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REGULATORY MATTERS: Regulatory Matters Level 3 (Tables) | 12 Months Ended
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Dec. 31, 2023
Regulatory Assets and Liabilities, Other Disclosure [Abstract] |
Schedule of Regulatory Assets and Liabilities | The following table presents a summary of Idaho Power’s regulatory assets and liabilities (in thousands of dollars):
|  |  |  | As of December 31, 2023 |  |  |  |
|  | Remaining Amortization Period |  | Earning a Return(1) |  | Not Earning a Return |  | Total as of December 31,
Description |  |  |  |  | 2023 |  | 2022
Regulatory Assets: |  |  |  |  |  |  |  |  |  |
Income taxes(2) |  |  |  | $ | — |  |  | $ | 774,672 |  |  | $ | 774,672 |  |  | $ | 739,689 |
Unfunded postretirement benefits(3) |  |  |  | — |  |  | 87,318 |  |  | 87,318 |  |  | 70,254 |
Pension expense deferrals(4) |  |  |  | 253,744 |  |  | 1,500 |  |  | 255,244 |  |  | 249,503 |
Energy efficiency program costs(5) |  |  |  | — |  |  | — |  |  | — |  |  | 3,767 |
Power supply costs(6) |  | 2024-2025 |  | 134,816 |  |  | (19,291) |  |  | 115,525 |  |  | 129,309 |
Fixed cost adjustment(6) |  | 2024-2025 |  | 36,037 |  |  | 15,248 |  |  | 51,285 |  |  | 41,901 |
North Valmy plant settlements(6) |  | 2024-2028 |  | 82,917 |  |  | — |  |  | 82,917 |  |  | 90,747 |
Jim Bridger plant settlement(6) |  | 2024-2030 |  | 108,376 |  |  | 15,256 |  |  | 123,632 |  |  | 80,531 |
Wildfire Mitigation Plan deferral(6) |  |  |  | — |  |  | 51,329 |  |  | 51,329 |  |  | 27,078 |
Asset retirement obligations(7) |  |  |  | — |  |  | 35,270 |  |  | 35,270 |  |  | 28,780 |
Long-term service agreement |  | 2024-2043 |  | 12,679 |  |  | 8,276 |  |  | 20,955 |  |  | 22,114 |
Other |  | 2024-2056 |  | 2,330 |  |  | 52,573 |  |  | 54,903 |  |  | 18,288 |
Total |  |  |  | $ | 630,899 |  |  | $ | 1,022,151 |  |  | $ | 1,653,050 |  |  | $ | 1,501,961 |
Regulatory Liabilities: |  |  |  |  |  |  |  |  |  |
Income taxes(8) |  |  |  | $ | — |  |  | $ | 108,641 |  |  | $ | 108,641 |  |  | $ | 94,946 |
Depreciation-related excess deferred income taxes(9) |  |  |  | 147,950 |  |  | — |  |  | 147,950 |  |  | 158,634 |
Removal costs(7) |  |  |  | — |  |  | 175,369 |  |  | 175,369 |  |  | 180,087 |
Investment tax credits |  |  |  | — |  |  | 165,479 |  |  | 165,479 |  |  | 115,285 |
Deferred revenue-AFUDC(10) |  |  |  | 177,884 |  |  | 50,787 |  |  | 228,671 |  |  | 207,528 |
Energy efficiency program costs(5) |  |  |  | 1,507 |  |  | — |  |  | 1,507 |  |  | 154 |
Power supply costs(6) |  |  |  | 1,240 |  |  | — |  |  | 1,240 |  |  | — |
Mark-to-market liabilities |  |  |  | — |  |  | 88 |  |  | 88 |  |  | 59,544 |
Tax reform accrual for future amortization(11) |  |  |  | — |  |  | 40,891 |  |  | 40,891 |  |  | 32,793 |
Other |  |  |  | 8,383 |  |  | 4,334 |  |  | 12,717 |  |  | 11,630 |
Total |  |  |  | $ | 336,964 |  |  | $ | 545,589 |  |  | $ | 882,553 |  |  | $ | 860,601 |
(1) Earning a return includes either interest or a return on the investment as a component of rate base at the allowed rate of return. The interest rate on deferral accounts is published annually by the IPUC and OPUC. The applicable rates for 2023 were 2% and 4.5%, respectively. (2) Represents flow-through income tax accounting differences which have a corresponding deferred tax liability disclosed in Note 2 - "Income Taxes." (3) Represents the unfunded obligation of Idaho Power’s pension and postretirement benefit plans, which are discussed in Note 11 - "Benefit Plans." (4) Idaho Power records a regulatory asset for the difference between net periodic pension cost and pension cost considered for rate-making purposes relating to Idaho Power's defined benefit pension plan. In its Idaho jurisdiction, Idaho Power’s inclusion of pension costs for the establishment of retail rates is based upon contributions made to the pension plan. This regulatory