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Asset Retirement Obligations | 3 Months Ended
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Dec. 31, 2021
Asset Retirement Obligation Disclosure [Abstract] |
Asset Retirement Obligations | Asset Retirement Obligations During the three months ended December 31, 2021, TVA's total asset retirement obligations ("ARO") liability increased $157 million as a result of periodic accretion and revisions in estimate, partially offset by settlement projects that were conducted during the period. The nuclear and non-nuclear accretion amounts were deferred as regulatory assets. During the three months ended December 31, 2021, $34 million of the related regulatory assets were amortized into expense as these amounts were collected in rates. See Note 8 — Regulatory Assets and Liabilities. TVA maintains investment trusts to help fund its decommissioning obligations. See Note 15 — Fair Value Measurements — Investment Funds and Note 20 — Contingencies and Legal Proceedings — Contingencies — Decommissioning Costs for a discussion of the trusts' objectives and the current balances of the trusts.
Asset Retirement Obligation Activity |
| Nuclear |  | Non-Nuclear |  | Total |
Balance at September 30, 2021 | $ | 3,428 |  |  | $ | 3,574 |  |  | $ | 7,002 |  | (1)
Settlements | — |  |  | (61) |  |  | (61) |  |
Revisions in estimate | — |  |  | 163 |  |  | 163 |  |
Accretion (recorded as regulatory asset) | 38 |  |  | 17 |  |  | 55 |  |
Balance at December 31, 2021 | $ | 3,466 |  |  | $ | 3,693 |  |  | $ | 7,159 |  | (1)
Note (1) Includes $301 million and $266 million at December 31, 2021, and September 30, 2021, respectively, recorded in Current liabilities. The revisions in non-nuclear estimates increased the liability balance by $163 million for the three months ended December 31, 2021. TVA implemented revised depreciation rates during the first quarter of 2022 applicable to its completed plant as a result of the completion of a new depreciation study. The study includes a decline in the service life estimates of TVA’s coal-fired plants based on current planning assumptions to potentially retire the remainder of the coal-fired fleet by 2035. As a result of the change in the service life estimates reflected in the depreciation study, TVA performed an assessment of the assumptions used in the timing of cash flows related to its non-nuclear AROs. Based on the assessment, TVA identified changes to its projections of timing of certain asset retirement activities, resulting in an increase of $47 million to the asset retirement obligation. In addition, TVA completed an engineering review of its cost estimates for closure of certain areas containing coal fines at Paradise Fossil Plant, resulting in an increase of $119 million due to expected cost increases for necessary changes in activities associated with proper completion of the closure.

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- Definition The entire disclosure for an asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -URI http://asc.fasb.org/subtopic&trid=2175671 + Details
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