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Summary of Significant Accounting Policies [Text Block] | 12 Months Ended
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Sep. 30, 2025
Accounting Policies [Abstract] |
Summary of Significant Accounting Policies | 1. Summary of Significant Accounting Policies General The Tennessee Valley Authority ("TVA") is a corporate agency and instrumentality of the United States ("U.S.") that was created in 1933 by federal legislation in response to a proposal by President Franklin D. Roosevelt. TVA was created to, among other things, improve navigation on the Tennessee River, reduce the damage from destructive flood waters within the Tennessee River system and downstream on the lower Ohio and Mississippi Rivers, further the economic development of TVA's service area in the southeastern U.S., and sell the electricity generated at the facilities TVA operates. Today, TVA operates the nation's largest public power system and supplies power in most of Tennessee, northern Alabama, northeastern Mississippi, and southwestern Kentucky and in portions of northern Georgia, western North Carolina, and southwestern Virginia to a population of approximately 10 million people. TVA also manages the Tennessee River, its tributaries, and certain shorelines to provide, among other things, year-round navigation, flood damage reduction, and affordable and reliable electricity. Consistent with these primary purposes, TVA also manages the river system and public lands to provide recreational opportunities, adequate water supply, improved water quality, cultural and natural resource protection, and economic development. TVA performs these management duties in cooperation with other federal and state agencies that have jurisdiction and authority over certain aspects of the river system. In addition, the TVA Board of Directors ("TVA Board") has established two councils — the Regional Resource Stewardship Council and the Regional Energy Resource Council — to advise TVA on its stewardship activities in the Tennessee Valley and its energy resource activities. The power program has historically been separate and distinct from the stewardship programs. It is required to be self-supporting from power revenues and proceeds from power financings, such as proceeds from the issuance of bonds, notes, or other evidences of indebtedness (collectively, "Bonds"). Although TVA does not currently receive Congressional appropriations, it is required to make annual payments to the United States Department of the Treasury ("U.S. Treasury") as a return on the government's appropriation investment in TVA's power facilities (the "Power Program Appropriation Investment"). In the 1998 Energy and Water Development Appropriations Act, Congress directed TVA to fund essential stewardship activities related to its management of the Tennessee River system and nonpower or stewardship properties with power revenues in the event that there were insufficient appropriations or other available funds to pay for such activities in any fiscal year. Congress has not provided any appropriations to TVA to fund such activities since 1999. Consequently, during 2000, TVA began paying for essential stewardship activities primarily with power revenues, with the remainder funded with user fees and other forms of revenues derived in connection with those activities. The activities related to stewardship properties do not meet the criteria of an operating segment under accounting principles generally accepted in the United States of America ("GAAP"). Accordingly, these assets and properties are included as part of the power program, TVA's only operating segment. Power rates are established by the TVA Board as authorized by the Tennessee Valley Authority Act of 1933, as amended ("TVA Act"). The TVA Act requires TVA to charge rates for power that will produce gross revenues sufficient to provide funds for operation, maintenance, and administration of its power system; payments to states and counties in lieu of taxes ("tax equivalents"); debt service on outstanding indebtedness; payments to the U.S. Treasury in repayment of and as a return on the Power Program Appropriation Investment; and such additional margin as the TVA Board may consider desirable for investment in power system assets, retirement of outstanding Bonds in advance of maturity, additional reduction of the Power Program Appropriation Investment, and other purposes connected with TVA's power business. TVA fulfilled its requirement to repay $1.0 billion of the Power Program Appropriation Investment with the 2014 payment; therefore, this repayment obligation is no longer a component of rate setting. In setting TVA's rates, the TVA Board is charged by the TVA Act to have due regard for the primary objectives of the TVA Act, including the objective that power shall be sold at rates as low as are feasible. Rates set by the