NSTAR Electric Company PFD 4.25% (NSARP) 10-Q 6 Aug 21 2021 Q2 Quarterly report Financial data

COVER PAGE

COVER PAGE - shares	6 Months Ended
	Jun. 30, 2021	Jul. 31, 2021
Document And Entity [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity Registrant Name	EVERSOURCE ENERGY
Entity Incorporation, State or Country Code	MA
Entity Address, Address Line One	300 Cadwell Drive
Entity Address, City or Town	Springfield
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01104
City Area Code	800
Local Phone Number	286-5000
Entity File Number	001-05324
Entity Tax Identification Number	04-2147929
Title of 12(b) Security	Common Shares, $5.00 par value per share
Trading Symbol	ES
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Smaller Reporting Company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		343,643,255
Entity Central Index Key	0000072741
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false
The Connecticut Light and Power Company
Document And Entity [Line Items]
Entity Registrant Name	THE CONNECTICUT LIGHT AND POWER COMPANY
Entity Incorporation, State or Country Code	CT
Entity Address, Address Line One	107 Selden Street
Entity Address, City or Town	Berlin
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06037-1616
City Area Code	800
Local Phone Number	286-5000
Entity File Number	000-00404
Entity Tax Identification Number	06-0303850
Entity Filer Category	Non-accelerated Filer
Entity Smaller Reporting Company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		6,035,205
Entity Central Index Key	0000023426
Current Fiscal Year End Date	--12-31
NSTAR Electric Company
Document And Entity [Line Items]
Entity Registrant Name	NSTAR ELECTRIC COMPANY
Entity Incorporation, State or Country Code	MA
Entity Address, Address Line One	800 Boylston Street
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02199
City Area Code	800
Local Phone Number	286-5000
Entity File Number	001-02301
Entity Tax Identification Number	04-1278810
Entity Filer Category	Non-accelerated Filer
Entity Smaller Reporting Company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		200
Entity Central Index Key	0000013372
Current Fiscal Year End Date	--12-31
Public Service Company of New Hampshire
Document And Entity [Line Items]
Entity Registrant Name	PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE
Entity Incorporation, State or Country Code	NH
Entity Address, Address Line One	Energy Park
Entity Address, Address Line Two	780 North Commercial Street
Entity Address, City or Town	Manchester
Entity Address, State or Province	NH
Entity Address, Postal Zip Code	03101-1134
City Area Code	800
Local Phone Number	286-5000
Entity File Number	001-06392
Entity Tax Identification Number	02-0181050
Entity Filer Category	Non-accelerated Filer
Entity Smaller Reporting Company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		301
Entity Central Index Key	0000315256
Current Fiscal Year End Date	--12-31

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current Assets:
Cash	$ 217,397	$ 106,599
Receivables, Net (net of allowance for uncollectible accounts)	1,224,092	1,195,925
Unbilled Revenues	188,356	233,025
Fuel, Materials, Supplies and REC Inventory	187,692	265,599
Regulatory Assets	1,186,851	1,076,556
Prepayments and Other Current Assets	264,451	252,439
Total Current Assets	3,268,839	3,130,143
Property, Plant and Equipment, Net	31,878,551	30,882,523
Deferred Debits and Other Assets:
Regulatory Assets	5,246,381	5,493,330
Goodwill	4,453,618	4,445,988
Investments in Unconsolidated Affiliates	1,205,303	1,107,143
Marketable Securities	462,953	456,617
Other Long-Term Assets	718,995	583,854
Total Deferred Debits and Other Assets	12,087,250	12,086,932
Total Assets	47,234,640	46,099,598
Current Liabilities:
Notes Payable	2,002,500	1,249,325
Long-Term Debt – Current Portion	799,858	1,053,186
Rate Reduction Bonds – Current Portion	43,210	43,210
Accounts Payable	1,061,111	1,370,647
Regulatory Liabilities	532,467	389,430
Other Current Liabilities	665,424	809,214
Total Current Liabilities	5,104,570	4,915,012
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	4,258,986	4,095,339
Regulatory Liabilities	3,880,131	3,850,781
Derivative Liabilities	275,775	294,535
Asset Retirement Obligations	503,405	499,713
Accrued Pension, SERP and PBOP	1,455,479	1,653,788
Other Long-Term Liabilities	962,166	948,506
Total Deferred Credits and Other Liabilities	11,335,942	11,342,662
Long-Term Debt	15,851,362	15,125,876
Rate Reduction Bonds	475,307	496,912
Noncontrolling Interest – Preferred Stock of Subsidiaries	155,570	155,570
Common Shareholders' Equity:
Common Shares	1,789,092	1,789,092
Capital Surplus, Paid In	8,032,959	8,015,663
Retained Earnings	4,830,058	4,613,201
Accumulated Other Comprehensive Income (Loss)	(74,342)	(76,411)
Treasury Stock	(265,878)	(277,979)
Common Shareholders' Equity	14,311,889	14,063,566
Commitments and Contingencies (Note 9)
Total Liabilities and Capitalization	47,234,640	46,099,598
The Connecticut Light and Power Company
Current Assets:
Cash	198,390	90,801
Receivables, Net (net of allowance for uncollectible accounts)	496,612	459,214
Accounts Receivable from Affiliated Companies	38,840	17,486
Unbilled Revenues	58,191	57,407
Fuel, Materials, Supplies and REC Inventory	51,947	57,924
Regulatory Assets	458,609	345,622
Prepayments and Other Current Assets	44,357	83,950
Total Current Assets	1,346,946	1,112,404
Property, Plant and Equipment, Net	10,479,192	10,234,556
Deferred Debits and Other Assets:
Regulatory Assets	1,745,793	1,866,152
Other Long-Term Assets	273,279	242,862
Total Deferred Debits and Other Assets	2,019,072	2,109,014
Total Assets	13,845,210	13,455,974
Current Liabilities:
Accounts Payable	290,413	451,240
Accounts Payable to Affiliated Companies	97,558	51,118
Obligations to Third Party Suppliers	46,898	49,967
Regulatory Liabilities	219,813	137,166
Derivative Liabilities	70,935	68,767
Other Current Liabilities	104,670	102,060
Total Current Liabilities	830,287	860,318
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,460,962	1,408,343
Regulatory Liabilities	1,207,289	1,204,942
Derivative Liabilities	275,775	294,535
Accrued Pension, SERP and PBOP	364,990	478,325
Other Long-Term Liabilities	138,337	133,690
Total Deferred Credits and Other Liabilities	3,447,353	3,519,835
Long-Term Debt	4,335,639	3,914,835
Noncontrolling Interest – Preferred Stock of Subsidiaries	116,200	116,200
Common Shareholders' Equity:
Common Shares	60,352	60,352
Capital Surplus, Paid In	2,810,765	2,810,765
Retained Earnings	2,244,341	2,173,367
Accumulated Other Comprehensive Income (Loss)	273	302
Common Shareholders' Equity	5,115,731	5,044,786
Commitments and Contingencies (Note 9)
Total Liabilities and Capitalization	13,845,210	13,455,974
NSTAR Electric Company
Current Assets:
Cash	577	102
Receivables, Net (net of allowance for uncollectible accounts)	445,853	403,045
Accounts Receivable from Affiliated Companies	21,455	30,095
Unbilled Revenues	47,689	38,342
Fuel, Materials, Supplies and REC Inventory	74,638	133,894
Taxes Receivable	6,814	65,051
Regulatory Assets	448,030	399,882
Prepayments and Other Current Assets	24,494	21,833
Total Current Assets	1,069,550	1,092,244
Property, Plant and Equipment, Net	10,437,198	10,123,062
Deferred Debits and Other Assets:
Regulatory Assets	1,236,379	1,304,019
Prepaid PBOP	216,692	204,138
Other Long-Term Assets	173,815	162,836
Total Deferred Debits and Other Assets	1,626,886	1,670,993
Total Assets	13,133,634	12,886,299
Current Liabilities:
Notes Payable	555,500	195,000
Notes Payable to Eversource Parent	21,500	21,300
Long-Term Debt – Current Portion	0	250,000
Accounts Payable	308,106	383,558
Accounts Payable to Affiliated Companies	90,385	95,703
Obligations to Third Party Suppliers	122,760	98,572
Renewable Portfolio Standards Compliance Obligations	47,041	127,536
Regulatory Liabilities	172,988	164,761
Other Current Liabilities	49,826	72,118
Total Current Liabilities	1,368,106	1,408,548
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	1,504,188	1,459,906
Regulatory Liabilities	1,552,053	1,550,390
Accrued Pension, SERP and PBOP	127,248	172,571
Other Long-Term Liabilities	348,504	337,245
Total Deferred Credits and Other Liabilities	3,531,993	3,520,112
Long-Term Debt	3,688,259	3,393,221
Noncontrolling Interest – Preferred Stock of Subsidiaries	43,000	43,000
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	2,053,942	1,993,942
Retained Earnings	2,447,823	2,527,167
Accumulated Other Comprehensive Income (Loss)	511	309
Common Shareholders' Equity	4,502,276	4,521,418
Commitments and Contingencies (Note 9)
Total Liabilities and Capitalization	13,133,634	12,886,299
Public Service Company of New Hampshire
Current Assets:
Cash	279	141
Receivables, Net (net of allowance for uncollectible accounts)	119,138	119,899
Accounts Receivable from Affiliated Companies	7,274	10,925
Unbilled Revenues	51,150	46,041
Fuel, Materials, Supplies and REC Inventory	23,333	26,829
Regulatory Assets	99,474	115,852
Prepaid Property Taxes	18,527	26,257
Special Deposits	35,109	36,767
Prepayments and Other Current Assets	5,215	10,788
Total Current Assets	359,499	393,499
Property, Plant and Equipment, Net	3,467,810	3,374,270
Deferred Debits and Other Assets:
Regulatory Assets	850,912	873,203
Other Long-Term Assets	21,492	23,733
Total Deferred Debits and Other Assets	872,404	896,936
Total Assets	4,699,713	4,664,705
Current Liabilities:
Notes Payable to Eversource Parent	48,600	46,300
Long-Term Debt – Current Portion	0	282,000
Rate Reduction Bonds – Current Portion	43,210	43,210
Accounts Payable	122,068	132,635
Accounts Payable to Affiliated Companies	28,191	43,397
Regulatory Liabilities	61,891	58,756
Other Current Liabilities	46,984	58,487
Total Current Liabilities	350,944	664,785
Deferred Credits and Other Liabilities:
Accumulated Deferred Income Taxes	546,568	537,627
Regulatory Liabilities	384,675	383,183
Accrued Pension, SERP and PBOP	169,001	184,715
Other Long-Term Liabilities	37,523	37,874
Total Deferred Credits and Other Liabilities	1,137,767	1,143,399
Long-Term Debt	1,163,710	817,070
Rate Reduction Bonds	475,307	496,912
Common Shareholders' Equity:
Common Shares	0	0
Capital Surplus, Paid In	1,088,134	928,134
Retained Earnings	483,927	615,018
Accumulated Other Comprehensive Income (Loss)	(76)	(613)
Common Shareholders' Equity	1,571,985	1,542,539
Commitments and Contingencies (Note 9)
Total Liabilities and Capitalization	$ 4,699,713	$ 4,664,705

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Allowance for uncollectible accounts	$ 425,769	$ 358,851
The Connecticut Light and Power Company
Allowance for uncollectible accounts	188,760	157,447
NSTAR Electric Company
Allowance for uncollectible accounts	98,031	91,583
Public Service Company of New Hampshire
Allowance for uncollectible accounts	$ 17,223	$ 17,157

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating Revenues	$ 2,122,538	$ 1,953,128	$ 4,948,378	$ 4,326,854
Operating Expenses:
Purchased Power, Fuel and Transmission	650,087	630,132	1,648,578	1,506,703
Operations and Maintenance	411,147	332,055	876,689	674,117
Depreciation	274,647	240,516	545,352	476,727
Amortization	5,611	23,397	113,624	73,172
Energy Efficiency Programs	128,955	115,354	317,018	263,747
Taxes Other Than Income Taxes	200,486	178,019	409,944	359,613
Total Operating Expenses	1,670,933	1,519,473	3,911,205	3,354,079
Operating Income, Net	451,605	433,655	1,037,173	972,775
Interest Expense	145,435	134,285	283,201	269,000
Other Income, Net	46,619	30,243	80,820	54,347
Income Before Income Tax Expense	352,789	329,613	834,792	758,122
Income Tax Expense	86,389	75,501	200,370	167,379
Net Income	266,400	254,112	634,422	590,743
Net Income Attributable to Noncontrolling Interests	1,880	1,880	3,759	3,759
Net Income Attributable to Common Shareholders	$ 264,520	$ 252,232	$ 630,663	$ 586,984
Basic Earnings Per Common Share (in dollars per share)	$ 0.77	$ 0.75	$ 1.83	$ 1.75
Diluted Earnings Per Common Share (in dollars per share)	$ 0.77	$ 0.75	$ 1.83	$ 1.75
Weighted Average Common Shares Outstanding:
Basic (in shares)	343,844,626	337,946,663	343,761,435	334,524,452
Diluted (in shares)	344,435,696	338,561,649	344,385,193	335,749,404
The Connecticut Light and Power Company
Operating Revenues	$ 829,597	$ 817,421	$ 1,816,871	$ 1,717,124
Operating Expenses:
Purchased Power, Fuel and Transmission	308,137	315,398	681,411	690,115
Operations and Maintenance	152,394	134,633	327,814	270,230
Depreciation	84,423	79,718	167,828	158,152
Amortization of Regulatory (Liabilities)/Assets, Net	(15,059)	(5,698)	47,716	850
Energy Efficiency Programs	29,524	32,347	65,097	67,826
Taxes Other Than Income Taxes	83,886	79,867	175,278	162,855
Total Operating Expenses	643,305	636,265	1,465,144	1,350,028
Operating Income, Net	186,292	181,156	351,727	367,096
Interest Expense	42,614	38,722	81,592	76,605
Other Income, Net	9,879	8,459	14,787	10,357
Income Before Income Tax Expense	153,557	150,893	284,922	300,848
Income Tax Expense	38,001	33,622	70,967	64,839
Net Income	115,556	117,271	213,955	236,009
NSTAR Electric Company
Operating Revenues	687,375	660,971	1,424,418	1,394,804
Operating Expenses:
Purchased Power, Fuel and Transmission	191,137	192,304	417,615	434,742
Operations and Maintenance	136,356	115,831	279,576	238,149
Depreciation	83,917	79,520	166,710	157,865
Amortization of Regulatory (Liabilities)/Assets, Net	(2,528)	19,604	15,890	46,612
Energy Efficiency Programs	64,273	56,756	139,373	125,423
Taxes Other Than Income Taxes	54,126	50,583	108,776	99,306
Total Operating Expenses	527,281	514,598	1,127,940	1,102,097
Operating Income, Net	160,094	146,373	296,478	292,707
Interest Expense	37,195	32,955	69,501	63,972
Other Income, Net	21,915	13,112	38,727	25,350
Income Before Income Tax Expense	144,814	126,530	265,704	254,085
Income Tax Expense	33,902	29,062	60,868	56,228
Net Income	110,912	97,468	204,836	197,857
Public Service Company of New Hampshire
Operating Revenues	278,849	255,224	572,284	531,592
Operating Expenses:
Purchased Power, Fuel and Transmission	80,513	82,560	172,122	176,698
Operations and Maintenance	56,537	54,017	111,201	101,146
Depreciation	29,825	24,750	59,293	49,084
Amortization of Regulatory (Liabilities)/Assets, Net	26,274	11,563	44,821	31,673
Energy Efficiency Programs	9,365	8,786	19,713	18,150
Taxes Other Than Income Taxes	23,453	20,457	45,603	40,158
Total Operating Expenses	225,967	202,133	452,753	416,909
Operating Income, Net	52,882	53,091	119,531	114,683
Interest Expense	13,821	14,607	28,452	29,087
Other Income, Net	4,260	3,626	8,427	6,817
Income Before Income Tax Expense	43,321	42,110	99,506	92,413
Income Tax Expense	8,688	10,478	20,197	21,180
Net Income	$ 34,633	$ 31,632	$ 79,309	$ 71,233

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net Income	$ 266,400	$ 254,112	$ 634,422	$ 590,743
Other Comprehensive Income (Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	445	387	852	616
Changes in Unrealized Gains/(Losses) on Marketable Securities	273	269	(463)	429
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	163	(103)	1,680	1,456
Net OCI	881	553	2,069	2,501
Comprehensive Income Attributable to Noncontrolling Interests	(1,880)	(1,880)	(3,759)	(3,759)
Comprehensive Income Attributable to Common Shareholders	265,401	252,785	632,732	589,485
The Connecticut Light and Power Company
Net Income	115,556	117,271	213,955	236,009
Other Comprehensive Income (Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	(6)	(6)	(13)	(13)
Changes in Unrealized Gains/(Losses) on Marketable Securities	9	9	(16)	15
Net OCI	3	3	(29)	2
Comprehensive Income Attributable to Common Shareholders	115,559	117,274	213,926	236,011
NSTAR Electric Company
Net Income	110,912	97,468	204,836	197,857
Other Comprehensive Income (Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	179	109	288	218
Changes in Unrealized Gains/(Losses) on Marketable Securities	2	2	(5)	3
Changes in Funded Status of Pension, SERP and PBOP Benefit Plans	(40)	(43)	(81)	(86)
Net OCI	141	68	202	135
Comprehensive Income Attributable to Common Shareholders	111,053	97,536	205,038	197,992
Public Service Company of New Hampshire
Net Income	34,633	31,632	79,309	71,233
Other Comprehensive Income (Loss), Net of Tax:
Qualified Cash Flow Hedging Instruments	266	269	564	538
Changes in Unrealized Gains/(Losses) on Marketable Securities	16	16	(27)	25
Net OCI	282	285	537	563
Comprehensive Income Attributable to Common Shareholders	$ 34,915	$ 31,917	$ 79,846	$ 71,796

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Adoption of New Accounting Standard	Common Shares	Capital Surplus, Paid In	Retained Earnings	Retained EarningsAdoption of New Accounting Standard	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	The Connecticut Light and Power Company	The Connecticut Light and Power CompanyAdoption of New Accounting Standard	The Connecticut Light and Power CompanyCommon Shares	The Connecticut Light and Power CompanyCapital Surplus, Paid In	The Connecticut Light and Power CompanyRetained Earnings	The Connecticut Light and Power CompanyRetained EarningsAdoption of New Accounting Standard	The Connecticut Light and Power CompanyAccumulated Other Comprehensive Income (Loss)	NSTAR Electric Company	NSTAR Electric CompanyAdoption of New Accounting Standard	NSTAR Electric CompanyCommon Shares	NSTAR Electric CompanyCapital Surplus, Paid In	NSTAR Electric CompanyRetained Earnings	NSTAR Electric CompanyRetained EarningsAdoption of New Accounting Standard	NSTAR Electric CompanyAccumulated Other Comprehensive Income (Loss)	Public Service Company of New Hampshire	Public Service Company of New HampshireAdoption of New Accounting Standard	Public Service Company of New HampshireCommon Shares	Public Service Company of New HampshireCapital Surplus, Paid In	Public Service Company of New HampshireRetained Earnings	Public Service Company of New HampshireRetained EarningsAdoption of New Accounting Standard	Public Service Company of New HampshireAccumulated Other Comprehensive Income (Loss)
Balance (in shares) at Dec. 31, 2019			329,880,645								6,035,205							200							301
Balance at Dec. 31, 2019	$ 12,629,994	$ (1,514)	$ 1,729,292	$ 7,087,768	$ 4,177,048	$ (1,514)	$ (65,059)	$ (299,055)	$ 4,387,825	$ (900)	$ 60,352	$ 2,535,765	$ 1,791,392	$ (900)	$ 316	$ 4,159,884	$ (161)	$ 0	$ 1,813,442	$ 2,346,287	$ (161)	$ 155	$ 1,391,733	$ (300)	$ 0	$ 903,134	$ 490,306	$ (300)	$ (1,707)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	336,633				336,633				118,738				118,738			100,390				100,390			39,601				39,601
Dividends on Preferred Stock	(1,880)				(1,880)				(1,390)				(1,390)			(490)				(490)
Dividends on Common Stock	(187,462)				(187,462)				(69,500)				(69,500)			(196,500)				(196,500)			(22,300)				(22,300)
Issuance of Common Shares (in shares)			5,960,000
Issuance of Common Shares	432,100		$ 29,800	402,300
Long-Term Incentive Plan Activity	(15,295)			(15,295)
Issuance of Treasury Shares (in shares)			570,542
Issuance of Treasury Shares	27,746			17,230				10,516
Capital Stock Expense	(12,314)			(12,314)
Other Comprehensive Income (Loss)	1,948						1,948		(1)						(1)	67						67	278						278
Balance (in shares) at Mar. 31, 2020			336,411,187								6,035,205							200							301
Balance at Mar. 31, 2020	13,209,956		$ 1,759,092	7,479,689	4,322,825		(63,111)	(288,539)	4,434,772		$ 60,352	2,535,765	1,838,340		315	4,063,190		$ 0	1,813,442	2,249,526		222	1,409,012		$ 0	903,134	507,307		(1,429)
Balance (in shares) at Dec. 31, 2019			329,880,645								6,035,205							200							301
Balance at Dec. 31, 2019	12,629,994	$ (1,514)	$ 1,729,292	7,087,768	4,177,048	$ (1,514)	(65,059)	(299,055)	4,387,825	$ (900)	$ 60,352	2,535,765	1,791,392	$ (900)	316	4,159,884	$ (161)	$ 0	1,813,442	2,346,287	$ (161)	155	1,391,733	$ (300)	$ 0	903,134	490,306	$ (300)	(1,707)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	590,743								236,009							197,857							71,233
Dividends on Preferred Stock	(3,800)
Other Comprehensive Income (Loss)	2,501								2							135							563
Balance (in shares) at Jun. 30, 2020			342,627,862								6,035,205							200							301
Balance at Jun. 30, 2020	13,805,258		$ 1,789,092	7,979,146	4,384,093		(62,558)	(284,515)	4,550,656		$ 60,352	2,535,765	1,954,221		318	4,160,236		$ 0	1,813,442	2,346,504		290	1,440,929		$ 0	903,134	538,939		(1,144)
Balance (in shares) at Mar. 31, 2020			336,411,187								6,035,205							200							301
Balance at Mar. 31, 2020	13,209,956		$ 1,759,092	7,479,689	4,322,825		(63,111)	(288,539)	4,434,772		$ 60,352	2,535,765	1,838,340		315	4,063,190		$ 0	1,813,442	2,249,526		222	1,409,012		$ 0	903,134	507,307		(1,429)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	254,112				254,112				117,271				117,271			97,468				97,468			31,632				31,632
Dividends on Preferred Stock	(1,880)				(1,880)				(1,390)				(1,390)			(490)				(490)
Dividends on Common Stock	(190,964)				(190,964)
Issuance of Common Shares (in shares)			6,000,000
Issuance of Common Shares	517,560		$ 30,000	487,560
Long-Term Incentive Plan Activity	7,694			7,694
Issuance of Treasury Shares (in shares)			216,675
Issuance of Treasury Shares	16,548			12,524				4,024
Capital Stock Expense	(8,321)			(8,321)
Other Comprehensive Income (Loss)	553						553		3						3	68						68	285						285
Balance (in shares) at Jun. 30, 2020			342,627,862								6,035,205							200							301
Balance at Jun. 30, 2020	$ 13,805,258		$ 1,789,092	7,979,146	4,384,093		(62,558)	(284,515)	4,550,656		$ 60,352	2,535,765	1,954,221		318	4,160,236		$ 0	1,813,442	2,346,504		290	1,440,929		$ 0	903,134	538,939		(1,144)
Balance (in shares) at Dec. 31, 2020	342,954,023		342,954,023								6,035,205							200							301
Balance at Dec. 31, 2020	$ 14,063,566		$ 1,789,092	8,015,663	4,613,201		(76,411)	(277,979)	5,044,786		$ 60,352	2,810,765	2,173,367		302	4,521,418		$ 0	1,993,942	2,527,167		309	1,542,539		$ 0	928,134	615,018		(613)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	368,023				368,023				98,398				98,398			93,924				93,924			44,676				44,676
Dividends on Preferred Stock	(1,880)				(1,880)				(1,390)				(1,390)			(490)				(490)
Dividends on Common Stock	(206,913)				(206,913)				(70,100)				(70,100)			(206,400)				(206,400)			(25,200)				(25,200)
Long-Term Incentive Plan Activity	(15,727)			(15,727)
Issuance of Treasury Shares (in shares)			480,275
Issuance of Treasury Shares	25,163			16,182				8,981
Other Comprehensive Income (Loss)	1,188						1,188		(32)						(32)	61						61	255						255
Balance (in shares) at Mar. 31, 2021			343,434,298								6,035,205							200							301
Balance at Mar. 31, 2021	$ 14,233,420		$ 1,789,092	8,016,118	4,772,431		(75,223)	(268,998)	5,071,662		$ 60,352	2,810,765	2,200,275		270	4,408,513		$ 0	1,993,942	2,414,201		370	1,562,270		$ 0	928,134	634,494		(358)
Balance (in shares) at Dec. 31, 2020	342,954,023		342,954,023								6,035,205							200							301
Balance at Dec. 31, 2020	$ 14,063,566		$ 1,789,092	8,015,663	4,613,201		(76,411)	(277,979)	5,044,786		$ 60,352	2,810,765	2,173,367		302	4,521,418		$ 0	1,993,942	2,527,167		309	1,542,539		$ 0	928,134	615,018		(613)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	634,422								213,955							204,836							79,309
Dividends on Preferred Stock	(3,800)
Other Comprehensive Income (Loss)	$ 2,069								(29)							202							537
Balance (in shares) at Jun. 30, 2021	343,601,103		343,601,103								6,035,205							200							301
Balance at Jun. 30, 2021	$ 14,311,889		$ 1,789,092	8,032,959	4,830,058		(74,342)	(265,878)	5,115,731		$ 60,352	2,810,765	2,244,341		273	4,502,276		$ 0	2,053,942	2,447,823		511	1,571,985		$ 0	1,088,134	483,927		(76)
Balance (in shares) at Mar. 31, 2021			343,434,298								6,035,205							200							301
Balance at Mar. 31, 2021	14,233,420		$ 1,789,092	8,016,118	4,772,431		(75,223)	(268,998)	5,071,662		$ 60,352	2,810,765	2,200,275		270	4,408,513		$ 0	1,993,942	2,414,201		370	1,562,270		$ 0	928,134	634,494		(358)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	266,400				266,400				115,556				115,556			110,912				110,912			34,633				34,633
Dividends on Preferred Stock	(1,880)				(1,880)				(1,390)				(1,390)			(490)				(490)
Dividends on Common Stock	(206,893)				(206,893)				(70,100)				(70,100)			(76,800)				(76,800)			(185,200)				(185,200)
Capital Contributions from Eversource Parent																60,000			60,000				160,000			160,000
Long-Term Incentive Plan Activity	6,162			6,162
Issuance of Treasury Shares (in shares)			166,805
Issuance of Treasury Shares	13,799			10,679				3,120
Other Comprehensive Income (Loss)	$ 881						881		3						3	141						141	282						282
Balance (in shares) at Jun. 30, 2021	343,601,103		343,601,103								6,035,205							200							301
Balance at Jun. 30, 2021	$ 14,311,889		$ 1,789,092	$ 8,032,959	$ 4,830,058		$ (74,342)	$ (265,878)	$ 5,115,731		$ 60,352	$ 2,810,765	$ 2,244,341		$ 273	$ 4,502,276		$ 0	$ 2,053,942	$ 2,447,823		$ 511	$ 1,571,985		$ 0	$ 1,088,134	$ 483,927		$ (76)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020
Statement of Stockholders' Equity [Abstract]
Dividends on Common Shares (in dollars per share)	$ 0.6025	$ 0.6025	$ 0.5675	$ 0.5675
Par value (in dollars per share)	$ 5		$ 5	$ 5

