Property, Plant, and Equipment

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Plant, and Equipment

PROPERTY, PLANT, AND EQUIPMENT

The following is a summary of Property, plant, and equipment by classification as of December 31:

	2018			2017
Property, plant, and equipment	(In millions)
DTE Electric
Generation	$	11,027		$	12,166
Distribution	9,153			8,637
Other	2,567			2,169
Total DTE Electric	22,747			22,972
DTE Gas
Distribution	3,823			3,523
Storage	548			533
Transmission and other	1,204			1,118
Total DTE Gas	5,575			5,174
Non-utility and other	3,488			3,278
Total DTE Energy	31,810			31,424
Accumulated depreciation and amortization
DTE Electric
Generation	(3,609		)	(4,403		)
Distribution	(2,974		)	(2,914		)
Other	(727		)	(667		)
Total DTE Electric	(7,310		)	(7,984		)
DTE Gas
Distribution	(1,283		)	(1,238		)
Storage	(165		)	(159		)
Transmission and other	(404		)	(384		)
Total DTE Gas	(1,852		)	(1,781		)
Non-utility and other	(998		)	(938		)
Total DTE Energy	(10,160		)	(10,703		)
Net DTE Energy Property, plant, and equipment	$	21,650		$	20,721
Net DTE Electric Property, plant, and equipment	$	15,437		$	14,988

The following is a summary of the Registrants' AFUDC and interest capitalized for the years ended December 31:

	DTE Energy				DTE Electric
	2018		2017		2018		2017
	(In millions)
Allowance for debt funds used during construction and interest capitalized	$	15	$	13	$	9	$	8
Allowance for equity funds used during construction	28		23		19		18
Total	$	43	$	36	$	28	$	26

The composite depreciation rate for DTE Electric was approximately 3.7%, 3.6%, and 3.5% in 2018, 2017 and 2016, respectively. The composite depreciation rate for DTE Gas was 2.7%, in 2018 and 2017, and 2.4% in 2016. The average estimated useful life for each major class of utility Property, plant, and equipment as of December 31, 2018 follows:

	Estimated Useful Lives in Years
Utility	Generation	Distribution	Storage
DTE Electric	40	41	N/A
DTE Gas	N/A	50	53

The estimated useful lives for DTE Electric's Other utility assets range from 3 to 62 years, while the estimated useful lives for DTE Gas' Transmission and other utility assets range from 5 to 70 years. The estimated useful lives for major classes of DTE Energy's non-utility assets and facilities range from 3 to 83 years.

The following is a summary of Depreciation and amortization expense for DTE Energy:

	2018		2017		2016
	(In millions)
Property, plant, and equipment	$	912	$	865	$	783
Regulatory assets and liabilities	212		165		193
	$	1,124	$	1,030	$	976

The following is a summary of Depreciation and amortization expense for DTE Electric:

	2018		2017		2016
	(In millions)
Property, plant, and equipment	$	657	$	620	$	582
Regulatory assets and liabilities	179		133		168
	$	836	$	753	$	750

Capitalized software costs are classified as Property, plant, and equipment and the related amortization is included in accumulated depreciation and amortization on the Registrants' Consolidated Financial Statements. The Registrants capitalize the costs associated with computer software developed or obtained for use in their businesses. The Registrants amortize capitalized software costs on a straight-line basis over the expected period of benefit, ranging from 1 to 15 years for DTE Energy and 3 to 15 years for DTE Electric.

The following balances for capitalized software relate to DTE Energy:

	Year Ended December 31,
	2018		2017		2016
	(In millions)
Amortization expense of capitalized software	$	108	$	101	$	89
Gross carrying value of capitalized software	$	905	$	890
Accumulated amortization of capitalized software	$	534	$	500

The following balances for capitalized software relate to DTE Electric:

	Year Ended December 31,
	2018		2017		2016
	(In millions)
Amortization expense of capitalized software	$	101	$	93	$	83
Gross carrying value of capitalized software	$	799	$	774
Accumulated amortization of capitalized software	$	463	$	423

DTE Energy is the lessor under certain operating leases for energy facilities and related equipment. Property under operating leases for DTE Energy is as follows:

	DTE Energy
	2018		2017
	(In millions)
Gross property under operating leases	$	447	$	327
Accumulated amortization of property under operating leases	$	148	$	108

The Registrants are the lessee under certain capital leases related to software and information technology related equipment. Property under capital leases for the Registrants is as follows:

	DTE Energy				DTE Electric
	2018		2017		2018		2017
	(In millions)
Gross property under capital leases	$	18	$	44	$	18	$	18
Accumulated amortization of property under capital leases	$	7	$	38	$	7	$	12