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Regulatory Matters (Tables) | 12 Months Ended
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Dec. 31, 2024
Regulated Operations [Abstract] |
Schedule of Changes in The Deferred Fuel and Purchased Power Regulatory Asset | The following table shows the changes in the deferred fuel and purchased power regulatory asset for 2024 and 2023 (dollars in thousands):
| Year Ended December 31,
| 2024 |  | 2023
Balance at beginning of period | $ | 463,195 |  |  | $ | 460,561 |
Deferred fuel and purchased power costs | 250,288 |  |  | 549,877 |
Amounts charged to customers | (425,886) |  |  | (547,243) |
Balance at end of period | $ | 287,597 |  |  | $ | 463,195 |
Schedule of Regulatory Assets | The detail of regulatory assets is as follows (dollars in thousands):
|  |  | December 31,
| Amortization Through |  | 2024 |  | 2023
Pension | (a) |  | $ | 750,976 |  |  | $ | 696,476 |
Deferred fuel and purchased power (b) (c) | 2025 |  | 287,597 |  |  | 463,195 |
Income taxes — AFUDC equity | 2054 |  | 192,936 |  |  | 189,058 |
Ocotillo deferral | 2034 |  | 114,775 |  |  | 128,636 |
SCR deferral (e) | 2038 |  | 83,123 |  |  | 89,477 |
Lease incentives | (g) |  | 70,541 |  |  | 46,615 |
Retired power plant costs | 2033 |  | 68,380 |  |  | 83,536 |
Deferred fuel and purchased power — mark-to-market (Note 15) | 2027 |  | 42,275 |  |  | 120,214 |
FERC Transmission true up | 2026 |  | 35,159 |  |  | 616 |
Income taxes — investment tax credit basis adjustment | 2056 |  | 34,834 |  |  | 34,230 |
Deferred compensation | 2036 |  | 33,108 |  |  | 33,972 |
Deferred property taxes | 2027 |  | 23,918 |  |  | 32,488 |
Palo Verde VIEs (Note 17) | 2046 |  | 20,611 |  |  | 20,772 |
Power supply adjustor - interest | 2025 |  | 11,525 |  |  | 19,416 |
Active Union Medical Trust | (f) |  | 9,673 |  |  | 12,747 |
Mead-Phoenix transmission line contributions in aid of construction (“CIAC”) | 2050 |  | 8,384 |  |  | 8,716 |
Navajo coal reclamation | 2026 |  | 7,905 |  |  | 10,883 |
Loss on reacquired debt | 2038 |  | 6,682 |  |  | 7,965 |
Tax expense adjustor mechanism (b) | 2031 |  | 4,534 |  |  | 5,190 |
Four Corners cost deferral | 2024 |  | — |  |  | 7,922 |
Other | Various |  | 3,522 |  |  | 3,912 |
Total regulatory assets (d) |  |  | $ | 1,810,458 |  |  | $ | 2,016,036 |
Less: current regulatory assets |  |  | $ | 420,969 |  |  | $ | 625,757 |
Total non-current regulatory assets |  |  | $ | 1,389,489 |  |  | $ | 1,390,279 |
(a)This asset represents the future recovery of pension benefit obligations and expense through retail rates. If these costs are disallowed by the ACC, this regulatory asset would be charged to OCI and result in lower future revenues. As a result of the 2019 Rate Case decision, the amount authorized for inclusion in rate base was determined using an averaging methodology, which resulted in a reduced return in retail rates. The 2022 Rate Case decision allows for the full return on the pension asset in rate base. See Note 7 for further discussion. (b)See “Cost Recovery Mechanisms” discussion above. (c)Subject to a carrying charge. (d)There are no regulatory assets for which the ACC has allowed recovery of costs, but not allowed a return by exclusion from rate base. FERC rates are set using a formula rate as described in “Transmission Rates, Transmission Cost Adjustor and Other Transmission Matters.” (e)See “Four Corners SCR Cost Recovery” discussion above. (f)Collected in retail rates. (g)Amortization periods vary based on specific terms of lease contract.
Schedule of Regulatory Liabilities | The detail of regulatory liabilities is as follows (dollars in thousands):
|  |  | December 31,
| Amortization Through |  | 2024 |  | 2023
Excess deferred income taxes - ACC — Tax Cuts and Jobs Act (a) | 2046 |  | $ | 888,896 |  |  | $ | 930,344 |
Excess deferred income taxes - FERC — Tax Cuts and Jobs Act (a) | 2058 |  | 207,400 |  |  | 214,667 |
Asset retirement obligations and removal costs | (d) |  | 358,403 |  |  | 486,751 |
Other postretirement benefits | (c) |  | 238,113 |  |  | 226,726 |
Four Corners coal reclamation | 2038 |  | 77,532 |  |  | 68,521 |
Renewable energy standard (b) | 2025 |  | 68,523 |  |  | 60,667 |
Income taxes — deferred investment tax credit | 2056 |  | 66,327 |  |  | 55,917 |
Income taxes — change in rates | 2053 |  | 59,133 |  |  | 43,251 |
Spent nuclear fuel | 2027 |  | 26,818 |  |  | 33,154 |
Demand side management (b) | 2025 |  | 23,927 |  |  | 14,374 |
Sundance maintenance | 2031 |  | 23,086 |  |  | 19,989 |
TCA Balancing Account (b) | 2026 |  | 14,834 |  |  | 3,425 |
Property tax deferral | 2027 |  | 4,785 |  |  | 10,850 |
Tax expense adjustor mechanism (b) | 2032 |  | 4,343 |  |  | 4,835 |
Other | Various |  | 113 |  |  | 2,317 |
Total regulatory liabilities |  |  | $ | 2,062,233 |  |  | $ | 2,175,788 |
Less: current regulatory liabilities |  |  | $ | 206,955 |  |  | $ | 209,923 |
Total non-current regulatory liabilities |  |  | $ | 1,855,278 |  |  | $ | 1,965,865 |
(a)For purposes of presentation on the Statement of Cash Flows, amortization of the regulatory liabilities for excess deferred income taxes are reflected as “Deferred income taxes” under Cash Flows From Operating Activities. (b)See “Cost Recovery Mechanisms” discussion above. (c)See Note 7. (d)In accordance with regulatory accounting, APS accrues removal costs for its regulated assets, even if there is no legal obligation for removal.

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- Definition Tabular disclosure of assets that are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 715 -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478574/980-715-50-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-2 + Details
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