary of Impact of VIEs on Consolidated Balance Sheets
At September 30
 20202019
Current liabilities 
Accrued interest$10 $11 
Accounts payable and accrued liabilities3 3 
Current maturities of long-term debt of variable interest entities41 39 
Total current liabilities
54 53 
Other liabilities
Other long-term liabilities23 25 
Long-term debt, net
Long-term debt of variable interest entities, net1,048 1,089 
Total liabilities$1,125 $1,167 
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.
v3.20.2
Asset Retirement Obligations Asset Retirement Obligations (Policies)
 12 Months Ended
Sep. 30, 2020
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.  These other property-related assets include, but are not limited to, easements and coal rights.  Activities involved with retiring these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site restoration.  Revisions to the estimates of asset retirement obligations ("AROs") are made whenever factors indicate that the timing or amounts of estimated cash flows have changed materially.  Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset.  See Note 9 —
Regulatory Assets and Liabilities — Nuclear Decommissioning Costs and Non-Nuclear Decommissioning Costs and Note 12 — Asset Retirement Obligations.
v3.20.2
Proprietary Capital Payments to the U.S. Treasury (Policies)
 12 Months Ended
Sep. 30, 2020
Equity [Abstract]  
Payments to U S Treasury
Payments to the U.S. Treasury

TVA paid the U.S. Treasury $6 million, $6 million, and $5 million in 2020, 2019, and 2018, 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 2.44 percent, 2.37 percent, and 2.09 percent for 2020, 2019, and 2018, respectively.
v3.20.2
Benefit Plans Benefit Plans (Policies)
 12 Months Ended
Sep. 30, 2020
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 recent plan design changes, future contributions are expected to exceed the expense calculated under U.S. GAAP. Accordingly, TVA will discontinue this regulatory accounting practice once all such deferred costs have been recovered, at which time it will recognize pension costs in accordance with U.S. GAAP.

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 remaining service period of participating employees expected to receive benefits. The current projected amortization periods of unrecognized net gain or loss is approximately 11 years for the pension plan and 12 years for the post-retirement plan.

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 have prior service costs/(credits) related to plan changes made in 2009, 2010, 2016, 2018, 2019, and 2020 with remaining amortization periods ranging from one to nine 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.
v3.20.2
Revenue (Policies)
 12 Months Ended
Sep. 30, 2020
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 are recorded in Other revenue. Revenues that are not related to the overall mission are recorded in Other income (expense), net.
Energy Prepayment Obligations

In 2004, TVA and its largest customer, Memphis Light, Gas and Water Division ("MLGW"), entered into an energy prepayment agreement under which MLGW prepaid TVA $1.5 billion for the future costs of electricity to be delivered by TVA to MLGW over a period of 180 months.  TVA accounted for the prepayment as unearned revenue and reported the obligation to deliver power under this arrangement as Energy prepayment obligations.  The arrangement ceased in 2019. Revenue was recognized in each year of the arrangement as electricity was delivered to MLGW based on the ratio of units of kilowatt hours delivered to total units of kilowatt hours under contract.  As of September 30, 2019, $1.5 billion had been recognized as non-cash revenue on a cumulative basis during the life of the agreement, $10 million and $100 million of which was recognized as non-cash revenue during 2019 and 2018, respectively.

Discounts to account for the time value of money, which are recorded as a reduction to electricity sales, amounted to $4 million and $46 million for the years ended September 30, 2019 and 2018, respectively.
v3.20.2
Property, Plant, and Equipment [Policy Text Block]
 12 Months Ended
Sep. 30, 2020
Property, Plant and Equipment [Abstract]  
Plant Retirement and Abandonment, Policy [Policy Text Block]
Financial Impact

As a result of TVA's decision to accelerate the retirements of Paradise and Bull Run, certain construction projects at these locations were identified as probable of abandonment or were no longer expected to be in service for greater than one year prior to the plants' retirement dates. The write-off of these projects resulted in $11 million and $151 million of Operating and maintenance expense during the years ended September 30, 2020 and 2019, respectively. TVA also recognized losses of $2 million and $19 million in Operating and maintenance expense related to additional materials and supplies inventory reserves and write-offs identified at Paradise during the years ended September 30, 2020 and 2019, respectively.

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 Paradise and Bull Run, TVA recognized an additional $387 million and $566 million of accelerated depreciation for the years ended September 30, 2020 and 2019, respectively.
v3.20.2
Summary of Significant Accounting Policies [Table Text Block]
 12 Months Ended
Sep. 30, 2020
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)
202020192018
Asset Class
Nuclear2.38 2.38 2.64 
Coal-fired(1)
3.62 4.96 2.32 
Hydroelectric1.60 1.61 1.57 
Gas and oil-fired3.04 3.00 2.93 
Transmission1.34 1.34 1.32 
Other7.26 7.16 5.90 
v3.20.2
Accounts Receivable, Net Accounts Receivable, Net (Tables)
 12 Months Ended
Sep. 30, 2020
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
 20202019
Power receivables$1,401 $1,624 
Other receivables128 115 
Accounts receivable, net(1)
$1,529 $1,739 
v3.20.2
Inventories, Net Inventories, Net (Tables)
 12 Months Ended
Sep. 30, 2020
Inventory, Net [Abstract]  
Inventories, Net
The table below summarizes the types and amounts of TVA's inventories:
Inventories, Net 
At September 30
 20202019
Materials and supplies inventory$770 $742 
Fuel inventory253 294 
RECs inventory, net15 16 
Allowance for inventory obsolescence(35)(53)
Inventories, net$1,003 $999 
v3.20.2
Net Completed Plant Net Completed Plant (Tables)
 12 Months Ended
Sep. 30, 2020
Property, Plant and Equipment, Net, by Type [Abstract]  
Net Completed Plant
Net completed plant consisted of the following:
Net Completed Plant
At September 30
 20202019
 CostAccumulated Depreciation 
Net		CostAccumulated DepreciationNet
Coal-fired(1)(2)
$18,613 $13,944 $4,669 $17,400 $12,538 $4,862 
Gas and oil-fired6,010 1,696 4,314 6,054 1,562 4,492 
Nuclear25,741 12,141 13,600 25,543 11,656 13,887 
Transmission8,283 3,140 5,143 7,932 3,083 4,849 
Hydroelectric3,410 1,090 2,320 3,163 1,051 2,112 
Other electrical plant1,981 1,146 835 1,920 1,110 810 
Intangible software3 2 1 3 1 2 
Multipurpose dams900 381 519 900 373 527 
Other stewardship29 10 19 29 10 19 
Total$64,970 $33,550 $31,420 $62,944 $31,384 $31,560 
v3.20.2
Other Long-Term Assets Other Long-Term Assets (Tables)
 12 Months Ended
Sep. 30, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [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
 2020
2019(1)
Loans and other long-term receivables, net$100 $125 
EnergyRight® receivables
69 81 
Prepaid long-term service agreements42 22 
Commodity contract derivative assets23 — 
Restricted cash and cash equivalents21 23 
Prepaid capacity payments11 19 
Other59 55 
Total other long-term assets$325 $325 
v3.20.2
Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Tables)
 12 Months Ended
Sep. 30, 2020
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
 2020
2019(1)
Current regulatory assets  
Unrealized losses on interest rate derivatives$114 $89 
Unrealized losses on commodity derivatives4 39 
Fuel cost adjustment receivable12 28 
Total current regulatory assets130 156 
Non-current regulatory assets  
Deferred pension costs and other post-retirement benefits costs5,193 4,756 
Non-nuclear decommissioning costs2,512 1,741 
Unrealized losses on interest rate derivatives1,506 1,241 
Nuclear decommissioning costs896 868 
Unrealized losses on commodity derivatives— 15 
Other non-current regulatory assets138 142 
Total non-current regulatory assets10,245 8,763 
Total regulatory assets$10,375 $8,919 
Current regulatory liabilities  
Fuel cost adjustment tax equivalents$115 $138 
Unrealized gains on commodity derivatives26 12 
Total current regulatory liabilities141 150 
Non-current regulatory liabilities  
Unrealized gains on commodity derivatives23 — 
Total non-current regulatory liabilities23 — 
Total regulatory liabilities$164 $150 
v3.20.2
Other Long-Term Liabilities Other Long-Term Liabilities (Tables)
 12 Months Ended
Sep. 30, 2020
Other Liabilities, Noncurrent [Abstract]  
Other Long-Term Liabilities The table below summarizes the types and amounts of Other long-term liabilities:
Other Long-Term Liabilities(1)
At September 30
 20202019
Interest rate swap liabilities$1,927 $1,676 
Operating lease liabilities171 — 
Currency swap liabilities123 193 
EnergyRight® financing obligation78 90 
Paradise pipeline financing obligation— 80 
Accrued long-term service agreements56 66 
Other193 203 
Total other long-term liabilities$2,548 $2,308 
v3.20.2
Asset Retirement Obligations Asset Retirement Obligations (Tables)
 12 Months Ended
Sep. 30, 2020
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligation Activity
Asset Retirement Obligation Activity
 NuclearNon-NuclearTotal
Balance at September 30, 2018$2,989 $1,790 $4,779 
Settlements(7)(82)(89)
Revisions in estimate— 50 50 
Additional obligations18 — 18 
Gallatin CCR— 672 672 
Accretion (recorded as regulatory asset)136 50 186 
Balance at September 30, 20193,136 2,480 5,616 
(1)
Settlements(1)(113)(114)
Revisions in estimate— 1,077 1,077 
Accretion (recorded as regulatory asset)143 63 206 
Balance at September 30, 2020$3,278 $3,507 $6,785 
(1)
Note
(1) Includes $345 million and $163 million at September 30, 2020 and 2019, respectively, in Current liabilities.
v3.20.2
Debt and Other Obligations Debt and Other Obligations (Tables)
 12 Months Ended
Sep. 30, 2020
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
 202020192018
Gross amount outstanding - discount notes$57 $922 $1,217 
Weighted average interest rate - discount notes0.06 %2.15 %2.05 %
Debt Securities Activity
The table below summarizes the long-term debt securities activity for the years ended September 30, 2020 and 2019.
Debt Securities Activity
For the years ended September 30
 20202019
Issues
2020 Series A(1)
$1,000 $— 
Discount on debt issues(3)— 
Total$997 $— 
Redemptions/Maturities(2)
  
electronotes®
$219 $5 
2013 Series A1,000 
2009 Series B28 30 
2018 Series A1,000 — 
1999 Series A PARRS (TVE)23 — 
1998 Series D PARRS (TVC)17 — 
1995 Series B140 — 
Total redemptions/maturities of power bonds1,427 1,035 
Notes payable23 46 
Variable interest entities39 38 
Total$1,489 $1,119 
Notes
(1) The 2020 Series A Bonds were issued at 99.7 percent of par.
(2) All redemptions were at 100 percent of par.
Debt Outstanding Total debt outstanding at September 30, 2020 and 2019, consisted of the following: 
Short-Term Debt
At September 30
 
CUSIP or Other Identifier
 
Maturity
 Call/(Put) Date 
Coupon Rate		20202019
Short-term debt, net of discounts$57 $922 
Current maturities of long-term debt of VIEs issued at par41 39 
Current maturities of notes payable— 23 
Current maturities of power bonds issued at par
880591EF5
12/15/20193.770%— 1 
880591EF56/15/20203.770%— 27 
880591EF512/15/20203.770%1 — 
880591EF56/15/20213.770%28 — 
88059TEL111/15/20192.650%— 1 
88059TEL15/15/20202.650%— 1 
880591EV03/15/20202.250%— 1,000 
880591EL22/15/20213.875%1,500 — 
880591DC36/7/20215.805%258 
(1)
— 
Total current maturities of power bonds issued at par   1,787 1,030 
Total current debt outstanding, net   $1,885 $2,014 
Note
(1) Includes net exchange gain from currency transactions of $73 million at September 30, 2020.
Long-Term Debt
At September 30
 
CUSIP or Other Identifier
 
Maturity
Coupon
Rate		Effective Call Date2020 Par2019 ParStock Exchange Listings
electronotes®(2)
5/15/2020 - 2/15/20432.375% - 3.625%
2/15/2015 - 2/15/2018 (5)
$— $217 None
880591EL22/15/20213.875%— 1,500 New York
880591DC36/7/20215.805%
(3)
— 

246 
(1)
New York, Luxembourg
880591EN88/15/20221.875%1,000 1,000 New York
880591ER99/15/20242.875%1,000 1,000 New York
880591EW85/15/20250.750%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(4)
6/1/20282.134%256 273 New York
880591409(4)
5/1/20292.216%208 232 New York
880591DM15/1/20307.125%1,000 1,000 New York, Luxembourg
880591DP46/7/20326.587%
(3)
323 
(1)
307 
(1)
New York, Luxembourg
880591DV17/15/20334.700%472 472 New York, Luxembourg
880591EF56/15/20343.770%218 246 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%
(3)
194 
(1)
185 
(1)
New York, Luxembourg
880591CF77/15/20456.235%7/15/2020— 140 New York
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
Subtotal 18,078 19,225  
Unamortized discounts, premiums, issue costs, and other  (122)(131) 
Total long-term outstanding power bonds, net  17,956 19,094  
Long-term debt of VIEs, net1,048 1,089 
Total long-term debt, net$19,004 $20,183 
Notes
(1)  Includes net exchange gain from currency transactions of $80 million and $191 million at September 30, 2020 and 2019, respectively.
(2)  Includes one electronotes® issue with partial maturities of principal for each required annual payment.
(3)  The coupon rate represents TVA's effective interest rate.
(4)  TVA PARRS, CUSIP numbers 880591300 and 880591409, may be redeemed under certain conditions.  See Put and Call Options above.
Maturities Due in the Year Ending September 30
Maturities Due in the Year Ending September 30
 20212022202320242025ThereafterTotal
Long-term power bonds, long-term debt of VIEs, and notes payable including current maturities(1)
$1,901 $1,071 $69 $1,058 $1,059 $15,957 $21,115 
Short-term debt, net of discounts57 — — — — — 57 
Note
(1) Long-term power bonds does not include non-cash items of foreign currency exchange gain of $153 million, unamortized debt issue costs of $45 million, and net discount on sale of Bonds of $77 million. Long-term debt of VIE does not include non-cash item of unamortized debt issue costs of $8 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, 2020
Maturity DateFacility LimitLetters of Credit OutstandingCash BorrowingsAvailability
December 2021$150 $38 $— $112 
June 20231,000 432 — 568 
September 20231,000 487 — 513 
February 2025500 500 — — 
     Total$2,650 $1,457 $— $1,193 
v3.20.2
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions (Tables)
 12 Months Ended
Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Summary of Derivative Instruments That Receive Hedge Accounting Treatment
The following tables summarize the accounting treatment that certain of TVA's financial derivative transactions receive:
Summary of Derivative Instruments That Receive Hedge Accounting Treatment (part 1) 
Amount of Mark-to-Market Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss)
For the years ended September 30
Derivatives in Cash Flow Hedging RelationshipObjective of Hedge TransactionAccounting for Derivative
Hedging Instrument		20202019
Currency swapsTo protect against changes in cash flows caused by changes in foreign currency exchange rates (exchange rate risk)Unrealized gains and losses are recorded in AOCI and reclassified to Interest expense to the extent they are offset by gains and losses on the hedged transaction$(1)$(114)
Summary of Derivative Instruments That Receive Hedge Accounting Treatment (part 2)(1)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income to Interest Expense
For the years ended September 30
Derivatives in Cash Flow Hedging Relationship20202019
Currency swaps$38 $(45)
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 $27 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 exchange gain 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
 
Derivative Type
Objective of Derivative(2)
Accounting for Derivative Instrument20202019
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 assets or liabilities

Realized gains and losses are recognized in Interest expense when incurred during the settlement period and are presented in operating cash flow		$(97)$(79)
Commodity contract derivativesTo protect against fluctuations in market prices of purchased coal or natural gas (price risk)Mark-to-market gains and losses are recorded as regulatory assets or liabilities