TVA Board are not subject to review or approval by any state or other federal regulatory body. Fiscal Year TVA's fiscal year ends September 30. Years (2025, 2024, etc.) refer to TVA's fiscal years unless they are preceded by "CY," in which case the references are to calendar years. Cost-Based Regulation Since the TVA Board is authorized by the TVA Act to set rates for power sold to its customers, TVA is self-regulated. Additionally, TVA's regulated rates are designed to recover its costs. Based on current projections, TVA believes that rates, set at levels that will recover TVA's costs, can be charged and collected. As a result of these factors, TVA records certain assets and liabilities that result from the regulated ratemaking process that would not be recorded under GAAP for non-regulated entities. Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates. Regulatory liabilities generally represent obligations to make refunds to customers for previous collections for costs that are not likely to be incurred or deferral of gains that will be credited to customers in future periods. TVA assesses whether the regulatory assets are probable of future recovery by considering factors such as applicable regulatory changes, potential legislation, and changes in technology. Based on these assessments, TVA believes the existing regulatory assets are probable of recovery. This determination reflects the current regulatory and political environment and is subject to change in the future. If future recovery of regulatory assets ceases to be probable, or TVA is no longer considered to be a regulated entity, then costs would be required to be written off. All regulatory asset write offs would be required to be recognized in earnings in the period in which future recovery ceases to be probable or in which TVA is no longer considered to be a regulated entity. Basis of Presentation The accompanying consolidated financial statements, which have been prepared in accordance with GAAP, include the accounts of TVA and variable interest entities ("VIEs") of which TVA is the primary beneficiary. See Note 12 — Variable Interest Entities. Intercompany balances and transactions have been eliminated in consolidation. Use of Estimates The preparation of financial statements requires TVA to estimate the effects of various matters that are inherently uncertain as of the date of the consolidated financial statements. Although the consolidated financial statements are prepared in conformity with GAAP, TVA is required to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the amounts of revenues and expenses reported during the reporting period. Each of these estimates varies in regard to the level of judgment involved and its potential impact on TVA's financial results. Estimates are considered critical either when a different estimate could have reasonably been used, or where changes in the estimate are reasonably likely to occur from period to period, and such use or change would materially impact TVA's financial condition, results of operations, or cash flows. Cash, Cash Equivalents, and Restricted Cash Cash includes cash on hand, non-interest bearing cash, and deposit accounts. All highly liquid investments with original maturities of three months or less are considered cash equivalents. Cash and cash equivalents that are restricted, as to withdrawal or use under the terms of certain contractual agreements, are recorded in Other long-term assets on the Consolidated Balance Sheets. Restricted cash and cash equivalents include cash held in trusts that are currently restricted for TVA economic development loans and for certain TVA environmental programs in accordance with agreements related to compliance with certain environmental regulations. See Note 23 — Commitments and Contingencies — Legal Proceedings — Environmental Agreements. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported on the Consolidated Balance Sheets and Consolidated Statements of Cash Flows:
Cash, Cash Equivalents, and Restricted Cash At September 30 (in millions)
| 2025 |  | 2024
Cash and cash equivalents | $ | 1,576 |  |  | $ | 502 |
Restricted cash and cash equivalents included in Other long-term assets | 21 |  |  | 21 |
Total cash, cash equivalents, and restricted cash | $ | 1,597 |  |  | $ | 523 |
