Property, Plant and Equipment, Net (Tables)

Property, plant and equipment, net consists of the following as of December 31 (in millions):



	Depreciable
	Life	2018			2017
Regulated assets:
Utility generation, transmission and distribution systems	5-80 years	$	77,288		$	74,660
Interstate natural gas pipeline assets	3-80 years	7,524			7,176
		84,812			81,836
Accumulated depreciation and amortization		(26,010		)	(24,478		)
Regulated assets, net		58,802			57,358

Nonregulated assets:
Independent power plants	5-30 years	6,826			6,010
Other assets	3-30 years	1,498			1,489
		8,324			7,499
Accumulated depreciation and amortization		(1,641		)	(1,542		)
Nonregulated assets, net		6,683			5,957

Net operating assets		65,485			63,315
Construction work-in-progress		3,110			2,556
Property, plant and equipment, net		$	68,595		$	65,871

Property, plant and equipment, net consists of the following as of December 31 (in millions):



	Depreciable Life	2018			2017

Utility plant in service:
Generation	20-70 years	$	13,727		$	12,107
Transmission	52-75 years	1,934			1,838
Electric distribution	20-75 years	3,672			3,380
Natural gas distribution	29-75 years	1,726			1,640
Utility plant in service		21,059			18,965
Accumulated depreciation and amortization		(5,941		)	(5,561		)
Utility plant in service, net		15,118			13,404
Nonregulated property, net:
Nonregulated property gross	20-50 years	7			7
Accumulated depreciation and amortization		(1		)	(1		)
Nonregulated property, net		6			6
		15,124			13,410
Construction work-in-progress		1,035			797
Property, plant and equipment, net		$	16,159		$	14,207

The average depreciation and amortization rates applied to depreciable utility plant for the years ended December 31 were as follows:

Property, plant and equipment, net consists of the following as of December 31 (in millions):



	Depreciable Life	2018			2017
Utility Plant:
Generation	14 - 67 years	$	12,606		$	12,490
Transmission	58 - 75 years	6,357			6,226
Distribution	20 - 70 years	7,030			6,792
Intangible plant⁽¹⁾	5 - 75 years	970			937
Other	5 - 60 years	1,483			1,435
Utility plant in service		28,446			27,880
Accumulated depreciation and amortization		(10,060		)	(9,366		)
Utility plant in service, net		18,386			18,514
Other non-regulated, net of accumulated depreciation and amortization	47 years	10			11
Plant, net		18,396			18,525
Construction work-in-progress		1,195			678
Property, plant and equipment, net		$	19,591		$	19,203


(1)	Computer software costs included in intangible plant are initially assigned a depreciable life of 5 to 10 years.

Property, plant and equipment, net consists of the following as of December 31 (in millions):



	Depreciable Life	2018			2017
Utility plant:
Generation	30 - 55 years	$	3,720		$	3,707
Distribution	20 - 65 years	3,411			3,314
Transmission	45 - 70 years	1,867			1,860
General and intangible plant	5 - 65 years	848			793
Utility plant		9,846			9,674
Accumulated depreciation and amortization		(3,076		)	(2,871		)
Utility plant, net		6,770			6,803
Other non-regulated, net of accumulated depreciation and amortization	45 years	1			1
Plant, net		6,771			6,804
Construction work-in-progress		97			73
Property, plant and equipment, net		$	6,868		$	6,877

Property, plant and equipment, net consists of the following as of December 31 (in millions):



	Depreciable Life	2018			2017
Utility plant:
Electric generation	25 - 60 years	$	1,144		$	1,144
Electric distribution	20 - 100 years	1,568			1,459
Electric transmission	50 - 100 years	835			786
Electric general and intangible plant	5 - 70 years	197			181
Natural gas distribution	35 - 70 years	403			390
Natural gas general and intangible plant	5 - 70 years	14			14
Common general	5 - 70 years	321			294
Utility plant		4,482			4,268
Accumulated depreciation and amortization		(1,593		)	(1,513		)
Utility plant, net		2,889			2,755
Other non-regulated, net of accumulated depreciation and amortization	70 years	5			5
Plant, net		2,894			2,760
Construction work-in-progress		90			132
Property, plant and equipment, net		$	2,984		$	2,892