Realized gains and losses due to contract settlements are recognized in Fuel expense as incurred		(1)— 
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 assets and liabilities. As such, there were no related gains (losses) recognized in income for these unrealized gains (losses) for the years ended September 30, 2020 and 2019.
(2) During the fourth quarter of 2020, TVA discontinued derivative accounting for forward coal contracts.
Fair Values of TVA Derivatives
Fair Values of TVA Derivatives
At September 30
 20202019
Derivatives That Receive Hedge Accounting Treatment:
 BalanceBalance Sheet PresentationBalanceBalance Sheet Presentation
Currency swaps    
£200 million Sterling
$(78)Accounts payable and accrued liabilities $(78)$(90)Accounts payable and accrued liabilities $(6); Other long-term liabilities $(84)
£250 million Sterling
(63)Accounts payable and accrued liabilities $(5); Other long-term liabilities $(58)(61)Accounts payable and accrued liabilities $(5); Other long-term liabilities $(56)
£150 million Sterling
(68)Accounts payable and accrued liabilities $(3); Other long-term liabilities $(65)(57)Accounts payable and accrued liabilities $(4); Other long-term liabilities $(53)
Derivatives That Do Not Receive Hedge Accounting Treatment:
 BalanceBalance Sheet PresentationBalanceBalance Sheet Presentation
Interest rate swaps    
$1.0 billion notional
$(1,449)Accounts payable and accrued liabilities $(43); Accrued interest $(37); Other long-term liabilities $(1,369)$(1,261)Accounts payable and
accrued liabilities $(29); Accrued interest $(33);
Other long-term liabilities
$(1,199)
$476 million notional
(588)Accounts payable and accrued liabilities $(22); Accrued interest $(10); Other long-term liabilities $(556)(498)Accounts payable and
accrued liabilities $(15); Accrued interest $(9);
Other long-term liabilities
$(474)
$42 million notional(4)Accounts payable and accrued liabilities $(2); Other long-term liabilities $(2)(5)Accounts payable and
accrued liabilities $(1); Accrued interest $(1); Other long-term liabilities $(3)
Commodity contract derivatives46 Other current assets $26; Other long-term assets $23; Accounts payable and accrued liabilities $(3)(41)Other current assets $12; Other long-term liabilities $(16); Accounts payable and accrued liabilities $(37)
Currency Swaps Outstanding TVA had the following currency swaps outstanding at September 30, 2020:
Currency Swaps Outstanding
September 30, 2020
Effective Date of Currency Swap ContractAssociated TVA Bond Issues Currency ExposureExpiration Date of SwapOverall Effective
Cost to TVA
1999£200 million20215.81%
2001£250 million20326.59%
2003£150 million20434.96%
Commodity Contract Derivatives
Commodity Contract Derivatives 
At September 30
 20202019
 
Number of Contracts
Notional AmountFair Value (MtM)Number of ContractsNotional Amount
Fair Value (MtM)
Coal contract derivatives—— million tons$— 89 million tons$(4)
Natural gas contract derivatives42302 million mmBtu$46 65330 million mmBtu$(37)
Offsetting Assets and Liabilities The amounts of TVA's derivative instruments as reported on the Consolidated Balance Sheets at September 30, 2020 and 2019, are shown in the table below.
Derivative Assets and Liabilities(1)
(in millions)
At September 30, 2020
At September 30, 2019
Assets
Commodity derivatives not subject to master netting or similar arrangement$49 $12 
Liabilities
Currency swaps(2)
$209 $208 
Interest rate swaps(2)
2,041 1,764 
Total derivatives subject to master netting or similar arrangement2,250 1,972 
Commodity derivatives not subject to master netting or similar arrangement3 53 
Total liabilities$2,253 $2,025 
Notes
(1) Offsetting amounts primarily include counterparty netting of derivative contracts, margin account deposits for futures commission merchants transactions, and cash collateral received or paid in accordance with the accounting guidance for derivatives and hedging transactions. There were no offsetting amounts on TVA's Consolidated Balance Sheets at either September 30, 2020 or 2019.
(2) Letters of credit of approximately $1.5 billion and $1.3 billion were posted as collateral at September 30, 2020 and 2019, respectively, to partially secure the liability positions of one of the currency swaps and one of the interest rate swaps in accordance with the collateral requirements for these derivatives.
v3.20.2
Fair Value Measurements (Tables)
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
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)
At or for the years ended September 30
FundFinancial Statement Presentation20202019
NDTRegulatory asset$37 $(112)
ARTRegulatory asset32 (70)
SERPOther income (expense)3 — 
DCPOther income (expense)2 (2)
  
Fair Value Measurements  
Fair Value Measurements
At September 30, 2020
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$500 $— $— $500 
Government debt securities(1)
485 40 — 525 
Corporate debt securities(2)
— 356 — 356 
Mortgage and asset-backed securities— 27 — 27 
Institutional mutual funds188 — — 188 
Forward debt securities contracts— 13 — 13 
Private equity funds measured at net asset value(3)
— — — 194 
Private real asset funds measured at net asset value(3)
— — — 168 
Private credit measured at net asset value(3)
— — — 53 
Commingled funds measured at net asset value(3)
— — — 1,174 
Total investments1,173 436 — 3,198 
Commodity contract derivatives— 49 — 49 
Total$1,173 $485 $— $3,247 
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(4)
$— $209 $— $209 
Interest rate swaps— 2,041 — 2,041 
Commodity contract derivatives— 3 — 3 
Total$— $2,253 $— $2,253 
Notes
(1) Includes government-sponsored entities.
(2) Includes both U.S. and foreign debt.
(3) Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been categorized in the fair value hierarchy. 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.
(4) 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, 2019
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$464 $— $— $464 
Government debt securities279 65 — 344 
Corporate debt securities— 417 — 417 
Mortgage and asset-backed securities— 32 — 32 
Institutional mutual funds250 — — 250 
Forward debt securities contracts— 22 — 22 
Private equity funds measured at net asset value(1)
— — — 140 
Private real asset funds measured at net asset value(1)
— — — 135 
    Private credit measured at net asset value(1)
— — — 33 
Commingled funds measured at net asset value(1)
— — — 1,131 
Total investments993 536 — 2,968 
Commodity contract derivatives— 7 5 12 
Total$993 $543 $5 $2,980 
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(2)
$— $208 $— $208 
Interest rate swaps— 1,764 — 1,764 
Commodity contract derivatives— 44 9 53 
Total$— $2,016 $9 $2,025 
Notes
(1) Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been categorized in the fair value hierarchy. 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.
(2) 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 Using Significant Unobservable Inputs
The following table presents a reconciliation of all commodity contract derivatives measured at fair value on a recurring basis using significant unobservable inputs (Level 3):
Fair Value Measurements Using Significant Unobservable Inputs
 Commodity Contract Derivatives
Balance at October 1, 2018$58 
Change in net unrealized gains (losses) deferred as regulatory assets and liabilities(62)
Balance at September 30, 2019(4)
Settlements(1)
Change in net unrealized gains (losses) deferred as regulatory assets and liabilities5 
Balance at September 30, 2020$— 
  
Quantitative Information about Level 3 Fair Value Measurements
The following table presents quantitative information related to the significant unobservable inputs used in the measurement of fair value of TVA's assets and liabilities classified as Level 3 in the fair value hierarchy:
Quantitative Information about Level 3 Fair Value Measurements 
 
Fair Value at September 30, 2019
Valuation Technique(s)Unobservable InputsRange
Assets
Commodity contract derivatives$5 Pricing modelCoal supply and demand0.4 - 0.8 billion tons/year
Long-term market prices$12.10 - $94.51/ton
Liabilities
Commodity contract derivatives$9 Pricing modelCoal supply and demand0.4 - 0.8 billion tons/year
Long-term market prices$12.10 - $94.51/ton
  
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, 2020 and 2019, were as follows:
Estimated Values of Financial Instruments Not Recorded at Fair Value
 At September 30, 2020At September 30, 2019
 Valuation ClassificationCarrying
Amount		Fair
Value		Carrying
Amount		Fair
Value
EnergyRight® receivables (including current portion)
Level 2$87 $86 $101 $100 
Loans and other long-term receivables, net (including current portion)Level 2$105 $93 $131 $120 
EnergyRight® financing obligations (including current portion)
Level 2$97 $108 $113 $126 
Unfunded loan commitmentsLevel 2$— $2 $— $10 
Membership interests of VIEs subject to mandatory redemption (including current portion)Level 2$26 $35 $28 $37 
Long-term outstanding power bonds (including current maturities), netLevel 2$19,743 $26,630 $20,124 $26,059 
Long-term debt of VIEs (including current maturities), netLevel 2$1,089 $1,419 $1,128 $1,371 
Long-term notes payable (including current maturities)Level 2$— $— $23 $23 
  
v3.20.2
Proprietary Capital (Tables)
 12 Months Ended
Sep. 30, 2020
Equity [Abstract]  
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]
Accumulated Other Comprehensive Income (Loss)

The items included in AOCI consist of market valuation adjustments for certain derivative instruments.  See Note 15 — Risk Management Activities and Derivative Transactions.
Stockholders' Equity Note [Abstract]  
Summary of Proprietary Capital Activity
The table below summarizes TVA's activities related to appropriated funds and retained earnings.
Summary of Proprietary Capital Activity
At or for the years ended September 30
 20202019
Power ProgramNonpower
 Programs		Power ProgramNonpower
 Programs
Appropriation Investment$258 $4,351 $258 $4,351 
Proprietary Capital    
Balance at beginning of year10,823 (3,795)9,404 (3,787)
Net income (loss) for year1,360 (8)1,425 (8)
Return on power program appropriation investment(6)— (6)— 
Balance at end of year12,177 (3,803)10,823 (3,795)
Net proprietary capital at September 30$12,435 $548 $11,081 $556 
v3.20.2
Other Income (Expense), Net Other Income (Expense), Net (Tables)
 12 Months Ended
Sep. 30, 2020
Other Income and Expenses [Abstract]  
Other Income (Expense), Net
Income and expenses not related to TVA's operating activities are summarized in the following table:
Other Income (Expense), Net
For the years ended September 30
 202020192018
Bellefonte deposit$— $21 $— 
Interest income18 25 23 
External services12 13 14 
Gains (losses) on investments9 3 6 
Miscellaneous(3)— 7 
Total other income (expense), net$36 $62 $50 
v3.20.2
Benefit Plans Benefit Plans (Tables)
 12 Months Ended
Sep. 30, 2020
Retirement Benefits [Abstract]  
Obligations and Funded Status
The changes in plan obligations, assets, and funded status for the years ended September 30, 2020 and 2019, were as follows:
Obligations and Funded Status
For the years ended September 30
795,900,000 Pension BenefitsOther Post-Retirement Benefits
 2020201920202019
Change in benefit obligation    
Benefit obligation at beginning of year$13,312 $11,725 $499 $428 
Service cost55 44 16 11 
Interest cost415 499 16 18 
Plan participants' contributions6 7 — — 
Collections(1)
— — 20 22 
Actuarial (gain) loss 614 1,756 39 78 
Plan change2 7 — — 
Net transfers (to) from variable fund/401(k) plan2 1 — — 
Expenses paid(5)(6)— — 
Benefits paid(726)(721)(46)(58)
Benefit obligation at end of year13,675 13,312 544 499 
Change in plan assets    
Fair value of net plan assets at beginning of year7,980 8,003 — — 
Actual return on plan assets397 389 — — 
Plan participants' contributions6 7 — — 
Collections(1)
— — 20 22 
Net transfers (to) from variable fund/401(k) plan2 1 — — 
Employer contributions305 307 26 36 
Expenses paid(5)(6)— — 
Benefits paid(726)(721)(46)(58)
Fair value of net plan assets at end of year7,959 7,980 — — 
Funded status$(5,716)$(5,332)$(544)$(499)
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, 2020 and 2019, 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
 Pension BenefitsOther Post-Retirement Benefits
 2020201920202019
Regulatory assets (liabilities)$5,115 $4,731 $78 $25 
Accounts payable and accrued liabilities(5)(5)(28)(28)
Pension and post-retirement benefit obligations(1)
(5,711)(5,327)(516)(471)
Note
(1) The table above excludes $390 million and $383 million of post-employment benefit costs that are recorded in Post-retirement and post-employment benefit obligations on the Consolidated Balance Sheets at September 30, 2020 and 2019, respectively.
Post-Retirement Benefit Costs Deferred as Regulatory Assets
Unrecognized amounts included in regulatory assets or liabilities yet to be recognized as components of accrued benefit cost at September 30, 2020 and 2019, consisted of the following:
Post-Retirement Benefit Costs Deferred as Regulatory Assets (Liabilities)
At September 30
 Pension BenefitsOther Post-Retirement Benefits
 2020201920202019
Unrecognized prior service credit$(615)$(714)$(112)$(135)
Unrecognized net loss5,620 5,350 190 160 
Amount capitalized due to actions of regulator110 95 — — 
Total regulatory assets (liabilities)$5,115 $4,731 $78 $25 
Projected Benefit Obligations and Accumulated Benefit Obligations in Excess of Plan Assets
The projected benefit obligation, accumulated benefit obligation, and fair value of plan assets for the pension plan at September 30, 2020 and 2019, were as follows:
Projected Benefit Obligations and Accumulated Benefit Obligations in Excess of Plan Assets
At September 30
 20202019
Projected benefit obligation$13,675 $13,312 
Accumulated benefit obligation13,613 13,246 
Fair value of net plan assets7,959 7,980 
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, 2020, 2019, and 2018 were as follows:
Components of Net Periodic Benefit Cost
For the years ended September 30
 Pension BenefitsOther Post-Retirement Benefits
 202020192018202020192018
Service cost$55 $44 $53 $16 $11 $14 
Interest cost415 499 473 16 18 19 
Expected return on plan assets(488)(477)(478)— — — 
Amortization of prior service credit(97)(99)(99)(24)(24)(22)
Recognized net actuarial loss436 336 409 10 4 8 
Total net periodic benefit cost as actuarially determined321 303 358 18 9 19 
Amount expensed (capitalized) due to actions of regulator(15)1 (54)— — — 
Net periodic benefit cost$306 $304 $304 $18 $9 $19 
Expected Amortization of Regulatory Assets in Next Fiscal Year
The amounts in the regulatory asset that are expected to be recognized as components of net periodic benefit cost during the next fiscal year are as follows:
Expected Amortization of Regulatory Assets in 2021
At September 30, 2020
 Pension BenefitsOther Post-Retirement
Benefits		Total
Prior service credit$(97)$(18)$(115)
Net actuarial loss447 12 459 
Amounts expensed due to actions of regulator28 — 28 
Actuarial Assumptions
Actuarial Assumptions Utilized to Determine Benefit Obligations at September 30
 Pension BenefitsOther Post-Retirement Benefits
 2020201920202019
Discount rate2.75%3.20%3.05%3.30%
Rate of compensation increase3.43%3.50%N/AN/A
Cost of living adjustment (COLA)(1)
2.00%2.00%2.00%2.00%
Pre-Medicare eligible
Current health care cost trend rate(2)
N/AN/A6.50%6.75%
Ultimate health care cost trend rateN/AN/A5.00%5.00%
Year ultimate trend rate is reachedN/AN/A20272027
Post-Medicare eligible
Current health care cost trend rateN/AN/A—%—%
Ultimate health care cost trend rateN/AN/A4.00%4.00%
Year ultimate trend rate is reachedN/AN/A20242023
Notes
(1) The COLA assumption is the ultimate long-term rate. The calendar year rate for 2021 is assumed to be one percent, and for years thereafter the ultimate is used.
(2) In 2019, TVA reset the pre-Medicare health care cost trend rates assumption with an initial rate of 6.75 percent, declining 0.25 percent per year until it reaches the ultimate rate of 5.00 percent in 2027. For 2020, TVA maintained this trend assumption for pre-Medicare per capita claims cost with a current health care cost rate of 6.50 percent. However, to account for cumulative delayed medical care due to the COVID-19 pandemic and the expected spending as the demand for care returns, the pre-Medicare per capita retiree contributions current health care cost trend rate is 11.93 percent, and in 2022 assumed to return to 6.25 percent in line with the health care cost trend rates assumption.
Actuarial Assumptions Utilized to Determine Net Periodic Benefit Cost for the Years Ended September 30(1)
 Pension BenefitsOther Post-Retirement Benefits
 202020192018202020192018
Discount rate3.20 %4.35 %3.85 %3.30 %4.40 %3.95 %
Expected return on plan assets(2)
6.75 %6.75 %6.75 %N/AN/AN/A
Cost of living adjustment (COLA)(3)
2.00 %2.00 %2.00 %2.00 %2.00 %2.00 %
Rate of compensation increase3.43 %3.50 %5.34 %N/AN/AN/A
Pre-Medicare eligible
Current health care cost trend rateN/AN/AN/A6.75 %6.25 %6.50 %
Ultimate health care cost trend rateN/AN/AN/A5.00 %5.00 %5.00 %
Year ultimate trend rate is reachedN/AN/AN/A202720242024
Post-Medicare eligible
Current health care cost trend rateN/AN/AN/A— %— %— %
Ultimate health care cost trend rateN/AN/AN/A4.00 %4.00 %4.00 %
Year ultimate trend rate is reachedN/AN/AN/A202320212021
Notes
(1) The actuarial assumptions used to determine the benefit obligations at September 30 of each year are subsequently used to determine net periodic benefit cost
for the following year except the rate of compensation increase assumption.
(2) The actual return on assets for 2020, 2019, and 2018 were 5.11%, 4.99%, and 5.84%, respectively.
(3) The COLA assumption is the ultimate rate. The actual calendar year rate is used in determining the expense, and for years thereafter the ultimate rate is used.
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
At September 30, 2020
 
