ASSET RETIREMENT OBLIGATIONS

Eversource, including CL&P, NSTAR Electric, PSNH and WMECO, recognizes a liability for the fair value of an ARO on the obligation date if the liability's fair value can be reasonably estimated and is conditional on a future event. Settlement dates and future costs are reasonably estimated when sufficient information becomes available. Management has identified various categories of AROs, primarily certain assets containing asbestos and hazardous contamination, and has performed fair value calculations reflecting expected probabilities for settlement scenarios.

The fair value of an ARO is recorded as a liability in Other Long-Term Liabilities with a corresponding amount included in Property, Plant and Equipment, Net on the balance sheets. The ARO assets are depreciated, and the ARO liabilities are accreted over the estimated life of the obligation and the corresponding credits are recorded as accumulated depreciation and ARO liabilities, respectively. As the Regulated companies are rate-regulated on a cost-of-service basis, these companies apply regulatory accounting guidance and both the depreciation and accretion costs associated with the Regulated companies' AROs are recorded as increases to Regulatory Assets on the balance sheets.

A reconciliation of the beginning and ending carrying amounts of ARO liabilities are as follows:



Eversource (Millions of Dollars)	As of December 31,
Eversource (Millions of Dollars)	2016			2015
Balance as of Beginning of Year	$	430.1		$	426.3
Liabilities Incurred During the Year	1.3			6.6
Liabilities Settled During the Year	(19.0		)	(18.2		)
Accretion	22.9			26.5
Revisions in Estimated Cash Flows	(8.9		)	(11.1		)
Balance as of End of Year	$	426.4		$	430.1



	As of December 31,
	2016										2015
(Millions of Dollars)	CL&P		NSTAR Electric			PSNH		WMECO			CL&P			NSTAR Electric			PSNH			WMECO
Balance as of Beginning of Year	$	33.8	$	35.3		$	21.6	$	5.7		$	35.3		$	34.3		$	20.6		$	5.9
Liabilities Incurred During the Year	—		—			0.5		—			—			6.2			0.4			—
Liabilities Settled During the Year	—		(0.3		)	—		(0.1		)	—			(1.5		)	—			(0.1		)
Accretion	2.2		1.7			1.4		0.3			2.2			1.8			1.3			0.4
Revisions in Estimated Cash Flows	—		—			—		—			(3.7		)	(5.5		)	(0.7		)	(0.5		)
Balance as of End of Year	$	36.0	$	36.7		$	23.5	$	5.9		$	33.8		$	35.3		$	21.6		$	5.7

Eversource's amounts include CYAPC and YAEC's AROs of $308.6 million and $319.1 million as of December 31, 2016 and 2015, respectively. The fair value of the ARO for CYAPC and YAEC includes uncertainties of the fuel off-load dates related to the DOE's timing of performance regarding its obligation to dispose of the spent nuclear fuel and high level waste. The incremental asset recorded as an offset to the ARO liability was fully depreciated since the plants have no remaining useful life. Any changes in the assumptions used to calculate the fair value of the ARO liability are recorded with a corresponding offset to the related regulatory asset. The assets held in the CYAPC and YAEC nuclear decommissioning trusts are restricted for settling the ARO and all other decommissioning obligations. For further information on the assets held in the nuclear decommissioning trusts, see Note 5, "Marketable Securities," to the financial statements.