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating Activities:
Net Income	$ 634,422	$ 590,743
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	545,352	476,727
Deferred Income Taxes	120,390	86,550
Uncollectible Expense	27,683	20,579
Pension, SERP and PBOP (Income)/Expense, Net	(6,391)	5,441
Pension and PBOP Contributions	(72,400)	(1,323)
Regulatory Over/(Under) Recoveries, Net	46,835	(58,501)
Amortization	113,624	73,172
Other	(154,065)	(40,764)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(85,261)	(66,460)
Fuel, Materials, Supplies and REC Inventory	77,907	59,332
Taxes Receivable/Accrued, Net	(9,113)	120,717
Accounts Payable	(285,670)	(169,251)
Other Current Assets and Liabilities, Net	(145,868)	(91,587)
Net Cash Flows Provided by Operating Activities	807,445	1,005,375
Investing Activities:
Investments in Property, Plant and Equipment	(1,423,223)	(1,400,198)
Proceeds from Sales of Marketable Securities	253,842	250,589
Purchases of Marketable Securities	(240,729)	(239,698)
Investments in Unconsolidated Affiliates, Net	(100,527)	(12,324)
Other Investing Activities	12,661	11,129
Net Cash Flows Used in Investing Activities	(1,497,976)	(1,390,502)
Financing Activities:
Issuance of Common Shares, Net of Issuance Costs	0	929,025
Cash Dividends on Common Shares	(402,211)	(366,817)
Cash Dividends on Preferred Stock	(3,759)	(3,759)
Increase/(Decrease) in Notes Payable	753,175	(741,870)
Repayment of Rate Reduction Bonds	(21,605)	(21,605)
Issuance of Long-Term Debt	1,525,000	940,000
Retirement of Long-Term Debt	(1,022,000)	(270,456)
Other Financing Activities	(35,008)	(19,534)
Net Cash Flows (Used in)/Provided by Financing Activities	793,592	444,984
Net Increase in Cash and Restricted Cash	103,061	59,857
Cash and Restricted Cash - Beginning of Period	264,950	117,063
Cash and Restricted Cash - End of Period	368,011	176,920
The Connecticut Light and Power Company
Operating Activities:
Net Income	213,955	236,009
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	167,828	158,152
Deferred Income Taxes	41,886	33,275
Uncollectible Expense	6,614	6,187
Pension, SERP and PBOP (Income)/Expense, Net	3,803	5,886
Pension and PBOP Contributions	(37,880)	0
Regulatory Over/(Under) Recoveries, Net	(22,121)	(45,886)
Amortization of Regulatory (Liabilities)/Assets, Net	47,716	850
Other	(62,137)	(43,064)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(104,262)	(49,800)
Taxes Receivable/Accrued, Net	33,049	31,139
Accounts Payable	(80,007)	(49,574)
Other Current Assets and Liabilities, Net	15,513	(244)
Net Cash Flows Provided by Operating Activities	223,957	282,930
Investing Activities:
Investments in Property, Plant and Equipment	(393,323)	(407,175)
Other Investing Activities	157	146
Net Cash Flows Used in Investing Activities	(393,166)	(407,029)
Financing Activities:
Cash Dividends on Common Shares	(140,200)	(69,500)
Cash Dividends on Preferred Stock	(2,779)	(2,779)
Issuance of Long-Term Debt	425,000	0
Increase in Notes Payable to Eversource Parent	0	208,200
Other Financing Activities	(5,180)	(795)
Net Cash Flows (Used in)/Provided by Financing Activities	276,841	135,126
Net Increase in Cash and Restricted Cash	107,632	11,027
Cash and Restricted Cash - Beginning of Period	99,809	4,971
Cash and Restricted Cash - End of Period	207,441	15,998
NSTAR Electric Company
Operating Activities:
Net Income	204,836	197,857
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	166,710	157,865
Deferred Income Taxes	28,742	26,062
Uncollectible Expense	7,394	6,826
Pension, SERP and PBOP Income, Net	(12,990)	(9,296)
Pension and PBOP Contributions	(10,000)	0
Regulatory Over/(Under) Recoveries, Net	(12,562)	(59,685)
Amortization of Regulatory (Liabilities)/Assets, Net	15,890	46,612
Other	(40,315)	(12,534)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(49,324)	(36,627)
Fuel, Materials, Supplies and REC Inventory	59,256	53,599
Taxes Receivable/Accrued, Net	57,584	5,279
Accounts Payable	(88,729)	(49,881)
Other Current Assets and Liabilities, Net	(80,605)	(113,276)
Net Cash Flows Provided by Operating Activities	245,887	212,801
Investing Activities:
Investments in Property, Plant and Equipment	(426,053)	(447,545)
Other Investing Activities	43	40
Net Cash Flows Used in Investing Activities	(426,010)	(447,505)
Financing Activities:
Cash Dividends on Common Shares	(283,200)	(196,500)
Cash Dividends on Preferred Stock	(980)	(980)
Increase in Notes Payable to Eversource Parent	200	7,800
Increase/(Decrease) in Notes Payable	360,500	131,500
Issuance of Long-Term Debt	300,000	400,000
Retirement of Long-Term Debt	(250,000)	(95,000)
Capital Contributions from Eversource Parent	60,000	0
Other Financing Activities	(5,909)	(4,946)
Net Cash Flows (Used in)/Provided by Financing Activities	180,611	241,874
Net Increase in Cash and Restricted Cash	488	7,170
Cash and Restricted Cash - Beginning of Period	17,410	6,312
Cash and Restricted Cash - End of Period	17,898	13,482
Public Service Company of New Hampshire
Operating Activities:
Net Income	79,309	71,233
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	59,293	49,084
Deferred Income Taxes	(842)	9,193
Uncollectible Expense	3,226	1,255
Regulatory Over/(Under) Recoveries, Net	(6,965)	(31,159)
Amortization of Regulatory (Liabilities)/Assets, Net	44,821	31,673
Other	(14,445)	(5,191)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(3,717)	(3,237)
Fuel, Materials, Supplies and REC Inventory	3,496	2,212
Taxes Receivable/Accrued, Net	9,183	(5,790)
Accounts Payable	(29,320)	8,219
Other Current Assets and Liabilities, Net	(5,736)	(8,673)
Net Cash Flows Provided by Operating Activities	138,303	118,819
Investing Activities:
Investments in Property, Plant and Equipment	(134,256)	(169,239)
Other Investing Activities	270	250
Net Cash Flows Used in Investing Activities	(133,986)	(168,989)
Financing Activities:
Cash Dividends on Common Shares	(210,400)	(22,300)
Repayment of Rate Reduction Bonds	(21,605)	(21,605)
Issuance of Long-Term Debt	350,000	0
Retirement of Long-Term Debt	(282,000)	0
Capital Contributions from Eversource Parent	160,000	0
Increase in Notes Payable to Eversource Parent	2,300	92,300
Other Financing Activities	(2,941)	(43)
Net Cash Flows (Used in)/Provided by Financing Activities	(4,646)	48,352
Net Increase in Cash and Restricted Cash	(329)	(1,818)
Cash and Restricted Cash - Beginning of Period	39,555	36,688
Cash and Restricted Cash - End of Period	$ 39,226	$ 34,870

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES A. Basis of Presentation Eversource Energy is a public utility holding company primarily engaged, through its wholly-owned regulated utility subsidiaries, in the energy delivery business. Eversource Energy's wholly-owned regulated utility subsidiaries consist of CL&P, NSTAR Electric and PSNH (electric utilities), Yankee Gas, NSTAR Gas and Eversource Gas Company of Massachusetts (EGMA) (natural gas utilities) and Aquarion (water utilities). Eversource provides energy delivery and/or water service to approximately 4.3 million electric, natural gas and water customers through nine regulated utilities in Connecticut, Massachusetts and New Hampshire. The unaudited condensed consolidated financial statements of Eversource, NSTAR Electric and PSNH include the accounts of each of their respective subsidiaries. Intercompany transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements of Eversource, NSTAR Electric and PSNH and the unaudited condensed financial statements of CL&P are herein collectively referred to as the "financial statements." The combined notes to the financial statements have been prepared pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures included in annual financial statements prepared in accordance with GAAP have been omitted pursuant to such rules and regulations. The accompanying financial statements should be read in conjunction with the Combined Notes to Financial Statements included in Item 8, "Financial Statements and Supplementary Data," of the Eversource 2020 Form 10-K, which was filed with the SEC on February 17, 2021. The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The financial statements contain, in the opinion of management, all adjustments (including normal, recurring adjustments) necessary to present fairly Eversource's, CL&P's, NSTAR Electric's and PSNH's financial position as of June 30, 2021 and December 31, 2020, and the results of operations, comprehensive income and common shareholders' equity for the three and six months ended June 30, 2021 and 2020 and the cash flows for the six months ended June 30, 2021 and 2020. The results of operations and comprehensive income for the three and six months ended June 30, 2021 and 2020 and the cash flows for the six months ended June 30, 2021 and 2020 are not necessarily indicative of the results expected for a full year. Eversource's consolidated financial information includes the results of the acquisition of the assets of Columbia Gas of Massachusetts (CMA) on October 9, 2020. The natural gas distribution assets acquired from CMA on October 9, 2020 were assigned to EGMA. Eversource consolidates the operations of CYAPC and YAEC, both of which are inactive regional nuclear power companies engaged in the long-term storage of their spent nuclear fuel. Eversource consolidates CYAPC and YAEC because CL&P's, NSTAR Electric's and PSNH's combined ownership and voting interests in each of these entities is greater than 50 percent. Intercompany transactions between CL&P, NSTAR Electric, PSNH and the CYAPC and YAEC companies have been eliminated in consolidation of the Eversource financial statements. Eversource holds several equity ownership interests that are not consolidated and are accounted for under the equity method. Eversource's utility subsidiaries' electric, natural gas and water distribution and transmission businesses are subject to rate-regulation that is based on cost recovery and meets the criteria for application of accounting guidance for entities with rate-regulated operations, which considers the effect of regulation on the differences in the timing of the recognition of certain revenues and expenses from those of other businesses and industries. See Note 2, "Regulatory Accounting," for further information. COVID-19 has adversely affected customers, workers and the U.S. economy. We provide a critical service to our customers and have taken extensive measures to maintain its safety and reliability. We continue to address the impacts of the COVID-19 pandemic and how the related developments affect Eversource. We are in the early re-entry phase of our pandemic response plan, in which the majority of our employees under remote work arrangements are starting to transition back to the workplace. We have not experienced significant impacts directly related to the pandemic that have materially affected our current operations, our workforce, or results of operations. The extent of the impact to us in the future will vary, and depend on the duration, scope and severity of the pandemic and the resulting impact on economic, health care and capital market conditions. The future impact will also depend on the outcome of future proceedings before our state regulatory commissions to recover our incremental costs associated with COVID-19, which include uncollectible customer receivable expenses. Based on the status of our COVID-19 regulatory dockets, communications with our state regulatory commissions, and policies and practices in the jurisdictions in which we operate, we believe our state regulatory commissions in Connecticut and Massachusetts will allow us to recover our incremental costs associated with COVID-19, which include uncollectible customer receivable expenses, while balancing the impact on our customers’ bills and our operating cash flows. See Note 1C, "Summary of Significant Accounting Policies - Allowance for Uncollectible Accounts," for discussion of our evaluation of the allowance for doubtful accounts as of June 30, 2021 in light of the COVID-19 pandemic and Note 2, "Regulatory Accounting," for the amount of net incremental COVID-19 costs deferred on our balance sheet. Certain reclassifications of prior period data were made in the accompanying financial statements to conform to the current period presentation. B. Accounting Standards Accounting Standards Recently Adopted: On January 1, 2021, the Company adopted Accounting Standards Update (ASU) 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes , which eliminates certain exceptions to the general principles of current income tax guidance in ASC 740 and simplifies and improves consistency in application of that income tax guidance through clarifications of and amendments to ASC 740. The ASU did not have a material impact on the financial statements of Eversource, CL&P, NSTAR Electric and PSNH. C. Allowance for Uncollectible Accounts Receivables, Net on the balance sheets primarily includes trade receivables from retail customers and customers related to wholesale transmission contracts, wholesale market sales, sales of RECs and property rentals. Receivables, Net also includes customer receivables for the purchase of electricity from a competitive third party supplier, the current portion of customer energy efficiency loans, property damage receivables and other miscellaneous receivables. There is no material concentration of receivables. Receivables are recorded at amortized cost, net of a credit loss provision (or allowance for uncollectible accounts). Receivables are presented net of expected credit losses at estimated net realizable value by maintaining an allowance for uncollectible accounts. The current expected credit loss (CECL) model is applied to receivables for purposes of calculating the allowance for uncollectible accounts. This model is based on expected losses and results in the recognition of estimated expected credit losses, including uncollectible amounts for both billed and unbilled revenues, over the life of the receivable at the time a receivable is recorded. The allowance for uncollectible accounts is determined based upon a variety of judgments and factors, including the application of an estimated uncollectible percentage to each receivable aging category. Factors in determining credit loss include historical collection, write-off experience, and management's assessment of collectability from customers, including current conditions, reasonable forecasts, and expectations of future collectability and collection efforts. Management continuously assesses the collectability of receivables and adjusts estimates based on actual experience and future expectations based on economic indicators, collection efforts and other factors. Management also monitors the aging analysis of receivables to determine if there are changes in the collections of accounts receivable. Receivable balances are written off against the allowance for uncollectible accounts when the customer accounts are no longer in service and these balances are deemed to be uncollectible. As of June 30, 2021, management evaluated the adequacy of the allowance for uncollectible accounts in light of the COVID-19 pandemic and the related economic downturn. This evaluation included an analysis of collection and customer payment trends, economic conditions, delinquency statistics, aging-based quantitative assessments, the impact on residential customer bills because of energy usage and change in rates, flexible payment plans and financial hardship arrearage management programs being offered to customers, and COVID-19 developments, including any potential federal governmental pandemic relief programs and the expansion of unemployment benefit initiatives, which help to mitigate the potential for increasing customer account delinquencies. Additionally, management considered past economic declines and corresponding uncollectible reserves as part of the current assessment. This evaluation has shown that our operating companies have experienced an increase in aged receivables and lower cash collections from customers because of the length of the moratorium on disconnections in Connecticut and Massachusetts, and the economic slowdown resulting from the COVID-19 pandemic. Based upon the evaluation performed, in the first half of 2021, management increased the allowance for uncollectible accounts for amounts incurred as a result of COVID-19 by $32.1 million for Eversource ($12.3 million for CL&P, $6.3 million for NSTAR Electric, and $14.7 million at our natural gas businesses). These COVID-19 related uncollectible amounts were deferred either as incremental regulatory costs at our Connecticut and Massachusetts utilities or deferred through existing regulatory tracking mechanisms that recover uncollectible energy supply costs, as management believes it is probable that these costs will ultimately be recovered from customers in future rates. As of June 30, 2021, the total amount incurred as a result of COVID-19 included in the allowance for uncollectible accounts was $63.6 million at Eversource ($15.1 million at CL&P, $17.3 million at NSTAR Electric, and $30.1 million at our natural gas businesses). On July 7, 2021, the NHPUC issued an order to New Hampshire utilities that concluded that recovery of incremental bad debt or waived late fees related to the COVID-19 pandemic would be addressed in a future rate case to the extent those costs are relevant at that time. The NHPUC concluded that New Hampshire utilities would not be permitted to establish a regulatory asset for these items. As a result of the order, in the second quarter of 2021, PSNH removed its $0.6 million deferral of net incremental COVID-19 costs. In New Hampshire, the moratorium on disconnections of non-hardship residential and commercial customers ended in late 2020 and PSNH has resumed disconnection activities, which has resulted in improved collection of outstanding customer receivable balances. In Connecticut, the moratorium on disconnections of commercial customers ended in June 2021, but is still in place for residential customers. In Massachusetts, the moratorium on disconnections of commercial customers and residential customers ended in September 2020 and July 2021, respectively. Disconnection activities have largely resumed after these moratoria have expired. Management concluded that the reserve balance as of June 30, 2021 adequately reflected the collection risk and net realizable value for Eversource’s receivables. Management will continue to evaluate the adequacy of the uncollectible allowance in future reporting periods based on an ongoing assessment of accounts receivable collections, delinquency statistics, and analysis of aging-based quantitative assessments. The PURA allows CL&P and Yankee Gas to accelerate the recovery of accounts receivable balances attributable to qualified customers under financial or medical duress (uncollectible hardship accounts receivable) outstanding for greater than 180 days and 90 days, respectively. The DPU allows NSTAR Electric, NSTAR Gas and EGMA to recover in rates amounts associated with certain uncollectible hardship accounts receivable. These uncollectible hardship customer account balances are included in Regulatory Assets or Other Long-Term Assets on the balance sheets. Hardship customers are protected from shut-off in certain circumstances, and historical collection experience has reflected a higher default risk as compared to the rest of the receivable population. Management uses a higher credit risk profile for this pool of trade receivables as compared to non-hardship receivables. The allowance for uncollectible hardship accounts is included in the total uncollectible allowance balance. The total allowance for uncollectible accounts is included in Receivables, Net on the balance sheets. The activity in the allowance for uncollectible accounts by portfolio segment is as follows: Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Hardship Accounts Retail (Non-Hardship), Total Allowance Hardship Accounts Retail (Non-Hardship), Total Allowance Hardship Accounts Retail (Non-Hardship), Total Allowance Total Allowance Three Months Ended 2021 Beginning Balance $ 197.3 $ 194.4 $ 391.7 $ 138.4 $ 36.7 $ 175.1 $ 31.1 $ 58.2 $ 89.3 $ 17.3 Uncollectible Expense — 11.4 11.4 — 2.8 2.8 — 3.5 3.5 2.0 Uncollectible Costs Deferred (1) 16.6 24.5 41.1 9.3 8.3 17.6 4.9 6.9 11.8 (0.3) Write-Offs (3.4) (18.1) (21.5) (2.3) (5.4) (7.7) (0.1) (7.7) (7.8) (2.0) Recoveries Collected 0.2 2.9 3.1 0.2 0.8 1.0 — 1.2 1.2 0.2 Ending Balance $ 210.7 $ 215.1 $ 425.8 $ 145.6 $ 43.2 $ 188.8 $ 35.9 $ 62.1 $ 98.0 $ 17.2 Six Months Ended 2021 Beginning Balance $ 194.8 $ 164.1 $ 358.9 $ 129.1 $ 28.3 $ 157.4 $ 39.7 $ 51.9 $ 91.6 $ 17.2 Uncollectible Expense — 27.7 27.7 — 6.6 6.6 — 7.4 7.4 3.2 Uncollectible Costs Deferred (1) 22.0 51.6 73.6 21.2 15.7 36.9 (3.5) 15.2 11.7 0.8 Write-Offs (6.7) (34.8) (41.5) (5.2) (9.3) (14.5) (0.3) (15.2) (15.5) (4.5) Recoveries Collected 0.6 6.5 7.1 0.5 1.9 2.4 — 2.8 2.8 0.5 Ending Balance $ 210.7 $ 215.1 $ 425.8 $ 145.6 $ 43.2 $ 188.8 $ 35.9 $ 62.1 $ 98.0 $ 17.2 Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Hardship Accounts Retail (Non-Hardship), Total Allowance Hardship Accounts Retail (Non-Hardship), Total Allowance Hardship Accounts Retail (Non-Hardship), Total Allowance Total Allowance Three Months Ended 2020 Beginning Balance $ 172.2 $ 89.9 $ 262.1 $ 110.7 $ 20.2 $ 130.9 $ 38.5 $ 32.6 $ 71.1 $ 11.2 Uncollectible Expense — 9.2 9.2 — 3.0 3.0 — 3.1 3.1 0.6 Uncollectible Costs Deferred (1) 7.1 8.5 15.6 8.6 1.6 10.2 (3.7) 3.5 (0.2) 1.1 Write-Offs (4.4) (16.6) (21.0) (3.6) (6.0) (9.6) (0.2) (6.2) (6.4) (1.3) Recoveries Collected 0.6 3.5 4.1 0.6 1.6 2.2 — 1.1 1.1 0.2 Ending Balance $ 175.5 $ 94.5 $ 270.0 $ 116.3 $ 20.4 $ 136.7 $ 34.6 $ 34.1 $ 68.7 $ 11.8 Six Months Ended 2020 Beginning Balance $ 143.3 $ 81.5 $ 224.8 $ 80.1 $ 17.2 $ 97.3 $ 43.9 $ 31.5 $ 75.4 $ 10.5 ASU 2016-13 Implementation 21.6 2.2 23.8 21.3 0.9 22.2 (1.6) 0.3 (1.3) 0.3 Uncollectible Expense — 20.6 20.6 — 6.2 6.2 — 6.8 6.8 1.3 Uncollectible Costs Deferred (1) 18.9 17.0 35.9 21.5 3.4 24.9 (7.1) 6.9 (0.2) 2.4 Write-Offs (9.1) (33.4) (42.5) (7.4) (9.5) (16.9) (0.6) (14.2) (14.8) (3.0) Recoveries Collected 0.8 6.6 7.4 0.8 2.2 3.0 — 2.8 2.8 0.3 Ending Balance $ 175.5 $ 94.5 $ 270.0 $ 116.3 $ 20.4 $ 136.7 $ 34.6 $ 34.1 $ 68.7 $ 11.8 (1) These expected credit losses are deferred as regulatory costs on the balance sheets, as these amounts are ultimately recovered in rates. Amounts include uncollectible costs for hardship accounts and other customer receivables, including uncollectible amounts related to COVID-19 and uncollectible energy supply costs. D. Fair Value Measurements Fair value measurement guidance is applied to derivative contracts that are not elected or designated as "normal purchases" or "normal sales" (normal) and to the marketable securities held in trusts. Fair value measurement guidance is also applied to valuations of the investments used to calculate the funded status of pension and PBOP plans, the nonrecurring fair value measurements of nonfinancial assets such as goodwill, long-lived assets, equity method investments, and AROs, and in the valuation of the acquisition of CMA's assets in 2020. The fair value measurement guidance was also applied in estimating the fair value of preferred stock, long-term debt and RRBs. Fair Value Hierarchy: In measuring fair value, Eversource uses observable market data when available in order to minimize the use of unobservable inputs. Inputs used in fair value measurements are categorized into three fair value hierarchy levels for disclosure purposes. The entire fair value measurement is categorized based on the lowest level of input that is significant to the fair value measurement. Eversource evaluates the classification of assets and liabilities measured at fair value on a quarterly basis. The levels of the fair value hierarchy are described below: Level 1 - Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities as of the reporting date. Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis. Level 2 - Inputs are quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs are observable. Level 3 - Quoted market prices are not available. Fair value is derived from valuation techniques in which one or more significant inputs or assumptions are unobservable. Where possible, valuation techniques incorporate observable market inputs that can be validated to external sources such as industry exchanges, including prices of energy and energy-related products. Uncategorized - Investments that are measured at net asset value are not categorized within the fair value hierarchy. Determination of Fair Value: The valuation techniques and inputs used in Eversource's fair value measurements are described in Note 4, "Derivative Instruments," Note 5, "Marketable Securities," and Note 10, "Fair Value of Financial Instruments," to the financial statements. E. Other Income, Net The components of Other Income, Net on the statements of income were as follows: For the Three Months Ended June 30, 2021 June 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service $ 22.1 $ 4.3 $ 10.2 $ 2.7 $ 10.7 $ 0.9 $ 7.1 $ 1.6 AFUDC Equity 9.2 1.7 6.2 0.3 10.8 3.9 5.3 1.2 Equity in Earnings of Unconsolidated Affiliates (1) 4.7 — 0.1 — 5.9 — 0.1 — Investment Income 1.9 1.2 0.6 0.3 1.8 2.2 — 0.3 Interest Income 8.4 2.7 4.8 0.9 1.0 1.4 0.5 0.5 Other 0.3 — — 0.1 — 0.1 0.1 — Total Other Income, Net $ 46.6 $ 9.9 $ 21.9 $ 4.3 $ 30.2 $ 8.5 $ 13.1 $ 3.6 For the Six Months Ended June 30, 2021 June 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service $ 42.2 $ 7.0 $ 20.2 $ 5.4 $ 23.4 $ 2.1 $ 15.0 $ 3.5 AFUDC Equity 18.4 3.4 12.4 0.9 21.4 7.9 10.3 2.6 Equity in Earnings of Unconsolidated Affiliates (1) 8.4 — 0.2 — 9.8 — 0.2 — Investment Income/(Loss) 1.3 1.5 0.8 0.4 (2.5) (1.3) (1.3) (0.2) Interest Income 9.9 2.8 4.9 1.6 1.8 1.6 0.7 0.8 Other 0.6 0.1 0.2 0.1 0.4 0.1 0.5 0.1 Total Other Income, Net $ 80.8 $ 14.8 $ 38.7 $ 8.4 $ 54.3 $ 10.4 $ 25.4 $ 6.8 (1) Equity in earnings of unconsolidated affiliates includes $2.1 million of pre-tax unrealized gains associated with an investment in a renewable energy fund for the three and six months ended June 30, 2021. For the three and six months ended June 30, 2020, equity in earnings of unconsolidated affiliates included $2.4 million of primarily realized gains associated with this investment. F. Other Taxes Eversource's companies that serve customers in Connecticut collect gross receipts taxes levied by the state of Connecticut from their customers. These gross receipts taxes are recorded separately with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the statements of income as follows: For the Three Months Ended For the Six Months Ended (Millions of Dollars) June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 Eversource $ 39.9 $ 37.6 $ 88.5 $ 80.7 CL&P 35.4 33.1 74.6 68.6 As agents for state and local governments, Eversource's companies that serve customers in Connecticut and Massachusetts collect certain sales taxes that are recorded on a net basis with no impact on the statements of income. G. Supplemental Cash Flow Information Non-cash investing activities include plant additions included in Accounts Payable as follows: (Millions of Dollars) As of June 30, 2021 As of June 30, 2020 Eversource $ 344.8 $ 336.1 CL&P 66.4 95.0 NSTAR Electric 103.8 75.5 PSNH 33.9 48.3 The following table reconciles cash as reported on the balance sheets to the cash and restricted cash balance as reported on the statements of cash flows: As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Cash as reported on the Balance Sheets $ 217.4 $ 198.4 $ 0.6 $ 0.3 $ 106.6 $ 90.8 $ 0.1 $ 0.1 Restricted cash included in: Special Deposits 71.8 8.6 17.2 35.1 73.6 8.7 17.2 36.8 Marketable Securities 34.1 0.4 0.1 0.6 41.2 0.3 0.1 0.6 Other Long-Term Assets 44.7 — — 3.2 43.6 — — 2.1 Cash and Restricted Cash as reported on the Statements of Cash Flows $ 368.0 $ 207.4 $ 17.9 $ 39.2 $ 265.0 $ 99.8 $ 17.4 $ 39.6 Special Deposits represent cash collections related to the PSNH RRB customer charges that are held in trust, required ISO-NE cash deposits, and CYAPC and YAEC cash balances. Special Deposits are included in Current Assets on the balance sheets. Restricted cash included in Marketable Securities represents money market funds held in trusts to fund certain non-qualified executive benefits and restricted trusts to fund CYAPC and YAEC's spent nuclear fuel storage obligations. Restricted cash included in Other Long-Term Assets includes $41.5 million related to an Energy Relief Fund for energy efficiency and clean energy measures in the Merrimack Valley, and an additional energy efficiency program established under the terms of the EGMA settlement agreement.

