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Asset Retirement Obligations and Accrued Environmental Costs | 6 Months Ended
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Jun. 30, 2025
Asset Retirement Obligation Disclosure [Abstract] |
Asset Retirement Obligations and Accrued Environmental Costs | 8. Asset Retirement Obligations and Accrued Environmental Costs
|  | June 30, 2025 |  | December 31, 2024
Asset retirement obligations |  | $ | 511 |  |  | $ | 498 |
Accrued environmental costs |  | 21 |  |  | 21 |
Total asset retirement obligations and accrued environmental costs |  | 532 |  |  | 519 |
Less: asset retirement obligations and accrued environmental costs due within one year (a) |  | 54 |  |  | 51 |
Asset retirement obligations and accrued environmental costs due after one year |  | $ | 478 |  |  | $ | 468 |
__________________ (a)Presented as “Other current liabilities” on the Consolidated Balance Sheets. Asset Retirement Obligations Certain subsidiaries of the Company have legal retirement obligations for the decommissioning and environmental remediation costs associated with our current and former generation, which include activities such as structure removal and remediation of coal piles, wastewater basins, and ash impoundments. Most of these obligations, except remediation of some ash impoundments, are not expected to be paid until several years, or decades, in the future. The Company’s most significant obligations are associated with the: (i) decommissioning of Susquehanna, which the NDT is expected to fund; and (ii) coal ash disposal units of legacy coal-fired generation facilities which, for certain obligations, the Company has posted surety bonds (some of which have been collateralized with LCs). The carrying value of these AROs include assumptions of estimated future retirement and remediation cash expenditures, cost escalation rates, probabilistic cash flow models, and discount rates. As environmental regulations issued by the EPA or other rulemaking entities may require the Company to revise and (or) recognize new AROs, the carrying value of AROs, in particular those associated with legacy coal-fired generation facilities, may be impacted by current or future regulatory rulemaking. As of June 30, 2025, the fair values of certain AROs as a result of the EPA CCR Rule cannot be determined. See Note 9 for additional information on the EPA CCR Rule and the regulatory timeline that is expected to determine the associated scope of work. Additionally, certain subsidiaries of the Company have legal retirement obligations associated with the removal, disposal, and (or) monitoring of asbestos-containing material at certain generation facilities. Given that the ultimate volume of asbestos-containing material is not yet known, the fair value of these obligations cannot be reasonably estimated. These obligations will be recognized upon a change in economic events or other circumstances which enables the fair value to be estimable. The changes of the ARO carrying value during the period were:
December 31, 2024 |  | $ | 498 |
Obligations settled |  | (12) |
Changes in estimates and (or) settlement dates |  | (3) |
Accretion expense |  | 28 |
June 30, 2025 |  | $ | 511 |
The disaggregation of ARO carrying values on the Consolidated Balance Sheets were:
|  | June 30, 2025 |  | December 31, 2024
Supplemental Information |  |  |  |
Nuclear (a) |  | $ | 257 |  |  | $ | 242 |
Non-nuclear (b) |  | 254 |  |  | 256 |
Carrying value |  | $ | 511 |  |  | $ | 498 |
__________________ (a)Obligations are expected to be settled with available funds in the NDT at the time of decommissioning. See Note 11 for additional information on the NDT. (b)Certain obligations are: (i) partially supported by surety bonds, some of which have been collateralized with LCs; or (ii) partially prefunded under phased installment agreements. See “Talen Montana Financial Assurance” in Note 9 for information on Talen Montana’s requirement to provide financial assurance for certain environmental decommissioning and remediation liabilities related to Colstrip.

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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://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481850/410-20-50-1 Reference 2: 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 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -SubTopic 20 -Topic 410 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481850/410-20-50-2 + Details
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