asset account represents the difference between cumulative cash contributions and amounts collected in rates. Deferred costs are amortized into expense as the amounts are provided for in Idaho retail revenues. (5) The energy efficiency asset and liability represent the separate Idaho and Oregon jurisdiction balances at December 31, 2022, and December 31, 2023, respectively. During 2023, the balances changed from an asset to a liability in the Idaho jurisdiction. (6) This item is discussed in more detail in this Note 3 - "Regulatory Matters." (7) Asset retirement obligations and removal costs are discussed in Note 13 - "Asset Retirement Obligations (ARO)." (8) Represents the tax gross-up related to the depreciation-related excess deferred income taxes and investment tax credits included in this table and has a corresponding deferred tax asset disclosed in Note 2 - "Income Taxes." (9) In 2017, income tax reform reduced deferred income tax assets and liabilities. For depreciation-related temporary differences under the normalized tax accounting method, the resulting excess deferred taxes will flow back to customers ratably over the remaining regulatory lives of Idaho Power's plant assets under the alternative method provided in the statute. (10) Idaho Power is collecting revenue in the Idaho jurisdiction for AFUDC on HCC relicensing costs but is deferring revenue recognition of the amounts collected until the license is issued and the asset is placed in service under the new license. (11) Represents amount accrued under the May 2018 Idaho tax reform settlement stipulation (described below) for the future amortization of existing or future unspecified regulatory deferrals that would otherwise be a future liability recoverable from Idaho customers.
Schedule of Power Cost Adjustment Changes | The table below summarizes the three most recent Idaho-jurisdiction PCA rate adjustments, which also include non-PCA-related rate adjustments as ordered by the IPUC:
Effective Date |  | $ Change (millions) |  | Notes
June 1, 2023 |  | $ | 105.1 |  |  | The $105.1 million increase in PCA rates reflects higher market energy and natural gas prices, combined with lower-than-expected low-cost hydropower generation and limited coal supply. The increased rate also reflects an expectation of continued elevated market energy prices and natural gas prices in the forecast period.
June 1, 2022 |  | $ | 94.9 |  |  | The increase in PCA rates reflected a forecasted reduction in low-cost hydroelectric generation as well as higher costs associated with market energy prices and natural gas prices. The rate also reflected $0.6 million of 2021 earnings shared with customers under the 2018 Settlement Stipulation described below.
June 1, 2021 |  | $ | 39.1 |  |  | The net increase in PCA rates reflected a forecasted reduction in low-cost hydroelectric generation as well as higher costs associated with forecasted PURPA power purchases. The net increase in PCA rates also reflected a smaller credit to customers through the true-up component.
Schedule of Fixed Cost Rate Adjustments | The following table summarizes FCA amounts approved for collection in the prior three FCA years:
FCA Year |  | Period Rates in Effect |  | Annual Amount (in millions)
2022 |  | June 1, 2023-May 31, 2024 |  | $25.1
2021 |  | June 1, 2022-May 31, 2023 |  | $35.2
2020 |  | June 1, 2021-May 31, 2022 |  | $38.3
Schedule of Open Access Transmission Rates | Idaho Power's OATT rates submitted to the FERC in Idaho Power's four most recent annual OATT Final Informational Filings were as follows:
Applicable Period |  | OATT Rate (per kW-year)
October 1, 2023 to September 30, 2024 |  | $ | 30.74 |
October 1, 2022 to September 30, 2023 |  | $ | 31.42 |
October 1, 2021 to September 30, 2022 |  | $ | 31.19 |
October 1, 2020 to September 30, 2021 |  | $ | 29.95 |

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