REGULATORY ACCOUNTING

REGULATORY ACCOUNTING	6 Months Ended
	Jun. 30, 2021
Regulated Operations [Abstract]
REGULATORY ACCOUNTING	REGULATORY ACCOUNTING Eversource's utility companies are subject to rate regulation that is based on cost recovery and meets the criteria for application of accounting guidance for rate-regulated operations, which considers the effect of regulation on the timing of the recognition of certain revenues and expenses. The regulated companies' financial statements reflect the effects of the rate-making process. The rates charged to the customers of Eversource's regulated companies are designed to collect each company's costs to provide service, plus a return on investment. The application of accounting guidance for rate-regulated enterprises results in recording regulatory assets and liabilities. Regulatory assets represent the deferral of incurred costs that are probable of future recovery in customer rates. Regulatory assets are amortized as the incurred costs are recovered through customer rates. Regulatory liabilities represent either revenues received from customers to fund expected costs that have not yet been incurred or probable future refunds to customers. Management believes it is probable that each of the regulated companies will recover its respective investments in long-lived assets and the regulatory assets that have been recorded. If management were to determine that it could no longer apply the accounting guidance applicable to rate-regulated enterprises, or if management could not conclude it is probable that costs would be recovered from customers in future rates, the applicable costs would be charged to net income in the period in which the determination is made. Regulatory Assets: The components of regulatory assets were as follows: As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH Benefit Costs $ 2,625.1 $ 551.7 $ 653.9 $ 255.1 $ 2,794.2 $ 632.3 $ 690.0 $ 267.6 Income Taxes, Net 755.4 460.5 112.2 17.4 747.1 458.9 110.4 15.2 Securitized Stranded Costs 500.5 — — 500.5 522.1 — — 522.1 Storm Restoration Costs, Net 745.9 500.2 169.5 76.2 765.6 515.1 186.4 64.1 Regulatory Tracker Mechanisms 950.9 347.5 378.8 79.1 850.5 246.6 332.2 95.3 Derivative Liabilities 279.7 279.7 — — 296.3 293.1 — — Goodwill-related 306.2 — 262.9 — 314.7 — 270.2 — Asset Retirement Obligations 118.2 33.2 55.8 4.0 118.4 32.1 58.6 3.9 Other Regulatory Assets 151.4 31.6 51.3 18.1 161.0 33.7 56.1 20.9 Total Regulatory Assets 6,433.3 2,204.4 1,684.4 950.4 6,569.9 2,211.8 1,703.9 989.1 Less: Current Portion 1,186.9 458.6 448.0 99.5 1,076.6 345.6 399.9 115.9 Total Long-Term Regulatory Assets $ 5,246.4 $ 1,745.8 $ 1,236.4 $ 850.9 $ 5,493.3 $ 1,866.2 $ 1,304.0 $ 873.2 Regulatory Costs in Long-Term Assets: Eversource's regulated companies had $255.6 million (including $115.5 million for CL&P, $77.1 million for NSTAR Electric and $3.1 million for PSNH) and $196.9 million (including $84.1 million for CL&P, $69.8 million for NSTAR Electric and $4.3 million for PSNH) of additional regulatory costs as of June 30, 2021 and December 31, 2020, respectively, that were included in long-term assets on the balance sheets. These amounts represent incurred costs for which recovery has not yet been specifically approved by the applicable regulatory agency. However, based on regulatory policies or past precedent on similar costs, management believes it is probable that these costs will ultimately be approved and recovered from customers in rates. As of June 30, 2021 and December 31, 2020, these regulatory costs included net incremental COVID-19 related costs deferred of $45.8 million and $24.0 million at Eversource, respectively, of which, $39.1 million and $15.8 million, respectively, related to non-tracked uncollectible expense and the remainder related to facilities and fleet cleaning, sanitizing costs and supplies for personal protective equipment. Net incremental COVID-19 related costs deferred at CL&P and NSTAR Electric totaled $13.2 million and $15.8 million, respectively, as of June 30, 2021, and $4.7 million and $11.9 million, respectively, as of December 31, 2020, and primarily related to deferred non-tracked uncollectible expense. Regulatory Liabilities: The components of regulatory liabilities were as follows: As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH EDIT due to Tax Cuts and Jobs Act of 2017 $ 2,748.6 $ 1,005.4 $ 1,030.5 $ 364.2 $ 2,778.6 $ 1,010.7 $ 1,044.0 $ 371.5 Cost of Removal 657.1 108.7 374.4 17.1 624.8 98.4 363.6 12.9 Benefit Costs 70.4 — 60.2 — 83.6 — 72.5 — Regulatory Tracker Mechanisms 474.7 190.3 147.7 51.0 366.5 148.9 139.7 47.8 AFUDC - Transmission 78.7 43.9 34.8 — 76.8 44.6 32.2 — Other Regulatory Liabilities 383.1 78.8 77.5 14.3 309.9 39.5 63.2 9.8 Total Regulatory Liabilities 4,412.6 1,427.1 1,725.1 446.6 4,240.2 1,342.1 1,715.2 442.0 Less: Current Portion 532.5 219.8 173.0 61.9 389.4 137.2 164.8 58.8 Total Long-Term Regulatory Liabilities $ 3,880.1 $ 1,207.3 $ 1,552.1 $ 384.7 $ 3,850.8 $ 1,204.9 $ 1,550.4 $ 383.2 Recent Regulatory Developments: CL&P Tropical Storm Isaias Costs: On August 4, 2020, Tropical Storm Isaias caused catastrophic damage to our electric distribution system, which resulted in significant numbers and durations of customer outages, primarily in Connecticut. In terms of customer outages, this storm was one of the worst in CL&P’s history. PURA will investigate the prudence of costs incurred by CL&P to restore service in response to Tropical Storm Isaias. That investigation is expected to occur either in a separate proceeding not yet initiated or as part of CL&P’s next rate review proceeding. Tropical Storm Isaias resulted in deferred storm restoration costs of approximately $225 million at CL&P and $243 million at Eversource as of June 30, 2021. The estimated cost of restoration may continue to change as additional cost information becomes available and final storm costs are deferred or capitalized. Although PURA found that CL&P’s performance in its preparation for and response to Tropical Storm Isaias fell below applicable performance standards in certain instances, CL&P believes it will be able to present credible evidence in a future proceeding demonstrating there is no reasonably close causal connection between the alleged sub-standard performance and the storm costs incurred. While it is possible that some amount of storm costs may be disallowed by PURA in a future proceeding, any such amount cannot be estimated at this time. CL&P continues to believe that these storm restoration costs associated with Tropical Storm Isaias were prudently incurred and meet the criteria for cost recovery; and as a result, management does not expect the storm cost review by PURA to have a material impact on the financial position or results of operations of Eversource or CL&P. CL&P Tropical Storm Isaias Response Investigation: On April 28, 2021, PURA issued a final decision on CL&P’s compliance with its emergency response plan that concluded CL&P failed to comply with certain storm performance standards and was imprudent in certain instances. See Note 9G, “Commitments and Contingencies - CL&P Tropical Storm Isaias Response Investigation,” for an assessment by PURA accrued and recorded within current regulatory liabilities on CL&P’s balance sheet and for further information. PURA New Rate Design and Rate Review Proceeding: Pursuant to an October 2020 Connecticut law, PURA opened a proceeding related to new rate designs to consider the implementation of an interim rate decrease, low-income and economic development rates for electric customers, and a review of that rate design implementation process. The proceeding has separate phases. The first phase of the proceeding is not expected to have a material impact on CL&P’s earnings, financial position, or cash flows. In the second phase of this case, PURA is considering a potential interim rate decrease for CL&P. It is unclear how such a decrease would relate to the 90 basis point reduction PURA ordered as part of its April 28, 2021 decision concerning Tropical Storm Isaias. It is also unclear how long such a decrease, if implemented, would last. As a result, we cannot predict the ultimate outcome or the resulting financial impact on CL&P. A negative outcome in this phase of the proceeding could adversely impact CL&P’s future revenues, earnings and cash flows. Hearings commenced in May 2021. We expect to receive a draft decision on the interim rate decrease in September 2021, with a final decision in October 2021.

PROPERTY, PLANT AND EQUIPMENT A

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION	6 Months Ended
	Jun. 30, 2021
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION	PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION The following tables summarize property, plant and equipment by asset category: Eversource As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) Distribution - Electric $ 17,104.8 $ 16,703.2 Distribution - Natural Gas 6,227.8 6,111.2 Transmission - Electric 12,296.8 11,954.0 Distribution - Water 1,772.7 1,743.1 Solar 200.4 201.5 Utility 37,602.5 36,713.0 Other (1) 1,386.9 1,269.0 Property, Plant and Equipment, Gross 38,989.4 37,982.0 Less: Accumulated Depreciation Utility (8,756.6) (8,476.3) Other (525.8) (477.6) Total Accumulated Depreciation (9,282.4) (8,953.9) Property, Plant and Equipment, Net 29,707.0 29,028.1 Construction Work in Progress 2,171.6 1,854.4 Total Property, Plant and Equipment, Net $ 31,878.6 $ 30,882.5 As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) CL&P NSTAR PSNH CL&P NSTAR PSNH Distribution - Electric $ 6,989.4 $ 7,716.5 $ 2,439.2 $ 6,820.7 $ 7,544.4 $ 2,378.4 Transmission - Electric 5,653.4 4,866.5 1,778.6 5,512.0 4,701.3 1,742.4 Solar — 200.4 — — 201.5 — Property, Plant and Equipment, Gross 12,642.8 12,783.4 4,217.8 12,332.7 12,447.2 4,120.8 Less: Accumulated Depreciation (2,559.4) (3,182.8) (879.9) (2,475.4) (3,074.1) (848.9) Property, Plant and Equipment, Net 10,083.4 9,600.6 3,337.9 9,857.3 9,373.1 3,271.9 Construction Work in Progress 395.8 836.6 129.9 377.3 750.0 102.4 Total Property, Plant and Equipment, Net $ 10,479.2 $ 10,437.2 $ 3,467.8 $ 10,234.6 $ 10,123.1 $ 3,374.3 (1) These assets are primarily comprised of computer software, hardware and equipment at Eversource Service and buildings at The Rocky River Realty Company.

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	6 Months Ended
	Jun. 30, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS	DERIVATIVE INSTRUMENTS The electric and natural gas companies purchase and procure energy and energy-related products, which are subject to price volatility, for their customers. The costs associated with supplying energy to customers are recoverable from customers in future rates. These regulated companies manage the risks associated with the price volatility of energy and energy-related products through the use of derivative and non-derivative contracts. Many of the derivative contracts meet the definition of, and are designated as, normal and qualify for accrual accounting under the applicable accounting guidance. The costs and benefits of derivative contracts that meet the definition of normal are recognized in Operating Expenses on the statements of income, as applicable, as electricity or natural gas is delivered. Derivative contracts that are not designated as normal are recorded at fair value as current or long-term Derivative Assets or Derivative Liabilities on the balance sheets. For the electric and natural gas companies, regulatory assets or regulatory liabilities are recorded to offset the fair values of derivatives, as contract settlement amounts are recovered from, or refunded to, customers in their respective energy supply rates. The gross fair values of derivative assets and liabilities with the same counterparty are offset and reported as net Derivative Assets or Derivative Liabilities, with current and long-term portions, on the balance sheets. The following table presents the gross fair values of contracts, categorized by risk type, and the net amounts recorded as current or long-term derivative assets or liabilities: As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) Fair Value Hierarchy Commodity Supply and Price Risk Netting (1) Net Amount Commodity Supply and Price Risk Netting (1) Net Amount Current Derivative Assets: CL&P Level 3 $ 14.1 $ (0.4) $ 13.7 $ 13.7 $ (0.4) $ 13.3 Long-Term Derivative Assets: CL&P Level 3 55.0 (1.7) 53.3 58.7 (1.8) 56.9 Current Derivative Liabilities: CL&P Level 3 (70.9) — (70.9) (68.8) — (68.8) Other Level 2 — — — (3.3) 0.1 (3.2) Long-Term Derivative Liabilities: CL&P Level 3 (275.8) — (275.8) (294.5) — (294.5) (1) Amounts represent derivative assets and liabilities that Eversource elected to record net on the balance sheets. These amounts are subject to master netting agreements or similar agreements for which the right of offset exists. Derivative Contracts at Fair Value with Offsetting Regulatory Amounts Commodity Supply and Price Risk Management : As required by regulation, CL&P, along with UI, has capacity-related contracts with generation facilities. CL&P has a sharing agreement with UI, with 80 percent of the costs or benefits of each contract borne by or allocated to CL&P and 20 percent borne by or allocated to UI. The combined capacities of these contracts as of both June 30, 2021 and December 31, 2020 were 675 MW. The capacity contracts extend through 2026 and obligate both CL&P and UI to make or receive payments on a monthly basis to or from the generation facilities based on the difference between a set capacity price and the capacity market price received in the ISO-NE capacity markets. As of December 31, 2020, Eversource had New York Mercantile Exchange (NYMEX) financial contracts for natural gas futures in order to reduce variability associated with the price of 8.9 million MMBtu of natural gas. These contracts were classified as Level 2 in the fair value hierarchy. NSTAR Gas terminated its financial contracts swap program in April 2021. For the three months ended June 30, 2021 and 2020, there were gains of $0.9 million and losses of less than $0.1 million, respectively, deferred as regulatory costs, which reflect the change in fair value associated with Eversource's derivative contracts. For the six months ended June 30, 2021 and 2020, there were losses of $10.2 million and $18.0 million, respectively. Fair Value Measurements of Derivative Instruments The fair value of derivative contracts classified as Level 3 utilizes significant unobservable inputs. The fair value is modeled using income techniques, such as discounted cash flow valuations adjusted for assumptions related to exit price. Significant observable inputs for valuations of these contracts include energy and energy-related product prices in future years for which quoted prices in an active market exist. Fair value measurements categorized in Level 3 of the fair value hierarchy are prepared by individuals with expertise in valuation techniques, pricing of energy and energy-related products, and accounting requirements. The future capacity prices for periods that are not quoted in an active market or established at auction are based on available market data and are escalated based on estimates of inflation in order to address the full term of the contract. Valuations of derivative contracts using a discounted cash flow methodology include assumptions regarding the timing and likelihood of scheduled payments and also reflect non-performance risk, including credit, using the default probability approach based on the counterparty's credit rating for assets and the Company's credit rating for liabilities. Valuations incorporate estimates of premiums or discounts that would be required by a market participant to arrive at an exit price, using historical market transactions adjusted for the terms of the contract. The following is a summary of Level 3 derivative contracts and the range of the significant unobservable inputs utilized in the valuations over the duration of the contracts: As of June 30, 2021 As of December 31, 2020 CL&P Range Weighted Average (1) Period Covered Range Weighted Average (1) Period Covered Capacity Prices $2.61 $ 2.61 per kW-Month 2025 - 2026 $ 4.30 — $5.30 $ 4.63 per kW-Month 2024 - 2026 Forward Reserve Prices $ 0.54 — $0.90 $ 0.72 per kW-Month 2021 - 2024 $ 0.54 — $0.90 $ 0.72 per kW-Month 2021 - 2024 (1) Unobservable inputs were weighted by the relative future capacity and forward reserve prices and contractual MWs over the periods covered. Exit price premiums of 6.0 percent through 10.4 percent, or a weighted average of 9.3 percent, are also applied to these contracts and reflect the uncertainty and illiquidity premiums that would be required based on the most recent market activity available for similar type contracts. The risk premium was weighted by the relative fair value of the net derivative instruments. Significant increases or decreases in future capacity or forward reserve prices in isolation would decrease or increase, respectively, the fair value of the derivative liability. Any increases in risk premiums would increase the fair value of the derivative liability. Changes in these fair values are recorded as a regulatory asset or liability and do not impact net income. The following table presents changes in the Level 3 category of derivative assets and derivative liabilities measured at fair value on a recurring basis. The derivative assets and liabilities are presented on a net basis. CL&P For the Three Months Ended June 30, For the Six Months Ended June 30, (Millions of Dollars) 2021 2020 2021 2020 Derivatives, Net: Fair Value as of Beginning of Period $ (293.1) $ (333.8) $ (293.1) $ (329.2) Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets 0.9 (1.3) (11.5) (17.6) Settlements 12.5 13.1 24.9 24.8 Fair Value as of End of Period $ (279.7) $ (322.0) $ (279.7) $ (322.0)

