Property Plant and Equipment Property Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

Public Utility Property, Plant, and Equipment

Major classes of property, plant and equipment

(Millions of Dollars)	Dec. 31, 2020		Dec. 31, 2019
Property, plant and equipment, net
Electric plant	$	15,736	$	14,362
Natural gas plant	5,037		4,631
Common and other property	1,191		1,113
Plant to be retired (a)	225		260
CWIP	510		913
Total property, plant and equipment	22,699		21,279
Less accumulated depreciation	(5,229)		(5,124)
Property, plant and equipment, net	$	17,470	$	16,155

(a)Includes regulator-approved retirements of Comanche Units 1 and 2 and jointly owned Craig Unit 1. Also includes PSCo’s planned retirement of jointly owned Craig Unit 2.

Schedule of Jointly Owned Utility Plants

Joint Ownership of Generation, Transmission and Gas Facilities

Jointly owned assets as of Dec. 31, 2020:

(Millions of Dollars, Except Percent Owned)	Plant in Service		Accumulated Depreciation		CWIP		Percent Owned
Electric generation:
Hayden Unit 1	$	153	$	92	$	—	76	%
Hayden Unit 2	150		73		—		37
Hayden common facilities	42		25		—		53
Craig Units 1 and 2	81		44		—		10
Craig common facilities	39		24		—		7
Comanche Unit 3	899		137		16		67
Comanche common facilities	25		2		—		82
Electric transmission:
Transmission and other facilities	176		59		2		Various
Gas transmission:
Rifle, CO to Avon, CO	22		8		—		60
Gas transmission compressor	8		1		—		50
Total	$	1,595	$	465	$	18