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REGULATORY MATTERS: | 12 Months Ended
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Dec. 31, 2025
Regulated Operations [Abstract] |
Regulatory Matters | REGULATORY MATTERS IDACORP’s and Idaho Power’s financial statements reflect the effects of the different ratemaking principles followed by the jurisdictions regulating Idaho Power. Included below is a summary of Idaho Power's regulatory assets and liabilities, as well as a discussion of notable regulatory matters affecting customer rates. Regulatory Assets and Liabilities The application of accounting principles related to regulated operations sometimes results in Idaho Power recording some expenses and revenues in a different period than when an unregulated enterprise would record those expenses and revenues. Regulatory assets represent incurred costs that have been deferred because it is probable they will be recovered from customers through future rates. Regulatory liabilities represent obligations to make refunds to customers for previous collections, or represent amounts collected in advance of incurring an expense. The following table presents a summary of Idaho Power’s regulatory assets and liabilities (in thousands of dollars):
|  |  |  | As of December 31, 2025 |  |  |  |
|  | Remaining Amortization Period |  | Earning a Return(1) |  | Not Earning a Return |  | Total as of December 31,
Description |  |  |  |  | 2025 |  | 2024
Regulatory Assets: |  |  |  |  |  |  |  |  |  |
Income taxes(2) |  |  |  | $ | — |  |  | $ | 821,346 |  |  | $ | 821,346 |  |  | $ | 811,054 |
Pension expense deferrals(3) |  |  |  | 245,508 |  |  | 1,832 |  |  | 247,340 |  |  | 252,197 |
Mark-to-market assets(4) |  |  |  | — |  |  | 49,520 |  |  | 49,520 |  |  | 28,118 |
Unfunded postretirement benefits(5) |  |  |  | — |  |  | — |  |  | — |  |  | 18,824 |
Power supply costs(6) |  |  |  | — |  |  | — |  |  | — |  |  | 18,507 |
Fixed cost adjustment(6) |  | 2026-2027 |  | 8,205 |  |  | (1,350) |  |  | 6,855 |  |  | 17,761 |
North Valmy plant settlements(6) |  | 2026-2033 |  | 83,941 |  |  | — |  |  | 83,941 |  |  | 80,767 |
Jim Bridger plant settlement(6) |  | 2026-2030 |  | 151,739 |  |  | 12,921 |  |  | 164,660 |  |  | 147,451 |
Wildfire Mitigation Plan deferral(6) |  |  |  | — |  |  | 91,670 |  |  | 91,670 |  |  | 63,966 |
Asset retirement obligations(7) |  |  |  | — |  |  | 62,166 |  |  | 62,166 |  |  | 37,842 |
Long-term service agreement |  | 2026-2043 |  | 11,313 |  |  | 7,326 |  |  | 18,639 |  |  | 19,796 |
Other |  | 2026-2056 |  | 4,596 |  |  | 13,725 |  |  | 18,321 |  |  | 11,089 |
Total |  |  |  | $ | 505,302 |  |  | $ | 1,059,156 |  |  | $ | 1,564,458 |  |  | $ | 1,507,372 |
Regulatory Liabilities: |  |  |  |  |  |  |  |  |  |
Income taxes(8) |  |  |  | $ | — |  |  | $ | 121,489 |  |  | $ | 121,489 |  |  | $ | 127,634 |
Depreciation-related excess deferred income taxes(9) |  |  |  | 128,180 |  |  | — |  |  | 128,180 |  |  | 137,903 |
Removal costs(7) |  |  |  | — |  |  | 162,652 |  |  | 162,652 |  |  | 166,181 |
Investment tax credits |  |  |  | — |  |  | 235,724 |  |  | 235,724 |  |  | 230,322 |
Deferred revenue-AFUDC(10) |  |  |  | 224,083 |  |  | 56,896 |  |  | 280,979 |  |  | 250,942 |
Energy efficiency program costs |  |  |  | 16,493 |  |  | — |  |  | 16,493 |  |  | 9,277 |
Power supply costs(6) |  | 2026-2027 |  | 42,419 |  |  | — |  |  | 42,419 |  |  | 3,949 |
Unfunded postretirement benefits(5) |  |  |  | — |  |  | 11,785 |  |  | 11,785 |  |  | — |
Tax reform accrual for future amortization(11) |  |  |  | — |  |  | 44,423 |  |  | 44,423 |  |  | 42,266 |
Other |  |  |  | 4,168 |  |  | 3,839 |  |  | 8,007 |  |  | 15,852 |
Total |  |  |  | $ | 415,343 |  |  | $ | 636,808 |  |  | $ | 1,052,151 |  |  | $ | 984,326 |