MARKETABLE SECURITIES

MARKETABLE SECURITIES	6 Months Ended
	Jun. 30, 2021
Investments, Debt and Equity Securities [Abstract]
MARKETABLE SECURITIES	MARKETABLE SECURITIES Eversource holds marketable securities that are primarily used to fund certain non-qualified executive benefits. The trusts that hold marketable securities are not subject to regulatory oversight by state or federal agencies. CYAPC and YAEC maintain legally restricted trusts, each of which holds marketable securities, to fund the spent nuclear fuel removal obligations of their nuclear fuel storage facilities. Equity Securities: Unrealized gains and losses on equity securities held in Eversource's non-qualified executive benefit trust are recorded in Other Income, Net on the statements of income. The fair value of these equity securities as of June 30, 2021 and December 31, 2020 was $39.9 million and $40.9 million, respectively. For the three months ended June 30, 2021 and 2020, there were unrealized gains of $1.9 million and $6.6 million respectively, recorded in Other Income, Net related to these equity securities. For the six months ended June 30, 2021 and 2020, there were unrealized gains of $3.0 million and unrealized losses of $2.5 million, respectively. Eversource's equity securities also include CYAPC's and YAEC's marketable securities held in spent nuclear fuel trusts, which had fair values of $207.3 million and $205.1 million as of June 30, 2021 and December 31, 2020, respectively. Unrealized gains and losses for these spent nuclear fuel trusts are subject to regulatory accounting treatment and are recorded in Marketable Securities with the corresponding offset to Other Long-Term Liabilities on the balance sheets, with no impact on the statements of income. Available-for-Sale Debt Securities: The following is a summary of the available-for-sale debt securities, which are recorded at fair value and are included in current and long-term Marketable Securities on the balance sheets. As of June 30, 2021 As of December 31, 2020 Eversource (Millions of Dollars) Amortized Cost Pre-Tax Pre-Tax Fair Value Amortized Cost Pre-Tax Pre-Tax Fair Value Debt Securities $ 224.0 $ 7.0 $ (0.1) $ 230.9 $ 213.1 $ 11.2 $ (0.1) $ 224.2 Eversource's debt securities include CYAPC's and YAEC's marketable securities held in spent nuclear fuel trusts in the amounts of $198.4 million and $192.5 million as of June 30, 2021 and December 31, 2020, respectively. Unrealized gains and losses on available-for-sale debt securities held in Eversource's non-qualified benefit trust are recorded in Accumulated Other Comprehensive Income, excluding amounts related to credit losses or losses on securities intended to be sold, which are recorded in Other Income, Net. There have been no significant unrealized losses and no credit losses for the three and six months ended June 30, 2021 and 2020, and no allowance for credit losses as of June 30, 2021. Factors considered in determining whether a credit loss exists include adverse conditions specifically affecting the issuer, the payment history, ratings and rating changes of the security, and the severity of the impairment. For asset-backed debt securities, underlying collateral and expected future cash flows are also evaluated. Debt securities included in Eversource's non-qualified benefit trust portfolio are investment-grade bonds with a lower default risk based on their credit quality. As of June 30, 2021, the contractual maturities of available-for-sale debt securities were as follows: Eversource (Millions of Dollars) Amortized Cost Fair Value Less than one year (1) $ 36.5 $ 36.5 One to five years 67.5 69.4 Six to ten years 49.7 51.4 Greater than ten years 70.3 73.6 Total Debt Securities $ 224.0 $ 230.9 (1) Amounts in the Less than one year category include securities in the CYAPC and YAEC spent nuclear fuel trusts, which are restricted and are classified in long-term Marketable Securities on the balance sheets. Realized Gains and Losses: Realized gains and losses are recorded in Other Income, Net for Eversource's benefit trust and are offset in Other Long-Term Liabilities for CYAPC and YAEC. Eversource utilizes the specific identification basis method for the Eversource non-qualified benefit trust, and the average cost basis method for the CYAPC and YAEC spent nuclear fuel trusts to compute the realized gains and losses on the sale of marketable securities. Fair Value Measurements: The following table presents the marketable securities recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy: Eversource (Millions of Dollars) As of June 30, 2021 As of December 31, 2020 Level 1: Mutual Funds and Equities $ 247.2 $ 246.0 Money Market Funds 34.1 41.2 Total Level 1 $ 281.3 $ 287.2 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 100.8 $ 72.9 Corporate Debt Securities 62.8 63.8 Asset-Backed Debt Securities 13.6 11.9 Municipal Bonds 6.4 24.0 Other Fixed Income Securities 13.2 10.4 Total Level 2 $ 196.8 $ 183.0 Total Marketable Securities $ 478.1 $ 470.2 U.S. government issued debt securities are valued using market approaches that incorporate transactions for the same or similar bonds and adjustments for yields and maturity dates. Corporate debt securities are valued using a market approach, utilizing recent trades of the same or similar instruments and also incorporating yield curves, credit spreads and specific bond terms and conditions. Asset-backed debt securities include collateralized mortgage obligations, commercial mortgage backed securities, and securities collateralized by auto loans, credit card loans or receivables. Asset-backed debt securities are valued using recent trades of similar instruments, prepayment assumptions, yield curves, issuance and maturity dates, and tranche information. Municipal bonds are valued using a market approach that incorporates reported trades and benchmark yields. Other fixed income securities are valued using pricing models, quoted prices of securities with similar characteristics, and discounted cash flows.

SHORT-TERM AND LONG-TERM DEBT

SHORT-TERM AND LONG-TERM DEBT	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
SHORT-TERM AND LONG-TERM DEBT	SHORT-TERM AND LONG-TERM DEBT Short-Term Debt - Commercial Paper Programs and Credit Agreements : Eversource parent has a $2.00 billion commercial paper program allowing Eversource parent to issue commercial paper as a form of short-term debt. Eversource parent, CL&P, PSNH, NSTAR Gas, Yankee Gas and Aquarion Water Company of Connecticut are parties to a five-year $1.45 billion revolving credit facility, which terminates on December 6, 2024. Eversource parent and EGMA have a short-term $550 million revolving credit facility, which terminates on October 20, 2021. These revolving credit facilities serve to backstop Eversource parent's $2.00 billion commercial paper program. NSTAR Electric has a $650 million commercial paper program allowing NSTAR Electric to issue commercial paper as a form of short-term debt. NSTAR Electric is also a party to a five-year $650 million revolving credit facility, which terminates on December 6, 2024. The revolving credit facility serves to backstop NSTAR Electric's $650 million commercial paper program. The amount of borrowings outstanding and available under the commercial paper programs were as follows: Borrowings Outstanding as of Available Borrowing Capacity as of Weighted-Average Interest Rate as of June 30, 2021 December 31, 2020 June 30, 2021 December 31, 2020 June 30, 2021 December 31, 2020 (Millions of Dollars) Eversource Parent Commercial Paper Program $ 1,447.0 $ 1,054.3 $ 553.0 $ 945.7 0.19 % 0.25 % NSTAR Electric Commercial Paper Program 555.5 195.0 94.5 455.0 0.11 % 0.16 % There were no borrowings outstanding on the revolving credit facilities as of June 30, 2021 or December 31, 2020. CL&P and PSNH have uncommitted line of credit agreements totaling $450 million and $300 million, respectively, which will expire on May 12, 2022. There are no borrowings outstanding on either the CL&P or PSNH uncommitted line of credit agreements as of June 30, 2021. Amounts outstanding under the commercial paper programs are included in Notes Payable and classified in current liabilities on the Eversource and NSTAR Electric balance sheets, as all borrowings are outstanding for no more than 364 days at one time. The Company expects the future operating cash flows of Eversource, CL&P, NSTAR Electric and PSNH, along with existing borrowing availability and access to both debt and equity markets, will be sufficient to meet any working capital and future operating requirements, and capital investment forecasted opportunities. Intercompany Borrowings: Eversource parent uses its available capital resources to provide loans to its subsidiaries to assist in meeting their short-term borrowing needs. Eversource parent records intercompany interest income from its loans to subsidiaries, which is eliminated in consolidation. Intercompany loans from Eversource parent to its subsidiaries are eliminated in consolidation on Eversource's balance sheets. As of June 30, 2021, there were intercompany loans from Eversource parent to PSNH of $48.6 million, and to a subsidiary of NSTAR Electric of $21.5 million. As of December 31, 2020, there were intercompany loans from Eversource parent to PSNH of $46.3 million, and to a subsidiary of NSTAR Electric of $21.3 million. Intercompany loans from Eversource parent are included in Notes Payable to Eversource Parent and classified in current liabilities on the respective subsidiary's balance sheets. Availability under Long-Term Debt Issuance Authorizations: On March 31, 2021, the DPU approved NSTAR Electric's request for authorization to issue up to $1.6 billion in long-term debt through December 31, 2023. On May 18, 2021, EGMA filed a petition with the DPU for authorization to issue up to $725 million in long-term debt through December 31, 2023. Currently, EGMA has no external long-term debt and has long-term intercompany borrowings from Eversource parent. The remaining Eversource operating companies, including CL&P and PSNH, have utilized the long-term debt authorizations in place with the respective regulatory commissions. Long-Term Debt Issuances and Repayments: The following table summarizes long-term debt issuances and repayments: (Millions of Dollars) Issuance/(Repayment) Issue Date or Repayment Date Maturity Date Use of Proceeds for Issuance/ CL&P: 2.05% Series A First Mortgage Bonds $ 425.0 June 2021 July 2031 Repaid short-term debt, paid capital expenditures and working capital NSTAR Electric: 3.10% 2021 Debentures 300.0 May 2021 June 2051 Refinanced investments in eligible green expenditures, which were previously financed in 2019 and 2020 3.50% Series F Senior Notes (250.0) June 2021 September 2021 Paid on par call date in advance of maturity date PSNH: 4.05% Series Q First Mortgage Bonds (122.0) March 2021 June 2021 Paid on par call date in advance of maturity date 3.20% Series R First Mortgage Bonds (160.0) June 2021 September 2021 Paid on par call date in advance of maturity date 2.20% Series V First Mortgage Bonds 350.0 June 2021 June 2031 Repaid short-term debt, including short-term debt used to redeem Series R First Mortgage Bonds, paid capital expenditures and working capital Other: Eversource Parent 2.50% Series I Senior Notes (450.0) February 2021 March 2021 Paid on par call date in advance of maturity date Eversource Parent 2.55% Series S Senior Notes 350.0 March 2021 March 2031 Repaid short-term debt, including short-term debt used to redeem Series I Senior Notes Aquarion Water Company of Connecticut 3.31% Senior Notes 100.0 April 2021 April 2051 Repaid 5.50% Notes, repaid short-term debt, paid capital expenditures and working capital Aquarion Water Company of Connecticut 5.50% Notes (40.0) April 2021 April 2021 Paid at maturity In

RATE REDUCTION BONDS AND VARIAB

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES	6 Months Ended
	Jun. 30, 2021
Rate Reduction Bonds and Variable Interest Entity [Abstract]
RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES	RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES Rate Reduction Bonds: In May 2018, PSNH Funding, a wholly-owned subsidiary of PSNH, issued $635.7 million of securitized RRBs in multiple tranches with a weighted average interest rate of 3.66 percent, and final maturity dates ranging from 2026 to 2035. The RRBs are expected to be repaid by February 1, 2033. RRB payments consist of principal and interest and are paid semi-annually, beginning on February 1, 2019. The RRBs were issued pursuant to a finance order issued by the NHPUC in January 2018 to recover remaining costs resulting from the divestiture of PSNH’s generation assets. PSNH Funding was formed solely to issue RRBs to finance PSNH's unrecovered remaining costs associated with the divestiture of its generation assets. PSNH Funding is considered a VIE primarily because the equity capitalization is insufficient to support its operations. PSNH has the power to direct the significant activities of the VIE and is most closely associated with the VIE as compared to other interest holders. Therefore, PSNH is considered the primary beneficiary and consolidates PSNH Funding in its consolidated financial statements. The following tables summarize the impact of PSNH Funding on PSNH's balance sheets and income statements: (Millions of Dollars) PSNH Balance Sheets: As of June 30, 2021 As of December 31, 2020 Restricted Cash - Current Portion (included in Current Assets) $ 34.9 $ 36.8 Restricted Cash - Long-Term Portion (included in Other Long-Term Assets) 3.2 2.1 Securitized Stranded Cost (included in Regulatory Assets) 500.5 522.1 Other Regulatory Liabilities (included in Regulatory Liabilities) 8.9 9.1 Accrued Interest (included in Other Current Liabilities) 7.7 8.0 Rate Reduction Bonds - Current Portion 43.2 43.2 Rate Reduction Bonds - Long-Term Portion 475.3 496.9 (Millions of Dollars) PSNH Income Statements: For the Three Months Ended For the Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net) $ 10.8 $ 10.8 $ 21.6 $ 21.6 Interest Expense on RRB Principal (included in Interest Expense) 4.6 5.0 9.3 10.0

PENSION BENEFITS AND POSTRETIRE

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION	6 Months Ended
	Jun. 30, 2021
Postemployment Benefits [Abstract]
PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION	PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION Eversource provides defined benefit retirement plans (Pension Plans) that cover eligible employees. In addition to the Pension Plans, Eversource maintains non-qualified defined benefit retirement plans (SERP Plans), which provide benefits in excess of Internal Revenue Code limitations to eligible participants consisting of current and retired employees. Eversource also provides defined benefit postretirement plans (PBOP Plans) that provide life insurance and a health reimbursement arrangement created for the purpose of reimbursing retirees and dependents for health insurance premiums and certain medical expenses to eligible employees that meet certain age and service eligibility requirements. The components of net periodic benefit plan expense/(income) for the Pension, SERP and PBOP Plans, prior to amounts capitalized as Property, Plant and Equipment or deferred as regulatory assets for future recovery, are shown below. The service cost component of net periodic benefit plan expense/(income), less the capitalized portion, is included in Operations and Maintenance expense on the statements of income. The remaining components of net periodic benefit plan expense/(income), less the deferred portion, are included in Other Income, Net on the statements of income. Pension, SERP and PBOP expense reflected in the statements of cash flows for CL&P, NSTAR Electric and PSNH does not include intercompany allocations of net periodic benefit plan expense/(income), as these amounts are cash settled on a short-term basis. Pension and SERP PBOP For the Three Months Ended June 30, 2021 For the Three Months Ended June 30, 2021 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 18.4 $ 5.5 $ 3.9 $ 2.2 $ 3.3 $ 0.6 $ 0.6 $ 0.3 Interest Cost 27.1 6.7 6.7 3.6 4.2 0.8 1.1 0.4 Expected Return on Plan Assets (87.4) (21.7) (27.1) (11.8) (19.8) (2.6) (9.2) (1.5) Actuarial Loss 47.8 10.8 15.3 5.2 1.3 0.4 0.5 0.1 Prior Service Cost/(Credit) 0.3 — 0.1 — (5.3) 0.3 (4.2) 0.1 Total Net Periodic Benefit Plan Expense/(Income) $ 6.2 $ 1.3 $ (1.1) $ (0.8) $ (16.3) $ (0.5) $ (11.2) $ (0.6) Intercompany Expense/(Income) Allocations N/A $ 2.3 $ 2.5 $ 0.7 N/A $ (0.6) $ (0.6) $ (0.2) Pension and SERP PBOP For the Six Months Ended June 30, 2021 For the Six Months Ended June 30, 2021 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH Service Cost $ 39.7 $ 11.8 $ 7.9 $ 4.4 $ 6.8 $ 1.2 $ 1.2 $ 0.6 Interest Cost 59.7 14.0 13.4 7.2 8.6 1.6 2.2 0.9 Expected Return on Plan Assets (196.3) (43.3) (54.0) (23.7) (39.5) (5.2) (18.5) (3.0) Actuarial Loss 109.4 23.8 30.8 10.1 3.9 0.8 1.1 0.3 Prior Service Cost/(Credit) 0.6 — 0.2 — (10.6) 0.5 (8.4) 0.2 Total Net Periodic Benefit Plan Expense/(Income) $ 13.1 $ 6.3 $ (1.7) $ (2.0) $ (30.8) $ (1.1) $ (22.4) $ (1.0) Intercompany Expense/(Income) Allocations N/A $ 3.6 $ 4.0 $ 1.2 N/A $ (0.9) $ (1.0) $ (0.3) Pension and SERP PBOP For the Three Months Ended June 30, 2020 For the Three Months Ended June 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH Service Cost $ 18.7 $ 5.4 $ 3.8 $ 2.0 $ 2.0 $ 0.4 $ 0.5 $ 0.2 Interest Cost 44.3 9.3 9.7 4.8 6.4 1.0 1.6 0.8 Expected Return on Plan Assets (99.3) (19.8) (25.7) (11.1) (18.7) (2.5) (8.5) (1.4) Actuarial Loss 50.7 9.7 14.0 3.9 2.0 0.2 0.5 0.3 Prior Service Cost/(Credit) 0.3 — 0.1 — (5.2) 0.2 (4.3) 0.1 Total Net Periodic Benefit Plan Expense/(Income) $ 14.7 $ 4.6 $ 1.9 $ (0.4) $ (13.5) $ (0.7) $ (10.2) $ — Intercompany Expense/(Income) Allocations N/A $ 2.4 $ 2.3 $ 0.8 N/A $ (0.2) $ (0.2) $ (0.1) Pension and SERP PBOP For the Six Months Ended June 30, 2020 For the Six Months Ended June 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH Service Cost $ 38.3 $ 11.1 $ 7.6 $ 4.2 $ 4.9 $ 0.9 $ 1.1 $ 0.4 Interest Cost 88.6 18.8 19.3 9.7 12.2 2.2 3.3 1.4 Expected Return on Plan Assets (199.6) (39.8) (51.5) (22.4) (36.8) (4.9) (17.0) (2.8) Actuarial Loss 100.0 19.7 27.3 8.0 4.1 0.6 1.2 0.4 Prior Service Cost/(Credit) 0.6 — 0.2 — (10.6) 0.4 (8.5) 0.2 Total Net Periodic Benefit Plan Expense/(Income) $ 27.9 $ 9.8 $ 2.9 $ (0.5) $ (26.2) $ (0.8) $ (19.9) $ (0.4) Intercompany Expense/(Income) Allocations N/A $ 4.3 $ 4.2 $ 1.4 N/A $ (0.6) $ (0.6) $ (0.3)

