v3.25.4
Jointly Owned Facilities (Details)
$ in Millions
Dec. 31, 2025
USD ($)
Wyodak Plant  
Jointly Owned Utility Plant Interests [Line Items]  
Ownership Interest 20.00% [1]
Plant in Service $ 123.5 [1]
Construction Work in Progress 0.0 [1]
Less Accumulated Depreciation (80.1) [1]
Plant Net of Accumulated Depreciation $ 43.4
Transmission Tie  
Jointly Owned Utility Plant Interests [Line Items]  
Ownership Interest 35.00%
Plant in Service $ 24.5
Construction Work in Progress 0.0
Less Accumulated Depreciation (8.7)
Plant Net of Accumulated Depreciation $ 15.8
Wygen III Generating Facility  
Jointly Owned Utility Plant Interests [Line Items]  
Ownership Interest 52.00% [2]
Plant in Service $ 144.3 [2]
Construction Work in Progress 0.4 [2]
Less Accumulated Depreciation (31.3) [2]
Plant Net of Accumulated Depreciation $ 113.4
Wygen I Generating Facility  
Jointly Owned Utility Plant Interests [Line Items]  
Ownership Interest 76.50% [3]
Plant in Service $ 119.4 [3]
Construction Work in Progress 0.5 [3]
Less Accumulated Depreciation (64.2) [3]
Plant Net of Accumulated Depreciation $ 55.7
[1] In addition to supplying South Dakota Electric with coal for its share of the Wyodak Plant, our mine supplies PacifiCorp’s share of the coal under a separate long-term agreement through December 31, 2026, with an annual renewal option for one-year extensions. This coal supply agreement is collateralized by a mortgage on and a security interest in some of WRDC’s coal reserves.
[2] South Dakota Electric retains responsibility for plant operations. WRDC supplies fuel to Wygen III for the life of the plant.
[3] Black Hills Wyoming retains responsibility for plant operations. WRDC supplies fuel to Wygen I for the life of the plant.