 
Actuarial Assumption
Change in Assumption
Impact on 2020 Pension Cost
Impact on 2020 Projected Benefit Obligation
Discount rate(0.25)%$17 $418 
Rate of return on plan assets(0.25)%18 N/A
Cost of living adjustments0.25 %30 270 
Sensitivity to Changes in Assumed Health Care Cost Trend Rates
The following chart reflects the sensitivity of post-retirement benefit cost to changes in the health care trend rate:
Sensitivity to Changes in Assumed Health Care Cost Trend Rates
At September 30, 2020
 1% Increase1% Decrease
Effect on total of service and interest cost components for the year$4 $(4)
Effect on end-of-year accumulated post-retirement benefit obligation70 (68)
Asset Holdings and Fair Value Measurements s consistent with the asset allocation policy. At September 30, 2020 and 2019, the asset holdings of TVARS included the following:
Asset Holdings of TVARS
At September 30
  Plan Assets at September 30
Asset CategoryTarget Allocation20202019
Global public equity32 %36 %37 %
Private equity8 %13 %10 %
Safety oriented fixed income20 %18 %18 %
Opportunistic fixed income20 %15 %12 %
Public real assets10 %10 %15 %
Private real assets10 %8 %8 %
Total100 %100 %100 %
Fair Value Measurements

    The following table provides the fair value measurement amounts for assets held by TVARS at September 30, 2020:
TVA Retirement System
At September 30, 2020
 
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$1,624 $1,621 $— $3 
Preferred securities11 — 11 — 
Debt securities   
Corporate debt securities1,421 — 1,418 3 
Residential mortgage-backed securities317 — 314 3 
    Debt securities issued by U.S. Treasury701 701 — — 
Debt securities issued by foreign governments
231 — 179 52 
Asset-backed securities
116 — 88 28 
Debt securities issued by state/local governments
23 — 23 — 
Commercial mortgage-backed securities
91 — 86 5 
Commingled funds measured at net asset value(3)
Equity931 — — — 
Debt203 — — — 
Blended102 — — — 
Institutional mutual funds277 277 — — 
Cash equivalents and other short-term investments338 77 261 — 
Private credit measured at net asset value(3)
166 — — — 
Private equity measured at net asset value(3)
1,003 — — — 
Private real assets measured at net asset value(3)
629 — — — 
Securities lending collateral167 — 167 — 
Derivatives    
Futures
3 3 — — 
Swaps10 — 10 — 
Options2 — 2 — 
Foreign currency forward receivable2 — 2 — 
Total assets$8,368 $2,679 $2,561 $94 
Liabilities    
Derivatives
Futures$1 $1 $— $— 
Foreign currency forward payable3 — 3 — 
Swaps6 — 6 — 
Options2 — 2 — 
Securities sold under agreements to repurchase123 — 123 — 
Total liabilities$135 $1 $134 $— 
Notes
(1)  Excludes approximately $107 million in net payables associated with security purchases and sales and various other payables.
(2)  Excludes a $167 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 net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy.
    The following table provides the fair value measurement amounts for assets held by TVARS at September 30, 2019:
TVA Retirement System
At September 30, 2019
 
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$1,766 $1,762 $— $4 
Preferred securities10 1 9 — 
Debt securities   
Corporate debt securities1,387 — 1,382 5 
Residential mortgage-backed securities427 — 424 3 
Debt securities issued by U.S. Treasury807 807 — — 
Debt securities issued by foreign governments210 — 209 1 
Asset-backed securities144 — 116 28 
Debt securities issued by state/local governments18 — 18 — 
Commercial mortgage-backed securities
81 — 80 1 
Commingled funds measured at net asset value(3)
Equity795 — — — 
Debt308 — — — 
Commodities217 — — — 
Blended125 — — — 
Institutional mutual funds97 97 — — 
Cash equivalents and other short-term investments329 1 328 — 
Certificates of deposit3 — 3 — 
Private credit measured at net asset value(3)
78 — — — 
Private equity measured at net asset value(3)
778 — — — 
Private real assets measured at net asset value(3)
659 — — — 
Securities lending collateral224 — 224 — 
Derivatives
Futures
2 2 — — 
Swaps
5 — 5 — 
    Options1 — 1 — 
Foreign currency forward receivable1 — 1 — 
Total assets$8,472 $2,670 $2,800 $42 
Liabilities    
Derivatives
Futures$4 $4 $— $— 
Foreign currency forward payable1 — 1 — 
Swaps12 — 12 — 
Options1 — 1 — 
Securities sold under agreements to repurchase118 — 118 — 
Total liabilities$136 $4 $132 $— 
cNotes
(1)  Excludes approximately $132 million in net payables associated with security purchases and sales and various other payables.
(2)  Excludes a $224 million payable for collateral on loaned securities in connection with TVARS's participation in securities lending programs.
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
 Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Balance at October 1, 2018$58 
Net realized/unrealized gains (losses)4 
Purchases, sales, issuances, and settlements (net)(12)
Transfers in and/or out of Level 3(8)
Balance at September 30, 201942 
Net realized/unrealized gains (losses)46 
Purchases, sales, issuances, and settlements (net)11 
Transfers in and/or out of Level 3(5)
Balance at September 30, 2020$94 
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, 2020
 
Pension
Benefits(1)
Other Post-Retirement Benefits
2021$777 $28 
2022776 26 
2023773 24 
2024768 23 
2025767 22 
2026 - 20303,741 117 
Note
(1) Participants are assumed to receive the Fixed Fund in a lump sum in lieu of available annuity options allowed for certain grandfathered participants resulting in higher estimated pension benefits payments.
Amounts recognized on Consolidated Balance Sheets
Amounts Recognized on TVA's Consolidated Balance Sheets
At September 30
 20202019
Accounts payable and accrued liabilities$— $36 
Post-retirement and post-employment benefit obligations390 383 
v3.20.2
Commitments and Contingencies (Tables)
 12 Months Ended
Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]  
Schedule of lease/leaseback future minimum payments [Table Text Block] At September 30, 2020, the future minimum payments under leaseback obligations are shown below.
Lease/Leasebacks
Minimum payments due in years ending September 30
2021$207 
202225 
2023— 
2024— 
2025— 
Thereafter— 
Total$232 
Schedule of future minimum payments for membership interests subject to mandatory redemption [Table Text Block] At September 30, 2020, the mandatory redemptions for each of the next five years are shown below:
 20212022202320242025
Membership interests of variable interest entity subject to mandatory redemption$3 $3 $2 $1 $1 
Energy Prepayment Obligations In addition to the commitments above, TVA had contractual obligations in the form of revenue discounts related to energy prepayments. TVA recognized $10 million of prepayment obligations and related interest payments of $4 million in revenue during 2019. The arrangement ceased in 2019. See Note 1 — Summary of Significant Accounting Policies — Energy Prepayment Obligations and Note 17 — Revenue.
Unfunded loan commitments At September 30, 2020, TVA's commitments under unfunded loan commitments were $1 million for 2021. TVA has no commitments under unfunded loan commitments for 2022 through 2025.
v3.20.2
Related Parties Related Parties (Tables)
 12 Months Ended
Sep. 30, 2020
Related Party Transactions [Abstract]  
Related Party Transactions Transactions with agencies of the federal government were as follows:
Related Party Transactions
For the years ended, or at, September 30
 202020192018
Revenue from sales of electricity$105 $118 $122 
Other income260 258 240 
Expenditures
Operating expenses224 222 220 
Additions to property, plant, and equipment9 10 8 
Cash and cash equivalents31 45 46 
Accounts receivable, net94 76 60 
Investment funds485 279 199 
Long-term accounts receivable27 53 46 
Accounts payable and accrued liabilities39 69 69 
Long-term power bonds, net1 — — 
Return on power program appropriation investment6 6 5 
v3.20.2
Unaudited Quarterly Financial Information Unaudited Quarterly Financial Information (Tables)
 12 Months Ended
Sep. 30, 2020
Quarterly Financial Information Disclosure [Abstract]  
Unaudited Quarterly Financial Information
Unaudited Quarterly Financial Information
2020
 FirstSecondThirdFourthTotal
Operating revenues$2,578 $2,521 $2,251 $2,899 $10,249 
Operating expenses2,046 1,914 1,716 1,862 7,538 
Operating income532 607 535 1,037 2,711 
Net income (loss)192 255 205 700 1,352 
Unaudited Quarterly Financial Information
2019
 FirstSecondThirdFourthTotal
Operating revenues$2,725 $2,750 $2,604 $3,239 $11,318 
Operating expenses1,960 2,158 2,088 2,301 8,507 
Operating income765 592 516 938 2,811 
Net income (loss)423 241 165 588 1,417 
v3.20.2
Revenue (Tables)
 12 Months Ended
Sep. 30, 2020
Revenue from Contract with Customer [Abstract]  
Revenue Recognition, Incentives [Policy Text Block] 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. In 2020 and 2019, TVA recorded a total of $318 million and $310 million, respectively, in incentives as a reduction of revenue. 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, 2020 and 2019, the outstanding unpaid incentives were $172 million and $157 million, respectively. Incentives that have been paid out may be subject to claw back if the customer fails to meet certain program requirements. Additionally, in May 2020, TVA established flexibility provisions to support the continued operations and recovery of participating customers experiencing financial and operational hardships as a result of the COVID-19 pandemic and corresponding economic downturn. These provisions have not had a material impact to TVA.
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 are recorded in Other revenue. Revenues that are not related to the overall mission are recorded in Other income (expense), net.
Energy Prepayment Obligations

In 2004, TVA and its largest customer, Memphis Light, Gas and Water Division ("MLGW"), entered into an energy prepayment agreement under which MLGW prepaid TVA $1.5 billion for the future costs of electricity to be delivered by TVA to MLGW over a period of 180 months.  TVA accounted for the prepayment as unearned revenue and reported the obligation to deliver power under this arrangement as Energy prepayment obligations.  The arrangement ceased in 2019. Revenue was recognized in each year of the arrangement as electricity was delivered to MLGW based on the ratio of units of kilowatt hours delivered to total units of kilowatt hours under contract.  As of September 30, 2019, $1.5 billion had been recognized as non-cash revenue on a cumulative basis during the life of the agreement, $10 million and $100 million of which was recognized as non-cash revenue during 2019 and 2018, respectively.

Discounts to account for the time value of money, which are recorded as a reduction to electricity sales, amounted to $4 million and $46 million for the years ended September 30, 2019 and 2018, respectively.
Disaggregation of Revenue [Table Text Block]
Disaggregated Revenue

In 2020, the revenues generated from TVA's electricity sales were $10.1 billion and accounted for virtually all of TVA's revenues. TVA's 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)
 202020192018
Alabama
$1,439 $1,593 $1,600 
Georgia
249 270 267 
Kentucky
624 691 696 
Mississippi
941 1,063 1,052 
North Carolina
65 74 66 
Tennessee
6,740 7,419 7,350 
Virginia
42 45 48 
Subtotal10,100 11,155 11,079 
Off-system sales4 4 7 
Revenue capitalized during pre-commercial plant operations(1)
— — (11)
Revenue from sales of electricity10,104 11,159 11,075 
Other revenue145 159 158 
Total operating revenues$10,249 $11,318 $11,233 
Note
(1) Represents revenue capitalized during pre-commercial operations of $11 million at Allen CC in 2018. See Note 1 — Summary of Significant Accounting Policies — Pre-Commercial Plant Operations.

    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)
 202020192018
Revenue from sales of electricity  
Local power companies(1)
$9,406 $10,351 $10,262 
Industries directly served588 686 695 
Federal agencies and other110 122 129 
Revenue capitalized during pre-commercial plant operations(2)
— — (11)
Revenue from sales of electricity10,104 11,159 11,075 
Other revenue145 159 158 
Total operating revenues$10,249 $11,318 $11,233 
Notes
(1) The amount for the years ended September 30, 2020 and 2019, is net of $163 million and $14 million, respectively, of wholesale bill credits to LPCs participating in the long-term Partnership Agreement. There were no such credits in 2018.
(2) Represents revenue capitalized during pre-commercial operations of $11 million at Allen CC in 2018. See Note 1 — Summary of Significant Accounting Policies — Pre-Commercial Plant Operations.

    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 20-year Partnership Agreement option that better aligns the length of LPC contracts with TVA's long-term commitments. These agreements are automatically extended each year after their initial effective date, contingent upon certain circumstances, including limited rate increases going forward. Participating LPCs will 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. In June 2020, TVA provided participating LPCs a flexibility option that allows them to locally generate up to approximately five percent of average total hourly energy sales over the prior five years in order to meet their individual customers' needs. As of November 16, 2020, 142 LPCs had signed the 20-year Partnership Agreement with TVA, and 64 LPCs had signed a Flexibility Agreement.

In August 2020, the TVA Board approved a $200 million Pandemic Relief Credit. The 2.5 percent base rate credit will be applied beginning in October 2020 and will remain in effect through the end of 2021. The credit will apply to service provided to TVA's local power company customers, their large commercial and industrial customers, and TVA directly served customers.
    The number of LPCs with the contract arrangements described below, the revenues derived from such arrangements during 2020, and the percentage of TVA's total operating revenues during 2020 represented by these revenues are summarized in the tables below:
TVA Local Power Company Contracts
At or for the year ended September 30, 2020
Contract Arrangements(1)
Number of LPCs Revenue from Sales of Electricity to LPCs
(in millions)		Percentage of Total Operating Revenues
20-year termination notice142 $7,666 74.8 %
5-year termination notice11 1,740 17.0 %
Total(2)
153 $9,406 91.8 %
Notes
(1) Ordinarily, the LPCs and TVA have the same termination notice period; however, in contracts with two of the LPCs with five-year termination notices, 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.
(2) TVA wholesale power contracts decreased to 153 in 2020 due to a merger between two LPCs in July 2020.
                                                 
    TVA's two largest LPCs — MLGW and 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 2020. In May 2020, MLGW published a draft IRP to guide energy choices in the future, and in July 2020, TVA made a proposal to MLGW that highlights the benefits of remaining a TVA customer. In August 2020, MLGW published a final IRP and announced its plan to issue requests for proposal to validate the cost estimates included in the IRP. In addition, certain other LPCs are evaluating options for future energy choices.
Contract with Customer, Asset and Liability [Table Text Block]
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 does not have any material contract assets as of September 30, 2020.