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES A. Environmental Matters Eversource, CL&P, NSTAR Electric and PSNH are subject to environmental laws and regulations intended to mitigate or remove the effect of past operations and improve or maintain the quality of the environment. These laws and regulations require the removal or the remedy of the effect on the environment of the disposal or release of certain specified hazardous substances at current and former operating sites. Eversource, CL&P, NSTAR Electric and PSNH have an active environmental auditing and training program and each believes it is substantially in compliance with all enacted laws and regulations. The number of environmental sites and related reserves for which remediation or long-term monitoring, preliminary site work or site assessment is being performed are as follows: As of June 30, 2021 As of December 31, 2020 Number of Sites Reserve Number of Sites Reserve Eversource 62 $ 108.8 63 $ 102.4 CL&P 14 10.7 15 12.3 NSTAR Electric 12 3.9 12 4.7 PSNH 9 6.6 9 7.1 The increase in the reserve balance was due primarily to a change in cost estimate at an NSTAR Gas MGP site under investigation for which we now know of additional remediation that is required. Included in the number of sites and reserve amounts above are former MGP sites that were operated several decades ago and manufactured natural gas from coal and other processes, which resulted in certain by-products remaining in the environment that may pose a potential risk to human health and the environment, for which Eversource may have potential liability. The reserve balances related to these former MGP sites were $101.0 million and $92.2 million as of June 30, 2021 and December 31, 2020, respectively, and related primarily to the natural gas business segment. These reserve estimates are subjective in nature as they take into consideration several different remediation options at each specific site. The reliability and precision of these estimates can be affected by several factors, including new information concerning either the level of contamination at the site, the extent of Eversource's, CL&P's, NSTAR Electric's and PSNH's responsibility for remediation or the extent of remediation required, recently enacted laws and regulations or changes in cost estimates due to certain economic factors. It is possible that new information or future developments could require a reassessment of the potential exposure to required environmental remediation. As this information becomes available, management will continue to assess the potential exposure and adjust the reserves accordingly. B. Long-Term Contractual Arrangements The following is an update to the current status of long-term contractual arrangements set forth in Note 13B of the Eversource 2020 Form 10-K. Renewable Energy : Renewable energy contracts include non-cancelable commitments under contracts of NSTAR Electric for the purchase of energy and RECs from renewable energy facilities. NSTAR Electric (Millions of Dollars) 2021 2022 2023 2024 2025 Thereafter Total Renewable Energy $ 48.1 $ 103.6 $ 229.3 $ 339.4 $ 346.2 $ 6,527.7 $ 7,594.3 The table has been updated to include long-term commitments of NSTAR Electric pertaining to the Massachusetts Clean Energy 83D contract, for which construction commenced in 2021. Estimated costs under this contract are expected to begin in 2023 and range between $150 million and $415 million per year under a 20-year contract, totaling approximately $6.7 billion. C. Guarantees and Indemnifications In the normal course of business, Eversource parent provides credit assurances on behalf of its subsidiaries, including CL&P, NSTAR Electric and PSNH, in the form of guarantees. Management does not anticipate a material impact to net income or cash flows as a result of these various guarantees and indemnifications. Guarantees issued on behalf of unconsolidated entities, including equity method offshore wind investments, for which Eversource parent is the guarantor, are recorded at fair value as a liability on the balance sheet at the inception of the guarantee. Eversource regularly reviews performance risk under these guarantee arrangements, and in the event it becomes probable that Eversource parent will be required to perform under the guarantee, the amount of probable payment will be recorded. The fair value of guarantees issued on behalf of unconsolidated entities are recorded within Other Long-Term Liabilities on the balance sheet, and was $0.5 million as of June 30, 2021. The following table summarizes Eversource parent's exposure to guarantees and indemnifications of its subsidiaries and affiliates to external parties: As of June 30, 2021 Company (Obligor) Description Maximum Exposure Expiration Dates North East Offshore LLC Construction-related purchase agreements with third-party contractors (1) $ 29.7 (1) Eversource Investment LLC Funding and indemnification obligations of North East Offshore LLC (2) — (2) Sunrise Wind LLC OREC capacity production (3) 2.2 (3) South Fork Wind, LLC Transmission interconnection 1.6 — Bay State Wind LLC Real estate purchase 2.5 2022 Various Surety bonds (4) 59.5 2021 - 2023 Rocky River Realty Company and Lease payments for real estate 4.4 2024 (1) Eversource parent issued guarantees on behalf of its 50 percent-owned affiliate, North East Offshore LLC (NEO), under which Eversource parent agreed to guarantee 50 percent of NEO’s performance of obligations under certain purchase agreements with third-party contactors, in an amount not to exceed $1.3 billion with an expiration date in 2025. Eversource parent also issued a separate guarantee to Ørsted on behalf of NEO, under which Eversource parent agreed to guarantee 50 percent of NEO’s payment obligations under certain offshore wind project construction-related agreements with Ørsted in an aggregate amount not to exceed $62.5 million. Any amounts paid under this guarantee to Ørsted will count toward, but not increase, the maximum amount of the Funding Guarantee described in Note 2, below. The guarantee expires upon the full performance of the guaranteed obligations. (2) Eversource parent issued a guarantee (Funding Guarantee) on behalf of Eversource Investment LLC (EI), its wholly-owned subsidiary that holds a 50 percent ownership interest in NEO, under which Eversource parent agreed to guarantee certain funding obligations and certain indemnification payments of EI under the Amended and Restated Limited Liability Company Operating Agreement of NEO, in an amount not to exceed $910 million. The guaranteed obligations include payment of EI's funding obligations during the construction phase of NEO’s underlying offshore wind projects and indemnification obligations associated with third party credit support for its investment in NEO. Eversource parent’s obligations under the Funding Guarantee expire upon the full performance of the guaranteed obligations. (3) Eversource parent issued a guarantee on behalf of its 50 percent-owned affiliate, Sunrise Wind LLC, whereby Eversource parent will guarantee Sunrise Wind LLC's performance of certain obligations, in an amount not to exceed $15.4 million, under the Offshore Wind Renewable Energy Certificate Purchase and Sale Agreement (the Agreement). The Agreement was executed on October 23, 2019, by and between the New York State Energy Research and Development Authority (NYSERDA) and Sunrise Wind LLC. The guarantee expires upon the full performance of the guaranteed obligations. (4) Surety bond expiration dates reflect termination dates, the majority of which will be renewed or extended. Certain surety bonds contain credit ratings triggers that would require Eversource parent to post collateral in the event that the unsecured debt credit ratings of Eversource parent are downgraded. Letter of Credit : On September 16, 2020, Eversource parent entered into a guarantee on behalf of EI, which holds Eversource's investments in offshore wind-related equity method investments, under which Eversource parent would guarantee EI's obligations under a letter of credit facility with a financial institution that EI may request in an aggregate amount of up to approximately $25 million. D. Spent Nuclear Fuel Obligations - Yankee Companies CL&P, NSTAR Electric and PSNH have plant closure and fuel storage cost obligations to the Yankee Companies, which have each completed the physical decommissioning of their respective nuclear power facilities and are now engaged in the long-term storage of their spent fuel. The Yankee Companies fund these costs through litigation proceeds received from the DOE and, to the extent necessary, through wholesale, FERC-approved rates charged under power purchase agreements with several New England utilities, including CL&P, NSTAR Electric and PSNH. CL&P, NSTAR Electric and PSNH, in turn recover these costs from their customers through state regulatory commission-approved retail rates. The Yankee Companies collect amounts that management believes are adequate to recover the remaining plant closure and fuel storage cost estimates for the respective plants. Management believes CL&P and NSTAR Electric will recover their shares of these obligations from their customers. PSNH has recovered its total share of these costs from its customers. Spent Nuclear Fuel Litigation: The Yankee Companies have filed complaints against the DOE in the Court of Federal Claims seeking monetary damages resulting from the DOE's failure to accept delivery of, and provide for a permanent facility to store, spent nuclear fuel pursuant to the terms of the 1983 spent fuel and high-level waste disposal contracts between the Yankee Companies and the DOE. The court previously awarded the Yankee Companies damages for Phases I, II, III and IV of litigation resulting from the DOE's failure to meet its contractual obligations. These Phases covered damages incurred in the years 1998 through 2016, and the awarded damages have been received by the Yankee Companies with certain amounts of the damages refunded to their customers. DOE Phase V Damages - On March 25, 2021, each of the Yankee Companies filed a fifth set of lawsuits against the DOE in the Court of Federal Claims. The Yankee Companies are calculating and will be seeking monetary damages for CYAPC, YAEC and MYAPC, resulting from the DOE's failure to begin accepting spent nuclear fuel for disposal covering the years from 2017 to 2020 (DOE Phase V). E. FERC ROE Complaints Four separate complaints were filed at the FERC by combinations of New England state attorneys general, state regulatory commissions, consumer advocates, consumer groups, municipal parties and other parties (collectively, the Complainants). In each of the first three complaints, filed on October 1, 2011, December 27, 2012, and July 31, 2014, respectively, the Complainants challenged the NETOs' base ROE of 11.14 percent that had been utilized since 2005 and sought an order to reduce it prospectively from the date of the final FERC order and for the separate 15-month complaint periods. In the fourth complaint, filed April 29, 2016, the Complainants challenged the NETOs' base ROE billed of 10.57 percent and the maximum ROE for transmission incentive (incentive cap) of 11.74 percent, asserting that these ROEs were unjust and unreasonable. The ROE originally billed during the period October 1, 2011 (beginning of the first complaint period) through October 15, 2014 consisted of a base ROE of 11.14 percent and incentives up to 13.1 percent. On October 16, 2014, the FERC set the base ROE at 10.57 percent and the incentive cap at 11.74 percent for the first complaint period. This was also effective for all prospective billings to customers beginning October 16, 2014. This FERC order was vacated on April 14, 2017 by the U.S. Court of Appeals for the D.C. Circuit (the Court). All amounts associated with the first complaint period have been refunded, which totaled $38.9 million (pre-tax and excluding interest) at Eversource and reflected both the base ROE and incentive cap prescribed by the FERC order. The refund consisted of $22.4 million for CL&P, $13.7 million for NSTAR Electric and $2.8 million for PSNH. Eversource has recorded a reserve of $39.1 million (pre-tax and excluding interest) for the second complaint period as of June 30, 2021 and December 31, 2020. This reserve represents the difference between the billed rates during the second complaint period and a 10.57 percent base ROE and 11.74 percent incentive cap. The reserve consisted of $21.4 million for CL&P, $14.6 million for NSTAR Electric and $3.1 million for PSNH as of June 30, 2021 and December 31, 2020. On October 16, 2018, FERC issued an order on all four complaints describing how it intends to address the issues that were remanded by the Court. FERC proposed a new framework to determine (1) whether an existing ROE is unjust and unreasonable and, if so, (2) how to calculate a replacement ROE. Initial briefs were filed by the NETOs, Complainants and FERC Trial Staff on January 11, 2019 and reply briefs were filed on March 8, 2019. The NETOs' brief was supportive of the overall ROE methodology determined in the October 16, 2018 order provided the FERC does not change the proposed methodology or alter its implementation in a manner that has a material impact on the results. The FERC order included illustrative calculations for the first complaint using FERC's proposed frameworks with financial data from that complaint. Those illustrative calculations indicated that for the first complaint period, for the NETOs, which FERC concludes are of average financial risk, the preliminary just and reasonable base ROE is 10.41 percent and the preliminary incentive cap on total ROE is 13.08 percent. If the results of the illustrative calculations were included in a final FERC order for each of the complaint periods, then a 10.41 percent base ROE and a 13.08 percent incentive cap would not have a significant impact on our financial statements for all of the complaint periods. These preliminary calculations are not binding and do not represent what we believe to be the most likely outcome of a final FERC order. On November 21, 2019, FERC issued Opinion No. 569 affecting the two pending transmission ROE complaints against the Midcontinent ISO (MISO) transmission owners, in which FERC adopted a new methodology for determining base ROEs. Various parties sought rehearing. On December 23, 2019, the NETOs filed supplementary materials in the NETOs' four pending cases to respond to this new methodology because of the uncertainty of the applicability to the NETOs’ cases. On May 21, 2020, the FERC issued its order in Opinion No. 569-A on the rehearing of the MISO transmission owners' cases, in which FERC again changed its methodology for determining the MISO transmission owners' base ROEs. Various parties appealed the MISO transmission owners' opinion. On November 19, 2020, the FERC issued Opinion No. 569-B denying rehearing of Opinion No. 569-A and reaffirmed the methodology previously adopted in Opinion No. 569-A. The new methodology differs significantly from the methodology proposed by FERC in its October 16, 2018 order to determine the NETOs' base ROEs in its four pending cases. Given the significant uncertainty regarding the applicability of the FERC opinions in the MISO transmission owners' two complaint cases to the NETOs' pending four complaint cases, Eversource concluded that there is no reasonable basis for a change to the reserve or recognized ROEs for any of the complaint periods at this time. As well, Eversource cannot reasonably estimate a range of any gain or loss for any of the four complaint proceedings at this time. Eversource, CL&P, NSTAR Electric and PSNH currently record revenues at the 10.57 percent base ROE and incentive cap at 11.74 percent established in the October 16, 2014 FERC order. A change of 10 basis points to the base ROE used to establish the reserves would impact Eversource's after-tax earnings by an average of approximately $3 million for each of the four 15-month complaint periods. F. Eversource and NSTAR Electric Boston Harbor Civil Action In 2016, the United States Attorney on behalf of the United States Army Corps of Engineers filed a civil action in the United States District Court for the District of Massachusetts against NSTAR Electric, HEEC, and the Massachusetts Water Resources Authority (together with NSTAR Electric and HEEC, the "Defendants"). The action alleged that the Defendants failed to comply with certain permitting requirements related to the placement of the HEEC-owned electric distribution cable beneath Boston Harbor. The parties reached a settlement pursuant to which HEEC agreed to install a new 115kV distribution cable across Boston Harbor to Deer Island, utilizing a different route, and remove portions of the existing cable. Construction of the new distribution cable was completed in August 2019, and removal of the portions of the existing cable was completed in January 2020. All issues surrounding the current permit from the United States Army Corps of Engineers are expected to be resolved, and subsequently, such litigation then dismissed with prejudice. G. CL&P Tropical Storm Isaias Response Investigation In August 2020, PURA opened a docket to investigate the preparation for and response to Tropical Storm Isaias by Connecticut utilities, including CL&P. On April 28, 2021, PURA issued a final decision on CL&P’s compliance with its emergency response plan that concluded CL&P failed to comply with certain storm performance standards and was imprudent in certain instances. Specifically, PURA concluded that CL&P did not satisfy the performance standards for managing its municipal liaison program, timely removing electrical hazards from blocked roads, communicating critical information to its customers, or meeting its obligation to secure adequate external contractor and mutual aid resources in a timely manner. Based on its findings, PURA ordered CL&P to adjust its future rates in a pending or future rate proceeding to reflect a monetary penalty in the form of a downward adjustment of 90 basis points in its allowed rate of return on equity (ROE), which is currently 9.25 percent. In its decision, PURA explained that additional monetary penalties and further enforcement orders pursuant to Connecticut statute would be considered in a separate proceeding that was initiated on May 6, 2021. On June 10, 2021, CL&P appealed the April 28, 2021 PURA decision. On May 6, 2021, as part of the penalty proceeding, PURA issued a notice of violation that included an assessment of $30 million, consisting of a $28.4 million civil penalty for non-compliance with storm performance standards to be provided as credits on customer bills and a $1.6 million fine for violations of accident reporting requirements to be paid to the State of Connecticut’s general fund. On July 14, 2021, PURA issued a final decision in this penalty proceeding that included an assessment of $28.6 million, maintaining the $28.4 million performance penalty and reducing the $1.6 million fine for accident reporting to $0.2 million. PURA directed the $28.4 million performance penalty to be credited to customers on electric bills beginning on August 1, 2021 through July 31, 2022. The $28.4 million is the maximum statutory penalty amount under applicable Connecticut law in effect at the time of Tropical Storm Isaias, which is 2.5 percent of CL&P’s annual distribution revenues. Management has accrued PURA’s assessment in the first quarter of 2021. As of June 30, 2021, the liability for the assessment was recorded as a current regulatory liability on CL&P’s balance sheet and as a charge to Operations and Maintenance expense on the six months ended June 30, 2021 income statement. The after-tax earnings impact of this charge was $0.07 per share. The Company believes it has meritorious defenses and intends to vigorously defend CL&P’s position, but does not have an estimate of the ultimate outcome on CL&P’s financial position, results of operations or cash flows at this time. The estimated annual impact of a 90 basis point ROE reduction at CL&P would be a decrease of approximately $31 million of future annual revenues and approximately $21 million of lower annual earnings. The ROE reduction would impact revenues and earnings prospectively, once new rates are established. PURA stated it intends to use its interim rate decrease proceeding that is currently pending to implement the storm-related return on equity penalty ordered in the April 28, 2021 decision, which is subject to our pending court appeal. In light of our pending court appeal, coupled with the uncertainty of how long that penalty, if implemented, would last, we cannot predict the ultimate outcome or the resulting financial impact on CL&P.

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	FAIR VALUE OF FINANCIAL INSTRUMENTS The following methods and assumptions were used to estimate the fair value of each of the following financial instruments: Preferred Stock, Long-Term Debt and Rate Reduction Bonds: The fair value of CL&P's and NSTAR Electric's preferred stock is based upon pricing models that incorporate interest rates and other market factors, valuations or trades of similar securities and cash flow projections. The fair value of long-term debt and RRB debt securities is based upon pricing models that incorporate quoted market prices for those issues or similar issues adjusted for market conditions, credit ratings of the respective companies and treasury benchmark yields. The fair values provided in the table below are classified as Level 2 within the fair value hierarchy. Carrying amounts and estimated fair values are as follows: Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Carrying Fair Carrying Fair Carrying Fair Carrying Fair As of June 30, 2021: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 166.4 $ 116.2 $ 122.2 $ 43.0 $ 44.2 $ — $ — Long-Term Debt 16,651.2 18,364.0 4,335.6 5,049.8 3,688.3 4,208.4 1,163.7 1,239.0 Rate Reduction Bonds 518.5 579.6 — — — — 518.5 579.6 As of December 31, 2020: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 169.1 $ 116.2 $ 123.4 $ 43.0 $ 45.7 $ — $ — Long-Term Debt 16,179.1 18,420.1 3,914.8 4,800.9 3,643.2 4,294.0 1,099.1 1,207.0 Rate Reduction Bonds 540.1 603.4 — — — — 540.1 603.4 Derivative Instruments and Marketable Securities: Derivative instruments and investments in marketable securities are carried at fair value. For further information, see Note 4, "Derivative Instruments," and Note 5, "Marketable Securities," to the financial statements. See Note 1D, "Summary of Significant Accounting Policies – Fair Value Measurements," for the fair value measurement policy and the fair value hierarchy.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS)	ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) The changes in accumulated other comprehensive income/(loss) by component, net of tax, are as follows: For the Six Months Ended June 30, 2021 For the Six Months Ended June 30, 2020 Eversource (Millions of Dollars) Qualified Unrealized Defined Total Qualified Unrealized Defined Total Balance as of January 1st $ (1.4) $ 1.1 $ (76.1) $ (76.4) $ (3.0) $ 0.7 $ (62.8) $ (65.1) OCI Before Reclassifications — (0.5) (2.4) (2.9) — 0.4 (1.6) (1.2) Amounts Reclassified from AOCI 0.9 — 4.1 5.0 0.6 — 3.1 3.7 Net OCI 0.9 (0.5) 1.7 2.1 0.6 0.4 1.5 2.5 Balance as of June 30th $ (0.5) $ 0.6 $ (74.4) $ (74.3) $ (2.4) $ 1.1 $ (61.3) $ (62.6) Defined benefit plan OCI amounts before reclassifications relate to actuarial gains and losses that arose during the year and were recognized in AOCI. The unamortized actuarial gains and losses and prior service costs on the defined benefit plans are amortized from AOCI into Other Income, Net over the average future employee service period, and are reflected in amounts reclassified from AOCI.

COMMON SHARES

COMMON SHARES	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
COMMON SHARES	COMMON SHARES The following table sets forth the Eversource parent common shares and the shares of common stock of CL&P, NSTAR Electric and PSNH that were authorized and issued, as well as the respective per share par values: Shares Authorized as of June 30, 2021 and December 31, 2020 Issued as of Par Value June 30, 2021 December 31, 2020 Eversource $ 5 380,000,000 357,818,402 357,818,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 200 200 PSNH $ 1 100,000,000 301 301 Treasury Shares: As of June 30, 2021 and December 31, 2020, there were 14,217,299 and 14,864,379 Eversource common shares held as treasury shares, respectively. As of June 30, 2021 and December 31, 2020, Eversource common shares outstanding we re 343,601,103 and 342,954,023, respectively.

COMMON SHAREHOLDERS' EQUITY AND

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	COMMON SHARES The following table sets forth the Eversource parent common shares and the shares of common stock of CL&P, NSTAR Electric and PSNH that were authorized and issued, as well as the respective per share par values: Shares Authorized as of June 30, 2021 and December 31, 2020 Issued as of Par Value June 30, 2021 December 31, 2020 Eversource $ 5 380,000,000 357,818,402 357,818,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 200 200 PSNH $ 1 100,000,000 301 301 Treasury Shares: As of June 30, 2021 and December 31, 2020, there were 14,217,299 and 14,864,379 Eversource common shares held as treasury shares, respectively. As of June 30, 2021 and December 31, 2020, Eversource common shares outstanding we re 343,601,103 and 342,954,023, respectively.

EARNINGS PER SHARE

EARNINGS PER SHARE	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE Basic EPS is computed based upon the weighted average number of common shares outstanding during each period. Diluted EPS is computed on the basis of the weighted average number of common shares outstanding plus the potential dilutive effect of certain share-based compensation awards as if they were converted into outstanding common shares. The dilutive effect of unvested RSU and performance share awards is calculated using the treasury stock method. RSU and performance share awards are included in basic weighted average common shares outstanding as of the date that all necessary vesting conditions have been satisfied. There were no antidilutive share awards excluded from the computation of diluted EPS for the three and six months ended June 30, 2021. For the three and six months ended June 30, 2020, there were 158,242 and 79,121 antidilutive share awards excluded from the EPS computation respectively, as their impact would have been antidilutive. Antidilutive shares pertained to a purchase option extended to underwriters in connection with Eversource’s common share issuance on June 15, 2020. The following table sets forth the components of basic and diluted EPS: Eversource (Millions of Dollars, except share information) For the Three Months Ended For the Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 Net Income Attributable to Common Shareholders $ 264.5 $ 252.2 $ 630.7 $ 587.0 Weighted Average Common Shares Outstanding: Basic 343,844,626 337,946,663 343,761,435 334,524,452 Dilutive Effect of: Share-Based Compensation Awards and Other 591,070 614,986 623,758 681,110 Equity Forward Sale Agreement — — — 543,842 Total Dilutive Effect 591,070 614,986 623,758 1,224,952 Diluted 344,435,696 338,561,649 344,385,193 335,749,404 Basic and Diluted EPS $ 0.77 $ 0.75 $ 1.83 $ 1.75

REVENUES

REVENUES	6 Months Ended
	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
REVENUES	REVENUES The following tables present operating revenues disaggregated by revenue source: For the Three Months Ended June 30, 2021 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 882.1 $ 174.2 $ — $ 36.0 $ — $ — $ 1,092.3 Commercial 594.1 89.6 — 16.1 — (1.3) 698.5 Industrial 82.0 34.8 — 1.1 — (4.4) 113.5 Total Retail Tariff Sales Revenues 1,558.2 298.6 — 53.2 — (5.7) 1,904.3 Wholesale Transmission Revenues — — 416.9 — 20.3 (345.9) 91.3 Wholesale Market Sales Revenues 97.2 15.7 — 1.0 — — 113.9 Other Revenues from Contracts with Customers 25.1 1.0 3.4 1.2 309.7 (307.0) 33.4 Total Revenues from Contracts with Customers 1,680.5 315.3 420.3 55.4 330.0 (658.6) 2,142.9 Alternative Revenue Programs (4.8) (3.4) (9.3) (2.7) — (1.2) (21.4) Other Revenues (1) 0.8 (0.1) 0.2 0.1 — — 1.0 Total Operating Revenues $ 1,676.5 $ 311.8 $ 411.2 $ 52.8 $ 330.0 $ (659.8) $ 2,122.5 For the Six Months Ended June 30, 2021 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,948.1 $ 641.1 $ — $ 63.7 $ — $ — $ 2,652.9 Commercial 1,154.0 297.4 — 29.8 — (2.7) 1,478.5 Industrial 165.0 90.8 — 2.2 — (8.0) 250.0 Total Retail Tariff Sales Revenues 3,267.1 1,029.3 — 95.7 — (10.7) 4,381.4 Wholesale Transmission Revenues — — 811.2 — 39.5 (666.9) 183.8 Wholesale Market Sales Revenues 246.3 42.0 — 1.8 — — 290.1 Other Revenues from Contracts with Customers 43.4 2.4 6.8 2.4 633.5 (628.3) 60.2 Total Revenues from Contracts with Customers 3,556.8 1,073.7 818.0 99.9 673.0 (1,305.9) 4,915.5 Alternative Revenue Programs 18.2 18.6 (6.6) (0.9) — 1.0 30.3 Other Revenues (1) 1.9 — 0.5 0.2 — — 2.6 Total Operating Revenues $ 3,576.9 $ 1,092.3 $ 811.9 $ 99.2 $ 673.0 $ (1,304.9) $ 4,948.4 For the Three Months Ended June 30, 2020 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 916.0 $ 116.1 $ — $ 39.7 $ — $ — $ 1,071.8 Commercial 526.0 67.8 — 15.9 — (1.3) 608.4 Industrial 77.7 21.1 — 1.2 — (3.4) 96.6 Total Retail Tariff Sales Revenues 1,519.7 205.0 — 56.8 — (4.7) 1,776.8 Wholesale Transmission Revenues — — 383.4 — 19.2 (332.2) 70.4 Wholesale Market Sales Revenues 60.5 10.1 — 0.9 — — 71.5 Other Revenues from Contracts with Customers 21.1 1.4 3.3 0.9 264.6 (262.8) 28.5 Total Revenues from Contracts with Customers 1,601.3 216.5 386.7 58.6 283.8 (599.7) 1,947.2 Alternative Revenue Programs 14.2 (5.3) (10.2) (3.2) — 9.4 4.9 Other Revenues (1) 0.7 — 0.2 0.1 — — 1.0 Total Operating Revenues $ 1,616.2 $ 211.2 $ 376.7 $ 55.5 $ 283.8 $ (590.3) $ 1,953.1 For the Six Months Ended June 30, 2020 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,879.7 $ 354.1 $ — $ 67.5 $ — $ — $ 2,301.3 Commercial 1,133.0 202.4 — 30.6 — (2.3) 1,363.7 Industrial 157.5 49.5 — 2.3 — (6.6) 202.7 Total Retail Tariff Sales Revenues 3,170.2 606.0 — 100.4 — (8.9) 3,867.7 Wholesale Transmission Revenues — — 719.7 — 36.6 (615.8) 140.5 Wholesale Market Sales Revenues 151.5 23.2 — 1.8 — — 176.5 Other Revenues from Contracts with Customers 42.6 2.8 6.6 2.0 541.9 (538.9) 57.0 Total Revenues from Contracts with Customers 3,364.3 632.0 726.3 104.2 578.5 (1,163.6) 4,241.7 Alternative Revenue Programs 53.1 26.9 19.6 (2.1) — (18.1) 79.4 Other Revenues (1) 4.2 0.9 0.4 0.3 — — 5.8 Total Operating Revenues $ 3,421.6 $ 659.8 $ 746.3 $ 102.4 $ 578.5 $ (1,181.7) $ 4,326.9 For the Three Months Ended June 30, 2021 For the Three Months Ended June 30, 2020 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenues from Contracts with Customers Retail Tariff Sales Residential $ 440.8 $ 304.7 $ 136.6 $ 469.3 $ 311.5 $ 135.2 Commercial 215.7 296.1 82.8 199.3 261.0 66.1 Industrial 28.4 29.1 24.5 33.3 24.8 19.6 Total Retail Tariff Sales Revenues 684.9 629.9 243.9 701.9 597.3 220.9 Wholesale Transmission Revenues 195.7 160.1 61.1 191.4 142.5 49.5 Wholesale Market Sales Revenues 68.1 18.9 10.2 39.3 13.2 8.0 Other Revenues from Contracts with Customers 9.5 15.3 4.4 8.1 11.1 5.9 Total Revenues from Contracts with Customers 958.2 824.2 319.6 940.7 764.1 284.3 Alternative Revenue Programs (1.1) (15.3) 2.3 (7.5) 3.6 7.9 Other Revenues (1) (0.2) 0.7 0.5 0.2 0.7 — Eliminations (127.3) (122.2) (43.6) (116.0) (107.4) (37.0) Total Operating Revenues $ 829.6 $ 687.4 $ 278.8 $ 817.4 $ 661.0 $ 255.2 For the Six Months Ended June 30, 2021 For the Six Months Ended June 30, 2020 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenues from Contracts with Customers Retail Tariff Sales Residential $ 986.6 $ 667.1 $ 294.4 $ 959.2 $ 642.4 $ 278.1 Commercial 429.9 564.4 160.6 425.6 562.9 145.3 Industrial 65.2 53.6 46.2 67.3 51.6 38.6 Total Retail Tariff Sales Revenues 1,481.7 1,285.1 501.2 1,452.1 1,256.9 462.0 Wholesale Transmission Revenues 384.6 307.2 119.4 343.2 277.3 99.2 Wholesale Market Sales Revenues 177.8 43.4 25.1 104.0 27.6 19.9 Other Revenues from Contracts with Customers 16.8 27.0 7.6 17.0 21.8 11.8 Total Revenues from Contracts with Customers 2,060.9 1,662.7 653.3 1,916.3 1,583.6 592.9 Alternative Revenue Programs 7.8 (1.5) 5.3 37.1 23.0 12.6 Other Revenues (1) 0.1 1.8 0.5 1.9 2.1 0.6 Eliminations (251.9) (238.6) (86.8) (238.2) (213.9) (74.5) Total Operating Revenues $ 1,816.9 $ 1,424.4 $ 572.3 $ 1,717.1 $ 1,394.8 $ 531.6 (1) Other Revenues include certain fees charged to customers that are not considered revenue from contracts with customers. Other Revenues also include lease revenues under lessor accounting guidance