TVA's balance of Cash and cash equivalents increased at September 30, 2025 due to the issuance of long-term bonds in the fourth quarter in anticipation of cash needed to pay bond maturities in November 2025. Allowance for Uncollectible Accounts TVA recognizes an allowance that reflects the current estimate for credit losses expected to be incurred over the life of the financial assets based on historical experience, current conditions, and/or reasonable and supportable forecasts that affect the collectability of the reported amounts. The appropriateness of the allowance is evaluated at the end of each reporting period. To determine the allowance for trade receivables, TVA considers historical experience and other currently available information, including events such as customer bankruptcy and/or a customer failing to fulfill payment arrangements by the due date. TVA's corporate credit department also performs an assessment of the financial condition of customers and the credit quality of the receivables. In addition, TVA reviews other reasonable and supportable forecasts to determine if the allowance for uncollectible amounts should be further adjusted in accordance with the accounting guidance for Current Expected Credit Losses. As of September 30, 2025, TVA adopted the practical expedient in accordance with the accounting guidance for Current Expected Credit Losses, to assume that the current conditions as of the balance sheet date will remain unchanged for the remaining life of the asset when developing a reasonable and supportable forecast as part of estimating expected credit losses for trade receivables based on TVA's corporate credit department assessment of the financial condition of customers and the credit quality of the receivables. To determine the allowance for loans receivables, TVA aggregates loans into the appropriate pools based on the existence of similar risk characteristics such as collateral types and internal assessed credit risks. In situations where a loan exhibits unique risk characteristics and is no longer expected to experience similar risks to the rest of its pool, the loan will be evaluated separately. TVA derives an annual loss rate based on historical loss and then adjusts the rate to reflect TVA's consideration of available information on current conditions and reasonable and supportable future forecasts. This information may include economic and business conditions, default trends, and other internal and external factors. For periods beyond the reasonable and supportable forecast period, TVA uses the current calculated long-term average historical loss rate for the remaining life of the loan portfolio. The allowance for uncollectible accounts was $14 million and less than $1 million at September 30, 2025, and 2024, respectively, for trade accounts receivable. At September 30, 2025, the allowance for uncollectible accounts included $14 million related to one local power company customer ("LPC"). Additionally, loans receivable of $86 million and $105 million at September 30, 2025 and 2024, respectively, are included in Accounts receivable, net and Other long-term assets for the current and long-term portions, respectively. Loans receivable are reported net of allowances for uncollectible accounts of $2 million at both September 30, 2025 and 2024. Revenues TVA recognizes revenue from contracts with customers to depict the transfer of goods or services to customers in an amount to which the entity expects to be entitled in exchange for those goods or services. For the generation and transmission of electricity, this is generally at the time the power is delivered to a metered customer delivery point for the customer's consumption or distribution. As a result, revenues from power sales are recorded as electricity is delivered to customers. In addition to power sales invoiced and recorded during the month, TVA accrues estimated unbilled revenues for power sales provided to five customers whose billing date occurs prior to the end of the month. Exchange power sales are presented in the accompanying Consolidated Statements of Operations as a component of sales of electricity. Exchange power sales are sales of excess power after meeting TVA native load and directly served requirements. Native load refers to the customers on whose behalf a company, by statute, franchise, regulatory requirement, or contract, has undertaken an obligation to serve. TVA engages in other arrangements in addition to power sales. Certain other revenue from activities related to TVA's overall mission is recorded in Other revenue. Revenues that are not related to the overall mission are recorded in Other income, net. Inventories Certain Fuel, Materials, and Supplies. Materials and supplies inventories are valued using an average unit cost method. A new average cost is computed after each inventory purchase transaction, and inventory issuances are priced at the latest moving weighted average unit cost. Coal, fuel oil, and natural gas inventories are valued using an average cost method. A new weighted average cost is computed monthly, and monthly issues are priced accordingly. Renewable Energy Certificates. TVA accounts for Renewable Energy Certificates ("RECs") using the specific identification cost method. RECs that are acquired through power purchases are recorded as inventory and charged to purchased power expense when the RECs are subsequently used or sold. TVA assigns a value to the RECs at the inception of the power purchase arrangement using a relative