(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 2025 were 5.0% 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) 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. (4) This item is discussed in more detail in Note 16 - "Derivative Financial Instruments." (5) Represents the unfunded obligation of Idaho Power’s pension and postretirement benefit plans, which are discussed in Note 12 - "Benefit Plans." (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 14 - "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) 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. Idaho Power’s regulatory assets and liabilities are typically amortized over the period in which they are reflected in customer rates. In the event that recovery of Idaho Power’s costs through rates becomes unlikely or uncertain, regulatory accounting would no longer apply to some or all of Idaho Power’s operations and the items above may represent stranded investments. If not allowed full recovery of these items, Idaho Power would be required to write off the applicable portion, which could have a materially adverse financial impact. Power Cost Adjustment Mechanisms and Deferred Power Supply Costs In both its Idaho and Oregon jurisdictions, Idaho Power's power cost adjustment mechanisms address the volatility of power supply costs and provide for annual adjustments to the rates charged to its retail customers. The power cost adjustment mechanisms compare Idaho Power's actual net power supply costs (primarily fuel and purchased power less wholesale energy sales) against net power supply costs being recovered in Idaho Power's retail rates. Under the power cost adjustment mechanisms, certain differences between actual net power supply costs incurred by Idaho Power and costs being recovered in retail rates are recorded as a deferred charge or accrued as a credit on the balance sheets for future recovery or refund. The power supply costs deferred or accrued primarily result from changes in the levels of Idaho Power's own hydroelectric generation, changes in contracted power purchase prices and volumes, changes in wholesale market prices and transaction volumes, and changes in fuel prices. Idaho Jurisdiction Power Cost Adjustment Mechanism: In the Idaho jurisdiction, the annual PCA consists of (a) a forecast component, based on a forecast of net power supply costs in the coming year as compared with net power supply costs included in base rates; and (b) a balancing component that trues up the difference between the previous year’s actual net power supply costs and the costs collected in the previous year's forecast component. The latter component ensures that, over time, the actual collection or refund of net power supply costs matches the amounts authorized. The Idaho-jurisdiction PCA year runs from April 1 through March 31. Amounts deferred or accrued during the PCA year are primarily recovered or refunded during the subsequent June 1 through May 31 period. The PCA mechanism includes: •a cost or benefit sharing ratio that allocates the deviations in net power supply expenses between customers (95 percent) and Idaho Power (5 percent), with the exceptions of expenses associated with PURPA power purchases, export credit mechanisms, a battery storage lease, and demand response incentive payments, which are allocated 100 percent to customers; and •a sales-based adjustment intended to ensure that power supply expense recovery resulting solely from sales volume changes does not distort the results of the mechanism. Beginning April 1, 2024, the difference between actual and base-level third-party transmission wheeling revenues are tracked and incorporated into the balancing component of the PCA, as authorized by the IPUC in March 2025. In May 2025, the IPUC issued an order approving a $94.8 million net decrease in PCA revenues as compared with the prior collection period, effective for the PCA collection period from June 1, 2025, to May 31, 2026. The net decrease in PCA revenues reflected a decrease in the balancing adjustment, which was due primarily to the completed recovery of the 2023 deferred PCA costs, which were recovered over a two-year period as ordered by the IPUC. The 2025 Settlement Stipulation, described in more detail below, modified PCA collection effective January 1, 2026, to account for the new system base level NPSE of $468.8 million. The table below summarizes the three most recent Idaho-jurisdiction PCA rate adjustments from Idaho Power's annual PCA filings, which also include non-PCA-related rate adjustments as ordered by the IPUC:
Effective Date |  | $ Change (millions) |  | Notes
June 1, 2025 |  | $ | (94.8) |  |  | The $94.8 million net decrease in PCA rates reflects a decrease in the balancing adjustment, which is due primarily to the completed recovery of the 2023 balancing adjustment, which was recovered over two years.
June 1, 2024 |  | $ | (35.7) |  |  | The $35.7 million net decrease in PCA rates reflected forecasted improved hydropower generation during the April 2024 to March 2025 PCA deferral period.
