Property, Plant and Equipment

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment [Text Block]

Property, Plant and Equipment

(a) Property, Plant and Equipment

Property, plant and equipment includes the following:



	Weighted Average Useful	December 31,
	Lives (in years)	2017		2016
		(in millions)
Transmission	45	$	2,767	$	2,402
Distribution	30	7,178		6,965
Other	15	1,551		1,473
Total		11,496		10,840
Accumulated depreciation		3,633		3,443
Property, plant and equipment, net		$	7,863	$	7,397

(b) Depreciation and Amortization

The following table presents depreciation and amortization expense for 2017, 2016 and 2015:



	Year Ended December 31,
	2017		2016		2015
	(in millions)
Depreciation expense	$	354	$	349	$	316
Amortization of securitized regulatory assets	329		455		365
Other amortization	41		34		24
Total depreciation and amortization	$	724	$	838	$	705

A reconciliation of the changes in the ARO liability is as follows:



	December 31,
	2017		2016
	(in millions)
Beginning balance	$	33	$	37
Accretion expense	1		1
Revisions in estimates of cash flows	1		(5		)
Ending balance	$	35	$	33

Houston Electric recorded AROs associated with the removal of asbestos and asbestos-containing material in its buildings, including substation building structures. Houston Electric also recorded AROs relating to treated wood poles for electric distribution, distribution transformers containing PCB (also known as Polychlorinated Biphenyl), and underground fuel storage tanks. The estimates of future liabilities were developed using historical information, and where available, quoted prices from outside contractors.

The increase of $1 million in the ARO from the revision in estimates in 2017 is primarily attributable to an increase in disposal costs for distribution poles, transformers and underground fuel storage tanks. There were no material additions or settlements during the years ended December 31, 2017 and 2016.