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Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Thousands | Jun. 30, 2026 | Dec. 31, 2025
--- | --- | ---
Detail of regulatory assets |  |
Total regulatory assets | $ 1,601,434 | $ 1,749,366
Less: current regulatory assets | 150,106 | 286,009
Total non-current regulatory assets | 1,451,328 | 1,463,357
Pension |  |
Detail of regulatory assets |  |
Total regulatory assets | 712,234 | 723,042
Income taxes — AFUDC equity |  |
Detail of regulatory assets |  |
Total regulatory assets | 209,567 | 203,890
Palo Verde sale leaseback noncontrolling interests acquisition |  |
Detail of regulatory assets |  |
Total regulatory assets | 151,506 | 151,506
Ocotillo deferral |  |
Detail of regulatory assets |  |
Total regulatory assets | 92,509 | 99,931
Lease incentive (Note 17) |  |
Detail of regulatory assets |  |
Total regulatory assets | 92,330 | 90,005
Deferred fuel and purchased power — mark-to-market (Note 10) |  |
Detail of regulatory assets |  |
Total regulatory assets | 78,831 | 29,330
SCR deferral |  |
Detail of regulatory assets |  |
Total regulatory assets | 74,217 | 77,186
Retired power plant costs |  |
Detail of regulatory assets |  |
Total regulatory assets | 47,312 | 56,809
Income taxes — investment tax credit basis adjustment (Note 5) |  |
Detail of regulatory assets |  |
Total regulatory assets | 41,691 | 42,459
Deferred compensation |  |
Detail of regulatory assets |  |
Total regulatory assets | 32,842 | 32,204
FERC transmission true up |  |
Detail of regulatory assets |  |
Total regulatory assets | 22,219 | 21,471
Deferred property taxes |  |
Detail of regulatory assets |  |
Total regulatory assets | 11,064 | 15,349
Palo Verde VIEs (Note 9) |  |
Detail of regulatory assets |  |
Total regulatory assets | 9,085 | 8,582
Mead-Phoenix transmission line — contributions in aid of construction |  |
Detail of regulatory assets |  |
Total regulatory assets | 7,886 | 8,052
Loss on reacquired debt |  |
Detail of regulatory assets |  |
Total regulatory assets | 5,180 | 5,653
Active union medical trust |  |
Detail of regulatory assets |  |
Total regulatory assets | 4,966 | 3,696
TEAM |  |
Detail of regulatory assets |  |
Total regulatory assets | 3,551 | 3,879
PSA - interest |  |
Detail of regulatory assets |  |
Total regulatory assets | 769 | 5,679
Navajo coal reclamation |  |
Detail of regulatory assets |  |
Total regulatory assets | 361 | 2,516
Deferred fuel and purchased power |  |
Detail of regulatory assets |  |
Total regulatory assets | 0 | 149,068
DSM |  |
Detail of regulatory assets |  |
Total regulatory assets | 0 | 15,706
Other |  |
Detail of regulatory assets |  |
Total regulatory assets | $ 3,314 | $ 3,353

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- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + 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 + Details
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