standalone selling price approach. RECs created through TVA-owned asset generation are recorded at zero cost. Emission Allowances. TVA accounts for emission allowances using the specific identification cost method. Allowances that are acquired through third party purchases are recorded as inventory at cost and charged to operating expense based on tons emitted during the respective compliance periods. Allowance for Inventory Obsolescence. TVA reviews materials and supplies inventories by category and usage on a periodic basis. Each category is assigned a probability of becoming obsolete based on the type of material and historical usage data. TVA has a fleet-wide inventory management policy for each generation type. Based on the estimated value of the inventory, TVA adjusts its allowance for inventory obsolescence. Pre-Commercial Plant Operations As part of the process of completing the construction of a generating unit, the electricity produced is used to serve the demands of the electric system. TVA estimates revenues earned during pre-commercial operations at the fair value of the energy delivered based on TVA's hourly incremental dispatch cost. Pre-commercial plant operations began on Paradise Combustion Turbine ("CT") Units 5-7 in the first quarter of 2024, and the units became operational on December 29, 2023. Estimated revenue of $3 million related to this project was capitalized to offset project costs for the year ended September 30, 2024. TVA also capitalized related fuel costs for this project of $3 million for the year ended September 30, 2024. Pre-commercial plant operations began on Johnsonville Aeroderivative CT Units 21-30 during 2025. Units 21-25 and 27-30 became operational on May 6, 2025, and Unit 26 became operational on August 20, 2025. Estimated revenue of $4 million related to this project was capitalized to offset project costs for the year ended September 30, 2025. TVA also capitalized related fuel costs for this project of $7 million for the year ended September 30, 2025. Property, Plant, and Equipment, and Depreciation Property, Plant, and Equipment. Additions to plant are recorded at cost, which includes direct and indirect costs. The cost of current repairs and minor replacements is charged to operating expense. When property, plant, and equipment is retired, accumulated depreciation is charged for the original cost of the assets. Gains or losses are only recognized upon the sale of land or an entire operating unit. TVA capitalizes certain costs incurred in connection with developing or obtaining internal-use software. Capitalized software costs are included in Property, plant, and equipment on the Consolidated Balance Sheets and are generally amortized over seven years. Nuclear Fuel. Nuclear fuel, which is included in Property, plant, and equipment, is valued using the average cost method for raw materials and the specific identification method for nuclear fuel in a reactor. Amortization of nuclear fuel in a reactor is calculated on a units-of-production basis and is included in fuel expense. TVA and the Department of Energy ("DOE") are parties to an interagency agreement (referred to as the Down-blend Offering for Tritium), under which surplus DOE highly enriched uranium and other uranium is processed by third-party contractors into low-enriched uranium, which is then fabricated into nuclear fuel for use in TVA's nuclear power plants. Production of the low-enriched uranium began in 2019 and will continue through the end of the interagency agreement term in September 2027. After that date, any remaining uranium in storage will be managed to ensure that the uranium is unencumbered by policy restrictions, so that it can be used in connection with the production of tritium. Under the terms of the interagency agreement, 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 $334 million in reimbursements from the DOE, which is recorded as a reduction in nuclear fuel inventory costs. At September 30, 2025, TVA recorded $6 million in Accounts receivable, net related to this agreement. Depreciation. TVA accounts for depreciation of its properties using the composite depreciation convention of accounting. Under the composite method, assets with similar economic characteristics are grouped and depreciated as one asset. Depreciation is generally computed on a straight-line basis over the estimated service lives of the various classes of assets. The estimation of asset useful lives requires management judgment, supported by external depreciation studies of historical asset retirement experience. Depreciation rates are determined based on external depreciation studies that are updated approximately every five years, with the latest study implemented in 2022. Depreciation expense for the years ended September 30, 2025, 2024, and 2023 was $1.9 billion, $1.8 billion, and $1.9 billion, respectively. Depreciation expense expressed as a percentage of the average annual depreciable completed plant was 3.04 percent for 2025, 2.92 percent for 2024, and 3.14 percent for 2023. Average depreciation rates by asset class are as follows:
Property, Plant, and Equipment Depreciation Rates At September 30 (percent)
| 2025 |  | 2024 |  | 2023
Asset Class |  |  |  |  |
Nuclear | 2.71 |  |  | 2.71 |  |  | 2.73 |
Coal-fired(1) | 4.82 |  |  | 4.13 |  |  | 4.98 |
Hydroelectric | 1.82 |  |  | 1.83 |  |  | 1.82 |
Gas and oil-fired | 3.16 |  |  | 3.31 |  |  | 3.17 |
Transmission | 1.55 |  |  | 1.52 |  |  | 1.52 |
Other | 5.22 |  |  | 4.98 |  |  | 4.43 |
Note (1) The rates include the acceleration of depreciation related to retiring certain coal-fired units and potentially retiring the remainder of the coal-fired fleet by 2035. See Note 8 — Plant Closures. Reacquired Rights. TVA previously entered into leasing transactions to obtain third-party financing for 24 peaking CTs as well as certain qualified technological equipment and software. All of the lease proceeds were accounted for as financing obligations due to TVA’s continuing involvement with the combustion turbine facilities and the qualified technological equipment and software during the leaseback term. These financial obligations were paid off, and TVA acquired the residual leasehold interests for all of this equipment and recorded the cash consideration as reacquired rights, which is an intangible asset included in property, plant, and equipment on the Consolidated Balance Sheet. At September 30, 2025 and 2024, property, plant, and equipment includes intangible reacquired rights, net of amortization, of $301 million and $312 million, respectively. Reacquired rights are amortized over the estimated useful lives of the underlying CTs which range from 30 to 35 years. Amortization expense was $11 million, $11 million, and $10 million for the years ended September 30, 2025, 2024, and 2023, respectively, and accumulated amortization at September 30, 2025 and 2024 totaled $74 million and $63 million, respectively. At September 30, 2025, the estimated aggregate amortization expense for each of the next five years and thereafter is shown below:
|  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | 2030 |  | Thereafter
Reacquired Rights |  | $ | 11 |  |  | $ | 12 |  |  | $ | 11 |  |  | $ | 11 |  |  | $ | 12 |  |  | $ | 244 |
Impairment of Assets. TVA evaluates long-lived assets for impairment when events or changes in circumstances indicate that the carrying value of such assets may not be recoverable. For long-lived assets, TVA bases its evaluation on impairment indicators such as the nature of the assets, the future economic benefit of the assets, any historical or future profitability measurements, regulatory approval and ability to set rates at levels that allow for recoverability of the assets, and other external market conditions or factors that may be present. If such impairment indicators are present or other factors exist that indicate that the carrying amount of an asset may not be recoverable, TVA determines whether an impairment has occurred based on an estimate of undiscounted cash flows attributable to the asset as compared with the carrying value of the asset. If an impairment has occurred, the amount of the impairment recognized is measured as the excess of the asset's carrying value over its fair value. Additionally, TVA regularly evaluates construction projects. If the project is canceled or deemed to have no future economic benefit, the project is written off as an asset impairment or, upon TVA Board approval, reclassified as a regulatory asset and amortized over the Board-approved period. See Note 8 — Plant Closures. Leases TVA recognizes a lease asset and lease liability for leases with terms of greater than 12 months. Lease assets represent TVA's right to use an underlying asset for the lease term, and lease liabilities represent TVA's obligation to make lease payments arising from the lease, both of which are recognized based on the present value of the future minimum lease payments over the lease term at the commencement date. TVA has certain lease agreements that include variable lease payments that are based on energy production levels. These variable lease payments are not included in the measurement of the lease assets or lease liabilities but are recognized in the period in which the expenses are incurred. While not specifically structured as leases, certain power purchase agreements ("PPAs") are deemed to contain a lease of the underlying generating units when the terms convey the right to control the use of the assets. Amounts recorded for these leases are generally based on the amount of the scheduled capacity payments due over the remaining terms of the PPAs, the terms of which vary. The total lease obligations included in Accounts payable and accrued liabilities, Other long-term liabilities, and Finance lease liabilities