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Summary of Significant Accounting Policies (Details-1) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Trade Receivables, Allowance for Doubtful Accounts, and Concentration Risk |  |  |
Late payment charge on upaid receivables | 1.00% |  |
Accounts receivable, allowance for credit loss, writeoff | $ 4,300 | $ 4,000 |
Accounts receivable, allowance for credit loss, period increase | 5,900 | 4,900 |
Accounts receivable, allowance for credit loss | 10,600 | 9,000 |
Allowance for Funds Used During Construction |  |  |
AFUDC - borrowed funds | 2,400 | 2,200 | $ 2,000
AFUDC - equity funds | 6,200 | 5,700 | 5,800
Capitalized Software Costs |  |  |
Capitalized software | 64,400 | 67,500 |
Capitalized software - accumulated amortization | 84,500 | 74,400 |
Capitalized software - amortization | 10,100 | 10,500 | 10,400
Capitalized Software Hosting Agreement Costs |  |  |
Capitalized software hosting agreement | 8,800 | 8,500 |
Capitalized software hosting agreement - accumulated amortization | 17,900 | 14,600 |
Capitalized software hosting agreement - amortization expense | 3,300 | 3,200 | 2,900
Tangible Asset Impairment Charges [Abstract] |  |  |
Impairment, Long-Lived Asset, Held-for-Use | $ 0 | 0 | 0
Excise taxes |  |  |
License fee tax rate, electric, retail sales | 3.19% |  |
License fee tax rate, electric, resale by purchaser | 1.59% |  |
License fee tax rate, natural gas | 0.97% |  |
License fee tax expense | $ 17,000 | $ 17,000 | $ 16,500
Minimum [Member] |  |  |
Capitalized Software Hosting Agreement Costs |  |  |
Capitalized software hosting agreement, useful life | 3 years |  |
Minimum [Member] | Capitalized Software [Member] |  |  |
Property, Plant, and Equiptment |  |  |
Property, plant, and equipment, useful life | 3 years |  |
Maximum [Member] |  |  |
Capitalized Software Hosting Agreement Costs |  |  |
Capitalized software hosting agreement, useful life | 13 years |  |
Maximum [Member] | Capitalized Software [Member] |  |  |
Property, Plant, and Equiptment |  |  |
Property, plant, and equipment, useful life | 15 years |  |
PSCW [Member] |  |  |
Allowance for Funds Used During Construction |  |  |
Authorized AFUDC rate | 50.00% | 50.00% | 50.00%
Rate at which AFUDC was capitalized | 7.72% | 7.73% | 7.11%
Authorized AFUDC rate - Signficiant projects (100%) | 100.00% | 100.00% | 100.00%
Electric [Member] |  |  |
Property, Plant, and Equiptment |  |  |
Composite straight-line depreciation rates | 3.70% | 3.80% | 3.80%
Gas [Member] |  |  |
Property, Plant, and Equiptment |  |  |
Composite straight-line depreciation rates | 2.20% | 2.10% | 2.10%
Non Regulated Energy [Member] |  |  |
Property, Plant, and Equiptment |  |  |
Composite straight-line depreciation rates | 2.30% | 2.30% | 2.30%
MGE Power Elm Road [Member] |  |  |
Principles of Consolidation |  |  |
Ownership percentage by parent | 100.00% |  |
MGE Power West Campus [Member] |  |  |
Principles of Consolidation |  |  |
Ownership percentage by parent | 100.00% |  |

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