    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.
Energy Prepayment Obligation [Table Text Block] Energy Prepayment Obligations. In 2004, TVA and its largest customer, MLGW, entered into an energy prepayment agreement under which MLGW prepaid TVA $1.5 billion for the future costs of electricity to be delivered by TVA to MLGW over a period of 15 years.  TVA accounted for the prepayment as unearned revenue and reported the obligation to deliver power under this arrangement as Energy prepayment obligations.  The arrangement ceased in 2019. TVA recognized approximately $100 million of noncash revenue in each year of the arrangement as electricity was delivered to MLGW based on the ratio of units of kilowatt hours delivered to total units of kilowatt hours under contract. As of September 30, 2019, $1.5 billion had been recognized as noncash revenue on a cumulative basis during the life of the agreement, $100 million of which was recognized as noncash revenue and a corresponding reduction in the balance of Energy prepayment obligations during 2018. During 2019, $10 million was recognized as noncash revenue and a corresponding reduction in the balance of Energy prepayment obligations. Discounts to account for the time value of money, which were recorded as a reduction to electricity sales, amounted to $4 million and $46 million during 2019 and 2018, respectively.
v3.20.2
Leases (Table Text Block)
 12 Months Ended
Sep. 30, 2020
Leases [Abstract]  
Amounts Recognized on Balance Sheets The following table provides additional information regarding the presentation of leases on the Consolidated Balance Sheets at September 30, 2020:
Amounts Recognized on TVA's Consolidated Balance Sheets
At September 30, 2020
Assets
  OperatingOperating lease assets, net of amortization$232 
  FinanceFinance leases516 
Total lease assets$748 
Liabilities
Current
  OperatingAccounts payable and accrued liabilities$63 
  FinanceAccounts payable and accrued liabilities41 
Non-current
  OperatingOther long-term liabilities171 
  FinanceFinance lease liabilities525 
Total lease liabilities$800 
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 26 years. The components of lease costs for the year September 30, 2020, were as follows:
Lease Costs
For the year ended September 30, 2020
Operating lease costs(1)
$84 
Variable lease costs(1)
75 
Short-term lease costs(1)
7 
Finance lease costs
Amortization of lease assets(2)
15 
Interest on lease liabilities(3)(4)
33 
Total finance lease costs48 
     Total lease costs$214 
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. TVA's rental expense for operating leases was approximately $97 million and $92 million for the years ended September 30, 2019 and 2018, respectively.
(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 Year Ended September 30, 2020
Operating cash flows for operating leases$85 
Operating cash flows for finance leases33 
Financing cash flows for finance leases15 
Lease assets obtained in exchange for lease obligations (non-cash)
Operating leases(1)
$110 
Finance leases394 
Note
(1) Amount excludes operating lease assets recorded as a result of the adoption of the new lease standard.
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. At September 30, 2020, the weighted average remaining lease term in years and the weighted average discount rate for TVA's operating and financing leases were as follows:
Weighted Averages
At September 30, 2020
Weighted average remaining lease terms
Operating leases5 years
Finance leases12 years
Weighted average discount rate(1)
Operating leases1.6%
Finance leases21.8%
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, 2020:
Future Minimum Lease Payments
Minimum Payments Due at September 30, 2020
Operating leases
2021$66 
202251 
202339 
202437 
202534 
Thereafter16 
Minimum annual payments243 
Less: present value discount(9)
Operating present value of net minimum lease payments$234 
Finance leases
2021$92 
202293 
202392 
202487 
202586 
   Thereafter592 
Minimum annual payments1,042 
Less: amount representing interest(476)
Finance present value of net minimum lease payments$566 
v3.20.2
Summary of Significant Accounting Policies - General (Details)
People in Millions, $ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
People
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2015
USD ($)
Accounting Policies [Abstract]          
Cash and Cash Equivalents, at Carrying Value $ 500 $ 299      
Allowance for uncollectible accounts - loans   1      
Revenue Capitalized During Pre-Commercial Operations 0 0 $ 11    
Fuel Cost Capitalized During Pre-Commercial Operations   19      
Recorded cost for emission allowances granted by the Environmental Protection Agency 0        
Reimbursements from DOE 89        
Restricted Cash and Investments, Noncurrent 21 23      
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents 521 322 $ 322 $ 311  
Accounts receivable from DOE 6        
Appropriation-investment power program $ 258 258     $ 1,000
Population of Service Area [Line Items]          
Population of service area | People 10        
Total          
Accounting Policies [Abstract]          
Discounts reducing electricity sales $ 4 46      
MLGW          
Accounting Policies [Abstract]          
Deferred revenue, revenue recognized   $ 100      
v3.20.2
Summary of Significant Accounting Policies - Reclassificatons (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Reclassifications    
Finance Lease, Liability $ 525 $ 182
v3.20.2
Summary of Significant Accounting Policies - Allowance for Uncollectible Accounts (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Portion at Other than Fair Value Measurement [Member]    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Financing Receivable, after Allowance for Credit Loss $ 105 $ 131
Financing Receivable, after Allowance for Credit Loss $ 93 120
Period of time for customers to fulfill payment arrangements 90 days  
Allowance for uncollectible accounts - receivables   1
Allowance for uncollectible accounts - loans   1
Fuel Cost Capitalized During Pre-Commercial Operations   $ 19
v3.20.2
Summary of Significant Accounting Policies - Property, Plant, and Equipment, and Depreciation (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Property, Plant, and Equipment, and Depreciation      
Depreciation $ 1,600 $ 1,800 $ 1,300
Composite depreciation rate for completed plant 2.74% 3.09% 2.45%
Accelerated depreciation   $ 566 $ 48
Reacquired Rights $ 192 200  
Amortization of Reacquired Rights $ 8 8 8
Capitalized software amortization period seven years    
Unamortized computer software costs $ 54 63  
Amortization expense of capitalized computer software costs $ 42 $ 38 $ 32
Nuclear      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 2.38% 2.38% 2.64%
Coal-fired      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 3.62% 4.96% 2.32%
Hydroelectric      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 1.60% 1.61% 1.57%
Gas and oil-fired      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 3.04% 3.00% 2.93%
Transmission      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 1.34% 1.34% 1.32%
Other      
Property, Plant, and Equipment, and Depreciation      
Composite depreciation rate for completed plant 7.26% 7.16% 5.90%
v3.20.2
Summary of Significant Accounting Policies - Energy Prepayment Obligations and Discounts on Sales (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2004
Energy Prepayment Obligations and Discounts on Sales        
Accounts Receivable, Allowance for Credit Loss, Current   $ 1    
MLGW prepayment       $ 1,500
MLGW prepayment period       180 months
Recognition of Deferred Revenue $ 0 $ 10 $ 100  
MLGW        
Energy Prepayment Obligations and Discounts on Sales        
Recognition of Deferred Revenue $ 1,500      
Deferred revenue expected recognition each year 10 million 100 million   100 million
Deferred revenue, revenue recognized   $ 100    
Total        
Energy Prepayment Obligations and Discounts on Sales        
Discounts reducing electricity sales $ 4 $ 46    
v3.20.2
Summary of Significant Accounting Policies - Leases (Details)
$ in Millions
Sep. 30, 2020
USD ($)
Leases  
Finance lease under PPA $ 500
Operating lease under PPA $ 174
v3.20.2
Impact of New Accounting Standards and Interpretations (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Oct. 01, 2019
Sep. 30, 2019
Lessee, Lease, Description [Line Items]      
Operating Lease, Right-of-Use Asset $ 232 $ 205 $ 0
Operating Lease, Liability     $ 210
v3.20.2
Accounts Receivable, Net Accounts Receivable, Net (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Power receivables $ 1,401 $ 1,624
Other receivables 128 115
Allowance for uncollectible accounts [1] (1)  
Accounts receivable, net 1,529 $ 1,739
Available Credit on Public Power Support and Stabilization Program 1,000  
Subsequent Credit on Public Power Support and Stabilization Program $ 1  
[1] Allowance for uncollectible accounts was less than $1 million at September 30, 2020 and 2019, and therefore is not represented in the table above.
v3.20.2
Inventories, Net Inventories, Net (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Inventories, Net    
Materials and supplies inventory $ 770 $ 742
Fuel inventory 253 294
RECs inventory, net 15 16
Allowance for inventory obsolescence (35) (53)
Inventories, net $ 1,003 $ 999
v3.20.2
Net Completed Plant Net Completed Plant (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Completed Plant    
Completed plant cost $ 64,970 $ 62,944
Accumulated depreciation 33,550 31,384
Net completed plant 31,420 31,560
Revisions to asset retirement costs 1,100  
Coal-fired    
Completed Plant    
Completed plant cost 18,613 17,400
Accumulated depreciation 13,944 12,538
Net completed plant 4,669 4,862
Gas and oil-fired    
Completed Plant    
Completed plant cost 6,010 6,054
Accumulated depreciation 1,696 1,562
Net completed plant 4,314 4,492
Nuclear    
Completed Plant    
Completed plant cost 25,741 25,543
Accumulated depreciation 12,141 11,656
Net completed plant 13,600 13,887
Transmission    
Completed Plant    
Completed plant cost 8,283 7,932
Accumulated depreciation 3,140 3,083
Net completed plant 5,143 4,849
Hydroelectric    
Completed Plant    
Completed plant cost 3,410 3,163
Accumulated depreciation 1,090 1,051
Net completed plant 2,320 2,112
Other electrical plant    
Completed Plant    
Completed plant cost 1,981 1,920
Accumulated depreciation 1,146 1,110
Net completed plant 835 810
Computer Software, Intangible Asset [Member]    
Completed Plant    
Completed plant cost 3 3
Accumulated depreciation 2 1
Net completed plant 1 2
Multipurpose dams    
Completed Plant    
Completed plant cost 900 900
Accumulated depreciation 381 373
Net completed plant 519 527
Other stewardship    
Completed Plant    
Completed plant cost 29 29
Accumulated depreciation 10 10
Net completed plant $ 19 $ 19
v3.20.2
Other Long-Term Assets Other Long-Term Assets (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Other Long-Term Assets    
EnergyRight receivables $ 86 $ 100
Prepaid Expense, Noncurrent 42 22
Restricted Cash and Investments, Noncurrent 21 23
Total other long-term assets 325 325
Impact on secured borrowings 1  
Prepaid Expense, Current 3 5
Accounts Receivable [Member]    
Other Long-Term Assets    
EnergyRight receivables 18 20
Other long-term assets    
Other Long-Term Assets    
EnergyRight receivables 69 81
Loans and other long-term receivables, net 100 125
Commodity contract derivative assets 23 0
Restricted Cash and Investments, Noncurrent   23
Prepaid capacity payments 11 19
Other $ 59 $ 55
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  
v3.20.2
Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Regulatory Assets and Liabilities      
Non-current regulatory liabilities $ 23 $ 0  
Accelerated Amortization of Deferred Nuclear Generating Units and Training Costs     $ 857
Accelerated recovery for Kingston ash spill 266    
Current regulatory assets 130 156  
Regulatory assets 10,245 8,763  
Regulatory Assets 10,375 8,919  
Current regulatory liabilities 141 150  
Regulatory asset amount expensed 23 261 $ 2
Gallatin CCR   672  
Regulatory Liabilities 164 150  
Reclass Environmental agreements to Other reg assets   12  
Deferred Project Costs [Member]      
Regulatory Assets and Liabilities      
Gallatin coal combustion residual facilities estimated cost to cap and close 114 89  
Regulatory Asset      
Regulatory Assets and Liabilities      
Regulatory assets 138 142  
Removal Costs [Member]      
Regulatory Assets and Liabilities      
Regulatory assets 1,506 1,241  
Unrealized losses on interest rate derivatives      
Regulatory Assets and Liabilities      
Current regulatory assets 4 39  
Regulatory assets 0 15  
Non-nuclear decommissioning costs      
Regulatory Assets and Liabilities      
Regulatory assets 2,512 1,741  
Pension Costs [Member]      
Regulatory Assets and Liabilities      
Regulatory assets 5,193 4,756  
Deferred Fuel Costs [Member]      
Regulatory Assets and Liabilities      
Current regulatory assets 12 28  
Nuclear decommissioning costs      
Regulatory Assets and Liabilities      
Regulatory assets 896 868  
Unrealized gains/losses on commodity derivatives      
Regulatory Assets and Liabilities      
Non-current regulatory liabilities 23 0  
Current regulatory liabilities 26 12  
Fuel cost adjustment tax equivalents      
Regulatory Assets and Liabilities      
Current regulatory liabilities $ 115 $ 138  
v3.20.2
Asset Acquisitions and Business Combinations (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2019
Sep. 30, 2020
Sep. 20, 2017
Business Combinations and Settlement of Preexisting Relationships [Abstract]      
Percentage equity interests acquired     100.00%
Total cash consideration $ 36    
Fair value of assets acquired     $ 110
Fair value of liabilities assumed   $ 78 74
Amortization expense of SPE's acquired 1    
Loss on extinguishment $ 3    
Lease/leaseback obligations settled     71
Reacquisition price     $ 74
v3.20.2
Variable Interest Entities (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2013
Sep. 30, 2012
Jan. 17, 2012
Liabilities            
Current maturities of long-term debt of variable interest entities issued at par $ 41 $ 39        
Liabilities, Current 4,711 4,312        
Other long-term liabilities 2,548 2,308        
Long-term debt of variable interest entities, net 1,048 1,089        
VIE Financing            
Face Amount $ 40         $ 100
Rate of Return SHLLC 7.00%          
Accrued interest $ 10 11        
Accounts Payable and Accrued Liabilities   1        
Liabilities 39,893 38,842        
SCCG            
VIE Financing            
Face Amount       $ 360    
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 54 53        
Other long-term liabilities 23 25        
VIE Financing            
Accounts Payable and Accrued Liabilities 3 3        
Liabilities 1,125 1,167     $ 1,000  
Interest Expense $ (54) $ (56) $ (58)      
v3.20.2
Other Long-Term Liabilities Other Long-Term Liabilities (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Other Long-Term Liabilities    
Interest rate swaps $ 2,041 $ 1,764
Derivative Liability 277  
Accounts Payable and Accrued Liabilities   1
Capital lease obligations 25 223
Currency swap liabilities 209 208 [1]
EnergyRight financing obligation 108 126
Non-current regulatory liabilities 23 0
Total other long-term liabilities 2,548 2,308
Deferral of EnergyRight laons 1  
Finance Lease, Liability 525 182
Other long-term liabilities    
Other Long-Term Liabilities    
Interest rate swaps 1,927 1,676
Capital lease obligations 171 0
Currency swap liabilities 123 193
EnergyRight financing obligation 78 90
Environmental agreements liability 0 80
Membership interests of VIE subject to mandatory redemption 56 66
Other 193 203
Accounts payable and accrued liabilities    
Other Long-Term Liabilities    
Interest rate swaps 114 88
Service agreements 15 12
EnergyRight financing obligation $ 19 $ 23
[1] See Note 15 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.
v3.20.2
Asset Retirement Obligations Asset Retirement Obligations (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Liabilities Settled [Line Items]      
Increase in ARO liability $ 1,200    
Change in estimate [1] 1,077 $ 50  
Costs for asbestos   114  
Allen West ARO increase 273 33  
Paradise ARO increase (decrease)   57  
Allen East ARO increase (decrease)   44  
Gallatin CCR ARO increase (decrease) 173 672  
Additional obligations [1]   18  
Gallatin CCR   672  
Balance [1] 6,785 5,616 $ 4,779
Asset Retirement Obligation, Liabilities Settled [1] 114 89  
Accretion (recorded as regulatory asset) [1] 206 186  
Asset Retirement Obligation, Current 345 163  
Amortization and Depreciation of Decontaminating and Decommissioning Assets 169 144 144
Total ARO change due to CCR 129    
Change in ARO from operating CCR facilities 38    
Change in ARO from inactive CCR facilities 91    
Increase in CCR post-closure care 460    
Change in plant decommissioning obligations 19    
Accounts payable and accrued liabilities      
Liabilities Settled [Line Items]      
Asset Retirement Obligation, Current 345 163  
Nuclear      
Liabilities Settled [Line Items]      
Revision of estimate (other non nuclear) 0 (250)  
Change in estimate   0  
Additional obligations   18  
Gallatin CCR   0  
Balance 3,278 3,136 2,989
Asset Retirement Obligation, Liabilities Settled 1 7  
Accretion (recorded as regulatory asset) 143 136  
Non-nuclear      
Liabilities Settled [Line Items]      
Change in estimate 1,077 50  
Additional obligations   0  
Gallatin CCR   672  
Balance 3,507 2,480 $ 1,790
Asset Retirement Obligation, Liabilities Settled 113 82  
Accretion (recorded as regulatory asset) $ 63 $ 50  
[1] (1) Includes $345 million and $163 million at September 30, 2020 and 2019, respectively, in Current liabilities.
v3.20.2
Debt and Other Obligations Debt and Other Obligations - General (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Jan. 17, 2012
Debt Instrument    
Interest rate   7.10%
Debt ceiling $ 30,000  
Face Amount $ 40 $ 100
v3.20.2
Debt and Other Obligations Debt and Other Obligations - Secured Debt of VIEs (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Aug. 09, 2013
Jan. 17, 2012
Portion at Other than Fair Value Measurement [Member]        
Variable Interest Entities        
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount $ 26 $ 28    
Long-term debt of variable interest entities (including current maturities) 1,089 1,128    
Face Amount 40     $ 100