SEGMENT INFORMATION

SEGMENT INFORMATION	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION Eversource is organized into the Electric Distribution, Electric Transmission, Natural Gas Distribution and Water Distribution reportable segments and Other based on a combination of factors, including the characteristics of each segments' services, the sources of operating revenues and expenses and the regulatory environment in which each segment operates. These reportable segments represent substantially all of Eversource's total consolidated revenues. Revenues from the sale of electricity, natural gas and water primarily are derived from residential, commercial and industrial customers and are not dependent on any single customer. The Electric Distribution reportable segment includes the results of NSTAR Electric's solar power facilities. Eversource's reportable segments are determined based upon the level at which Eversource's chief operating decision maker assesses performance and makes decisions about the allocation of company resources. The remainder of Eversource's operations is presented as Other in the tables below and primarily consists of 1) the equity in earnings of Eversource parent from its subsidiaries and intercompany interest income, both of which are eliminated in consolidation, and interest expense related to the debt of Eversource parent, 2) the revenues and expenses of Eversource Service, most of which are eliminated in consolidation, 3) the operations of CYAPC and YAEC, 4) the results of other unregulated subsidiaries, which are not part of its core business, and 5) Eversource parent's equity ownership interests that are not consolidated, which primarily include the offshore wind business, a natural gas pipeline owned by Enbridge, Inc., and a renewable energy investment fund. In the ordinary course of business, Yankee Gas, NSTAR Gas and EGMA purchase natural gas transmission services from the Enbridge, Inc. natural gas pipeline project described above. These affiliate transaction costs total $77.7 million annually and are classified as Purchased Power, Fuel and Transmission on the Eversource statements of income. Each of Eversource's subsidiaries, including CL&P, NSTAR Electric and PSNH, has one reportable segment. Cash flows used for investments in plant included in the segment information below are cash capital expenditures that do not include amounts incurred but not paid, cost of removal, AFUDC related to equity funds, and the capitalized portions of pension and PBOP expense. Eversource's segment information is as follows: For the Three Months Ended June 30, 2021 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Operating Revenues $ 1,676.5 $ 311.8 $ 411.2 $ 52.8 $ 330.0 $ (659.8) $ 2,122.5 Depreciation and Amortization (132.3) (34.6) (74.5) (11.5) (28.4) 1.1 (280.2) Other Operating Expenses (1,360.3) (257.7) (121.9) (25.4) (285.7) 660.3 (1,390.7) Operating Income, Net $ 183.9 $ 19.5 $ 214.8 $ 15.9 $ 15.9 $ 1.6 $ 451.6 Interest Expense $ (61.1) $ (14.6) $ (32.6) $ (8.1) $ (41.8) $ 12.8 $ (145.4) Other Income, Net 29.9 4.6 6.8 0.9 309.2 (304.8) 46.6 Net Income Attributable to Common Shareholders 121.6 4.1 137.6 8.9 282.7 (290.4) 264.5 For the Six Months Ended June 30, 2021 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 3,576.9 $ 1,092.3 $ 811.9 $ 99.2 $ 673.0 $ (1,304.9) $ 4,948.4 Depreciation and Amortization (354.3) (80.3) (148.0) (22.8) (55.7) 2.1 (659.0) Other Operating Expenses (2,890.8) (793.6) (237.3) (50.5) (585.2) 1,305.2 (3,252.2) Operating Income $ 331.8 $ 218.4 $ 426.6 $ 25.9 $ 32.1 $ 2.4 $ 1,037.2 Interest Expense $ (114.4) $ (28.5) $ (65.3) $ (16.0) $ (83.4) $ 24.4 $ (283.2) Other Income, Net 50.6 8.5 12.2 1.9 733.4 (725.8) 80.8 Net Income Attributable to Common Shareholders 214.9 151.6 273.0 12.6 677.6 (699.0) 630.7 Cash Flows Used for Investments in Plant 510.4 305.9 443.2 53.8 109.9 — 1,423.2 For the Three Months Ended June 30, 2020 Eversource (Millions of Dollars) Electric Natural Gas Distribution (1) Electric Water Distribution Other (1) Eliminations (1) Total Operating Revenues $ 1,616.2 $ 211.2 $ 376.7 $ 55.5 $ 283.8 $ (590.3) $ 1,953.1 Depreciation and Amortization (140.7) (21.2) (68.8) (10.8) (22.7) 0.3 (263.9) Other Operating Expenses (1,293.3) (176.1) (111.2) (25.4) (243.1) 593.5 (1,255.6) Operating Income $ 182.2 $ 13.9 $ 196.7 $ 19.3 $ 18.0 $ 3.5 $ 433.6 Interest Expense $ (54.3) $ (10.7) $ (32.1) $ (8.4) $ (37.6) $ 8.8 $ (134.3) Other Income, Net 16.4 0.4 10.6 — 303.2 (300.4) 30.2 Net Income Attributable to Common Shareholders 115.0 2.6 129.5 10.4 282.8 (288.1) 252.2 For the Six Months Ended June 30, 2020 Eversource (Millions of Dollars) Electric Natural Gas Distribution (1) Electric Water Distribution Other (1) Eliminations (1) Total Operating Revenues $ 3,421.6 $ 659.8 $ 746.3 $ 102.4 $ 578.5 $ (1,181.7) $ 4,326.9 Depreciation and Amortization (308.1) (40.3) (136.2) (22.2) (44.0) 0.9 (549.9) Other Operating Expenses (2,732.9) (487.7) (218.0) (50.4) (500.0) 1,184.8 (2,804.2) Operating Income $ 380.6 $ 131.8 $ 392.1 $ 29.8 $ 34.5 $ 4.0 $ 972.8 Interest Expense $ (107.4) $ (22.0) $ (62.7) $ (17.1) $ (80.3) $ 20.5 $ (269.0) Other Income, Net 28.9 1.8 15.7 0.1 686.9 (679.1) 54.3 Net Income Attributable to Common Shareholders 245.1 88.6 256.2 12.5 639.2 (654.6) 587.0 Cash Flows Used for Investments in Plant 563.2 205.6 460.8 46.0 124.6 — 1,400.2 (1) On October 9, 2020, Eversource completed the CMA asset acquisition, with Yankee Energy System, Inc. (Yankee parent) as the acquiring entity. Yankee parent is the parent company of Yankee Gas, NSTAR Gas, EGMA and Hopkinton LNG Corp. As a result of the acquisition, in the fourth quarter of 2020, our chief operating decision maker assessed the performance of the Natural Gas Distribution segment including Yankee parent. Previously, Yankee parent was presented within Other and its equity in earnings were eliminated in consolidation. Prior comparative periods were revised to conform to the current period segment presentation. The following table summarizes Eversource's segmented total assets: Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total As of June 30, 2021 $ 25,904.6 $ 6,593.2 $ 12,289.3 $ 2,419.6 $ 21,669.0 $ (21,641.1) $ 47,234.6 As of December 31, 2020 24,981.9 6,450.5 11,695.0 2,375.2 22,089.4 (21,492.4) 46,099.6

ACQUISITION OF ASSETS OF COLUMB

ACQUISITION OF ASSETS OF COLUMBIA GAS OF MASSACHUSETTS	6 Months Ended
	Jun. 30, 2021
Business Combination and Asset Acquisition [Abstract]
ACQUISITION OF ASSETS OF COLUMBIA GAS OF MASSACHUSETTS	ACQUISITION OF ASSETS OF COLUMBIA GAS OF MASSACHUSETTS On October 9, 2020, Eversource acquired certain assets and liabilities that comprised the NiSource Inc. (NiSource) natural gas distribution business in Massachusetts, which was previously doing business as CMA, pursuant to an asset purchase agreement (the Agreement) entered into on February 26, 2020 between Eversource and NiSource. The cash purchase price was $1.1 billion, plus a working capital amount of $68.6 million, as finalized in the first quarter of 2021. The natural gas distribution assets acquired from CMA were assigned to EGMA, an indirect wholly-owned subsidiary of Eversource formed in 2020. The LNG assets acquired from CMA were assigned to Hopkinton LNG Corp. Preliminary Purchase Price Allocation : The purchase price allocation reflects measurement period adjustments recorded as of June 30, 2021 to reduce the fair values of certain regulatory and plant assets and certain liabilities acquired, resulting in a corresponding increase to Goodwill, based on new information received during the measurement period. The preliminary allocation of the cash purchase price is as follows: (Millions of Dollars) Current Assets $ 138 Restricted Cash 57 PP&E 1,184 Goodwill 50 Other Noncurrent Assets, excluding Goodwill 131 Other Current Liabilities (81) Other Noncurrent Liabilities (310) Cash Purchase Price $ 1,169

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation Eversource Energy is a public utility holding company primarily engaged, through its wholly-owned regulated utility subsidiaries, in the energy delivery business. Eversource Energy's wholly-owned regulated utility subsidiaries consist of CL&P, NSTAR Electric and PSNH (electric utilities), Yankee Gas, NSTAR Gas and Eversource Gas Company of Massachusetts (EGMA) (natural gas utilities) and Aquarion (water utilities). Eversource provides energy delivery and/or water service to approximately 4.3 million electric, natural gas and water customers through nine regulated utilities in Connecticut, Massachusetts and New Hampshire. The unaudited condensed consolidated financial statements of Eversource, NSTAR Electric and PSNH include the accounts of each of their respective subsidiaries. Intercompany transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements of Eversource, NSTAR Electric and PSNH and the unaudited condensed financial statements of CL&P are herein collectively referred to as the "financial statements." The combined notes to the financial statements have been prepared pursuant to the rules and regulations of the SEC. Certain information and footnote disclosures included in annual financial statements prepared in accordance with GAAP have been omitted pursuant to such rules and regulations. The accompanying financial statements should be read in conjunction with the Combined Notes to Financial Statements included in Item 8, "Financial Statements and Supplementary Data," of the Eversource 2020 Form 10-K, which was filed with the SEC on February 17, 2021. The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The financial statements contain, in the opinion of management, all adjustments (including normal, recurring adjustments) necessary to present fairly Eversource's, CL&P's, NSTAR Electric's and PSNH's financial position as of June 30, 2021 and December 31, 2020, and the results of operations, comprehensive income and common shareholders' equity for the three and six months ended June 30, 2021 and 2020 and the cash flows for the six months ended June 30, 2021 and 2020. The results of operations and comprehensive income for the three and six months ended June 30, 2021 and 2020 and the cash flows for the six months ended June 30, 2021 and 2020 are not necessarily indicative of the results expected for a full year. Eversource's consolidated financial information includes the results of the acquisition of the assets of Columbia Gas of Massachusetts (CMA) on October 9, 2020. The natural gas distribution assets acquired from CMA on October 9, 2020 were assigned to EGMA. Eversource consolidates the operations of CYAPC and YAEC, both of which are inactive regional nuclear power companies engaged in the long-term storage of their spent nuclear fuel. Eversource consolidates CYAPC and YAEC because CL&P's, NSTAR Electric's and PSNH's combined ownership and voting interests in each of these entities is greater than 50 percent. Intercompany transactions between CL&P, NSTAR Electric, PSNH and the CYAPC and YAEC companies have been eliminated in consolidation of the Eversource financial statements. Eversource holds several equity ownership interests that are not consolidated and are accounted for under the equity method. Eversource's utility subsidiaries' electric, natural gas and water distribution and transmission businesses are subject to rate-regulation that is based on cost recovery and meets the criteria for application of accounting guidance for entities with rate-regulated operations, which considers the effect of regulation on the differences in the timing of the recognition of certain revenues and expenses from those of other businesses and industries. See Note 2, "Regulatory Accounting," for further information. COVID-19 has adversely affected customers, workers and the U.S. economy. We provide a critical service to our customers and have taken extensive measures to maintain its safety and reliability. We continue to address the impacts of the COVID-19 pandemic and how the related developments affect Eversource. We are in the early re-entry phase of our pandemic response plan, in which the majority of our employees under remote work arrangements are starting to transition back to the workplace. We have not experienced significant impacts directly related to the pandemic that have materially affected our current operations, our workforce, or results of operations. The extent of the impact to us in the future will vary, and depend on the duration, scope and severity of the pandemic and the resulting impact on economic, health care and capital market conditions. The future impact will also depend on the outcome of future proceedings before our state regulatory commissions to recover our incremental costs associated with COVID-19, which include uncollectible customer receivable expenses. Based on the status of our COVID-19 regulatory dockets, communications with our state regulatory commissions, and policies and practices in the jurisdictions in which we operate, we believe our state regulatory commissions in Connecticut and Massachusetts will allow us to recover our incremental costs associated with COVID-19, which include uncollectible customer receivable expenses, while balancing the impact on our customers’ bills and our operating cash flows. See Note 1C, "Summary of Significant Accounting Policies - Allowance for Uncollectible Accounts," for discussion of our evaluation of the allowance for doubtful accounts as of June 30, 2021 in light of the COVID-19 pandemic and Note 2, "Regulatory Accounting," for the amount of net incremental COVID-19 costs deferred on our balance sheet. Certain reclassifications of prior period data were made in the accompanying financial statements to conform to the current period presentation.
Accounting Standards	Accounting Standards Accounting Standards Recently Adopted: On January 1, 2021, the Company adopted Accounting Standards Update (ASU) 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes , which eliminates certain exceptions to the general principles of current income tax guidance in ASC 740 and simplifies and improves consistency in application of that income tax guidance through clarifications of and amendments to ASC 740. The ASU did not have a material impact on the financial statements of Eversource, CL&P, NSTAR Electric and PSNH.
Allowance for Uncollectible Accounts	Allowance for Uncollectible Accounts Receivables, Net on the balance sheets primarily includes trade receivables from retail customers and customers related to wholesale transmission contracts, wholesale market sales, sales of RECs and property rentals. Receivables, Net also includes customer receivables for the purchase of electricity from a competitive third party supplier, the current portion of customer energy efficiency loans, property damage receivables and other miscellaneous receivables. There is no material concentration of receivables. Receivables are recorded at amortized cost, net of a credit loss provision (or allowance for uncollectible accounts). Receivables are presented net of expected credit losses at estimated net realizable value by maintaining an allowance for uncollectible accounts. The current expected credit loss (CECL) model is applied to receivables for purposes of calculating the allowance for uncollectible accounts. This model is based on expected losses and results in the recognition of estimated expected credit losses, including uncollectible amounts for both billed and unbilled revenues, over the life of the receivable at the time a receivable is recorded. The allowance for uncollectible accounts is determined based upon a variety of judgments and factors, including the application of an estimated uncollectible percentage to each receivable aging category. Factors in determining credit loss include historical collection, write-off experience, and management's assessment of collectability from customers, including current conditions, reasonable forecasts, and expectations of future collectability and collection efforts. Management continuously assesses the collectability of receivables and adjusts estimates based on actual experience and future expectations based on economic indicators, collection efforts and other factors. Management also monitors the aging analysis of receivables to determine if there are changes in the collections of accounts receivable. Receivable balances are written off against the allowance for uncollectible accounts when the customer accounts are no longer in service and these balances are deemed to be uncollectible. As of June 30, 2021, management evaluated the adequacy of the allowance for uncollectible accounts in light of the COVID-19 pandemic and the related economic downturn. This evaluation included an analysis of collection and customer payment trends, economic conditions, delinquency statistics, aging-based quantitative assessments, the impact on residential customer bills because of energy usage and change in rates, flexible payment plans and financial hardship arrearage management programs being offered to customers, and COVID-19 developments, including any potential federal governmental pandemic relief programs and the expansion of unemployment benefit initiatives, which help to mitigate the potential for increasing customer account delinquencies. Additionally, management considered past economic declines and corresponding uncollectible reserves as part of the current assessment. This evaluation has shown that our operating companies have experienced an increase in aged receivables and lower cash collections from customers because of the length of the moratorium on disconnections in Connecticut and Massachusetts, and the economic slowdown resulting from the COVID-19 pandemic. Based upon the evaluation performed, in the first half of 2021, management increased the allowance for uncollectible accounts for amounts incurred as a result of COVID-19 by $32.1 million for Eversource ($12.3 million for CL&P, $6.3 million for NSTAR Electric, and $14.7 million at our natural gas businesses). These COVID-19 related uncollectible amounts were deferred either as incremental regulatory costs at our Connecticut and Massachusetts utilities or deferred through existing regulatory tracking mechanisms that recover uncollectible energy supply costs, as management believes it is probable that these costs will ultimately be recovered from customers in future rates. As of June 30, 2021, the total amount incurred as a result of COVID-19 included in the allowance for uncollectible accounts was $63.6 million at Eversource ($15.1 million at CL&P, $17.3 million at NSTAR Electric, and $30.1 million at our natural gas businesses). On July 7, 2021, the NHPUC issued an order to New Hampshire utilities that concluded that recovery of incremental bad debt or waived late fees related to the COVID-19 pandemic would be addressed in a future rate case to the extent those costs are relevant at that time. The NHPUC concluded that New Hampshire utilities would not be permitted to establish a regulatory asset for these items. As a result of the order, in the second quarter of 2021, PSNH removed its $0.6 million deferral of net incremental COVID-19 costs. In New Hampshire, the moratorium on disconnections of non-hardship residential and commercial customers ended in late 2020 and PSNH has resumed disconnection activities, which has resulted in improved collection of outstanding customer receivable balances. In Connecticut, the moratorium on disconnections of commercial customers ended in June 2021, but is still in place for residential customers. In Massachusetts, the moratorium on disconnections of commercial customers and residential customers ended in September 2020 and July 2021, respectively. Disconnection activities have largely resumed after these moratoria have expired. Management concluded that the reserve balance as of June 30, 2021 adequately reflected the collection risk and net realizable value for Eversource’s receivables. Management will continue to evaluate the adequacy of the uncollectible allowance in future reporting periods based on an ongoing assessment of accounts receivable collections, delinquency statistics, and analysis of aging-based quantitative assessments. The PURA allows CL&P and Yankee Gas to accelerate the recovery of accounts receivable balances attributable to qualified customers under financial or medical duress (uncollectible hardship accounts receivable) outstanding for greater than 180 days and 90 days, respectively. The DPU allows NSTAR Electric, NSTAR Gas and EGMA to recover in rates amounts associated with certain uncollectible hardship accounts receivable. These uncollectible hardship customer account balances are included in Regulatory Assets or Other Long-Term Assets on the balance sheets. Hardship customers are protected from shut-off in certain circumstances, and historical collection experience has reflected a higher default risk as compared to the rest of the receivable population. Management uses a higher credit risk profile for this pool of trade receivables as compared to non-hardship receivables. The allowance for uncollectible hardship accounts is included in the total uncollectible allowance balance.
Fair Value Measurements	Fair Value Measurements Fair value measurement guidance is applied to derivative contracts that are not elected or designated as "normal purchases" or "normal sales" (normal) and to the marketable securities held in trusts. Fair value measurement guidance is also applied to valuations of the investments used to calculate the funded status of pension and PBOP plans, the nonrecurring fair value measurements of nonfinancial assets such as goodwill, long-lived assets, equity method investments, and AROs, and in the valuation of the acquisition of CMA's assets in 2020. The fair value measurement guidance was also applied in estimating the fair value of preferred stock, long-term debt and RRBs. Fair Value Hierarchy: In measuring fair value, Eversource uses observable market data when available in order to minimize the use of unobservable inputs. Inputs used in fair value measurements are categorized into three fair value hierarchy levels for disclosure purposes. The entire fair value measurement is categorized based on the lowest level of input that is significant to the fair value measurement. Eversource evaluates the classification of assets and liabilities measured at fair value on a quarterly basis. The levels of the fair value hierarchy are described below: Level 1 - Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities as of the reporting date. Active markets are those in which transactions for the asset or liability occur in sufficient frequency and volume to provide pricing information on an ongoing basis. Level 2 - Inputs are quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs are observable. Level 3 - Quoted market prices are not available. Fair value is derived from valuation techniques in which one or more significant inputs or assumptions are unobservable. Where possible, valuation techniques incorporate observable market inputs that can be validated to external sources such as industry exchanges, including prices of energy and energy-related products. Uncategorized - Investments that are measured at net asset value are not categorized within the fair value hierarchy.
Other Taxes	Other TaxesEversource's companies that serve customers in Connecticut collect gross receipts taxes levied by the state of Connecticut from their customers. These gross receipts taxes are recorded separately with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the statements of incomeAs agents for state and local governments, Eversource's companies that serve customers in Connecticut and Massachusetts collect certain sales taxes that are recorded on a net basis with no impact on the statements of income.
Restricted Cash	Special Deposits represent cash collections related to the PSNH RRB customer charges that are held in trust, required ISO-NE cash deposits, and CYAPC and YAEC cash balances. Special Deposits are included in Current Assets on the balance sheets. Restricted cash included in Marketable Securities represents money market funds held in trusts to fund certain non-qualified executive benefits and restricted trusts to fund CYAPC and YAEC's spent nuclear fuel storage obligations. Restricted cash included in Other Long-Term Assets includes $41.5 million related to an Energy Relief Fund for energy efficiency and clean energy measures in the Merrimack Valley, and an additional energy efficiency program established under the terms of the EGMA settlement agreement.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Allowance for Uncollectible Accounts	The activity in the allowance for uncollectible accounts by portfolio segment is as follows: Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Hardship Accounts Retail (Non-Hardship), Total Allowance Hardship Accounts Retail (Non-Hardship), Total Allowance Hardship Accounts Retail (Non-Hardship), Total Allowance Total Allowance Three Months Ended 2021 Beginning Balance $ 197.3 $ 194.4 $ 391.7 $ 138.4 $ 36.7 $ 175.1 $ 31.1 $ 58.2 $ 89.3 $ 17.3 Uncollectible Expense — 11.4 11.4 — 2.8 2.8 — 3.5 3.5 2.0 Uncollectible Costs Deferred (1) 16.6 24.5 41.1 9.3 8.3 17.6 4.9 6.9 11.8 (0.3) Write-Offs (3.4) (18.1) (21.5) (2.3) (5.4) (7.7) (0.1) (7.7) (7.8) (2.0) Recoveries Collected 0.2 2.9 3.1 0.2 0.8 1.0 — 1.2 1.2 0.2 Ending Balance $ 210.7 $ 215.1 $ 425.8 $ 145.6 $ 43.2 $ 188.8 $ 35.9 $ 62.1 $ 98.0 $ 17.2 Six Months Ended 2021 Beginning Balance $ 194.8 $ 164.1 $ 358.9 $ 129.1 $ 28.3 $ 157.4 $ 39.7 $ 51.9 $ 91.6 $ 17.2 Uncollectible Expense — 27.7 27.7 — 6.6 6.6 — 7.4 7.4 3.2 Uncollectible Costs Deferred (1) 22.0 51.6 73.6 21.2 15.7 36.9 (3.5) 15.2 11.7 0.8 Write-Offs (6.7) (34.8) (41.5) (5.2) (9.3) (14.5) (0.3) (15.2) (15.5) (4.5) Recoveries Collected 0.6 6.5 7.1 0.5 1.9 2.4 — 2.8 2.8 0.5 Ending Balance $ 210.7 $ 215.1 $ 425.8 $ 145.6 $ 43.2 $ 188.8 $ 35.9 $ 62.1 $ 98.0 $ 17.2 Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Hardship Accounts Retail (Non-Hardship), Total Allowance Hardship Accounts Retail (Non-Hardship), Total Allowance Hardship Accounts Retail (Non-Hardship), Total Allowance Total Allowance Three Months Ended 2020 Beginning Balance $ 172.2 $ 89.9 $ 262.1 $ 110.7 $ 20.2 $ 130.9 $ 38.5 $ 32.6 $ 71.1 $ 11.2 Uncollectible Expense — 9.2 9.2 — 3.0 3.0 — 3.1 3.1 0.6 Uncollectible Costs Deferred (1) 7.1 8.5 15.6 8.6 1.6 10.2 (3.7) 3.5 (0.2) 1.1 Write-Offs (4.4) (16.6) (21.0) (3.6) (6.0) (9.6) (0.2) (6.2) (6.4) (1.3) Recoveries Collected 0.6 3.5 4.1 0.6 1.6 2.2 — 1.1 1.1 0.2 Ending Balance $ 175.5 $ 94.5 $ 270.0 $ 116.3 $ 20.4 $ 136.7 $ 34.6 $ 34.1 $ 68.7 $ 11.8 Six Months Ended 2020 Beginning Balance $ 143.3 $ 81.5 $ 224.8 $ 80.1 $ 17.2 $ 97.3 $ 43.9 $ 31.5 $ 75.4 $ 10.5 ASU 2016-13 Implementation 21.6 2.2 23.8 21.3 0.9 22.2 (1.6) 0.3 (1.3) 0.3 Uncollectible Expense — 20.6 20.6 — 6.2 6.2 — 6.8 6.8 1.3 Uncollectible Costs Deferred (1) 18.9 17.0 35.9 21.5 3.4 24.9 (7.1) 6.9 (0.2) 2.4 Write-Offs (9.1) (33.4) (42.5) (7.4) (9.5) (16.9) (0.6) (14.2) (14.8) (3.0) Recoveries Collected 0.8 6.6 7.4 0.8 2.2 3.0 — 2.8 2.8 0.3 Ending Balance $ 175.5 $ 94.5 $ 270.0 $ 116.3 $ 20.4 $ 136.7 $ 34.6 $ 34.1 $ 68.7 $ 11.8 (1) These expected credit losses are deferred as regulatory costs on the balance sheets, as these amounts are ultimately recovered in rates. Amounts include uncollectible costs for hardship accounts and other customer receivables, including uncollectible amounts related to COVID-19 and uncollectible energy supply costs.
Components of Other Income, Net	The components of Other Income, Net on the statements of income were as follows: For the Three Months Ended June 30, 2021 June 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service $ 22.1 $ 4.3 $ 10.2 $ 2.7 $ 10.7 $ 0.9 $ 7.1 $ 1.6 AFUDC Equity 9.2 1.7 6.2 0.3 10.8 3.9 5.3 1.2 Equity in Earnings of Unconsolidated Affiliates (1) 4.7 — 0.1 — 5.9 — 0.1 — Investment Income 1.9 1.2 0.6 0.3 1.8 2.2 — 0.3 Interest Income 8.4 2.7 4.8 0.9 1.0 1.4 0.5 0.5 Other 0.3 — — 0.1 — 0.1 0.1 — Total Other Income, Net $ 46.6 $ 9.9 $ 21.9 $ 4.3 $ 30.2 $ 8.5 $ 13.1 $ 3.6 For the Six Months Ended June 30, 2021 June 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Pension, SERP and PBOP Non-Service $ 42.2 $ 7.0 $ 20.2 $ 5.4 $ 23.4 $ 2.1 $ 15.0 $ 3.5 AFUDC Equity 18.4 3.4 12.4 0.9 21.4 7.9 10.3 2.6 Equity in Earnings of Unconsolidated Affiliates (1) 8.4 — 0.2 — 9.8 — 0.2 — Investment Income/(Loss) 1.3 1.5 0.8 0.4 (2.5) (1.3) (1.3) (0.2) Interest Income 9.9 2.8 4.9 1.6 1.8 1.6 0.7 0.8 Other 0.6 0.1 0.2 0.1 0.4 0.1 0.5 0.1 Total Other Income, Net $ 80.8 $ 14.8 $ 38.7 $ 8.4 $ 54.3 $ 10.4 $ 25.4 $ 6.8 (1) Equity in earnings of unconsolidated affiliates includes $2.1 million of pre-tax unrealized gains associated with an investment in a renewable energy fund for the three and six months ended June 30, 2021. For the three and six months ended June 30, 2020, equity in earnings of unconsolidated affiliates included $2.4 million of primarily realized gains associated with this investment.
Other Taxes	These gross receipts taxes are recorded separately with collections in Operating Revenues and with payments in Taxes Other Than Income Taxes on the statements of income as follows: For the Three Months Ended For the Six Months Ended (Millions of Dollars) June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 Eversource $ 39.9 $ 37.6 $ 88.5 $ 80.7 CL&P 35.4 33.1 74.6 68.6
Non-cash Investing Activities	Non-cash investing activities include plant additions included in Accounts Payable as follows: (Millions of Dollars) As of June 30, 2021 As of June 30, 2020 Eversource $ 344.8 $ 336.1 CL&P 66.4 95.0 NSTAR Electric 103.8 75.5 PSNH 33.9 48.3
Reconciliation of Cash Balances to Cash and Restricted Cash	The following table reconciles cash as reported on the balance sheets to the cash and restricted cash balance as reported on the statements of cash flows: As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Cash as reported on the Balance Sheets $ 217.4 $ 198.4 $ 0.6 $ 0.3 $ 106.6 $ 90.8 $ 0.1 $ 0.1 Restricted cash included in: Special Deposits 71.8 8.6 17.2 35.1 73.6 8.7 17.2 36.8 Marketable Securities 34.1 0.4 0.1 0.6 41.2 0.3 0.1 0.6 Other Long-Term Assets 44.7 — — 3.2 43.6 — — 2.1 Cash and Restricted Cash as reported on the Statements of Cash Flows $ 368.0 $ 207.4 $ 17.9 $ 39.2 $ 265.0 $ 99.8 $ 17.4 $ 39.6

