PROPERTY, PLANT AND EQUIPMENT

The following table summarizes the components of the electric generation and distribution assets and other property, plant and equipment with their estimated useful lives. The amounts are stated net of impairment losses recognized as further discussed in Note 21—Asset Impairment Expense.



	Estimated Useful Life	December 31,
	Estimated Useful Life	2013			2012
	(in years)	(in millions)
Electric generation and distribution facilities	6 - 68	$	27,619		$	26,385
Other buildings	5 - 50	1,726			2,616
Furniture, fixtures and equipment	3 - 30	312			386
Other	1 - 46	939			891
Total electric generation and distribution assets and other		30,596			30,278
Accumulated depreciation		(9,604		)	(9,145		)
Net electric generation and distribution assets and other⁽¹⁾⁽²⁾		$	20,992		$	21,133


⁽¹⁾	Net electric generation and distribution assets and other related to the Company's held-for-sale businesses of $1.2 billion and $1.3 billion as of December 31, 2013 and 2012, respectively, were excluded from the table above and were included in the noncurrent assets of discontinued and held-for-sale businesses in the consolidated balance sheets.


⁽²⁾	Net electric generation and distribution assets, and other include unamortized internal use software costs of $133 million and $141 million as of December 31, 2013 and 2012, respectively.

The following table summarizes depreciation expense (including the amortization of assets recorded under capital leases), amortization of internal use software and interest capitalized during development and construction on qualifying assets for the years ended December 31, 2013, 2012 and 2011:



	2013		2012		2011
	(in millions)
Depreciation expense (including amortization of assets recorded under capital leases)	$	1,193	$	1,173	$	1,078
Amortization of internal use software	36		45		42
Interest capitalized during development and construction	84		88		155

Property, plant and equipment, net of accumulated depreciation, of $15 billion and $16 billion was mortgaged, pledged or subject to liens as of December 31, 2013 and 2012, respectively.

The following table summarizes regulated and non-regulated generation and distribution property, plant and equipment and accumulated depreciation as of December 31, 2013 and 2012:



	December 31,
	2013			2012
	(in millions)
Regulated assets	$	13,031		$	13,395
Regulated accumulated depreciation	(4,732		)	(4,711		)
Regulated generation, distribution assets and other, net	8,299			8,684
Non-regulated assets	17,565			16,883
Non-regulated accumulated depreciation	(4,872		)	(4,434		)
Non-regulated generation, distribution assets and other, net	12,693			12,449
Net electric generation and distribution assets and other	$	20,992		$	21,133

The following table summarizes the amounts recognized, which were related to asset retirement obligations, for the years ended December 31, 2013 and 2012:



	2013			2012
	(in millions)
Balance at January 1	$	120		$	110
Additional liabilities incurred	1			3
Liabilities settled	(4		)	(3		)
Accretion expense	9			6
Change in estimated cash flows	16			3
Translation adjustments	—			1
Balance at December 31	$	142		$	120

The Company’s asset retirement obligations covered by the relevant guidance primarily include active ash landfills, water treatment basins and the removal or dismantlement of certain plants and equipment. There were no legally restricted assets for purposes of settling asset retirement obligations for the years ended December 31, 2013 and 2012.

Ownership of Coal-Fired Facilities

DP&L has undivided ownership interests in seven coal-fired generation facilities jointly owned with other utilities. As of December 31, 2013, DP&L had $24 million of construction work in process at such facilities. DP&L’s share of the operating costs of such facilities is included in Cost of Sales in the Consolidated Statement of Operations and its share of investment in the facilities is included in Property, Plant and Equipment in the Consolidated Balance Sheet. DP&L’s undivided ownership interest in such facilities at December 31, 2013 is as follows:



	DP&L Share			DP&L Investment
	Ownership		Production Capacity (MW)	Gross Plant In Service		Accumulated Depreciation		Construction Work In Process
				($ in millions)
Production units:
Beckjord Unit 6	50	%	207	$	2	$	1	$	—
Conesville Unit 4	17	%	129	24		—		—
East Bend Station	31	%	186	12		5		—
Killen Station	67	%	402	306		9		4
Miami Fort Units 7 and 8	36	%	368	212		13		1
Stuart Station	35	%	808	205		12		16
Zimmer Station	28	%	365	177		25		3
Transmission	various		—	41		4		—
Total			2,465	$	979	$	69	$	24