related to these agreements were $509 million and $75 million for finance and operating leases, respectively, at September 30, 2025. The total lease obligations included in Accounts payable and accrued liabilities, Other long-term liabilities, and Finance lease liabilities related to these agreements were $550 million and $121 million for finance and operating leases, respectively, at September 30, 2024. TVA has agreements with lease and non-lease components and has elected to separate lease and non-lease components. Consideration is allocated to lease and non-lease components generally based on relative standalone price basis. Variable lease costs included in the agreements are allocated based on the determination of lease and non-lease components. 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, 2025. Operating leases are recognized on a straight-line basis over the term of the lease agreement. Rent expense associated with short-term leases and variable leases is recorded in Operating and maintenance expense, Fuel expense, or Purchased power expense on the Consolidated Statements of Operations. Expenses associated with finance leases result in the separate presentation of interest expense on the lease liability and amortization expense of the related lease asset on the Consolidated Statements of Operations. Decommissioning Costs TVA recognizes legal obligations associated with the future retirement of certain tangible long-lived assets. These obligations relate to fossil fuel-fired generating plants, nuclear generating plants, hydroelectric generating plants/dams, transmission structures, and other property-related assets. Activities involved with retiring these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site restoration. Revisions to the forecasted costs of decommissioning activities are made whenever factors indicate that the timing or amounts of estimated cash flows have changed materially. Studies are updated for both nuclear and non-nuclear decommissioning costs at least every five years. Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset. See Note 11 — Regulatory Assets and Liabilities — Nuclear Decommissioning Costs and Non-Nuclear Decommissioning Costs and Note 14 — Asset Retirement Obligations. Investment Funds Investment funds consist primarily of trust funds designated to fund decommissioning requirements (see Note 23 — Commitments and Contingencies — Contingencies — Decommissioning Costs), the Supplemental Executive Retirement Plan ("SERP") (see Note 21 — Benefit Plans — Overview of Plans and Benefits — Supplemental Executive Retirement Plan), the Deferred Compensation Plan ("DCP"), and the Restoration Plan ("RP"). The Nuclear Decommissioning Trust ("NDT") holds funds primarily for the ultimate decommissioning of TVA's nuclear power plants. The Asset Retirement Trust ("ART") holds funds primarily for the costs related to the future closure and retirement of TVA's other long-lived assets. The NDT, ART, SERP, DCP, and RP funds are invested in portfolios of securities generally designed to achieve a return in line with overall equity and debt market performance. The NDT, ART, SERP, DCP, and RP funds are all classified as trading. Research and Development Costs Research and development costs are expensed when incurred. TVA's research programs include those related to power delivery technologies, emerging technologies, technologies related to generation (fossil fuel, nuclear, and hydroelectric), and environmental technologies. Tax Equivalents TVA is not subject to federal income taxation. In addition, neither TVA nor its property, franchises, or income is subject to taxation by states or their subdivisions. The TVA Act requires TVA to make payments to states and counties in which TVA conducts its power operations and in which TVA has acquired power properties previously subject to state and local taxation. The total amount of these payments is five percent of gross revenues from sales of power during the preceding year, excluding sales or deliveries to other federal agencies and off-system sales with other utilities, with a provision for minimum payments under certain circumstances. TVA calculates tax equivalent expense by subtracting the prior year fuel cost-related tax equivalent regulatory asset or liability from the payments made to the states and counties during the current year and adding back the current year fuel cost-related tax equivalent regulatory asset or liability. Fuel cost-related tax equivalent expense is recognized in the same accounting period in which the fuel cost-related revenue is recognized. Maintenance Costs TVA records maintenance costs and repairs related to its property, plant, and equipment on the Consolidated Statements of Operations as they are incurred except for the recording of certain regulatory assets for retirement and removal costs.

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