REGULATORY ACCOUNTING (Tables)

REGULATORY ACCOUNTING (Tables)	6 Months Ended
	Jun. 30, 2021
Regulated Operations [Abstract]
Components of Regulatory Assets	The components of regulatory assets were as follows: As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH Benefit Costs $ 2,625.1 $ 551.7 $ 653.9 $ 255.1 $ 2,794.2 $ 632.3 $ 690.0 $ 267.6 Income Taxes, Net 755.4 460.5 112.2 17.4 747.1 458.9 110.4 15.2 Securitized Stranded Costs 500.5 — — 500.5 522.1 — — 522.1 Storm Restoration Costs, Net 745.9 500.2 169.5 76.2 765.6 515.1 186.4 64.1 Regulatory Tracker Mechanisms 950.9 347.5 378.8 79.1 850.5 246.6 332.2 95.3 Derivative Liabilities 279.7 279.7 — — 296.3 293.1 — — Goodwill-related 306.2 — 262.9 — 314.7 — 270.2 — Asset Retirement Obligations 118.2 33.2 55.8 4.0 118.4 32.1 58.6 3.9 Other Regulatory Assets 151.4 31.6 51.3 18.1 161.0 33.7 56.1 20.9 Total Regulatory Assets 6,433.3 2,204.4 1,684.4 950.4 6,569.9 2,211.8 1,703.9 989.1 Less: Current Portion 1,186.9 458.6 448.0 99.5 1,076.6 345.6 399.9 115.9 Total Long-Term Regulatory Assets $ 5,246.4 $ 1,745.8 $ 1,236.4 $ 850.9 $ 5,493.3 $ 1,866.2 $ 1,304.0 $ 873.2
Components of Regulatory Liabilities	The components of regulatory liabilities were as follows: As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH EDIT due to Tax Cuts and Jobs Act of 2017 $ 2,748.6 $ 1,005.4 $ 1,030.5 $ 364.2 $ 2,778.6 $ 1,010.7 $ 1,044.0 $ 371.5 Cost of Removal 657.1 108.7 374.4 17.1 624.8 98.4 363.6 12.9 Benefit Costs 70.4 — 60.2 — 83.6 — 72.5 — Regulatory Tracker Mechanisms 474.7 190.3 147.7 51.0 366.5 148.9 139.7 47.8 AFUDC - Transmission 78.7 43.9 34.8 — 76.8 44.6 32.2 — Other Regulatory Liabilities 383.1 78.8 77.5 14.3 309.9 39.5 63.2 9.8 Total Regulatory Liabilities 4,412.6 1,427.1 1,725.1 446.6 4,240.2 1,342.1 1,715.2 442.0 Less: Current Portion 532.5 219.8 173.0 61.9 389.4 137.2 164.8 58.8 Total Long-Term Regulatory Liabilities $ 3,880.1 $ 1,207.3 $ 1,552.1 $ 384.7 $ 3,850.8 $ 1,204.9 $ 1,550.4 $ 383.2

PROPERTY, PLANT AND EQUIPMENT_2

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION (Tables)	6 Months Ended
	Jun. 30, 2021
Property, Plant and Equipment [Abstract]
Summary of Property, Plant, and Equipment	The following tables summarize property, plant and equipment by asset category: Eversource As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) Distribution - Electric $ 17,104.8 $ 16,703.2 Distribution - Natural Gas 6,227.8 6,111.2 Transmission - Electric 12,296.8 11,954.0 Distribution - Water 1,772.7 1,743.1 Solar 200.4 201.5 Utility 37,602.5 36,713.0 Other (1) 1,386.9 1,269.0 Property, Plant and Equipment, Gross 38,989.4 37,982.0 Less: Accumulated Depreciation Utility (8,756.6) (8,476.3) Other (525.8) (477.6) Total Accumulated Depreciation (9,282.4) (8,953.9) Property, Plant and Equipment, Net 29,707.0 29,028.1 Construction Work in Progress 2,171.6 1,854.4 Total Property, Plant and Equipment, Net $ 31,878.6 $ 30,882.5 As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) CL&P NSTAR PSNH CL&P NSTAR PSNH Distribution - Electric $ 6,989.4 $ 7,716.5 $ 2,439.2 $ 6,820.7 $ 7,544.4 $ 2,378.4 Transmission - Electric 5,653.4 4,866.5 1,778.6 5,512.0 4,701.3 1,742.4 Solar — 200.4 — — 201.5 — Property, Plant and Equipment, Gross 12,642.8 12,783.4 4,217.8 12,332.7 12,447.2 4,120.8 Less: Accumulated Depreciation (2,559.4) (3,182.8) (879.9) (2,475.4) (3,074.1) (848.9) Property, Plant and Equipment, Net 10,083.4 9,600.6 3,337.9 9,857.3 9,373.1 3,271.9 Construction Work in Progress 395.8 836.6 129.9 377.3 750.0 102.4 Total Property, Plant and Equipment, Net $ 10,479.2 $ 10,437.2 $ 3,467.8 $ 10,234.6 $ 10,123.1 $ 3,374.3 (1) These assets are primarily comprised of computer software, hardware and equipment at Eversource Service and buildings at The Rocky River Realty Company.

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Fair Values and Net Amounts of Contracts	The following table presents the gross fair values of contracts, categorized by risk type, and the net amounts recorded as current or long-term derivative assets or liabilities: As of June 30, 2021 As of December 31, 2020 (Millions of Dollars) Fair Value Hierarchy Commodity Supply and Price Risk Netting (1) Net Amount Commodity Supply and Price Risk Netting (1) Net Amount Current Derivative Assets: CL&P Level 3 $ 14.1 $ (0.4) $ 13.7 $ 13.7 $ (0.4) $ 13.3 Long-Term Derivative Assets: CL&P Level 3 55.0 (1.7) 53.3 58.7 (1.8) 56.9 Current Derivative Liabilities: CL&P Level 3 (70.9) — (70.9) (68.8) — (68.8) Other Level 2 — — — (3.3) 0.1 (3.2) Long-Term Derivative Liabilities: CL&P Level 3 (275.8) — (275.8) (294.5) — (294.5) (1) Amounts represent derivative assets and liabilities that Eversource elected to record net on the balance sheets. These amounts are subject to master netting agreements or similar agreements for which the right of offset exists.
Summary of Level 3 Derivative Contracts and Significant Unobservable Inputs Used	The following is a summary of Level 3 derivative contracts and the range of the significant unobservable inputs utilized in the valuations over the duration of the contracts: As of June 30, 2021 As of December 31, 2020 CL&P Range Weighted Average (1) Period Covered Range Weighted Average (1) Period Covered Capacity Prices $2.61 $ 2.61 per kW-Month 2025 - 2026 $ 4.30 — $5.30 $ 4.63 per kW-Month 2024 - 2026 Forward Reserve Prices $ 0.54 — $0.90 $ 0.72 per kW-Month 2021 - 2024 $ 0.54 — $0.90 $ 0.72 per kW-Month 2021 - 2024 (1) Unobservable inputs were weighted by the relative future capacity and forward reserve prices and contractual MWs over the periods covered.
Changes in the Level 3 Category of Derivative Assets Measured at Fair Value on a Recurring Basis	The following table presents changes in the Level 3 category of derivative assets and derivative liabilities measured at fair value on a recurring basis. The derivative assets and liabilities are presented on a net basis. CL&P For the Three Months Ended June 30, For the Six Months Ended June 30, (Millions of Dollars) 2021 2020 2021 2020 Derivatives, Net: Fair Value as of Beginning of Period $ (293.1) $ (333.8) $ (293.1) $ (329.2) Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets 0.9 (1.3) (11.5) (17.6) Settlements 12.5 13.1 24.9 24.8 Fair Value as of End of Period $ (279.7) $ (322.0) $ (279.7) $ (322.0)

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	6 Months Ended
	Jun. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Summary of Available-for-Sale Debt Securities	The following is a summary of the available-for-sale debt securities, which are recorded at fair value and are included in current and long-term Marketable Securities on the balance sheets. As of June 30, 2021 As of December 31, 2020 Eversource (Millions of Dollars) Amortized Cost Pre-Tax Pre-Tax Fair Value Amortized Cost Pre-Tax Pre-Tax Fair Value Debt Securities $ 224.0 $ 7.0 $ (0.1) $ 230.9 $ 213.1 $ 11.2 $ (0.1) $ 224.2
Contractual Maturities of Available-for-Sale Debt Securities	As of June 30, 2021, the contractual maturities of available-for-sale debt securities were as follows: Eversource (Millions of Dollars) Amortized Cost Fair Value Less than one year (1) $ 36.5 $ 36.5 One to five years 67.5 69.4 Six to ten years 49.7 51.4 Greater than ten years 70.3 73.6 Total Debt Securities $ 224.0 $ 230.9 (1) Amounts in the Less than one year category include securities in the CYAPC and YAEC spent nuclear fuel trusts, which are restricted and are classified in long-term Marketable Securities on the balance sheets.
Marketable Securities Recorded at Fair Value on a Recurring Basis by Level	The following table presents the marketable securities recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy: Eversource (Millions of Dollars) As of June 30, 2021 As of December 31, 2020 Level 1: Mutual Funds and Equities $ 247.2 $ 246.0 Money Market Funds 34.1 41.2 Total Level 1 $ 281.3 $ 287.2 Level 2: U.S. Government Issued Debt Securities (Agency and Treasury) $ 100.8 $ 72.9 Corporate Debt Securities 62.8 63.8 Asset-Backed Debt Securities 13.6 11.9 Municipal Bonds 6.4 24.0 Other Fixed Income Securities 13.2 10.4 Total Level 2 $ 196.8 $ 183.0 Total Marketable Securities $ 478.1 $ 470.2

SHORT-TERM AND LONG-TERM DEBT (

SHORT-TERM AND LONG-TERM DEBT (Tables)	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Borrowings Outstanding and Available under the Commercial Paper Programs	The amount of borrowings outstanding and available under the commercial paper programs were as follows: Borrowings Outstanding as of Available Borrowing Capacity as of Weighted-Average Interest Rate as of June 30, 2021 December 31, 2020 June 30, 2021 December 31, 2020 June 30, 2021 December 31, 2020 (Millions of Dollars) Eversource Parent Commercial Paper Program $ 1,447.0 $ 1,054.3 $ 553.0 $ 945.7 0.19 % 0.25 % NSTAR Electric Commercial Paper Program 555.5 195.0 94.5 455.0 0.11 % 0.16 %
Summary of Long-Term Debt Issuance and Repayments	The following table summarizes long-term debt issuances and repayments: (Millions of Dollars) Issuance/(Repayment) Issue Date or Repayment Date Maturity Date Use of Proceeds for Issuance/ CL&P: 2.05% Series A First Mortgage Bonds $ 425.0 June 2021 July 2031 Repaid short-term debt, paid capital expenditures and working capital NSTAR Electric: 3.10% 2021 Debentures 300.0 May 2021 June 2051 Refinanced investments in eligible green expenditures, which were previously financed in 2019 and 2020 3.50% Series F Senior Notes (250.0) June 2021 September 2021 Paid on par call date in advance of maturity date PSNH: 4.05% Series Q First Mortgage Bonds (122.0) March 2021 June 2021 Paid on par call date in advance of maturity date 3.20% Series R First Mortgage Bonds (160.0) June 2021 September 2021 Paid on par call date in advance of maturity date 2.20% Series V First Mortgage Bonds 350.0 June 2021 June 2031 Repaid short-term debt, including short-term debt used to redeem Series R First Mortgage Bonds, paid capital expenditures and working capital Other: Eversource Parent 2.50% Series I Senior Notes (450.0) February 2021 March 2021 Paid on par call date in advance of maturity date Eversource Parent 2.55% Series S Senior Notes 350.0 March 2021 March 2031 Repaid short-term debt, including short-term debt used to redeem Series I Senior Notes Aquarion Water Company of Connecticut 3.31% Senior Notes 100.0 April 2021 April 2051 Repaid 5.50% Notes, repaid short-term debt, paid capital expenditures and working capital Aquarion Water Company of Connecticut 5.50% Notes (40.0) April 2021 April 2021 Paid at maturity

RATE REDUCTION BONDS AND VARI_2

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES (Tables)	6 Months Ended
	Jun. 30, 2021
Rate Reduction Bonds and Variable Interest Entity [Abstract]
Summary of the Impact of Funding on the Balance Sheets and Income Statements	The following tables summarize the impact of PSNH Funding on PSNH's balance sheets and income statements: (Millions of Dollars) PSNH Balance Sheets: As of June 30, 2021 As of December 31, 2020 Restricted Cash - Current Portion (included in Current Assets) $ 34.9 $ 36.8 Restricted Cash - Long-Term Portion (included in Other Long-Term Assets) 3.2 2.1 Securitized Stranded Cost (included in Regulatory Assets) 500.5 522.1 Other Regulatory Liabilities (included in Regulatory Liabilities) 8.9 9.1 Accrued Interest (included in Other Current Liabilities) 7.7 8.0 Rate Reduction Bonds - Current Portion 43.2 43.2 Rate Reduction Bonds - Long-Term Portion 475.3 496.9 (Millions of Dollars) PSNH Income Statements: For the Three Months Ended For the Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net) $ 10.8 $ 10.8 $ 21.6 $ 21.6 Interest Expense on RRB Principal (included in Interest Expense) 4.6 5.0 9.3 10.0

PENSION BENEFITS AND POSTRETI_2

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION (Tables)	6 Months Ended
	Jun. 30, 2021
Postemployment Benefits [Abstract]
Components of Net Periodic Benefit Expense/(Income)	The components of net periodic benefit plan expense/(income) for the Pension, SERP and PBOP Plans, prior to amounts capitalized as Property, Plant and Equipment or deferred as regulatory assets for future recovery, are shown below. The service cost component of net periodic benefit plan expense/(income), less the capitalized portion, is included in Operations and Maintenance expense on the statements of income. The remaining components of net periodic benefit plan expense/(income), less the deferred portion, are included in Other Income, Net on the statements of income. Pension, SERP and PBOP expense reflected in the statements of cash flows for CL&P, NSTAR Electric and PSNH does not include intercompany allocations of net periodic benefit plan expense/(income), as these amounts are cash settled on a short-term basis. Pension and SERP PBOP For the Three Months Ended June 30, 2021 For the Three Months Ended June 30, 2021 (Millions of Dollars) Eversource CL&P NSTAR Electric PSNH Eversource CL&P NSTAR Electric PSNH Service Cost $ 18.4 $ 5.5 $ 3.9 $ 2.2 $ 3.3 $ 0.6 $ 0.6 $ 0.3 Interest Cost 27.1 6.7 6.7 3.6 4.2 0.8 1.1 0.4 Expected Return on Plan Assets (87.4) (21.7) (27.1) (11.8) (19.8) (2.6) (9.2) (1.5) Actuarial Loss 47.8 10.8 15.3 5.2 1.3 0.4 0.5 0.1 Prior Service Cost/(Credit) 0.3 — 0.1 — (5.3) 0.3 (4.2) 0.1 Total Net Periodic Benefit Plan Expense/(Income) $ 6.2 $ 1.3 $ (1.1) $ (0.8) $ (16.3) $ (0.5) $ (11.2) $ (0.6) Intercompany Expense/(Income) Allocations N/A $ 2.3 $ 2.5 $ 0.7 N/A $ (0.6) $ (0.6) $ (0.2) Pension and SERP PBOP For the Six Months Ended June 30, 2021 For the Six Months Ended June 30, 2021 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH Service Cost $ 39.7 $ 11.8 $ 7.9 $ 4.4 $ 6.8 $ 1.2 $ 1.2 $ 0.6 Interest Cost 59.7 14.0 13.4 7.2 8.6 1.6 2.2 0.9 Expected Return on Plan Assets (196.3) (43.3) (54.0) (23.7) (39.5) (5.2) (18.5) (3.0) Actuarial Loss 109.4 23.8 30.8 10.1 3.9 0.8 1.1 0.3 Prior Service Cost/(Credit) 0.6 — 0.2 — (10.6) 0.5 (8.4) 0.2 Total Net Periodic Benefit Plan Expense/(Income) $ 13.1 $ 6.3 $ (1.7) $ (2.0) $ (30.8) $ (1.1) $ (22.4) $ (1.0) Intercompany Expense/(Income) Allocations N/A $ 3.6 $ 4.0 $ 1.2 N/A $ (0.9) $ (1.0) $ (0.3) Pension and SERP PBOP For the Three Months Ended June 30, 2020 For the Three Months Ended June 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH Service Cost $ 18.7 $ 5.4 $ 3.8 $ 2.0 $ 2.0 $ 0.4 $ 0.5 $ 0.2 Interest Cost 44.3 9.3 9.7 4.8 6.4 1.0 1.6 0.8 Expected Return on Plan Assets (99.3) (19.8) (25.7) (11.1) (18.7) (2.5) (8.5) (1.4) Actuarial Loss 50.7 9.7 14.0 3.9 2.0 0.2 0.5 0.3 Prior Service Cost/(Credit) 0.3 — 0.1 — (5.2) 0.2 (4.3) 0.1 Total Net Periodic Benefit Plan Expense/(Income) $ 14.7 $ 4.6 $ 1.9 $ (0.4) $ (13.5) $ (0.7) $ (10.2) $ — Intercompany Expense/(Income) Allocations N/A $ 2.4 $ 2.3 $ 0.8 N/A $ (0.2) $ (0.2) $ (0.1) Pension and SERP PBOP For the Six Months Ended June 30, 2020 For the Six Months Ended June 30, 2020 (Millions of Dollars) Eversource CL&P NSTAR PSNH Eversource CL&P NSTAR PSNH Service Cost $ 38.3 $ 11.1 $ 7.6 $ 4.2 $ 4.9 $ 0.9 $ 1.1 $ 0.4 Interest Cost 88.6 18.8 19.3 9.7 12.2 2.2 3.3 1.4 Expected Return on Plan Assets (199.6) (39.8) (51.5) (22.4) (36.8) (4.9) (17.0) (2.8) Actuarial Loss 100.0 19.7 27.3 8.0 4.1 0.6 1.2 0.4 Prior Service Cost/(Credit) 0.6 — 0.2 — (10.6) 0.4 (8.5) 0.2 Total Net Periodic Benefit Plan Expense/(Income) $ 27.9 $ 9.8 $ 2.9 $ (0.5) $ (26.2) $ (0.8) $ (19.9) $ (0.4) Intercompany Expense/(Income) Allocations N/A $ 4.3 $ 4.2 $ 1.4 N/A $ (0.6) $ (0.6) $ (0.3)

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Environmental Sites and Related Reserves	The number of environmental sites and related reserves for which remediation or long-term monitoring, preliminary site work or site assessment is being performed are as follows: As of June 30, 2021 As of December 31, 2020 Number of Sites Reserve Number of Sites Reserve Eversource 62 $ 108.8 63 $ 102.4 CL&P 14 10.7 15 12.3 NSTAR Electric 12 3.9 12 4.7 PSNH 9 6.6 9 7.1
Non-Cancelable Commitments under Purchase Commitment Contracts	Renewable energy contracts include non-cancelable commitments under contracts of NSTAR Electric for the purchase of energy and RECs from renewable energy facilities. NSTAR Electric (Millions of Dollars) 2021 2022 2023 2024 2025 Thereafter Total Renewable Energy $ 48.1 $ 103.6 $ 229.3 $ 339.4 $ 346.2 $ 6,527.7 $ 7,594.3
Summary of Exposure to Guarantees and Indemnifications	The following table summarizes Eversource parent's exposure to guarantees and indemnifications of its subsidiaries and affiliates to external parties: As of June 30, 2021 Company (Obligor) Description Maximum Exposure Expiration Dates North East Offshore LLC Construction-related purchase agreements with third-party contractors (1) $ 29.7 (1) Eversource Investment LLC Funding and indemnification obligations of North East Offshore LLC (2) — (2) Sunrise Wind LLC OREC capacity production (3) 2.2 (3) South Fork Wind, LLC Transmission interconnection 1.6 — Bay State Wind LLC Real estate purchase 2.5 2022 Various Surety bonds (4) 59.5 2021 - 2023 Rocky River Realty Company and Lease payments for real estate 4.4 2024 (1) Eversource parent issued guarantees on behalf of its 50 percent-owned affiliate, North East Offshore LLC (NEO), under which Eversource parent agreed to guarantee 50 percent of NEO’s performance of obligations under certain purchase agreements with third-party contactors, in an amount not to exceed $1.3 billion with an expiration date in 2025. Eversource parent also issued a separate guarantee to Ørsted on behalf of NEO, under which Eversource parent agreed to guarantee 50 percent of NEO’s payment obligations under certain offshore wind project construction-related agreements with Ørsted in an aggregate amount not to exceed $62.5 million. Any amounts paid under this guarantee to Ørsted will count toward, but not increase, the maximum amount of the Funding Guarantee described in Note 2, below. The guarantee expires upon the full performance of the guaranteed obligations. (2) Eversource parent issued a guarantee (Funding Guarantee) on behalf of Eversource Investment LLC (EI), its wholly-owned subsidiary that holds a 50 percent ownership interest in NEO, under which Eversource parent agreed to guarantee certain funding obligations and certain indemnification payments of EI under the Amended and Restated Limited Liability Company Operating Agreement of NEO, in an amount not to exceed $910 million. The guaranteed obligations include payment of EI's funding obligations during the construction phase of NEO’s underlying offshore wind projects and indemnification obligations associated with third party credit support for its investment in NEO. Eversource parent’s obligations under the Funding Guarantee expire upon the full performance of the guaranteed obligations. (3) Eversource parent issued a guarantee on behalf of its 50 percent-owned affiliate, Sunrise Wind LLC, whereby Eversource parent will guarantee Sunrise Wind LLC's performance of certain obligations, in an amount not to exceed $15.4 million, under the Offshore Wind Renewable Energy Certificate Purchase and Sale Agreement (the Agreement). The Agreement was executed on October 23, 2019, by and between the New York State Energy Research and Development Authority (NYSERDA) and Sunrise Wind LLC. The guarantee expires upon the full performance of the guaranteed obligations.