June 1, 2023 |  | $ | 105.1 |  |  | The $105.1 million increase in PCA rates reflected higher market energy and natural gas prices, combined with lower than-expected low-cost hydropower generation and limited coal supply. The increased rate also reflected an expectation of continued elevated market energy prices and natural gas prices in the forecast period.
Oregon Jurisdiction Power Cost Adjustment Mechanism: Idaho Power’s power cost recovery mechanism in Oregon has two components: an APCU and a power cost adjustment mechanism (PCAM). The APCU allows Idaho Power to reestablish its Oregon base net power supply costs annually, separate from a general rate case, and to forecast net power supply costs for the upcoming water year. The PCAM is a true-up filed annually in February. The PCAM filing calculates the deviation between actual net power supply expenses incurred for the preceding calendar year and the net power supply expenses recovered through the APCU for the same period. In May 2025, the OPUC approved a settlement stipulation between Idaho Power and intervening parties for its APCU in Oregon. The settlement resulted in an overall rate decrease of $1.8 million in Oregon-jurisdictional rates effective June 1, 2025. Idaho Power's 2024 and 2023 June 1 APCU rate changes were a decrease of $6.9 million, and an increase of $7.7 million, respectively. Notable Idaho Base Rate Adjustments Idaho base rates were most recently established through a general rate case in 2025, which was resolved by the 2025 Settlement Stipulation, with rate changes effective January 1, 2026. Previously, base rates were established in the 2024 Idaho Limited-Issue Rate Case and in a general rate case in 2023, which was resolved by the 2023 Settlement Stipulation. 2025 Idaho General Rate Case: In May 2025, Idaho Power filed a general rate case with the IPUC. The general rate case was resolved in December 2025, when the IPUC issued an order (the Order) approving the 2025 Settlement Stipulation, entered into by Idaho Power, the Staff of the IPUC, and several of the intervening parties. The 2025 Settlement Stipulation contains the following significant terms, among other items: •Idaho Power will implement revised tariff schedules designed to increase annual Idaho-jurisdictional retail revenue by approximately $110.0 million, or 7.48 percent, effective January 1, 2026. The approximate $110.0 million of additional annual revenue is inclusive of a PCA rate increase of $13.1 million; •a 9.6 percent return on equity and a 7.41 percent authorized rate of return based on the filed cost of debt and capital structure, applied to an Idaho-jurisdictional rate base of approximately $4.9 billion (which is largely based on the average of monthly average plant balances for January through December 2025); •a base level NPSE of approximately $468.8 million, a decrease of $16.1 million from the currently approved base level NPSE; •updates to the FCA mechanism rates to reflect approved fixed costs and Idaho Power’s proposed rate designs; •continued deferral of certain wildfire mitigation related costs, including incremental vegetation management and insurance costs, as measured primarily from 2024 actual costs, through the earlier of Idaho Power's next general rate case or 2027; •modifications to Idaho Power’s ADITC and revenue sharing mechanism: (1) to include an additional amount of investment tax credits equal to the total of existing ADITCs not currently eligible for accelerated amortization under the mechanism and all investment tax credits generated through the end of calendar-year 2028; (2) to establish an annual cap of $55 million on the amount of accelerated amortization of ADITCs for calendar year 2026 and thereafter; (3) to re-affirm the existing minimum specified Idaho-jurisdiction return on year-end equity (Idaho ROE) of 9.12 percent for additional amortization of ADITCs; (4) to re-affirm the existing 9.6 percent Idaho ROE as the threshold for revenue sharing of Idaho-jurisdiction earnings between Idaho Power and Idaho customers; and (5) to continue to implement all revenue sharing through the PCA; and •agreement that Idaho Power’s share of capital expenditures at jointly-owned coal-fired plants through year-end 2024 are included for recovery in the stipulated revenue requirement. At the time of the 2025 Settlement Stipulation, Staff of the IPUC had completed its prudence review of capital projects included in the test year rate base through July 2025. The IPUC Staff will address the prudence of investments placed in service after July 2025 in Idaho Power’s next Idaho general rate case. Neither the Order nor the 2025 Settlement Stipulation precludes Idaho Power from filing another general rate case in Idaho at any time in the future. Under the modified ADITC and Revenue Sharing mechanism, if Idaho Power's annual Idaho ROE in any year exceeds 9.6 percent, the amount of earnings exceeding 9.6 percent will be allocated 80.0 percent to Idaho Power's Idaho customers as a rate reduction to be effective at the time of the subsequent year's PCA, and 20.0 percent to Idaho Power. In 2025, Idaho Power recorded amortization of $40.3 million of ADITC. Accordingly, at December 31, 2025, $167.8 million of ADITC remained available for future use under the terms of the 2025 Settlement Stipulation, the 2023 Settlement Stipulation, and the 2018 Settlement Stipulation described below. 