Interest rate       7.10%
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount 35 37 $ 40  
Long-term debt of variable interest entities (including current maturities) $ 1,419 $ 1,371    
v3.20.2
Debt and Other Obligations Debt and Other Obligations - Secured Notes of SPEs (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Sep. 20, 2017
Jan. 17, 2012
Nov. 14, 2001
Sep. 27, 2000
Secured notes            
Secured notes $ 40     $ 100    
Interest rate       7.10%    
Fair value of liabilities assumed 78   $ 74      
Notes Payable 0 $ 23        
Special purpose entity            
Secured notes            
Secured notes         $ 272 $ 255
Interest rate         5.572% 7.299%
9/20/17 Business Combination            
Secured notes            
Notes Payable $ 23          
v3.20.2
Debt and Other Obligations Debt and Other Obligations - Short-Term Debt (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2026
Sep. 30, 2024
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2019
Sep. 30, 2018
Short-Term Debt, Gross [Line Items]                
Short-term debt, net of discounts $ 57 $ 0 $ 0 $ 0 $ 0 $ 0 $ 922 $ 1,217
Short-term Borrowings Gross $ 57              
Weighted average interest rate - discount notes 0.06%           2.15% 2.05%
Foreign Currency Transaction Gain (Loss), Unrealized $ 153              
Foreign Currency Transaction Gain, before Tax $ 73              
v3.20.2
Debt and Other Obligations Debt and Other Obligations - Put and Call Options (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Units
Debt Instrument    
Amount of redeemable bond issues outstanding   $ 357
Call price   10000.00%
Bond issues with survivor's option | Units   217,000,000
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  
v3.20.2
Debt and Other Obligations Debt and Other Obligations - Debt Securities Activity (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2026
Sep. 30, 2024
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Jun. 30, 2020
Jul. 20, 2016
Jan. 17, 2012
Debt Instrument                      
Issues of power bonds $ 997 $ 0 $ 998                
Face Amount 40                   $ 100
Discount on debt issues (3) 0                  
Redemptions/Maturities of variable interest entities 39 38 36                
Redemptions/Maturities of power bonds 1,427 1,035 1,731                
Percent of par value                 99.70%    
Leaseback obligation settled as a result of acquisition                   $ 70  
Total Current maturities of power bonds issued at par 1,787 1,030                  
Interest rate                     7.10%
Short-term debt, net of discounts 57 922 $ 1,217 $ 0 $ 0 $ 0 $ 0 $ 0      
Current maturities of long-term debt of variable interest entities issued at par 41 39                  
Current maturities of notes payable 0 23                  
880591EL2                      
Debt Instrument                      
Total Current maturities of power bonds issued at par $ 1,500 0                  
Interest rate 3.875%                    
Debt Instrument, Maturity Date Feb. 15, 2021                    
880591DC3                      
Debt Instrument                      
Total Current maturities of power bonds issued at par $ 258 0                  
Interest rate 5.805%                    
Debt Instrument, Maturity Date Jun. 07, 2021                    
880591EF5 (12.15.20)                      
Debt Instrument                      
Total Current maturities of power bonds issued at par $ 1 0                  
Debt Instrument, Maturity Date Dec. 15, 2020                    
880591EF5                      
Debt Instrument                      
Total Current maturities of power bonds issued at par $ 0 1                  
Interest rate 3.77%                    
Debt Instrument, Maturity Date Dec. 15, 2019                    
880591EF5 (6.15.21)                      
Debt Instrument                      
Debt Instrument, Maturity Date Jun. 15, 2021                    
880591EF5 (6/15/2018)                      
Debt Instrument                      
Total Current maturities of power bonds issued at par $ 0 27                  
Debt Instrument, Maturity Date Jun. 15, 2020                    
880591EF5 (6/15/2021)                      
Debt Instrument                      
Total Current maturities of power bonds issued at par $ 28 0                  
PARRS 1998 Series D Bond                      
Debt Instrument                      
Redemptions/Maturities of power bonds 23 0                  
PARRS 1999 Series A Bond                      
Debt Instrument                      
Redemptions/Maturities of power bonds 1,000 0                  
2020 Series A                      
Debt Instrument                      
Redemptions/Maturities of power bonds $ 1,000 $ 0                  
Total                      
Debt Instrument                      
Debt Instrument, Redemption Period, End Date 1,489 1,119                  
Percent of par value 100.00%                    
Debt of variable interest entities                      
Debt Instrument                      
Redemptions/Maturities of variable interest entities $ 39 $ 38                  
Notes Payable                      
Debt Instrument                      
Redemptions/Maturities of notes payable 23 46                  
electronotes                      
Debt Instrument                      
Redemptions/Maturities of power bonds 219 5                  
2013 Series A [Member]                      
Debt Instrument                      
Redemptions/Maturities of power bonds 1,000                  
2009 Series B                      
Debt Instrument                      
Redemptions/Maturities of power bonds 28 30                  
1997 Series E [Member]                      
Debt Instrument                      
Redemptions/Maturities of power bonds 17                    
1995 Series B                      
Debt Instrument                      
Redemptions/Maturities of power bonds 140 0                  
Total                      
Debt Instrument                      
Debt Securities Issues $ 997 $ 0                  
v3.20.2
Debt and Other Obligations Debt and Other Obligations - Debt Outstanding (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2026
Sep. 30, 2024
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2018
Jan. 17, 2012
Short-term debt                  
Coupon rate                 7.10%
Short-term debt, net of discounts $ 922 $ 57 $ 0 $ 0 $ 0 $ 0 $ 0 $ 1,217  
Current maturities of long-term debt of variable interest entities issued at par 39 41              
Current maturities of notes payable 23 0              
Total Current maturities of power bonds issued at par 1,030 1,787              
Current maturities of power bonds 1,030 1,787              
Total current debt outstanding, net 2,014 1,885              
Long-term debt                  
Long-term power bonds, net 19,094 17,956              
Long-term power bonds [1] 19,225 18,078              
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net (131) (122)              
Long-term debt of variable interest entities, net 1,089 1,048              
Total long-term debt, net 20,183 19,004              
Foreign Currency Transaction Gain (Loss), before Tax 191 $ 80              
880591DX7                  
Short-term debt                  
Coupon rate [2]   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 246 $ 218              
880591DC3                  
Short-term debt                  
Coupon rate   5.805%              
Debt Instrument, Maturity Date   Jun. 07, 2021              
Long-term debt                  
Long-term power bonds, net 246 $ 0              
880591EL2                  
Short-term debt                  
Coupon rate   3.875%              
Debt Instrument, Maturity Date   Feb. 15, 2021              
Long-term debt                  
Long-term power bonds, net 1,500 $ 0              
electronotes                  
Long-term debt                  
Maturity date - earliest   May 15, 2020              
Maturity date - latest   Feb. 15, 2043              
Call date - earliest   Feb. 15, 2015              
Call date - latest   Feb. 15, 2018              
Long-term power bonds, net 217 $ 0              
880591EN8                  
Short-term debt                  
Coupon rate   1.875%              
Debt Instrument, Maturity Date   Aug. 15, 2022              
Long-term debt                  
Long-term power bonds, net 1,000 $ 1,000              
880591ER9                  
Short-term debt                  
Coupon rate   2.875%              
Debt Instrument, Maturity Date   Sep. 15, 2024              
Long-term debt                  
Long-term power bonds, net 1,000 $ 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 273 $ 256              
880591409                  
Short-term debt                  
Coupon rate   2.216%              
Debt Instrument, Maturity Date   May 01, 2029              
Long-term debt                  
Long-term power bonds, net 232 $ 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 307 $ 323              
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 185 $ 194              
880591CF7                  
Short-term debt                  
Coupon rate   6.235%              
Debt Instrument, Maturity Date   Jul. 15, 2045              
Long-term debt                  
Long-term power bonds, net 140 $ 0              
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 [2]   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 0 $ 1,000              
880591EF5 (6/15/2018)                  
Short-term debt                  
Total Current maturities of power bonds issued at par 27 $ 0              
Debt Instrument, Maturity Date   Jun. 15, 2020              
880591EF5                  
Short-term debt                  
Coupon rate   3.77%              
Total Current maturities of power bonds issued at par 1 $ 0              
Debt Instrument, Maturity Date   Dec. 15, 2019              
88059TEL1                  
Short-term debt                  
Coupon rate   2.65%              
Total Current maturities of power bonds issued at par 1 $ 0              
Debt Instrument, Maturity Date   Nov. 15, 2019              
88059TEL1 (5/15/2018)                  
Short-term debt                  
Total Current maturities of power bonds issued at par 1 $ 0              
Debt Instrument, Maturity Date   May 15, 2020              
880591EV0 [Member]                  
Short-term debt                  
Coupon rate   2.25%              
Total Current maturities of power bonds issued at par $ 1,000 $ 0              
Debt Instrument, Maturity Date   Mar. 15, 2020              
Minimum | electronotes                  
Short-term debt                  
Coupon rate   2.375%              
Maximum | electronotes                  
Short-term debt                  
Coupon rate   3.625%              
[1] Includes net exchange gain from currency transactions of $80 million and $191 million at September 30, 2020 and 2019
[2] The coupon rate represents TVA's effective interest rate.
v3.20.2
Debt and Other Obligations Debt and Other Obligations - Maturities Due (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2026
Sep. 30, 2024
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2018
Debt Instrument                
2018   $ 1,901            
2019   1,071            
2020   69            
2021   1,058            
2022   1,059            
Thereafter   15,957            
Total   21,115            
Short-term debt, net of discounts $ 922 57 $ 0 $ 0 $ 0 $ 0 $ 0 $ 1,217
Short-term debt, net of discounts total   57            
Foreign Currency Transaction Gain (Loss), before Tax $ 191 80            
Net discount on sale of Bonds   77            
Foreign Currency Transaction Gain (Loss), Unrealized   153            
Power bonds                
Debt Instrument                
Debt issuance costs   45            
Other long-term debt                
Debt Instrument                
Debt issuance costs   $ 8            
v3.20.2
Debt and Other Obligations Debt and Other Obligations - Credit Facility Agreements (Details)
Sep. 30, 2020
USD ($)
Credit_facilities
Sep. 30, 2019
USD ($)
Credit Facility Agreements    
Current borrowing capacity $ 150,000,000  
Line of Credit    
Credit Facility Agreements    
Current borrowing capacity 150,000,000  
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 1,000,000,000.0  
Long-term Line of Credit, Borrowings 4 0  
Long-term Line of Credit, Borrowings 3 0  
Long-term Line of Credit, Borrowings 1 0  
Long-term Line of Credit, Borrowings 2 0  
Line of Credit Facility, Remaining Borrowing Capacity 4 112,000,000  
Line of Credit Facility, Remaining Borrowing Capacity 2 568,000,000  
Line of Credit Facility, Remaining Borrowing Capacity 3 513,000,000  
Line of Credit Facility, Remaining Borrowing Capacity 1 0  
Line of Credit Facility, Remaining Borrowing Capacity 1,193,000,000  
Letter of Credit    
Credit Facility Agreements    
Amount of letters of credit outstanding 1,457,000,000 $ 1,300,000,000
Letters of Credit Outstanding, Amount 4 38,000,000  
Letters of Credit Outstanding, Amount 3 487,000,000  
Letters of Credit Outstanding, Amount 1 500,000,000  
Letter of Credit Outstanding, Amount 2 $ 432,000,000  
v3.20.2
Debt and Other Obligations Debt and Other Obligations - Lease/Leasebacks (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Sep. 20, 2017
Jul. 20, 2016
Lease/Leasebacks [Abstract]        
Percentage equity interests acquired     100.00%  
Leaseback obligation settled as a result of acquisition       $ 70
CT and QTE outstanding leaseback obligation $ 223 $ 263    
v3.20.2
Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Equity [Abstract]      
Reclassification on cash flow hedges from AOCI to interest expense $ 38 $ 45 $ 26
v3.20.2
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, 2020
Sep. 30, 2019
Sep. 30, 2018
Summary of Derivative Instruments That Receive Hedge Accounting Treatment      
Interest rate swaps $ 2,041,000,000 $ 1,764,000,000  
Net unrealized gain (loss) on future cash flow hedges (1,000,000) (114,000,000) $ 10,000,000
Reclassification to earnings from cash flow hedges 38,000,000 45,000,000 $ 26,000,000
Ineffective portion excluded from testing 0    
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred 27,000,000    
Accounts payable and accrued liabilities      
Summary of Derivative Instruments That Receive Hedge Accounting Treatment      
Interest rate swaps $ 114,000,000 $ 88,000,000  
v3.20.2
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, 2020
USD ($)
Sep. 30, 2019
USD ($)
Jun. 30, 2020
USD ($)
Derivative      
Unrealized gains/losses on derivatives $ 0    
Change in Unrealized gains (losses) on Interest Rate Derivatives 272,000,000 $ (565,000,000)  
Interest rate swaps 2,041,000,000 1,764,000,000  
Interest Rate Swap      
Derivative      
Amount of gain (loss) recognized in income on derivatives (97,000,000) (79,000,000)  
Fair value (588,000,000) (498,000,000)  
Commodity Contract Derivatives      
Derivative      
Amount of gain (loss) recognized in income on derivatives (1,000,000) 0  
Fair value $ 46,000,000 $ (41,000,000)  
Coal Contract Derivatives      
Derivative      
Number of contracts 0 8  
Notional amount 0 9,000,000  
Fair value $ 0 $ (4,000,000) $ 10,000,000
Natural Gas Contract Derivatives      
Derivative      
Number of contracts 42 65  
Notional amount 302,000,000 330,000,000  
Fair value $ 46,000,000 $ (37,000,000)  
Accounts payable and accrued liabilities      
Derivative      
Interest rate swaps 114,000,000 88,000,000  
Accounts payable and accrued liabilities | Interest Rate Swap      
Derivative      
Fair value (32,000,000) (24,000,000)  
Accounts payable and accrued liabilities | Commodity Contract Derivatives      
Derivative      
Fair value $ (3,000,000) $ (37,000,000)  
v3.20.2
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, 2020
Sep. 30, 2019
Derivatives, Fair Value    
Derivative Liability, Fair Value, Gross Liability $ 2,250  
Other Credit Derivatives [Member] | Other long-term liabilities    
Derivatives, Fair Value    
Fair value 49 $ 12
Other Credit Derivatives [Member] | Other current assets    
Derivatives, Fair Value    
Fair value 1,927 1,676
200 million Sterling currency swap    
Derivatives, Fair Value    
Derivative Liability, Fair Value, Gross Liability 209  
Fair value (78) (90)
200 million Sterling currency swap | Other long-term liabilities    
Derivatives, Fair Value    
Fair value 0 (84)
200 million Sterling currency swap | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value (78) (6)
250 million Sterling currency swap    
Derivatives, Fair Value    
Fair value (63) (61)
250 million Sterling currency swap | Other long-term liabilities    
Derivatives, Fair Value    
Fair value (58) (56)
250 million Sterling currency swap | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value (5) (5)
150 million Sterling currency swap    
Derivatives, Fair Value    
Fair value (68) (57)
150 million Sterling currency swap | Other long-term liabilities    
Derivatives, Fair Value    
Fair value (65) (53)
150 million Sterling currency swap | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value (3) (4)
$1.0 billion notional interest rate swap    
Derivatives, Fair Value    
Fair value (1,449) (1,261)
$1.0 billion notional interest rate swap | Other long-term liabilities    
Derivatives, Fair Value    
Fair value (1,369) (1,199)
$1.0 billion notional interest rate swap | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value (80) (62)
$476 million notional interest rate swap    
Derivatives, Fair Value    
Fair value (588) (498)
$476 million notional interest rate swap | Other long-term liabilities    
Derivatives, Fair Value    
Fair value (556) (474)
$476 million notional interest rate swap | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value (32) (24)
$42 million notional interest rate swap    
Derivatives, Fair Value    
Fair value (4) (5)
$42 million notional interest rate swap | Other long-term liabilities    
Derivatives, Fair Value    
Fair value (2) (3)
$42 million notional interest rate swap | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value (2) (2)
Commodity contract derivatives    
Derivatives, Fair Value    
Fair value 46 (41)
Commodity contract derivatives | Other long-term assets    
Derivatives, Fair Value    
Fair value 26 0
Commodity contract derivatives | Other long-term liabilities    
Derivatives, Fair Value    
Fair value 0 (16)
Commodity contract derivatives | Other current assets    
Derivatives, Fair Value    
Fair value 23 12
