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v3.26.1

Fair Value Measurements - Schedule of Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands | Jun. 30, 2026 | Dec. 31, 2025
--- | --- | ---
ASSETS |  |
Cash equivalents | $ 103 |
Nuclear decommissioning trusts: | 1,467,958 | $ 1,414,166
Nuclear decommissioning trust, other | 558,339 | 496,793
Other special use funds: | 431,869 | 434,827
Other special use funds, other | 6,968 | 3,199
Total assets | 1,899,935 | 1,857,380
Total assets, other | 563,300 | 489,032
Commodity contracts |  |
ASSETS |  |
Commodity contracts, other | (2,007) | (10,960)
Derivative asset, total | 5 | 8,387
LIABILITIES |  |
Derivative instruments, other | (284) | 8,399
Derivative liability, total | (81,127) | (36,636)
Equity securities |  |
ASSETS |  |
Nuclear decommissioning trusts: | 23,185 | 15,171
Nuclear decommissioning trust, other | 8,971 | (3,799)
Other special use funds: | 61,912 | 65,772
Other special use funds, other | 6,968 | 3,199
U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trusts: | 549,368 | 500,592
U.S. Treasury debt |  |
ASSETS |  |
Nuclear decommissioning trusts: | 394,337 | 364,943
Other special use funds: | 369,957 | 369,055
Corporate debt |  |
ASSETS |  |
Nuclear decommissioning trusts: | 250,143 | 242,176
Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trusts: | 213,368 | 230,695
Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trusts: | 18,146 | 37,572
Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trusts: | 19,411 | 23,017
Other equity securities |  |
ASSETS |  |
Other special use funds: | 4,000 |
Level 1 |  |
ASSETS |  |
Cash equivalents | 103 |
Nuclear decommissioning trusts: | 408,551 | 383,913
Other special use funds: | 424,901 | 431,628
Total assets | 833,555 | 815,541
Level 1 | Commodity contracts |  |
ASSETS |  |
Commodity contracts | 0 | 0
LIABILITIES |  |
Derivative instruments | 0 | 0
Level 1 | Pinnacle West Captive Insurance Cell |  |
ASSETS |  |
Other special use funds: | 42,200 | 40,300
Level 1 | Equity securities |  |
ASSETS |  |
Nuclear decommissioning trusts: | 14,214 | 18,970
Other special use funds: | 54,944 | 62,573
Level 1 | U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Level 1 | U.S. Treasury debt |  |
ASSETS |  |
Nuclear decommissioning trusts: | 394,337 | 364,943
Other special use funds: | 369,957 | 369,055
Level 1 | Corporate debt |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Level 1 | Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Level 1 | Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Level 1 | Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Level 2 |  |
ASSETS |  |
Cash equivalents | 0 |
Nuclear decommissioning trusts: | 501,068 | 533,460
Other special use funds: | 0 | 0
Total assets | 502,812 | 552,807
Level 2 | Commodity contracts |  |
ASSETS |  |
Commodity contracts | 1,744 | 19,347
LIABILITIES |  |
Derivative instruments | (47,713) | (21,325)
Level 2 | Equity securities |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Other special use funds: | 0 | 0
Level 2 | U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Level 2 | U.S. Treasury debt |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Other special use funds: | 0 | 0
Level 2 | Corporate debt |  |
ASSETS |  |
Nuclear decommissioning trusts: | 250,143 | 242,176
Level 2 | Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trusts: | 213,368 | 230,695
Level 2 | Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trusts: | 18,146 | 37,572
Level 2 | Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trusts: | 19,411 | 23,017
Level 3 |  |
ASSETS |  |
Cash equivalents | 0 |
Nuclear decommissioning trusts: | 0 | 0
Other special use funds: | 0 | 0
Total assets | 268 | 0
Level 3 | Commodity contracts |  |
ASSETS |  |
Commodity contracts | 268 | 0
LIABILITIES |  |
Derivative instruments | (33,130) | (23,710)
Level 3 | Equity securities |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Other special use funds: | 0 | 0
Level 3 | U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Level 3 | U.S. Treasury debt |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Other special use funds: | 0 | 0
Level 3 | Corporate debt |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Level 3 | Mortgage-backed securities |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Level 3 | Municipal bonds |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Level 3 | Other fixed income |  |
ASSETS |  |
Nuclear decommissioning trusts: | 0 | 0
Fair Value Measured at Net Asset Value Per Share | U.S. commingled equity funds |  |
ASSETS |  |
Nuclear decommissioning trusts: |  | $ 500,592
Nuclear decommissioning trust, other | $ 549,368 |

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