PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION

Utility property, plant and equipment is recorded at original cost. Original cost includes materials, labor, construction overheads and AFUDC for regulated property. The cost of repairs and maintenance is charged to Operations and Maintenance expense as incurred.

The following tables summarize property, plant and equipment by asset category:



Eversource	As of December 31,
(Millions of Dollars)	2018			2017
Distribution - Electric	$	15,071.1		$	14,410.5
Distribution - Natural Gas	3,546.2			3,244.2
Transmission - Electric	10,153.9			9,270.9
Distribution - Water	1,639.8			1,558.4
Solar	164.1			36.2
Utility	30,575.1			28,520.2
Other ⁽¹⁾	778.6			693.7
Property, Plant and Equipment, Gross	31,353.7			29,213.9
Less: Accumulated Depreciation
Utility	(7,126.2		)	(6,846.9		)
Other	(336.7		)	(286.9		)
Total Accumulated Depreciation	(7,462.9		)	(7,133.8		)
Property, Plant and Equipment, Net	23,890.8			22,080.1
Construction Work in Progress	1,719.6			1,537.4
Total Property, Plant and Equipment, Net	$	25,610.4		$	23,617.5



	As of December 31,
	2018									2017
(Millions of Dollars)	CL&P			NSTAR Electric			PSNH			CL&P			NSTAR Electric			PSNH
Distribution - Electric	$	6,176.4		$	6,756.4		$	2,178.6		$	5,888.3		$	6,479.0		$	2,083.4
Transmission - Electric	4,700.5			4,065.9			1,338.7			4,239.9			3,821.2			1,161.3
Solar	—			164.1			—			—			36.2			—
Property, Plant and Equipment, Gross	10,876.9			10,986.4			3,517.3			10,128.2			10,336.4			3,244.7
Less: Accumulated Depreciation	(2,302.6		)	(2,702.0		)	(772.9		)	(2,239.0		)	(2,550.2		)	(751.8		)
Property, Plant and Equipment, Net	8,574.3			8,284.4			2,744.4			7,889.2			7,786.2			2,492.9
Construction Work in Progress	335.4			510.3			135.7			381.8			460.3			149.4
Total Property, Plant and Equipment, Net	$	8,909.7		$	8,794.7		$	2,880.1		$	8,271.0		$	8,246.5		$	2,642.3


⁽¹⁾	These assets are primarily comprised of building improvements, computer software, hardware and equipment at Eversource Service.

Depreciation of utility assets is calculated on a straight-line basis using composite rates based on the estimated remaining useful lives of the various classes of property (estimated useful life for PSNH distribution and the water utilities). The composite rates, which are subject to approval by the appropriate state regulatory agency, include a cost of removal component, which is collected from customers over the lives of the plant assets and is recognized as a regulatory liability. Depreciation rates are applied to property from the time it is placed in service.

Upon retirement from service, the cost of the utility asset is charged to the accumulated provision for depreciation. The actual incurred removal costs are applied against the related regulatory liability.

The depreciation rates for the various classes of utility property, plant and equipment aggregate to composite rates as follows:



(Percent)	2018		2017		2016
Eversource	2.9	%	3.0	%	3.0	%
CL&P	2.8	%	2.8	%	2.7	%
NSTAR Electric	2.8	%	2.9	%	2.9	%
PSNH	2.8	%	3.1	%	3.1	%

The following table summarizes average remaining useful lives of depreciable assets:



	As of December 31, 2018
(Years)	Eversource	CL&P	NSTAR Electric	PSNH
Distribution - Electric	34.1	35.4	33.7	32.3
Distribution - Natural Gas	43.8	—	—	—
Transmission - Electric	41.3	38.0	45.3	42.9
Distribution - Water	33.3	—	—	—
Solar	24.9	—	24.9	—
Other	12.9	—	—	—