Commodity contract derivatives | Accounts payable and accrued liabilities    
Derivatives, Fair Value    
Fair value $ (3) $ (37)
v3.20.2
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Currency Swaps Outstanding (Details)
£ in Millions
 12 Months Ended
Sep. 30, 2020
GBP (£)
Bond_issues
Derivative  
Number of British pound sterling denominated bond transactions | Bond_issues 3
1999 Currency Swap Contract  
Derivative  
Effective Date of Currency Swap Contract 1999
Associated TVA bond issues currency exposure £ 200
Expiration Date of Swap 2021
Overall effective cost to TVA 5.81%
2001 Currency Swap Contract  
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 6.59%
2003 Currency Swap Contract  
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 4.96%
v3.20.2
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Counterparty Credit Risk (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
megawatts
Customers
Sep. 30, 2019
USD ($)
Derivative    
Receivables from power sales | $ $ 1,401 $ 1,624
Credit of Customers    
Derivative    
Number of customers that represent the percent of sales | Customers 2  
Percent of total sales by customers 17.00%  
Long-term Contract for Purchase of Electric Power [Domain]    
Derivative    
Megawatts | megawatts 440  
v3.20.2
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Offsetting of Derivative Assets (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Letter of Credit    
Offsetting Assets [Line Items]    
Amount of letters of credit outstanding $ 1,457 $ 1,300
Other Contract    
Offsetting Assets [Line Items]    
Gross Amounts of Recognized Assets, subject to master netting or similar arrangements $ 49  
Net Amounts of Assets Presented in the Balance Sheet   $ 12
v3.20.2
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Offsetting of Derivative Liabilities (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Offsetting Liabilities [Line Items]    
Gross Amounts of Recognized Liabilities, subject to master netting or similar arrangements $ 2,250  
Derivative Liability   $ 2,025
Total derivatives not subject to master netting or similar arrangement 3 53
Total 2,253  
Currency Swap    
Offsetting Liabilities [Line Items]    
Gross Amounts of Recognized Liabilities, subject to master netting or similar arrangements 209  
Derivative Liability [1]   208
Interest Rate Contract    
Offsetting Liabilities [Line Items]    
Gross Amounts of Recognized Liabilities, subject to master netting or similar arrangements 2,041  
Derivative Liability [1]   1,764
Total derivatives subject to master netting or similar arrangement    
Offsetting Liabilities [Line Items]    
Derivative Liability   1,972
Letter of Credit    
Offsetting Liabilities [Line Items]    
Amount of letters of credit outstanding $ 1,457 $ 1,300
[1] Letters of credit of approximately $1.5 billion and $1.3 billion were posted as collateral at September 30, 2020 and 2019, respectively, to partially secure the liability positions of one of the currency swaps and one of the interest rate swaps in accordance with the collateral requirements for these derivatives.
v3.20.2
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Other Derivative Instruments (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Derivative    
Forward Contract Derivative Asset, at Fair Value $ 13 $ 22
Fair Value, Inputs, Level 2    
Derivative    
Forward Contract Derivative Asset, at Fair Value $ 13 $ 22
v3.20.2
Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Collateral (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Derivative    
Likely collateral obligation increase if downgraded $ 22  
Collateralized Securities [Member]    
Derivative    
Aggregate fair value of derivative instruments with credit-risk related contingent features that were in a liability position 2,200  
Collateral obligations 1,500  
Letter of Credit    
Derivative    
Amount of letters of credit outstanding $ 1,457 $ 1,300
v3.20.2
Fair Value Measurements - Investments (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Long-term Investments $ 3,198 $ 2,968
Balance in the NDT 2,200  
Balance in the ART $ 866  
Period of time where the investor contributes capital to an investment in a private partnership - minimum three  
Period of time where the investor contributes capital to an investment in a private partnership - maximum four  
Minimum investment period 10 years  
Fair value of gross plan assets $ 8,368 8,472
Number of readily available quoted exchange prices for the investments 0  
Increase in NDT $ 123  
LTDCP    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) on investments 2 (2)
SERP    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) on investments 3 0
ART    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) on investments 32 (70)
NDT    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Unrealized gains (losses) on investments 37 $ (112)
Equity Funds [Member]    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Commitments, Fair Value Disclosure 218  
Real Estate Funds [Member]    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Commitments, Fair Value Disclosure 67  
Credit [Member]    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Commitments, Fair Value Disclosure 33  
Private equity    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Commitments, Fair Value Disclosure 133  
Private real estate funds    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Fair value of gross plan assets 54  
Private Credit [Member]    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
Commitments, Fair Value Disclosure 16  
Interest Payments relating to energy prepayment obligations    
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]    
2019 $ 4  
v3.20.2
Fair Value Measurements - Nonperformance Risk (Details)
$ in Millions
Sep. 30, 2020
USD ($)
Nonperformance Risk  
Derivative credit valuation adjustment, assets $ 1
Derivative credit valuation adjustment, liabilities $ 1
v3.20.2
Fair Value Measurements - Fair Value Measurements (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Investments    
Equity securities $ 500 $ 464
Government debt securities 525 344
Corporate debt securities 356 417
Mortgage and asset-backed securities 27 32
Institutional mutual funds 188 250
Forward debt securities contracts - asset 13 22
Private equity funds measured at net asset value 194 140
Private real estate measured at net asset value 168 135
Private credit measured at net asset value 53 33
Commingled funds measured at net asset value 1,174 1,131
Total investments 3,198 2,968
Commodity contract derivatives 49 12
Total 3,247 2,980
Liabilities    
Currency swaps 209 208 [1]
Interest rate swaps 2,041 1,764
Commodity contract derivatives 3 53
Total 2,253 2,025
Fair Value, Inputs, Level 1    
Investments    
Equity securities 500 464
Government debt securities 485 279
Corporate debt securities 0 0
Mortgage and asset-backed securities 0 0
Institutional mutual funds 188 250
Forward debt securities contracts - asset 0 0
Private equity funds measured at net asset value 0 0 [2]
Private real estate measured at net asset value 0 0 [2]
Private credit measured at net asset value 0 0
Commingled funds measured at net asset value 0 0 [2]
Total investments 1,173 993
Commodity contract derivatives 0 0
Total 1,173 993
Liabilities    
Currency swaps 0 0 [1]
Interest rate swaps 0 0
Commodity contract derivatives 0 0
Total 0 0
Fair Value, Inputs, Level 2    
Investments    
Equity securities 0 0
Government debt securities 40 65
Corporate debt securities 356 417
Mortgage and asset-backed securities 27 32
Institutional mutual funds 0 0
Forward debt securities contracts - asset 13 22
Private equity funds measured at net asset value 0 0 [2]
Private real estate measured at net asset value 0 0 [2]
Private credit measured at net asset value 0 0
Commingled funds measured at net asset value 0 0 [2]
Total investments 436 536
Commodity contract derivatives 49 7
Total 485 543
Liabilities    
Currency swaps 209 208 [1]
Interest rate swaps 2,041 1,764
Commodity contract derivatives 3 44
Total 2,253 2,016
Fair Value, Inputs, Level 3    
Investments    
Equity securities 0 0
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
Private equity funds measured at net asset value 0 0 [2]
Private real estate measured at net asset value 0 0 [2]
Private credit measured at net asset value 0 0
Commingled funds measured at net asset value 0 0 [2]
Total investments 0 0
Commodity contract derivatives 0 5
Total 0 5
Liabilities    
Currency swaps 0 0 [1]
Interest rate swaps 0 0
Commodity contract derivatives 0 9
Total $ 0 $ 9
[1] See Note 15 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.
[2] Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been categorized in the fair value hierarchy. 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.
v3.20.2
Fair Value Measurements - Fair Value Measurements Using Significant Unobservable Inputs (Details)
tons-per-year in Billions
 12 Months Ended
Sep. 30, 2020
USD ($)
tons-per-year
Sep. 30, 2019
USD ($)
tons-per-year
Sep. 30, 2018
USD ($)
Fair Value Measurements      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements $ (1,000,000)    
Commodity contract derivatives, assets 49,000,000 $ 12,000,000  
Commodity contract derivatives, liabilities $ 3,000,000 $ 53,000,000  
Minimum      
Assets      
Fair value measurements tons per year | tons-per-year 0.4 0.7  
Price per ton $ 12.10 $ 12.25  
Liabilities      
Fair value measurements tons per year | tons-per-year 0.4 0.7  
Price per ton $ 12.10 $ 12.25  
Maximum      
Assets      
Fair value measurements tons per year | tons-per-year 0.8 0.8  
Price per ton $ 94.51 $ 112.24  
Liabilities      
Fair value measurements tons per year | tons-per-year 0.8 0.8  
Price per ton $ 94.51 $ 112.24  
Commodity Contract Derivatives      
Fair Value Measurements      
Balance at beginning/end of period 0 (4,000,000) $ 58,000,000
Change in net unrealized gains (losses) deferred as regulatory assets and liabilities 5,000,000 (62,000,000)  
Fair Value, Inputs, Level 3      
Fair Value Measurements      
Commodity contract derivatives, assets 0 5,000,000  
Commodity contract derivatives, liabilities $ 0 $ 9,000,000  
v3.20.2
Fair Value Measurements - Estimated Values of Financial Instruments (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Aug. 09, 2013
Estimated Values of Financial Instruments (Level 2 Valuation)      
EnergyRight receivables (including current portion) $ 86 $ 100  
Financing Receivable, after Allowance for Credit Loss 93 120  
EnergyRight® financing obligations (including current portion) 108 126  
Unfunded Loan Commitments 2 10  
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount 35 37 $ 40
Long-term outstanding power bonds (including current maturities), net 26,630 26,059  
Long-term debt of variable interest entities (including current maturities) 1,419 1,371  
Long-term notes payable (including current maturities) 0 23  
Portion at Other than Fair Value Measurement [Member]      
Estimated Values of Financial Instruments (Level 2 Valuation)      
EnergyRight receivables (including current portion) 87 101  
Financing Receivable, after Allowance for Credit Loss 105 131  
EnergyRight® financing obligations (including current portion) 97 113  
Unfunded Loan Commitments 0 0  
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount 26 28  
Long-term outstanding power bonds (including current maturities), net 19,743 20,124  
Long-term debt of variable interest entities (including current maturities) 1,089 1,128  
Long-term notes payable (including current maturities) $ 0 $ 23  
v3.20.2
Proprietary Capital (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Appropriation Investment                      
Amount of appropriation investment that was repaid $ 1,000               $ 1,000    
Remaining appropriation investment 258               258    
Balance at beginning of year       $ 11,625       $ 10,283 11,625 $ 10,283 $ 9,133
Net income (loss) 700 $ 205 $ 255 192 $ 588 $ 165 $ 241 423 1,352 1,417 1,119
Return on power program appropriation investment                 (6) (6) (5)
Balance at end of year 12,932       11,625       12,932 11,625 $ 10,283
Net proprietary capital at September 30 $ 12,932       $ 11,625       $ 12,932 $ 11,625  
Computed average interest rate payable 2.44%       2.37%       2.44% 2.37% 2.09%
Nonpower Programs Appropriation Investment                      
Appropriation Investment                      
Balance at beginning of year       4,351         $ 4,351    
Balance at end of year $ 4,351       $ 4,351       4,351 $ 4,351  
Power Program Appropriation Investment                      
Appropriation Investment                      
Balance at beginning of year       258       258 258 258 $ 258
Net income (loss)                 0 0 0
Return on power program appropriation investment                 0 0 0
Balance at end of year 258       258       258 258 258
Power Program Retained Earnings                      
Appropriation Investment                      
Balance at beginning of year       10,823       9,404 10,823 9,404 8,282
Net income (loss)                 1,360 1,425 1,127
Return on power program appropriation investment                 (6) (6) (5)
Balance at end of year 12,177       10,823       12,177 10,823 9,404
Net proprietary capital at September 30 12,435       11,081       12,435 11,081  
Nonpower Programs Appropriation Investment, Net                      
Appropriation Investment                      
Balance at beginning of year       556       564 556 564 572
Net income (loss)                 (8) (8) (8)
Return on power program appropriation investment                 0 0 0
Balance at end of year 548       556       548 556 564
Nonpower Programs Retained Earnings                      
Appropriation Investment                      
Balance at beginning of year       $ (3,795)       $ (3,787) (3,795) (3,787)  
Return on power program appropriation investment                 0 0  
Balance at end of year (3,803)       (3,795)       (3,803) (3,795) (3,787)
Net proprietary capital at September 30 $ 548       $ 556       548 556  
Affiliated Entity                      
Appropriation Investment                      
Return on power program appropriation investment                 $ (6) $ (6) $ (5)
v3.20.2
Proprietary Capital - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss)        
Net effect on earnings $ 0 $ 0    
Net unrealized gain (loss) on future cash flow hedges   (1) $ (114) $ 10
Reclassification to earnings from cash flow hedges   38 $ 45 $ 26
Reclassification to earnings from cash flow hedges in the next twelve months   $ (27)    
v3.20.2
Other Income (Expense), Net Other Income (Expense), Net (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Other Income (Expense), Net      
Change in other income (expense) $ (26)    
Other income   $ 21 $ 0
Proceeds from Other Deposits 0 21  
Interest income 18 25 23
External services 12 13 14
Gain (Loss) on Investments 9 3 6
Miscellaneous   0 7
Miscellaneous (3)    
Total other income (expense), net 36 $ 62 $ 50
Change in interest income $ 7    
v3.20.2
Benefit Plans Components of Benefit Plans (Details) - USD ($)
 12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Defined Benefit Plan Disclosure        
Fixed and variable fund annual maximum contribution   $ 10,000    
Defined contribution plan contribution amount $ 92,000,000 $ 88,000,000 $ 84,000,000 $ 80,000,000
Minimum        
Defined Benefit Plan Disclosure        
Threshold for Deferral of Actuarial Gain/Loss Under Corridor Approach   10.00%    
v3.20.2
Benefit Plans Obligations and Funded Status (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]      
Amount related to change in number of participants $ 7    
Pension Benefits      
Change in benefit obligation      
Benefit obligation 13,675 $ 13,312  
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation 13,312 11,725  
Service cost 55 44 $ 53
Interest cost 415 499 $ 473
Plan participants' contributions 6 7  
Change in Plan Assets due to Collections [1] 0 0  
Collections [1] 0 0  
Actuarial loss (gain) 614 1,756  
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment 2 7  
Net transfers from variable fund/401(k) plan 2 1  
Expenses paid (5) (6)  
Benefits paid 726 721  
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets 7,959 7,980  
Change in plan assets      
Fair value of net plan assets 7,980 7,980  
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets   8,003  
Actual return on plan assets 397 389  
Employer contributions 305 307  
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]      
Funded status $ (5,716) $ (5,332)  
Discount rate 2.75% 3.20% 4.35%
Amount of defined benefit plan actuarial gain (loss) from change in COLA $ 69    
Amount of defined benefit plan actuarial gain (loss) from discount rate change (714) $ (1,600)  
Amount of defined benefit plan actuarial gain (loss) from change in mortality assumption (137) (14)  
Amount of defined benefit plan actuarial gain (loss) from change in demograhic and plan experience 74 147  
Amount of defined benefit plan actuarial gain (loss) from assumption change in elections 32    
Other Post-retirement Benefits      
Change in benefit obligation      
Benefit obligation 544 499  
Postconfirmation, Other Postretirement Obligations 499 428  
Service cost 16 11 $ 14
Interest cost 16 18 $ 19
Plan participants' contributions 0 0  
Change in Plan Assets due to Collections [1] 20 22  
Collections [1] 20 22  
Actuarial loss (gain) 39 78  
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment 0 0  
Net transfers from variable fund/401(k) plan 0 0  
Expenses paid 0 0  
Benefits paid 46 58  
Change in plan assets      
Fair value of net plan assets 0 0  
Actual return on plan assets 0 0  
Employer contributions 26 36  
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]      
Funded status $ (544) $ (499)  
Discount rate 3.05% 3.30%  
Amount of defined benefit plan actuarial gain (loss) from updated capita claims costs and retiree contributions $ (30) $ (24)  
Amount of change related to actual 4 7  
Amount of defined benefit plan actuarial gain (loss) from discount rate change $ (20) $ (71)  
Defined Benefit Plan, Assumptions Used in Calculation, Description 3.05 3.30 percent 4.40
Amount of defined benefit plan actuarial gain (loss) from change in health care trend rate assumptions $ 15 $ 24  
[1] Collections include retiree contributions as well as provider discounts and rebates.
v3.20.2
