Property, Plant and Equipment

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

Property, plant and equipment as of December 31, 2020, consisted of:


As of December 31, 2020	Regulated		Nonregulated		Total
(Millions)
Electric generation, distribution, transmission and other	$	16,364	$	12,854	$	29,218
Natural gas transportation, distribution and other	4,637		13		4,650
Other common operating property	—		274		274
Total Property, Plant and Equipment in Service	21,001		13,141		34,142
Total accumulated depreciation	(5,363)		(4,436)		(9,799)
Total Net Property, Plant and Equipment in Service	15,638		8,705		24,343
Construction work in progress	1,384		1,024		2,408
Total Property, Plant and Equipment	$	17,022	$	9,729	$	26,751

Property, plant and equipment as of December 31, 2019, consisted of:


As of December 31, 2019	Regulated		Nonregulated		Total
(Millions)
Electric generation, distribution, transmission and other	$	15,092	$	12,360	$	27,452
Natural gas transportation, distribution and other	4,373		13		4,386
Other common operating property	—		258		258
Total Property, Plant and Equipment in Service	19,465		12,631		32,096
Total accumulated depreciation	(4,968)		(4,090)		(9,058)
Total Net Property, Plant and Equipment in Service	14,497		8,541		23,038
Construction work in progress	1,271		887		2,158
Total Property, Plant and Equipment	$	15,768	$	9,428	$	25,196

Capitalized interest costs were $51 million, $51 million and $26 million for the years ended December 31, 2020, 2019 and 2018, respectively. Accrued liabilities for property, plant and equipment additions were $285 million, $357 million and $154 million as of December 31, 2020, 2019 and 2018, respectively.

We impaired or wrote off amounts of $7 million, $11 million and $0 for the years ended December 31, 2020, 2019 and 2018, respectively, resulting from reassessment of the economic feasibility of our various Renewables development projects under construction.

Depreciation expense for the years ended December 31, 2020, 2019 and 2018, amounted to $973 million, $918 million and $840 million, respectively.