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v3.25.4

LONG-TERM DEBT: Long-term Debt Level 4 (Details) - USD ($) $ in Thousands | Dec. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Debt Instrument [Line Items] |  |  |
Total first mortgage bonds |  | $ 3,345,000 | $ 2,945,000
Total pollution control revenue bonds |  | 116,300 | 116,300
American Falls bond guarantee |  | 0 | 19,885
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net |  | (13,962) | (7,523)
Debt, Long-Term and Short-Term, Combined Amount | [1] | 3,447,338 | 3,073,662
Current maturities of long-term debt |  | (116,300) | (19,885)
Long-Term Debt |  | $ 3,331,038 | $ 3,053,777
Idaho Power Company |  |  |
Debt Instrument [Line Items] |  |  |
Effective cost of outstanding debt |  | 5.13% | 5.03%
First Mortgage Bonds 1.90 Series L Due July 15 2030 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 80,000 | $ 80,000
Debt Instrument, Interest Rate, Stated Percentage |  | 1.90% | 1.90%
First mortgage bonds 6.00 Series due 2032 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 100,000 | $ 100,000
Debt Instrument, Interest Rate, Stated Percentage |  | 6.00% | 6.00%
First Mortgage Bonds 4.99 Series Due 2032 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 23,000 | $ 23,000
Debt Instrument, Interest Rate, Stated Percentage |  | 4.99% | 4.99%
First mortgage bonds 5.50 Series due 2033 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 70,000 | $ 70,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.50% | 5.50%
First mortgage bonds 5.50 Series due 2034 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 50,000 | $ 50,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.50% | 5.50%
First mortgage bonds 5.875 Series due 2034 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 55,000 | $ 55,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.875% | 5.875%
First Mortgage Bonds 5.20 Series M Due 2034 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 300,000 | $ 300,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.20% | 5.20%
First mortgage bonds 5.30 Series due 2035 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 60,000 | $ 60,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.30% | 5.30%
First mortgage bonds 6.30 Series due 2037 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 140,000 | $ 140,000
Debt Instrument, Interest Rate, Stated Percentage |  | 6.30% | 6.30%
First mortgage bonds 6.25 Series due 2037 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 100,000 | $ 100,000
Debt Instrument, Interest Rate, Stated Percentage |  | 6.25% | 6.25%
First mortgage bonds 4.85 Series due 2040 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 100,000 | $ 100,000
Debt Instrument, Interest Rate, Stated Percentage |  | 4.85% | 4.85%
First Mortgage Bonds 4.30 Series Due 2042 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 75,000 | $ 75,000
Debt Instrument, Interest Rate, Stated Percentage |  | 4.30% | 4.30%
First Mortgage Bonds 5.06 Series Due 2042 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 25,000 | $ 25,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.06% | 5.06%
First Mortgage Bonds 5.06 Series Due 2043 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 60,000 | $ 60,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.06% | 5.06%
First Mortgage Bonds 4.00 Series due 2043 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 75,000 | $ 75,000
Debt Instrument, Interest Rate, Stated Percentage |  | 4.00% | 4.00%
First mortgage bonds 3.65% Series due 2045 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 250,000 | $ 250,000
Debt Instrument, Interest Rate, Stated Percentage |  | 3.65% | 3.65%
First mortgage bonds 4.05 Series due 2046 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 120,000 | $ 120,000
Debt Instrument, Interest Rate, Stated Percentage |  | 4.05% | 4.05%
First Mortgage Bonds 4.20 K Series due 2048 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 450,000 | $ 450,000
Debt Instrument, Interest Rate, Stated Percentage |  | 4.20% | 4.20%
First Mortgage Bonds 5.20 Series Due 2053 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 62,000 | $ 62,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.20% | 5.20%
First Mortgage Bonds 5.5% Series K Due 2053 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 400,000 | $ 400,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.50% | 5.50%
First Mortgage Bonds 5.8% Series K Due 2054 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 350,000 | $ 350,000
Debt Instrument, Interest Rate, Stated Percentage |  | 5.80% | 5.80%
First Mortgage Bonds 5.7% Series K Due 2055 |  |  |
Debt Instrument [Line Items] |  |  |
First mortgage bonds |  | $ 400,000 | $ 0
Debt Instrument, Interest Rate, Stated Percentage |  | 5.70% | 5.70%
Pollution Control Bond 1.70 due 2026 |  |  |
Debt Instrument [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  | 1.70% | 1.70%
Pollution control revenue bonds 5.25 Series due 2026 | [2] | $ 116,300 | $ 116,300
Secured debt including Humboldt County and Sweetwater County pollution control revenue bonds |  |  |
Debt Instrument [Line Items] |  |  |
Total first mortgage bonds |  | $ 3,461,000 |
[1] | At December 31, 2025 and 2024, the overall effective cost rate of Idaho Power's outstanding debt was 5.13 percent and 5.03 percent, respectively.
[2] | Sweetwater County Pollution Control Revenue Bonds are secured by the first mortgage bonds, bringing the total first mortgage bonds outstanding at December 31, 2025, to $3.461 billion

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