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Property, Plant and Equipment
 12 Months Ended
Dec. 31, 2020
Property, Plant and Equipment [Abstract]  
Property, Plant and Equipment Property, Plant and Equipment
Major classes of property, plant and equipment as of December 31, 2020 and 2019 include:
(in thousands)20202019
Electric Plant in Service  
Production$1,172,362 $915,996 
Transmission690,647 647,474 
Distribution545,221 526,146 
General123,122 123,268 
Electric Plant in Service2,531,352 2,212,884 
Construction Work in Progress203,078 177,584 
Total Gross Electric Plant2,734,430 2,390,468 
Less Accumulated Depreciation and Amortization778,988 731,110 
Net Electric Plant$1,955,442 $1,659,358 
Nonelectric Property, Plant and Equipment
Equipment$197,389 $187,904 
Buildings and Leasehold Improvements55,441 53,412 
Land5,900 6,040 
Nonelectric Property, Plant and Equipment258,730 247,356 
Construction Work in Progress9,290 7,654 
Total Gross Nonelectric Property, Plant and Equipment268,020 255,010 
Less Accumulated Depreciation and Amortization174,189 160,574 
Net Nonelectric Property, Plant and Equipment93,831 94,436 
Net Property, Plant and Equipment$2,049,273 $1,753,794 
Depreciation expense for the years ended December 31, 2020, 2019 and 2018 totaled $78.6 million, $71.9 million and $69.7 million.
The following table provides OTP’s ownership percentages and amounts included in the December 31, 2020 and 2019 consolidated balance sheets for OTP’s share of each of these jointly owned facilities:
 (dollars in thousands)Ownership
Percentage		Electric Plant
in Service		Construction
Work in
Progress		Accumulated
Depreciation		Net Plant
December 31, 2020     
Big Stone Plant53.9 %$332,611 $2,552 $(103,504)$231,659 
Coyote Station35.0 %180,991 732 (108,603)73,120 
Big Stone South–Ellendale 345 kV line50.0 %106,353 — (2,433)103,920 
Fargo–Monticello 345 kV line14.2 %78,184 — (8,029)70,155 
Big Stone South–Brookings 345 kV line50.0 %53,036 — (2,822)50,214 
Brookings–Southeast Twin Cities 345 kV line4.8 %26,291 — (2,468)23,823 
Bemidji–Grand Rapids 230 kV line14.8 %16,331 — (2,670)13,661 
December 31, 2019
Big Stone Plant53.9 %$337,197 $384 $(98,654)$238,927 
Coyote Station35.0 %184,493 83 (108,248)76,328 
Big Stone South–Ellendale 345 kV line1
50.0 %106,343 — (819)105,524 
Fargo–Monticello 345 kV line14.2 %78,184 — (7,011)71,173 
Big Stone South–Brookings 345 kV line50.0 %53,036 — (2,016)51,020 
Brookings–Southeast Twin Cities 345 kV line4.8 %26,286 — (2,086)24,200 
Bemidji–Grand Rapids 230 kV line14.8 %16,331 — (233)16,098