2024 Idaho Limited-Issue Rate Case: Idaho Power filed the 2024 Idaho Limited-Issue Rate Case in May 2024, focused on revenue requirements for 2024 incremental plant additions and incremental ongoing labor costs. On December 31, 2024, the IPUC issued its order in the 2024 Idaho Limited-Issue Rate Case, providing that Idaho Power implement revised tariff schedules designed to increase annual Idaho-jurisdictional retail revenue by $50.6 million, or 3.7 percent, effective January 1, 2025. The order was subsequently modified by an errata issued on January 21, 2025, which reduced the revenue increase called for under the order to $50.1 million. The order did not adjust the overall rate of return approved in the 2023 Settlement Stipulation or make changes to Idaho regulatory mechanisms such as the PCA, FCA, and energy efficiency rider. 2023 Idaho General Rate Case: In June 2023, Idaho Power filed a general rate case with the IPUC. In December 2023, the IPUC issued an order approving the 2023 Settlement Stipulation settling the general rate case. The order and the 2023 Settlement Stipulation provided for the following significant terms, among other items: •Implementation of revised tariff schedules designed to increase annual Idaho-jurisdictional retail revenue by $54.7 million, or 4.25 percent, effective January 1, 2024. The $54.7 million of additional annual revenue was net of an Idaho-jurisdiction PCA rate decrease of $168.3 million and a reduction to annual energy efficiency rider collection of $3.5 million, each of which was transferred into base rates; •A 9.6 percent return on equity and a 7.247 percent authorized rate of return based on a non-specified cost of debt and capital structure, applied to an Idaho-jurisdictional rate base of approximately $3.8 billion; •Modifications to the PCA including establishment of a new level of base net power supply expense of $484.9 million, which included the transfer of $168.3 million from then-current PCA rates to base rates; •An annual $18 million increase in collection of Idaho Power’s regulatory asset associated with its defined benefit pension plan contributions; •Modifications to Idaho Power’s ADITC and revenue sharing mechanism beginning in 2024 to, among other items, (1) establish a minimum specified Idaho ROE of 9.12 percent for additional amortization of ADITCs; and (2) establish a 9.6 percent Idaho ROE as the threshold for revenue sharing of Idaho-jurisdiction earnings between Idaho Power and Idaho customers; and •Agreement that Idaho Power’s capital expenditures through year-end 2022 were prudently incurred. May 2018 Idaho Tax Reform Settlement Stipulation: In May 2018, the IPUC issued an order approving a settlement stipulation (2018 Settlement Stipulation) related to income tax reform. Beginning June 1, 2018, the 2018 Settlement Stipulation provided an annual (a) $18.7 million reduction to Idaho customer base rates and (b) $7.4 million amortization of existing regulatory deferrals for specified items or future amortization of other existing or future unspecified regulatory deferrals that would otherwise be a future regulatory asset recoverable from Idaho customers. The 2018 Settlement Stipulation also provided for the indefinite extension, with modifications, of a previous 2014 settlement stipulation beyond its termination date of December 31, 2019, with modified terms related to the ADITC and revenue sharing mechanism that became effective January 1, 2020. Idaho Power’s base rates and ADITC and revenue sharing mechanism were modified by the 2025 Settlement Stipulation and the 2023 Settlement Stipulation, as described above. North Valmy Base Rate Adjustment Settlement Stipulations: Idaho Power has settlement stipulations in place in Idaho and Oregon related to the end of its participation in coal-fired operations of both units of its jointly-owned North Valmy plant. Idaho Power ceased participation in coal-fired operations at unit 1 in 2019, and coal-fired operations at unit 2 ceased at the end of 2025. The IPUC-approved settlement stipulation provides for (1) accelerated depreciation for the North Valmy plant to allow the coal-related plant assets to be fully depreciated and recovered by December 31, 2028, (2) Idaho Power to use prudent and commercially reasonable efforts to end its participation in coal-fired operations at