Benefit Plans Amounts Recognized on TVA's Consolidated Balance Sheets (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Defined Benefit Plan Disclosure    
Regulatory assets $ 10,245 $ 8,763
Non-current regulatory liabilities (23) 0
Accounts payable and accrued liabilities (1,844) (1,649)
Pension and post-retirement benefit obligations (6,617) (6,181)
Pension Benefits    
Defined Benefit Plan Disclosure    
Amount capitalized due to actions of regulator 110 95
Regulatory assets 5,115 4,731
Accounts payable and accrued liabilities (5) (5)
Pension and post-retirement benefit obligations [1] (5,711) (5,327)
Other Post-retirement Benefits    
Defined Benefit Plan Disclosure    
Amount capitalized due to actions of regulator 0 0
Regulatory assets   25
Non-current regulatory liabilities (78)  
Accounts payable and accrued liabilities (28) (28)
Pension and post-retirement benefit obligations [1] (516) (471)
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent    
Defined Benefit Plan Disclosure    
Postemployment benefits liability, noncurrent $ 390 $ 383
[1] The table above excludes $390 million and $383 million of post-employment benefit costs that are recorded in Post-retirement and post-employment benefit obligations on the Consolidated Balance Sheets at September 30, 2020 and 2019, respectively.
v3.20.2
Benefit Plans Postretirement Benefit Costs Deferred as Regulatory Assets (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Defined Benefit Plan Disclosure    
Regulatory assets $ (10,245) $ (8,763)
Non-current regulatory liabilities 23 0
Pension Benefits    
Defined Benefit Plan Disclosure    
Unrecognized prior service cost (credit) (615) (714)
Unrecognized net loss 5,620 5,350
Amount capitalized due to actions of regulator (110) (95)
Regulatory assets (5,115) (4,731)
Other Post-retirement Benefits    
Defined Benefit Plan Disclosure    
Unrecognized prior service cost (credit) (112) (135)
Unrecognized net loss 190 160
Amount capitalized due to actions of regulator 0 0
Regulatory assets   $ (25)
Non-current regulatory liabilities $ 78  
v3.20.2
Benefit Plans Projected Benefit Obligations and Accumulated Benefit Obligations in Exess of Plan Assets (Details) - Pension Benefits - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Defined Benefit Plan Disclosure    
Projected benefit obligation   $ 13,312
Accumulated benefit obligation $ 13,613 13,246
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets 7,959 7,980
Fair value of net plan assets $ 7,980 $ 7,980
v3.20.2
Benefit Plans Components of Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Pension Benefits      
Defined Benefit Plan Disclosure      
Service cost $ 55 $ 44 $ 53
Interest cost 415 499 473
Expected return on plan assets 488 477 478
Amortization of prior service credit (97) (99) (99)
Recognized net actuarial loss (436) (336) (409)
Net periodic benefit cost as acutarially determined 321 303 358
Amount expensed (capitalized) due to actions of regulator 15 (1) 54
Total net period benefit cost 306 304 304
Other Post-retirement Benefits      
Defined Benefit Plan Disclosure      
Service cost 16 11 14
Interest cost 16 18 19
Expected return on plan assets 0 0 0
Amortization of prior service credit (24) (24) (22)
Recognized net actuarial loss (10) 4 8
Net periodic benefit cost as acutarially determined 18 9 19
Amount expensed (capitalized) due to actions of regulator 0 0 0
Total net period benefit cost $ 18 $ 9 $ 19
v3.20.2
Benefit Plans Expected Amortization of Regulatory Assets in Next Fiscal Year (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
Defined Benefit Plan Disclosure  
Prior service cost (credit) $ (115)
Net actuarial loss 459
Defined Benefit Plan Amortization From Regulatory Assets Of Amounts Capitalized due to Actions of Regulatory 28
Pension Benefits  
Defined Benefit Plan Disclosure  
Prior service cost (credit) (97)
Net actuarial loss 447
Defined Benefit Plan Amortization From Regulatory Assets Of Amounts Capitalized due to Actions of Regulatory 28
Other Post-retirement Benefits  
Defined Benefit Plan Disclosure  
Prior service cost (credit) (18)
Net actuarial loss 12
Defined Benefit Plan Amortization From Regulatory Assets Of Amounts Capitalized due to Actions of Regulatory $ 0
v3.20.2
Benefit Plans Actuarial Assumptions (Details) - USD ($)
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Defined Benefit Plan Disclosure      
Defined Benefit Plan, Cost of Living Adjustment Assumption 25.00%    
Pension Benefits      
Defined Benefit Plan Disclosure      
Discount rate 3.20% 4.35% 3.85%
Discount rate 2.75% 3.20% 4.35%
Rate of compensation increase 3.43% 3.50%  
Expected return on plan assets 6.75% 6.75% 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 3.43% 3.50% 5.34%
COLA percentage increase (decrease) 600.00%    
Other Post-retirement Benefits      
Defined Benefit Plan Disclosure      
Discount rate 3.30% 4.40% 3.95%
Discount rate 3.05% 3.30%  
Defined Benefit Plan, Cost of Living Adjustment Assumption 2.00% 2.00% 2.00%
Minimum      
Defined Benefit Plan Disclosure      
Rate of compensation increase 2.50%    
Maximum      
Defined Benefit Plan Disclosure      
Rate of compensation increase 14.00%    
Pre-Medicare Eligible [Member] | Other Post-retirement Benefits      
Defined Benefit Plan Disclosure      
Current health care cost trend rate(2) 6.75% 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 2027 2027  
Initial health care cost trend rate $ 0.0650 $ 0.0675  
Post-Medicare Eligible [Member] [Member] | Other Post-retirement Benefits      
Defined Benefit Plan Disclosure      
Current health care cost trend rate(2) 0.00% 0.00% 0.00%
Ultimate health care cost trend rate 4.00% 4.00% 4.00%
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate 2024 2023  
v3.20.2
Benefit Plans Sensitivity to Certain Changes in Pension Assumptions (Details) - USD ($)
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Defined Benefit Plan Disclosure      
Defined Benefit Plan, Cost of Living Adjustment Assumption 25.00%    
Discount rate      
Defined Benefit Plan Disclosure      
Change in Assumption (0.25%)    
Impact on Pension Cost $ 17,000,000    
Impact on Projected Benefit Obligation $ 418,000,000    
Rate of return on plan assets      
Defined Benefit Plan Disclosure      
Change in Assumption (0.25%)    
Impact on Pension Cost $ 18,000,000    
Cost of Living Adjustments [Domain]      
Defined Benefit Plan Disclosure      
Change in Assumption 0.25%    
Impact on Pension Cost $ 30,000,000    
Impact on Projected Benefit Obligation $ 270,000,000    
Other Post-retirement Benefits      
Defined Benefit Plan Disclosure      
Defined Benefit Plan, Cost of Living Adjustment Assumption 2.00% 2.00% 2.00%
Discount rate 3.05% 3.30%  
Actuarial assumption COLA $ 1.54 $ 0.0221 $ 0.0184
Pension Benefits      
Defined Benefit Plan Disclosure      
Defined Benefit Plan, Cost of Living Adjustment Assumption 2.00% 2.00% 2.00%
COLA percentage increase (decrease) 600.00%    
Discount rate 2.75% 3.20% 4.35%
Pre-Medicare Eligible [Member] | Other Post-retirement Benefits      
Defined Benefit Plan Disclosure      
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate 5.00% 5.00% 5.00%
v3.20.2
Benefit Plans Sensitivity to Changes in Assumed Health Care Cost Trend Rates (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
Maximum  
Defined Benefit Plan Disclosure  
Effect of one percentage point increase on total service and interest cost components $ 4
Effect of one percentage point increase on end-of-year accumulated postretirement benefit obligation 70
Minimum  
Defined Benefit Plan Disclosure  
Effect of one percentage point decrease on total service and interest cost components (4)
Effect of one percentage point decrease on end-of-year accumulated postretirement benefit obligation $ (68)
v3.20.2
Benefit Plans Asset Holdings (Details) - USD ($)
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Defined Benefit Plan Disclosure      
Target Allocation 100.00%    
Plan Asset Allocations 100.00% 100.00%  
Global public equity      
Defined Benefit Plan Disclosure      
Target Allocation 32.00%    
Plan Asset Allocations 36.00% 37.00%  
Public real assets      
Defined Benefit Plan Disclosure      
Target Allocation 10.00%    
Plan Asset Allocations 10.00% 15.00%  
Private equity      
Defined Benefit Plan Disclosure      
Target Allocation 8.00%    
Plan Asset Allocations 13.00% 10.00%  
Safety oriented fixed income      
Defined Benefit Plan Disclosure      
Target Allocation 20.00%    
Plan Asset Allocations 18.00% 18.00%  
Opportunistic fixed income      
Defined Benefit Plan Disclosure      
Target Allocation 20.00%    
Plan Asset Allocations 15.00% 12.00%  
Private real assets      
Defined Benefit Plan Disclosure      
Target Allocation 10.00%    
Plan Asset Allocations 8.00% 8.00%  
Other Post-retirement Benefits      
Defined Benefit Plan Disclosure      
Actuarial assumption COLA $ 1.54 $ 0.0221 $ 0.0184
v3.20.2
Benefit Plans Fair Value Measurements (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
Years
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Defined Benefit Plan Disclosure      
Fair value of gross plan assets $ 8,368 $ 8,472  
Estimated future decommissioning cost [1] 6,785 5,616 $ 4,779
Derivative liabilities 135 136  
Net payables 107 132  
Payables for collateral on loaned securities $ 167 224  
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 $ 2,679 2,670  
Derivative liabilities 1 4  
Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 2,561 2,800  
Derivative liabilities 134 132  
Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 42 58  
Estimated future decommissioning cost 94 42  
Derivative liabilities 0 0  
Equity securities      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 1,624 1,766  
Equity securities | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 1,621 1,762  
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 3 4  
Preferred securities      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 11 10  
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 11 9  
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 1,421 1,387  
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 1,418 1,382  
Corporate debt securities | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 3 5  
Residential mortgage-backed securities      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 317 427  
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 314 424  
Residential mortgage-backed securities | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 3 3  
Debt securities issued by U.S. Treasury and other U.S. government agencies      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 701 807  
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 701 807  
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 116 144  
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 88 116  
Asset-backed securities | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 28 28  
Debt securities issued by state/local governments      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 23 18  
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 23 18  
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 231 210  
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 179 209  
Debt securities issued by foreign governments | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 52 1  
Commercial mortgage-backed securities      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 91 81  
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 86 80  
Commercial mortgage-backed securities | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 5 1  
Equity security commingled funds      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 931 795  
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 203 308  
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  
Commodity commingled funds      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   217  
Commodity commingled funds | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   0  
Commodity commingled funds | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   0  
Commodity commingled funds | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   0  
Blended security commingled funds      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 102 125  
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 277 97  
Institutional mutual funds | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 277 97  
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 338 329  
Cash equivalents and other short-term investments | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 77 1  
Cash equivalents and other short-term investments | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 261 328  
Cash equivalents and other short-term investments | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Certificates of deposit      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   3  
Certificates of deposit | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   0  
Certificates of deposit | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   3  
Certificates of deposit | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   0  
Private Credit [Member]      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 166 78  
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 1,003 778  
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 629 659  
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 167 224  
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 167 224  
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 3 2  
Derivative liabilities 1 4  
Futures | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 3 2  
Derivative liabilities 1 4  
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 10    
Purchased options | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0    
Purchased options | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 10    
Purchased options | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0    
Interest Rate Swap      
Defined Benefit Plan Disclosure      
Derivative liabilities 6 12  
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 6 12  
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 1  
Derivative liabilities 3 1  
Foreign currency forward | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Derivative liabilities 0 0  
Foreign currency forward | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 2 1  
Derivative liabilities 3 1  
Foreign currency forward | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0 0  
Derivative liabilities 0 0  
Written options      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   5  
Written options | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   0  
Written options | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   5  
Written options | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets   0  
Credit default swaps      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 2    
Derivative liabilities 2 1  
Credit default swaps | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0    
Derivative liabilities 0 0  
Credit default swaps | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 2    
Derivative liabilities 2 1  
Credit default swaps | Fair Value, Inputs, Level 3      
Defined Benefit Plan Disclosure      
Fair value of gross plan assets 0    
Derivative liabilities 0 0  
Securities Sold under Agreements to Repurchase [Member]      
Defined Benefit Plan Disclosure      
Derivative liabilities 123 118  
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 123 118  
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    
[1] (1) Includes $345 million and $163 million at September 30, 2020 and 2019, respectively, in Current liabilities.
v3.20.2
Benefit Plans Fair Value Measurements Using Significant Unobservable Inputs (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Defined Benefit Plan Disclosure    
Net payables $ 107 $ 132
Payables for collateral on loaned securities 167 224
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]    
Fair value of gross plan assets 8,368 8,472
Private equity reclassed to private real asset   113
Private real estate reclassed to private real asset   546
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 42 58
Net realized/unrealized gains 46 4
Purchases, sales, issuances, and settlements, net 11 (12)
Transfers in and/or out of Level 3 (5) $ (8)
Fair value of net plan assets $ 94  
v3.20.2
Benefit Plans Estimated Future Benefit Payments (Details)
$ in Millions
Sep. 30, 2020
USD ($)
Pension Benefits  
Defined Benefit Plan Disclosure  
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months $ 777
Defined Benefit Plan, Expected Future Benefit Payments, Year Two 776
Defined Benefit Plan, Expected Future Benefit Payments, Year Three 773
Defined Benefit Plan, Expected Future Benefit Payments, Year Four 768
Defined Benefit Plan, Expected Future Benefit Payments, Year Five 767
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter 3,741
Other Post-retirement Benefits  
Defined Benefit Plan Disclosure  
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months 28
Defined Benefit Plan, Expected Future Benefit Payments, Year Two 26
Defined Benefit Plan, Expected Future Benefit Payments, Year Three 24
Defined Benefit Plan, Expected Future Benefit Payments, Year Four 23
Defined Benefit Plan, Expected Future Benefit Payments, Year Five 22
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter $ 117
v3.20.2
Benefit Plans Contributions (Details) - USD ($)
 12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Defined Benefit Plan Disclosure        
Defined contribution plan contribution amount $ 92,000,000 $ 88,000,000 $ 84,000,000 $ 80,000,000
Other postretirement benefit contributions   25,000,000 36,000,000  
Contribution related to TVARS case   5,000,000 4,000,000  
Expected Payment for Postretirement Benefits 28,000,000      
Supplemental Employee Retirement Plans, Defined Benefit        
Defined Benefit Plan Disclosure        
Defined Benefit Plan, Expected Payments Related to SERP 5,000,000      
Defined Benefit Plan, Related to SERP   5,000,000 7,000,000  
Other Post-retirement Benefits        
Defined Benefit Plan Disclosure        
Employer contributions   26,000,000 36,000,000  
Pension Benefits        
Defined Benefit Plan Disclosure        
Employer contributions   305,000,000 $ 307,000,000  
Other Pension Plans, Defined Benefit        
Defined Benefit Plan Disclosure        
Employer contributions   300,000,000    
Minimum | Other Pension Plans, Defined Benefit        
