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Asset Retirement Obligations | 12 Months Ended
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Dec. 31, 2023
Asset Retirement Obligation Disclosure [Abstract] |
Asset Retirement Obligations | Asset Retirement Obligations In 2023, the Company revised its cost estimates for existing Asset Retirement Obligations (“ARO”) for the following: •Cholla coal-fired power plant related to the closure of ponds and facilities, which resulted in an increase to the ARO of approximately $71 million, primarily due to changes in the planned pond closure methodology and increased corrective action cost estimates associated with the CCR Rule. See Note 10. •Four Corners coal-fired power plant, which resulted in a decrease of approximately $7 million. •Navajo coal-fired plant, which resulted in an increase of approximately $8 million. •Palo Verde received a new decommissioning study, which resulted in an increase to the ARO in the amount of $63 million, an increase in the plant in service of $59 million and a decrease in the regulatory liability of $4 million. In 2022, APS did not revise any cost estimates related to existing AROs, and no new AROs were necessary. See additional details in Notes 3 and 10. The following table shows the change in our AROs (dollars in thousands):
| 2023 |  | 2022
Asset retirement obligations at the beginning of year | $ | 797,762 |  |  | $ | 767,382 |
Changes attributable to: |  |  |
Accretion expense | 44,269 |  |  | 41,240 |
Settlements | (14,039) |  |  | (10,860) |
Estimated cash flow revisions | 135,323 |  |  | — |
Newly incurred obligation | 2,686 |  |  | — |
Asset retirement obligations at the end of year | $ | 966,001 |  |  | $ | 797,762 |
In accordance with regulatory accounting, APS accrues removal costs for its regulated utility assets, even if there is no legal obligation for removal. See detail of regulatory liabilities in Note 3.

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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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