the North Valmy plant as described above, (3) a balancing account to track the incremental costs, benefits, and required regulatory accounting associated with ceasing participation in coal-fired operations at the North Valmy plant, and (4) increased customer rates related to the associated incremental annual levelized revenue requirement. If actual costs incurred differ from forecasted amounts included in the settlement stipulation, collection or refund of any differences would be subject to regulatory approval. The 2025 Settlement Stipulation made modifications to the Idaho North Valmy settlement stipulation, including updated coal-related investments through 2024 and investment forecasts through 2025. On December 31, 2025, the accelerated depreciation associated with coal-related investments at the North Valmy plant was completed and the amounts removed from Oregon customer rates. Jim Bridger Power Plant Rate Base Adjustment and Recovery: In 2022, the IPUC authorized Idaho Power to (1) accelerate depreciation for the Jim Bridger plant to allow the coal-related plant assets to be fully depreciated and recovered by December 31, 2030, (2) establish a balancing account to track the incremental costs, benefits, and required regulatory accounting associated with its plan to cease participation in coal-fired operations at the Jim Bridger plant in 2028, and (3) increase customer rates related to the associated incremental annual levelized revenue requirement (Bridger Recovery Mechanism). The 2025 Settlement Stipulation made modifications to the Bridger Recovery Mechanism, including updated coal-related investments through 2024, updated investment forecasts through 2028, and the inclusion of total other O&M expenses associated with operations of the Jim Bridger plant. The Bridger Recovery Mechanism allows Idaho Power to earn a return on and recover through 2030 the net book value of coal-related assets at the Jim Bridger plant as of December 31, 2024, as well as forecasted coal-related investments. Idaho Power anticipates making future filings with the IPUC that may result in periodic adjustments to rates to true up variances between revenue collections and actual revenue requirement amounts. Recovery of Incremental AFUDC Associated with HCC: In March 2025, Idaho Power filed an application with the IPUC requesting an order authorizing an increase of $29.7 million in the annual cash collection of incremental financing costs, or AFUDC, associated with relicensing of the HCC project. In September 2025, the IPUC approved Idaho Power's proposed increase in annual cash collection to recover AFUDC associated with relicensing of the HCC project, effective October 1, 2025. Other Notable Idaho Regulatory Matters Affecting Customer Rates Fixed Cost Adjustment: The FCA mechanism, applicable to Idaho residential and small commercial customers, is designed to remove a portion of Idaho Power’s financial disincentive to invest in energy efficiency programs by separating (or decoupling) the recovery of fixed costs from the variable kWh charge and linking it instead to a set amount per customer. Under Idaho Power's current rate design, recovery of a portion of fixed costs is included in the variable kWh charge, which may result in over-collection or under-collection of fixed costs. To return over-collection to customers or to collect under-collection from customers, the FCA mechanism allows Idaho Power to accrue, or defer, the difference between the authorized fixed-cost recovery amount per customer and the actual fixed costs per customer recovered by Idaho Power during the year. The IPUC has discretion to cap the annual increase in the FCA recovery at 3 percent of base revenue, with any excess deferred for collection in a subsequent year. In May 2025, the IPUC issued an order approving a $39.8 million decrease in recovery from the FCA from $36.8 million to negative $3.1 million for the 2024 FCA deferral, reflecting a refund to residential and small commercial customers of the 2024 FCA deferral balance of $3.1 million, with new rates effective for the period from June 1, 2025 to May 31, 2026. Beginning with the 2026 FCA deferral, the 2025 Settlement Stipulation updated the authorized fixed-cost recovery amount per customer and per unit of energy within the FCA mechanism to support Idaho Power's proposed rate designs, as noted above. The following table summarizes FCA amounts approved for (refund) or collection in the prior three FCA years:
FCA Year |  | Period Rates in Effect |  | Annual Amount (in millions of dollars)
2024 |  | June 1, 2025 to May 31, 2026 |  | $(3.1)
2023 |  | June 1, 2024 to May 31, 2025 |  | $36.8
2022 |  | June 1, 2023 to May 31, 2024 |  | $25.1