Defined Benefit Plan Disclosure        
Employer contributions   $ 300,000,000    
Scenario, Forecast | Other Pension Plans, Defined Benefit        
Defined Benefit Plan Disclosure        
Employer contributions $ 300,000,000      
v3.20.2
Benefit Plans Other Postemployment Benefits (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Other Post-Employment Benefits        
Discount rate   0.69% 1.68% 3.05%
Period expense   $ 45 $ 59 $ 6
Postemployment benefits liability     419 $ 339
Payment of Workers Compensation Claims $ 32 74 39  
Accounts Payable and Accrued Liabilities        
Other Post-Employment Benefits        
Postemployment Benefits Liability, Current   0 36  
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent        
Other Post-Employment Benefits        
Postemployment benefits liability, noncurrent   $ 390 $ 383  
v3.20.2
Commitments and Contingencies - Table (Details)
$ in Millions
Sep. 30, 2020
USD ($)
megawatts
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Obligations      
Megawatts provided under transmission obligations | megawatts 1,450    
Accrual for Environmental Loss Contingencies, Gross $ 14 $ 15  
Estimated future decommissioning cost [1] 6,785 5,616 $ 4,779
Operating Leases, Future Minimum Payments Due, Next Twelve Months 66 76  
Operating Leases, Future Minimum Payments, Due in Two Years 51 75  
Operating Leases, Future Minimum Payments, Due in Three Years 39 60  
Operating Leases, Future Minimum Payments, Due in Four Years 37 12  
Operating Leases, Future Minimum Payments, Due in Five Years 34 3  
Operating Leases, Future Minimum Payments, Due Thereafter 16 2  
Total 243 228  
CT and QTE outstanding leaseback obligation 223 263  
Other Commitment, to be Paid, Year One 207    
Other Commitment, to be Paid, Year Two 25    
Other Commitment, to be Paid, Year Three 0    
Other Commitment, to be Paid, Year Four 0    
Other Commitment, to be Paid, Year Five 0    
Other Commitment, to be Paid, after Year Five 0    
Total 232    
Nuclear      
Obligations      
Estimated future decommissioning cost $ 3,278 $ 3,136 $ 2,989
[1] (1) Includes $345 million and $163 million at September 30, 2020 and 2019, respectively, in Current liabilities.
v3.20.2
Commitments and Contingencies - Energy Prepayment Obligations (Details)
$ in Millions
Sep. 30, 2020
USD ($)
Interest Payments relating to energy prepayment obligations  
Obligations  
2019 $ 4
v3.20.2
Commitments and Contingencies - Membership Interests of VIE Subject to Mandatory Redemption (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Aug. 09, 2013
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 $ 26 $ 28  
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount 35 $ 37 $ 40
Minimum payments on membership interests subject to mandatory redemption, due in next twelve months 3    
Other Commitment 232    
Minimum payments on membership interests subject to mandatory redemption, due in year two 3    
Minimum payments on membership interests subject to mandatory redemption, due in year three 2    
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    
v3.20.2
Commitments and Contingencies - Leases (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Leases      
Other Commitment, to be Paid, Year One $ 207    
CT and QTE outstanding leaseback obligation 223 $ 263  
Operating Leases, Future Minimum Payments Due, Next Twelve Months 66 76  
Operating Leases, Future Minimum Payments, Due in Two Years 51 75  
Operating Leases, Future Minimum Payments, Due in Three Years 39 60  
Operating Leases, Future Minimum Payments, Due in Four Years 37 12  
Operating Leases, Future Minimum Payments, Due in Five Years 34 3  
Operating Leases, Future Minimum Payments, Due Thereafter 16 2  
Total 243 228  
Other Commitment, to be Paid, Year Two 25    
Other Commitment, to be Paid, Year Three 0    
Other Commitment, to be Paid, Year Four 0    
Other Commitment, to be Paid, Year Five 0    
Other Commitment, to be Paid, after Year Five 0    
Other Commitment 232    
Estimated future decommissioning cost [1] $ 6,785 $ 5,616 $ 4,779
[1] (1) Includes $345 million and $163 million at September 30, 2020 and 2019, respectively, in Current liabilities.
v3.20.2
Commitments and Contingencies - Purchase Obligations (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
Megawatts
megawatts
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Obligations      
Megawatts provided under power purchase obligations 2,384    
Remaining terms of the agreements, high end of range 12 years    
Megawatts provided under transmission obligations | megawatts 1,450    
Power purchased under agreement | $ $ 202 $ 195 $ 188
Purchase Agreements Required by Federal Law      
Obligations      
Megawatts provided under power purchase obligations 268    
Number of generation sources under PPAs 111    
v3.20.2
Commitments and Contingencies - Contingencies (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
reactors
Procedures
Insurance_layers
Units
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Contingencies      
Loss Contingency, Damages Sought, Value $ 30    
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 145    
Maximum idemnity if a covered accident tasks or keeps a nuclear unit offline 490    
Maximum amount of retrospective premiums 43    
Estimated future decommissioning cost [1] $ 6,785 $ 5,616 $ 4,779
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 19 17 62
Possible additional future costs for compliance with Clean Air Act requirements 156    
Possible additional future costs for compliance with CCR requirements 949    
Possible additional future costs for compliance with Clean Water requirements. 190    
Estimated liability for cleanup and similar environmental work on a non-discounted basis 14 15  
Amount of insurance available for loss at any one site, max 2,800    
Nuclear      
Contingencies      
Estimated future decommissioning cost 3,278 3,136 2,989
Non-nuclear      
Contingencies      
Estimated future decommissioning cost $ 3,507 $ 2,480 $ 1,790
[1] (1) Includes $345 million and $163 million at September 30, 2020 and 2019, respectively, in Current liabilities.
v3.20.2
Commitments and Contingencies - Legal Proceedings (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
Agreements
Groups
Sep. 30, 2019
USD ($)
Legal Proceedings    
Possible additional future costs for compliance with CCR requirements $ 949  
Amount spent under environmental agreements 280  
Contribution related to TVARS case 5 $ 4
Possible additional future costs for compliance with Clean Water requirements. 190  
Amount remaining to be spent under environmental agreements 11  
Loss Contingency, Damages Sought, Value 30  
General    
Legal Proceedings    
Legal loss contingency accrual $ 14  
Environmental Agreements    
Legal Proceedings    
Number of similar environmental agreements entered into | Agreements 2  
Number of environmental agreements entered into with the EPA | Agreements 1  
Number of environmental agreements entered into with environmental advocacy groups | Groups 3  
Amount to be invested in certain environmental projects $ 290  
Other long-term liabilities | General    
Legal Proceedings    
Legal loss contingency accrual 12  
Accounts payable and accrued liabilities | General    
Legal Proceedings    
Legal loss contingency accrual $ 2  
v3.20.2
Commitments and Contingencies Unfunded loan commitments (Details)
$ in Millions
Sep. 30, 2020
USD ($)
Legal Proceedings  
2018 $ 1
Energy prepayment obligations  
Legal Proceedings  
Prepayment Obligations $ 10
v3.20.2
Related Parties Related Parties (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Related Parties                      
Remaining appropriation investment $ 258               $ 258    
Current borrowing capacity 150               150    
Revenue from sales of electricity 2,899 $ 2,251 $ 2,521 $ 2,578 $ 3,239 $ 2,604 $ 2,750 $ 2,725 10,249 $ 11,318 $ 11,233
Other income                   21 0
Long-term Investments 3,198       2,968       3,198 2,968  
Return on power program appropriation investment                 (6) (6) (5)
Related Party Transactions                      
Related Parties                      
Revenue from sales of electricity                 105 118 122
Other income                 260 258 240
Operating expenses                 224 222 220
Additions to property, plant, and equipment                 9 10 8
Cash and cash equivalents 31       45       31 45 46
Receivables from Customers 94       76       94 76 60
Long-term Investments 485       279       485 279 199
Receivables, Long-term Contracts or Programs 27       53       27 53 46
Accounts payable and accrued liabilities 39       69       39 69 69
Long-term power bonds, net $ 1       $ 0       1 0 0
Return on power program appropriation investment                 $ (6) $ (6) $ (5)
v3.20.2
Unaudited Quarterly Financial Information Unaudited Quarterly Financial Information (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Quarterly Financial Information Disclosure [Abstract]                      
Revenue from sales of electricity $ 2,899 $ 2,251 $ 2,521 $ 2,578 $ 3,239 $ 2,604 $ 2,750 $ 2,725 $ 10,249 $ 11,318 $ 11,233
Operating expenses 1,862 1,716 1,914 2,046 2,301 2,088 2,158 1,960 7,538 8,507 8,665
Operating income 1,037 535 607 532 938 516 592 765 2,711 2,811 2,568
Net income (loss) $ 700 $ 205 $ 255 $ 192 $ 588 $ 165 $ 241 $ 423 $ 1,352 $ 1,417 $ 1,119
v3.20.2
Revenue (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Other revenue                   $ 145 $ 159 $ 158
Off-system sales                   4 4 7
Sales of Electricity (subtotal)                   10,100 11,155 11,079
Electric revenue                   (10,104) (11,159) (11,075)
Revenue Capitalized During Pre-Commercial Operations                   0 0 11
Revenues $ 2,899 $ 2,251 $ 2,521 $ 2,578 $ 3,239 $ 2,604 $ 2,750 $ 2,725   10,249 11,318 11,233
Pandemic Relief Credit                 $ 200      
ALABAMA                        
Electric revenue                   (1,439) (1,593) (1,600)
GEORGIA                        
Electric revenue                   (249) (270) (267)
KENTUCKY                        
Electric revenue                   (624) (691) (696)
MISSISSIPPI                        
Electric revenue                   (941) (1,063) (1,052)
NORTH CAROLINA                        
Electric revenue                   (65) (74) (66)
TENNESSEE                        
Electric revenue                   (6,740) (7,419) (7,350)
VIRGINIA                        
Electric revenue                   $ (42) $ (45) $ (48)
v3.20.2
Revenue Customer Type (Details)
$ in Millions
 3 Months Ended 12 Months Ended
Sep. 30, 2020
USD ($)
Units
Jun. 30, 2020
USD ($)
Mar. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Sep. 30, 2019
USD ($)
Jun. 30, 2019
USD ($)
Mar. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Sep. 30, 2020
USD ($)
Units
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Sep. 30, 2004
USD ($)
Electric revenue                 $ 10,104 $ 11,159 $ 11,075  
Other revenue                 145 159 158  
Revenues $ 2,899 $ 2,251 $ 2,521 $ 2,578 $ 3,239 $ 2,604 $ 2,750 $ 2,725 $ 10,249 11,318 11,233  
Percent of sales of electricity to LPCs                 93.00%      
Bill credits for LTA                 $ (163) (14) 0  
Number of LPCs signed LTA | Units 142               142      
Percentage of total operating revenues                 91.80%      
Total number of LPCs | Units 153               153      
Number of LPCs signed Flexibility Agreement | Units 64               64      
Revenue Capitalized During Pre-Commercial Operations                 $ 0 $ 0 (11)  
MLGW's % of operating revenues                 9.00%      
NES's % of operating revenues                 8.00%      
MLGW prepayment                       $ 1,500
20-year contract arrangement [Member]                        
Percentage of total operating revenues                 74.80%      
5-year contract arrangement [Member]                        
Number of LPCs signed LTA | Units 11               11      
Percentage of total operating revenues                 17.00%      
MLGW                        
Deferred Revenue, Description                 10 million 100 million   100 million
TENNESSEE                        
Electric revenue                 $ 6,740 $ 7,419 7,350  
VIRGINIA                        
Electric revenue                 42 45 48  
NORTH CAROLINA                        
Electric revenue                 65 74 66  
MISSISSIPPI                        
Electric revenue                 941 1,063 1,052  
KENTUCKY                        
Electric revenue                 624 691 696  
GEORGIA                        
Electric revenue                 249 270 267  
ALABAMA                        
Electric revenue                 1,439 1,593 1,600  
Federal agencies and other [Member]                        
Electric revenue                 110 122 129  
20-year contract arrangement [Member]                        
Electric revenue                 7,666      
5-year contract arrangement [Member]                        
Electric revenue                 1,740      
Local Power Company [Member]                        
Electric revenue                 9,406 10,351 10,262  
Industries Directly Served [Member]                        
Electric revenue                 588 686 695  
Capitalized revenue during pre-commercial plant operations [Member]                        
Electric revenue                 $ 0 $ 0 $ 11  
v3.20.2
Revenue Local Power Company Contracts (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
Units
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Number of LPCs signed LTA | Units 142    
Electric revenue $ 10,104 $ 11,159 $ 11,075
Total number of LPCs | Units 153    
Percentage of total operating revenues 91.80%    
20-year contract arrangement [Member]      
Electric revenue $ 7,666    
5-year contract arrangement [Member]      
Electric revenue 1,740    
Local Power Company [Member]      
Electric revenue $ 9,406 $ 10,351 $ 10,262
5-year contract arrangement [Member]      
Number of LPCs signed LTA | Units 11    
Percentage of total operating revenues 17.00%    
v3.20.2
Revenue Energy Prepayment Obligations (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2004
Energy Prepayment Obligation [Line Items]        
Electric revenue $ 10,104 $ 11,159 $ 11,075  
Energy Prepayment Discount $ 4 $ 46    
MLGW        
Energy Prepayment Obligation [Line Items]        
Deferred Revenue, Description 10 million 100 million   100 million
v3.20.2
Revenue Economic Development Incentives (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Revenue from Contract with Customer [Abstract]    
Revenues $ 318 $ 310
Unpaid economic incentives $ 172 $ 157
v3.20.2
Plant Closures (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Property, Plant and Equipment [Abstract]    
Accelerated depreciation $ 387 $ 566
Completed Plant    
Accelerated depreciation $ 387 $ 566
Property, Plant and Equipment [Member]    
Completed Plant    
Property, Plant and Equipment, Dispositions 11 million 151 million
Property, Plant and Equipment, Disposals $ 2 $ 19
v3.20.2
Leases (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Oct. 01, 2019
Lessee, Lease, Description [Line Items]        
Operating Lease, Right-of-Use Asset $ 232 $ 0   $ 205
Finance Lease, Right-of-Use Asset, after Accumulated Amortization 516      
Total lease assets 748      
Accounts Payable and Accrued Liabilities   1    
Operating Lease, Liability, Noncurrent 171      
Finance Lease, Liability, Noncurrent 525      
Total lease liabilities 800      
Operating Lease, Cost 84      
Variable Lease, Cost 75      
Short-term Lease, Cost 7      
Finance Lease, Right-of-Use Asset, Amortization 15      
Finance Lease, Interest Expense 33      
Total finance lease costs 48      
Lease, Cost 214      
Operating Leases, Rent Expense   97 $ 92  
Operating Lease, Liability   $ 210    
Operating lease liability        
Lessee, Lease, Description [Line Items]        
Accounts Payable and Accrued Liabilities 63      
Finance lease liability        
Lessee, Lease, Description [Line Items]        
Accounts Payable and Accrued Liabilities $ 41      
v3.20.2
Leases, SoCF (Details)
$ in Millions
 12 Months Ended
Sep. 30, 2020
USD ($)
Lessee, Lease, Description [Line Items]  
Operating cash flows for operating leases $ 85
Operating cash flows for finance leases 33
Financing cash flows for finance leases 15
Lease assets obtained in exchange for lease obligations - finance 394
Lease assets obtained in exchange for lease obligations - operating $ 110
v3.20.2
Leases, Weighted Averages (Details)
Sep. 30, 2020
Lessee, Lease, Description [Line Items]  
Operating Lease, Weighted Average Remaining Lease Term 5 years
Finance Lease, Weighted Average Remaining Lease Term 12 years
Operating Lease, Weighted Average Discount Rate, Percent 1.60%
Finance Lease, Weighted Average Discount Rate, Percent 21.80%
v3.20.2
Leases, Future Minimum Payments (Details) - USD ($)
$ in Millions
Sep. 30, 2020
Sep. 30, 2019
Lessee, Lease, Description [Line Items]    
Operating Leases, Future Minimum Payments Due, Next Twelve Months $ 66 $ 76
Operating Leases, Future Minimum Payments, Due in Two Years 51 75
Operating Leases, Future Minimum Payments, Due in Three Years 39 60
Operating Leases, Future Minimum Payments, Due in Four Years 37 12
Operating Leases, Future Minimum Payments, Due in Five Years 34 3
Operating Leases, Future Minimum Payments, Due Thereafter 16 2
Total 243 228
Present value of future minimum lease payments, operating (9) 0
Operating present value of net minimum lease payments 234 228
Finance Lease, Liability, to be Paid, Year One 92 53
Finance Lease, Liability, to be Paid, Year Two 93 53
Finance Lease, Liability, to be Paid, Year Three 92 53
Finance Lease, Liability, to be Paid, Year Four 87 55
Finance Lease, Liability, to be Paid, Year Five 86 51
Finance Lease, Liability, Payments Due Thereafter 592 418
Finance Lease, Liability, Payment, Due 1,042 683
Finance Lease, Liability, Payment Amounts Representing Interest (476) (495)
Finance present value of net minimum lease payments 566 $ 188
Purchased Power Lease $ 89  
v3.20.2
Label Element Value
SCCG [Member]  
Debt Instrument, Interest Rate, Stated Percentage us-gaap_DebtInstrumentInterestRateStatedPercentage 3.846%
Holdco [Member]  
Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid us-gaap_DebtInstrumentPeriodicPaymentTermsBalloonPaymentToBePaid $ 10,000,000
JSCCG [Member]  
Debt Instrument, Interest Rate tve_DebtInstrumentInterestRate 4.626%