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Asset Retirement Obligations Asset Retirement Obligations (Policies) | 12 Months Ended
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Sep. 30, 2025
Asset Retirement Obligation Disclosure [Abstract] |
Asset Retirement Obligations, Policy | Decommissioning Costs TVA recognizes legal obligations associated with the future retirement of certain tangible long-lived assets. These obligations relate to fossil fuel-fired generating plants, nuclear generating plants, hydroelectric generating plants/dams, transmission structures, and other property-related assets. Activities involved with retiring these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site restoration. Revisions to the forecasted costs of decommissioning activities are made whenever factors indicate that the timing or amounts of estimated cash flows have changed materially. Studies are updated for both nuclear and non-nuclear decommissioning costs at least every five years. Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset. See Note 11 — Regulatory Assets and Liabilities — Nuclear Decommissioning Costs and Non-Nuclear Decommissioning Costs and Note 14 — Asset Retirement Obligations.

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- Definition Disclosure of accounting policy for legal obligation associated with retirement of long-lived asset that results from acquisition, construction, or development or from normal operation of long-lived asset. Excludes environmental remediation liability from improper or other-than-normal operation of long-lived asset, obligation arising in connection with leased property that meets definition of lease payments or variable lease payments and from plan to sell or otherwise dispose of a long-lived asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org/410-20/tableOfContent + Details
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