Wildfire Mitigation Cost Recovery: In September 2025, the IPUC granted Idaho Power's request to defer for future recovery an estimated $22.2 million of newly identified incremental O&M costs expected to be incurred in 2025 associated with expanded wildfire mitigation efforts. The IPUC also authorized the continued deferral of incremental insurance costs above the 2022 base established in the 2023 Settlement Stipulation. The 2025 Settlement Stipulation authorized Idaho Power to defer incremental O&M and insurance costs above the 2024 base through the earlier of the next general rate case or 2027. As of December 31, 2025, Idaho Power’s deferral balance of Idaho-jurisdiction costs related to the WMP was $88.2 million, of which $73.9 million is approved to be amortized and collected in Idaho rates. Hells Canyon Complex Relicensing Costs: In December 2025, Idaho Power filed an application with the IPUC requesting a determination that Idaho Power's expenditures from January 1, 2016 through year-end 2025 on relicensing of the HCC, including approximately $305 million incurred from January 1, 2016 through September 30, 2025, were prudently incurred, and thus eligible for inclusion in retail rates in a future regulatory proceeding. As of the date of this report, the case remains pending. Notable Oregon Regulatory Matters Affecting Customer Rates Oregon Base Rate Changes: Oregon base rates were most recently established in a general rate case that Idaho Power filed with the OPUC in December 2023 and a separate case approved by the OPUC in December 2025 described below. In September 2024, the OPUC issued an order approving the 2024 Oregon Settlement Stipulations, which are settlement stipulations among Idaho Power and intervening parties settling the general rate case. The OPUC order and the 2024 Oregon Settlement Stipulations contain the following significant terms, among other items: •Implementation of revised tariff schedules designed to increase annual Oregon-jurisdiction revenue by $6.7 million, or 12.14 percent; and •A 9.5 percent Oregon-jurisdiction return on year-end equity and a 7.302 percent Oregon-jurisdiction authorized rate of return based on a 5.104 percent cost of debt and capital structure of 50 percent debt and 50 percent equity, applied to an Oregon-jurisdictional rate base of approximately $188.9 million. The $188.9 million of rate base excludes rate base associated with Idaho Power's jointly-owned North Valmy coal facilities, the costs of which are recovered under the separate rate mechanism noted above. Rate changes from the 2024 Oregon Settlement Stipulations became effective on October 15, 2024. The 2024 Oregon Settlement Stipulations do not preclude Idaho Power from filing another general rate case or other limited issue proceeding in Oregon at any time in the future. In December 2025, the OPUC issued an order approving a decrease in Oregon rates reflecting three offsetting adjustments: a decrease in rates of $1.2 million due to the removal of coal-related costs at the North Valmy plant, a decrease in rates of $0.1 million to return an outstanding regulatory liability related to the former Boardman plant, and an increase in rates of $0.7 million to recover the amortization of deferred 2023 wildfire mitigation costs. The combined result was an overall rate decrease of $0.6 million or 0.9 percent, effective January 1, 2026. Wildfire Mitigation Cost Recovery: In December 2025, Idaho Power filed its 2026-2028 WMP with the OPUC along with an application requesting authorization to defer for future recovery an estimated $3.1 million of newly identified incremental costs expected to be incurred in 2026 associated with expanded wildfire mitigation efforts. As of the date of this report, the case remains pending. As of December 31, 2025, Idaho Power’s deferral balance of Oregon-jurisdiction costs related to the WMP was $3.5 million, of which $0.7 million is approved to be amortized and collected in Oregon rates. Federal Regulatory Matters - Open Access Transmission Tariff Rates Idaho Power uses a formula rate for transmission service provided under its OATT, which allows transmission rates to be updated annually based primarily on actual financial and operational data Idaho Power files with the FERC and allows Idaho Power to recover costs associated with its transmission system. Idaho Power's OATT rates submitted to the FERC in Idaho Power's four most recent annual OATT Final Informational Filings were as follows:
Period Rates in Effect |  | OATT Rate (per kW-year)
October 1, 2025 to September 30, 2026 |  | $ | 34.16 |
October 1, 2024 to September 30, 2025 |  | $ | 31.55 |
October 1, 2023 to September 30, 2024 |  | $ | 30.74 |
October 1, 2022 to September 30, 2023 |  | $ | 31.42 |
Idaho Power's current OATT rate is based on a net annual transmission revenue requirement of $148.5 million, which represents the OATT formulaic determination of Idaho Power's net cost of providing OATT-based transmission service.

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