Property, Plant and Equipment, Net (Tables)

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



	Depreciable
	Life	2017			2016
Regulated assets:
Utility generation, transmission and distribution systems	5-80 years	$	74,660		$	71,536
Interstate natural gas pipeline assets	3-80 years	7,176			6,942
		81,836			78,478
Accumulated depreciation and amortization		(24,478		)	(23,603		)
Regulated assets, net		57,358			54,875

Nonregulated assets:
Independent power plants	5-30 years	6,010			5,594
Other assets	3-30 years	1,489			1,002
		7,499			6,596
Accumulated depreciation and amortization		(1,542		)	(1,060		)
Nonregulated assets, net		5,957			5,536

Net operating assets		63,315			60,411
Construction work-in-progress		2,556			2,098
Property, plant and equipment, net		$	65,871		$	62,509

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



	Depreciable Life	2017			2016

Utility plant in service:
Generation	20-70 years	$	12,107		$	11,282
Transmission	52-75 years	1,838			1,726
Electric distribution	20-75 years	3,380			3,197
Gas distribution	29-75 years	1,640			1,565
Utility plant in service		18,965			17,770
Accumulated depreciation and amortization		(5,561		)	(5,448		)
Utility plant in service, net		13,404			12,322
Nonregulated property, net:
Nonregulated property gross	20-50 years	7			7
Accumulated depreciation and amortization		(1		)	(1		)
Nonregulated property, net		6			6
		13,410			12,328
Construction work-in-progress		797			493
Property, plant and equipment, net		$	14,207		$	12,821

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	2017			2016
Utility Plant:
Generation	14 - 67 years	$	12,490		$	12,371
Transmission	58 - 75 years	6,226			6,055
Distribution	20 - 70 years	6,792			6,590
Intangible plant⁽¹⁾	5 - 62 years	937			884
Other	5 - 60 years	1,435			1,384
Utility plant in service		27,880			27,284
Accumulated depreciation and amortization		(9,366		)	(8,790		)
Utility plant in service, net		18,514			18,494
Other non-regulated, net of accumulated depreciation and amortization	45 years	11			11
Plant, net		18,525			18,505
Construction work-in-progress		678			657
Property, plant and equipment, net		$	19,203		$	19,162


(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	2017			2016
Utility plant:
Generation	30 - 55 years	$	3,707		$	4,271
Distribution	20 - 65 years	3,314			3,231
Transmission	45 - 65 years	1,860			1,846
General and intangible plant	5 - 65 years	793			738
Utility plant		9,674			10,086
Accumulated depreciation and amortization		(2,871		)	(3,205		)
Utility plant, net		6,803			6,881
Other non-regulated, net of accumulated depreciation and amortization	45 years	1			2
Plant, net		6,804			6,883
Construction work-in-progress		73			114
Property, plant and equipment, net		$	6,877		$	6,997

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



	Depreciable Life	2017			2016
Utility plant:
Electric generation	25 - 60 years	$	1,144		$	1,137
Electric distribution	20 - 100 years	1,459			1,417
Electric transmission	50 - 100 years	786			771
Electric general and intangible plant	5 - 70 years	181			164
Natural gas distribution	35 - 70 years	390			381
Natural gas general and intangible plant	5 - 70 years	14			15
Common general	5 - 70 years	294			267
Utility plant		4,268			4,152
Accumulated depreciation and amortization		(1,513		)	(1,442		)
Utility plant, net		2,755			2,710
Other non-regulated, net of accumulated depreciation and amortization	70 years	5			5
Plant, net		2,760			2,715
Construction work-in-progress		132			107
Property, plant and equipment, net		$	2,892		$	2,822