Property, Plant and Equipment

SCE's property, plant and equipment included in the consolidated balance sheets is composed of the following:



	December 31,
(in millions)	2018			2017
Distribution	$	25,026		$	23,633
Transmission	13,800			13,127
Generation	3,598			3,468
General plant and other	4,398			4,534
Accumulated depreciation	(9,566		)	(9,355		)
	37,256			35,407
Construction work in progress	3,883			3,175
Nuclear fuel, at amortized cost	130			126
Total utility property, plant and equipment	$	41,269		$	38,708

Capitalized Software Costs

SCE capitalizes costs incurred during the application development stage of internal use software projects to property, plant, and equipment. SCE amortizes capitalized software costs ratably over the expected lives of the software, primarily ranging from 5 to 7 years and commencing upon operational use. Capitalized software costs, included in general plant and other above, were $1.0 billion and $1.1 billion at December 31, 2018 and 2017, respectively, and accumulated amortization was $0.5 billion and $0.6 billion, at December 31, 2018 and 2017, respectively. Amortization expense for capitalized software was $198 million, $233 million and $249 million in 2018, 2017 and 2016, respectively. At December 31, 2018, amortization expense is estimated to be $180 million, $145 million, $107 million, $59 million and $20 million for 2019 through 2023, respectively.

Jointly Owned Utility Projects

SCE owns undivided interests in several generating assets for which each participant provides its own financing. SCE's proportionate share of these assets is reflected in the consolidated balance sheets and included in the above table. SCE's proportionate share of expenses for each project is reflected in the consolidated statements of income.

The following is SCE's investment in each asset as of December 31, 2018:



(in millions)	Plant in Service		Construction Work in Progress		Accumulated Depreciation		Nuclear Fuel (at amortized cost)		Net Book Value		Ownership Interest
Transmission systems:
Eldorado	$	245	$	13	$	29	$	—	$	229	59	%
Pacific Intertie	217		73		75		—		215		50	%
Generating station:
Palo Verde (nuclear)	2,024		63		1,567		130		650		16	%
Total	$	2,486	$	149	$	1,671	$	130	$	1,094

In addition, SCE has ownership interests in jointly owned power poles with other companies.