Property, Plant and Equipment

12 Months Ended

Dec. 31, 2015

Property, Plant and Equipment [Abstract]

(a) Property, Plant and Equipment

Property, plant and equipment includes the following:



	Weighted Average Useful	December 31,
	Lives (Years)	2015		2014
		(in millions)
Transmission	41	$	2,196	$	2,057
Distribution	30	6,556		6,170
Other	16	1,390		1,166
Total		10,142		9,393
Accumulated depreciation		3,209		3,050
Property, plant and equipment, net		$	6,933	$	6,343

(b) Depreciation and Amortization

The following table presents depreciation and amortization expense for 2015, 2014 and 2013:



	Year Ended December 31,
	2015		2014		2013
	(in millions)
Depreciation expense	$	316	$	295	$	280
Amortization of securitized regulatory assets	365		441		383
Other amortization	24		32		22
Total depreciation and amortization	$	705	$	768	$	685

A reconciliation of the changes in the asset retirement obligation (ARO) liability is as follows:



	December 31,
	2015		2014
	(in millions)
Beginning balance	$	36	$	33
Accretion expense	1		1
Revisions in estimates of cash flows	—		2
Ending balance	$	37	$	36

CenterPoint Houston recorded AROs associated with the removal of asbestos and asbestos-containing material in its buildings, including substation building structures. CenterPoint Houston 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 $2 million in the ARO from the revision of estimate in 2014 is primarily attributable to an increase in the expected future cash flows for asbestos remediation. There were no material additions or settlements during the years ended December 31, 2015 and 2014.