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Carrying Amounts and Estimated Fair Values of Financial Instruments	Carrying amounts and estimated fair values are as follows: Eversource CL&P NSTAR Electric PSNH (Millions of Dollars) Carrying Fair Carrying Fair Carrying Fair Carrying Fair As of June 30, 2021: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 166.4 $ 116.2 $ 122.2 $ 43.0 $ 44.2 $ — $ — Long-Term Debt 16,651.2 18,364.0 4,335.6 5,049.8 3,688.3 4,208.4 1,163.7 1,239.0 Rate Reduction Bonds 518.5 579.6 — — — — 518.5 579.6 As of December 31, 2020: Preferred Stock Not Subject to Mandatory Redemption $ 155.6 $ 169.1 $ 116.2 $ 123.4 $ 43.0 $ 45.7 $ — $ — Long-Term Debt 16,179.1 18,420.1 3,914.8 4,800.9 3,643.2 4,294.0 1,099.1 1,207.0 Rate Reduction Bonds 540.1 603.4 — — — — 540.1 603.4

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Tables)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Changes in Accumulated Other Comprehensive Income/(Loss) by Component, Net of Tax	The changes in accumulated other comprehensive income/(loss) by component, net of tax, are as follows: For the Six Months Ended June 30, 2021 For the Six Months Ended June 30, 2020 Eversource (Millions of Dollars) Qualified Unrealized Defined Total Qualified Unrealized Defined Total Balance as of January 1st $ (1.4) $ 1.1 $ (76.1) $ (76.4) $ (3.0) $ 0.7 $ (62.8) $ (65.1) OCI Before Reclassifications — (0.5) (2.4) (2.9) — 0.4 (1.6) (1.2) Amounts Reclassified from AOCI 0.9 — 4.1 5.0 0.6 — 3.1 3.7 Net OCI 0.9 (0.5) 1.7 2.1 0.6 0.4 1.5 2.5 Balance as of June 30th $ (0.5) $ 0.6 $ (74.4) $ (74.3) $ (2.4) $ 1.1 $ (61.3) $ (62.6)

COMMON SHARES (Tables)

COMMON SHARES (Tables)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Common Shares Authorized and Issued	The following table sets forth the Eversource parent common shares and the shares of common stock of CL&P, NSTAR Electric and PSNH that were authorized and issued, as well as the respective per share par values: Shares Authorized as of June 30, 2021 and December 31, 2020 Issued as of Par Value June 30, 2021 December 31, 2020 Eversource $ 5 380,000,000 357,818,402 357,818,402 CL&P $ 10 24,500,000 6,035,205 6,035,205 NSTAR Electric $ 1 100,000,000 200 200 PSNH $ 1 100,000,000 301 301

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Components of Basic and Diluted EPS	The following table sets forth the components of basic and diluted EPS: Eversource (Millions of Dollars, except share information) For the Three Months Ended For the Six Months Ended June 30, 2021 June 30, 2020 June 30, 2021 June 30, 2020 Net Income Attributable to Common Shareholders $ 264.5 $ 252.2 $ 630.7 $ 587.0 Weighted Average Common Shares Outstanding: Basic 343,844,626 337,946,663 343,761,435 334,524,452 Dilutive Effect of: Share-Based Compensation Awards and Other 591,070 614,986 623,758 681,110 Equity Forward Sale Agreement — — — 543,842 Total Dilutive Effect 591,070 614,986 623,758 1,224,952 Diluted 344,435,696 338,561,649 344,385,193 335,749,404 Basic and Diluted EPS $ 0.77 $ 0.75 $ 1.83 $ 1.75

REVENUES (Tables)

REVENUES (Tables)	6 Months Ended
	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
Operating Revenues Disaggregated by Revenue Source	The following tables present operating revenues disaggregated by revenue source: For the Three Months Ended June 30, 2021 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 882.1 $ 174.2 $ — $ 36.0 $ — $ — $ 1,092.3 Commercial 594.1 89.6 — 16.1 — (1.3) 698.5 Industrial 82.0 34.8 — 1.1 — (4.4) 113.5 Total Retail Tariff Sales Revenues 1,558.2 298.6 — 53.2 — (5.7) 1,904.3 Wholesale Transmission Revenues — — 416.9 — 20.3 (345.9) 91.3 Wholesale Market Sales Revenues 97.2 15.7 — 1.0 — — 113.9 Other Revenues from Contracts with Customers 25.1 1.0 3.4 1.2 309.7 (307.0) 33.4 Total Revenues from Contracts with Customers 1,680.5 315.3 420.3 55.4 330.0 (658.6) 2,142.9 Alternative Revenue Programs (4.8) (3.4) (9.3) (2.7) — (1.2) (21.4) Other Revenues (1) 0.8 (0.1) 0.2 0.1 — — 1.0 Total Operating Revenues $ 1,676.5 $ 311.8 $ 411.2 $ 52.8 $ 330.0 $ (659.8) $ 2,122.5 For the Six Months Ended June 30, 2021 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,948.1 $ 641.1 $ — $ 63.7 $ — $ — $ 2,652.9 Commercial 1,154.0 297.4 — 29.8 — (2.7) 1,478.5 Industrial 165.0 90.8 — 2.2 — (8.0) 250.0 Total Retail Tariff Sales Revenues 3,267.1 1,029.3 — 95.7 — (10.7) 4,381.4 Wholesale Transmission Revenues — — 811.2 — 39.5 (666.9) 183.8 Wholesale Market Sales Revenues 246.3 42.0 — 1.8 — — 290.1 Other Revenues from Contracts with Customers 43.4 2.4 6.8 2.4 633.5 (628.3) 60.2 Total Revenues from Contracts with Customers 3,556.8 1,073.7 818.0 99.9 673.0 (1,305.9) 4,915.5 Alternative Revenue Programs 18.2 18.6 (6.6) (0.9) — 1.0 30.3 Other Revenues (1) 1.9 — 0.5 0.2 — — 2.6 Total Operating Revenues $ 3,576.9 $ 1,092.3 $ 811.9 $ 99.2 $ 673.0 $ (1,304.9) $ 4,948.4 For the Three Months Ended June 30, 2020 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 916.0 $ 116.1 $ — $ 39.7 $ — $ — $ 1,071.8 Commercial 526.0 67.8 — 15.9 — (1.3) 608.4 Industrial 77.7 21.1 — 1.2 — (3.4) 96.6 Total Retail Tariff Sales Revenues 1,519.7 205.0 — 56.8 — (4.7) 1,776.8 Wholesale Transmission Revenues — — 383.4 — 19.2 (332.2) 70.4 Wholesale Market Sales Revenues 60.5 10.1 — 0.9 — — 71.5 Other Revenues from Contracts with Customers 21.1 1.4 3.3 0.9 264.6 (262.8) 28.5 Total Revenues from Contracts with Customers 1,601.3 216.5 386.7 58.6 283.8 (599.7) 1,947.2 Alternative Revenue Programs 14.2 (5.3) (10.2) (3.2) — 9.4 4.9 Other Revenues (1) 0.7 — 0.2 0.1 — — 1.0 Total Operating Revenues $ 1,616.2 $ 211.2 $ 376.7 $ 55.5 $ 283.8 $ (590.3) $ 1,953.1 For the Six Months Ended June 30, 2020 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Revenues from Contracts with Customers Retail Tariff Sales Residential $ 1,879.7 $ 354.1 $ — $ 67.5 $ — $ — $ 2,301.3 Commercial 1,133.0 202.4 — 30.6 — (2.3) 1,363.7 Industrial 157.5 49.5 — 2.3 — (6.6) 202.7 Total Retail Tariff Sales Revenues 3,170.2 606.0 — 100.4 — (8.9) 3,867.7 Wholesale Transmission Revenues — — 719.7 — 36.6 (615.8) 140.5 Wholesale Market Sales Revenues 151.5 23.2 — 1.8 — — 176.5 Other Revenues from Contracts with Customers 42.6 2.8 6.6 2.0 541.9 (538.9) 57.0 Total Revenues from Contracts with Customers 3,364.3 632.0 726.3 104.2 578.5 (1,163.6) 4,241.7 Alternative Revenue Programs 53.1 26.9 19.6 (2.1) — (18.1) 79.4 Other Revenues (1) 4.2 0.9 0.4 0.3 — — 5.8 Total Operating Revenues $ 3,421.6 $ 659.8 $ 746.3 $ 102.4 $ 578.5 $ (1,181.7) $ 4,326.9 For the Three Months Ended June 30, 2021 For the Three Months Ended June 30, 2020 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenues from Contracts with Customers Retail Tariff Sales Residential $ 440.8 $ 304.7 $ 136.6 $ 469.3 $ 311.5 $ 135.2 Commercial 215.7 296.1 82.8 199.3 261.0 66.1 Industrial 28.4 29.1 24.5 33.3 24.8 19.6 Total Retail Tariff Sales Revenues 684.9 629.9 243.9 701.9 597.3 220.9 Wholesale Transmission Revenues 195.7 160.1 61.1 191.4 142.5 49.5 Wholesale Market Sales Revenues 68.1 18.9 10.2 39.3 13.2 8.0 Other Revenues from Contracts with Customers 9.5 15.3 4.4 8.1 11.1 5.9 Total Revenues from Contracts with Customers 958.2 824.2 319.6 940.7 764.1 284.3 Alternative Revenue Programs (1.1) (15.3) 2.3 (7.5) 3.6 7.9 Other Revenues (1) (0.2) 0.7 0.5 0.2 0.7 — Eliminations (127.3) (122.2) (43.6) (116.0) (107.4) (37.0) Total Operating Revenues $ 829.6 $ 687.4 $ 278.8 $ 817.4 $ 661.0 $ 255.2 For the Six Months Ended June 30, 2021 For the Six Months Ended June 30, 2020 (Millions of Dollars) CL&P NSTAR Electric PSNH CL&P NSTAR Electric PSNH Revenues from Contracts with Customers Retail Tariff Sales Residential $ 986.6 $ 667.1 $ 294.4 $ 959.2 $ 642.4 $ 278.1 Commercial 429.9 564.4 160.6 425.6 562.9 145.3 Industrial 65.2 53.6 46.2 67.3 51.6 38.6 Total Retail Tariff Sales Revenues 1,481.7 1,285.1 501.2 1,452.1 1,256.9 462.0 Wholesale Transmission Revenues 384.6 307.2 119.4 343.2 277.3 99.2 Wholesale Market Sales Revenues 177.8 43.4 25.1 104.0 27.6 19.9 Other Revenues from Contracts with Customers 16.8 27.0 7.6 17.0 21.8 11.8 Total Revenues from Contracts with Customers 2,060.9 1,662.7 653.3 1,916.3 1,583.6 592.9 Alternative Revenue Programs 7.8 (1.5) 5.3 37.1 23.0 12.6 Other Revenues (1) 0.1 1.8 0.5 1.9 2.1 0.6 Eliminations (251.9) (238.6) (86.8) (238.2) (213.9) (74.5) Total Operating Revenues $ 1,816.9 $ 1,424.4 $ 572.3 $ 1,717.1 $ 1,394.8 $ 531.6 (1) Other Revenues include certain fees charged to customers that are not considered revenue from contracts with customers. Other Revenues also include lease revenues under lessor accounting guidance

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Summary of Segment Information and Segmented Total Assets	Eversource's segment information is as follows: For the Three Months Ended June 30, 2021 Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total Operating Revenues $ 1,676.5 $ 311.8 $ 411.2 $ 52.8 $ 330.0 $ (659.8) $ 2,122.5 Depreciation and Amortization (132.3) (34.6) (74.5) (11.5) (28.4) 1.1 (280.2) Other Operating Expenses (1,360.3) (257.7) (121.9) (25.4) (285.7) 660.3 (1,390.7) Operating Income, Net $ 183.9 $ 19.5 $ 214.8 $ 15.9 $ 15.9 $ 1.6 $ 451.6 Interest Expense $ (61.1) $ (14.6) $ (32.6) $ (8.1) $ (41.8) $ 12.8 $ (145.4) Other Income, Net 29.9 4.6 6.8 0.9 309.2 (304.8) 46.6 Net Income Attributable to Common Shareholders 121.6 4.1 137.6 8.9 282.7 (290.4) 264.5 For the Six Months Ended June 30, 2021 Eversource (Millions of Dollars) Electric Distribution Natural Gas Distribution Electric Transmission Water Distribution Other Eliminations Total Operating Revenues $ 3,576.9 $ 1,092.3 $ 811.9 $ 99.2 $ 673.0 $ (1,304.9) $ 4,948.4 Depreciation and Amortization (354.3) (80.3) (148.0) (22.8) (55.7) 2.1 (659.0) Other Operating Expenses (2,890.8) (793.6) (237.3) (50.5) (585.2) 1,305.2 (3,252.2) Operating Income $ 331.8 $ 218.4 $ 426.6 $ 25.9 $ 32.1 $ 2.4 $ 1,037.2 Interest Expense $ (114.4) $ (28.5) $ (65.3) $ (16.0) $ (83.4) $ 24.4 $ (283.2) Other Income, Net 50.6 8.5 12.2 1.9 733.4 (725.8) 80.8 Net Income Attributable to Common Shareholders 214.9 151.6 273.0 12.6 677.6 (699.0) 630.7 Cash Flows Used for Investments in Plant 510.4 305.9 443.2 53.8 109.9 — 1,423.2 For the Three Months Ended June 30, 2020 Eversource (Millions of Dollars) Electric Natural Gas Distribution (1) Electric Water Distribution Other (1) Eliminations (1) Total Operating Revenues $ 1,616.2 $ 211.2 $ 376.7 $ 55.5 $ 283.8 $ (590.3) $ 1,953.1 Depreciation and Amortization (140.7) (21.2) (68.8) (10.8) (22.7) 0.3 (263.9) Other Operating Expenses (1,293.3) (176.1) (111.2) (25.4) (243.1) 593.5 (1,255.6) Operating Income $ 182.2 $ 13.9 $ 196.7 $ 19.3 $ 18.0 $ 3.5 $ 433.6 Interest Expense $ (54.3) $ (10.7) $ (32.1) $ (8.4) $ (37.6) $ 8.8 $ (134.3) Other Income, Net 16.4 0.4 10.6 — 303.2 (300.4) 30.2 Net Income Attributable to Common Shareholders 115.0 2.6 129.5 10.4 282.8 (288.1) 252.2 For the Six Months Ended June 30, 2020 Eversource (Millions of Dollars) Electric Natural Gas Distribution (1) Electric Water Distribution Other (1) Eliminations (1) Total Operating Revenues $ 3,421.6 $ 659.8 $ 746.3 $ 102.4 $ 578.5 $ (1,181.7) $ 4,326.9 Depreciation and Amortization (308.1) (40.3) (136.2) (22.2) (44.0) 0.9 (549.9) Other Operating Expenses (2,732.9) (487.7) (218.0) (50.4) (500.0) 1,184.8 (2,804.2) Operating Income $ 380.6 $ 131.8 $ 392.1 $ 29.8 $ 34.5 $ 4.0 $ 972.8 Interest Expense $ (107.4) $ (22.0) $ (62.7) $ (17.1) $ (80.3) $ 20.5 $ (269.0) Other Income, Net 28.9 1.8 15.7 0.1 686.9 (679.1) 54.3 Net Income Attributable to Common Shareholders 245.1 88.6 256.2 12.5 639.2 (654.6) 587.0 Cash Flows Used for Investments in Plant 563.2 205.6 460.8 46.0 124.6 — 1,400.2 (1) On October 9, 2020, Eversource completed the CMA asset acquisition, with Yankee Energy System, Inc. (Yankee parent) as the acquiring entity. Yankee parent is the parent company of Yankee Gas, NSTAR Gas, EGMA and Hopkinton LNG Corp. As a result of the acquisition, in the fourth quarter of 2020, our chief operating decision maker assessed the performance of the Natural Gas Distribution segment including Yankee parent. Previously, Yankee parent was presented within Other and its equity in earnings were eliminated in consolidation. Prior comparative periods were revised to conform to the current period segment presentation. The following table summarizes Eversource's segmented total assets: Eversource (Millions of Dollars) Electric Natural Gas Electric Water Distribution Other Eliminations Total As of June 30, 2021 $ 25,904.6 $ 6,593.2 $ 12,289.3 $ 2,419.6 $ 21,669.0 $ (21,641.1) $ 47,234.6 As of December 31, 2020 24,981.9 6,450.5 11,695.0 2,375.2 22,089.4 (21,492.4) 46,099.6

ACQUISITION OF ASSETS OF COLU_2

ACQUISITION OF ASSETS OF COLUMBIA GAS OF MASSACHUSETTS (Tables)	6 Months Ended
	Jun. 30, 2021
Business Combination and Asset Acquisition [Abstract]
Preliminary Allocation of the Cash Purchase Price	The preliminary allocation of the cash purchase price is as follows: (Millions of Dollars) Current Assets $ 138 Restricted Cash 57 PP&E 1,184 Goodwill 50 Other Noncurrent Assets, excluding Goodwill 131 Other Current Liabilities (81) Other Noncurrent Liabilities (310) Cash Purchase Price $ 1,169

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) customer in Millions, $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2021USD ($)	Jun. 30, 2021USD ($)utilitycustomer	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Summary of Accounting Policies [Line Items]
Number of electric, natural gas and water customers | customer		4.3
Allowance for uncollectible accounts for late fees and other receivable amounts	$ 425.8	$ 425.8	$ 391.7	$ 358.9	$ 270	$ 262.1	$ 224.8
COVID-19
Summary of Accounting Policies [Line Items]
Increase in the allowance for uncollectible accounts		32.1
Allowance for uncollectible accounts for late fees and other receivable amounts	63.6	63.6
CL&P
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts	188.8	$ 188.8	175.1	157.4	136.7	130.9	97.3
Period of accounts receivable recoverable under financial or medical duress		180 days
CL&P | COVID-19
Summary of Accounting Policies [Line Items]
Increase in the allowance for uncollectible accounts		$ 12.3
Allowance for uncollectible accounts for late fees and other receivable amounts	15.1	15.1
NSTAR Electric
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts	98	98	89.3	91.6	68.7	71.1	75.4
NSTAR Electric | COVID-19
Summary of Accounting Policies [Line Items]
Increase in the allowance for uncollectible accounts		6.3
Allowance for uncollectible accounts for late fees and other receivable amounts	17.3	17.3
PSNH
Summary of Accounting Policies [Line Items]
Allowance for uncollectible accounts for late fees and other receivable amounts	17.2	17.2	$ 17.3	$ 17.2	$ 11.8	$ 11.2	$ 10.5
PSNH | COVID-19
Summary of Accounting Policies [Line Items]
Reversal of deferred net incremental COVID-19 costs	0.6
EGMA | Other Long-Term Assets
Summary of Accounting Policies [Line Items]
Restricted cash	41.5	41.5
Natural Gas Businesses | COVID-19
Summary of Accounting Policies [Line Items]
Increase in the allowance for uncollectible accounts		14.7
Allowance for uncollectible accounts for late fees and other receivable amounts	$ 30.1	$ 30.1
Yankee Gas
Summary of Accounting Policies [Line Items]
Period of accounts receivable recoverable under financial or medical duress		90 days
Connecticut, Massachusetts and New Hampshire
Summary of Accounting Policies [Line Items]
Number of regulated utilities | utility		9

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Provision for Uncollectible Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 391,700	$ 262,100	$ 358,900	$ 224,800
Uncollectible Expense	11,400	9,200	27,683	20,579
Uncollectible Costs Deferred	41,100	15,600	73,600	35,900
Write-Offs	(21,500)	(21,000)	(41,500)	(42,500)
Recoveries Collected	3,100	4,100	7,100	7,400
Ending Balance	425,800	270,000	425,800	270,000
CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	175,100	130,900	157,400	97,300
Uncollectible Expense	2,800	3,000	6,614	6,187
Uncollectible Costs Deferred	17,600	10,200	36,900	24,900
Write-Offs	(7,700)	(9,600)	(14,500)	(16,900)
Recoveries Collected	1,000	2,200	2,400	3,000
Ending Balance	188,800	136,700	188,800	136,700
NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	89,300	71,100	91,600	75,400
Uncollectible Expense	3,500	3,100	7,394	6,826
Uncollectible Costs Deferred	11,800	(200)	11,700	(200)
Write-Offs	(7,800)	(6,400)	(15,500)	(14,800)
Recoveries Collected	1,200	1,100	2,800	2,800
Ending Balance	98,000	68,700	98,000	68,700
PSNH
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	17,300	11,200	17,200	10,500
Uncollectible Expense	2,000	600	3,226	1,255
Uncollectible Costs Deferred	(300)	1,100	800	2,400
Write-Offs	(2,000)	(1,300)	(4,500)	(3,000)
Recoveries Collected	200	200	500	300
Ending Balance	17,200	11,800	17,200	11,800
Hardship Accounts
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	197,300	172,200	194,800	143,300
Uncollectible Expense	0	0	0	0
Uncollectible Costs Deferred	16,600	7,100	22,000	18,900
Write-Offs	(3,400)	(4,400)	(6,700)	(9,100)
Recoveries Collected	200	600	600	800
Ending Balance	210,700	175,500	210,700	175,500
Hardship Accounts | CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	138,400	110,700	129,100	80,100
Uncollectible Expense	0	0	0	0
Uncollectible Costs Deferred	9,300	8,600	21,200	21,500
Write-Offs	(2,300)	(3,600)	(5,200)	(7,400)
Recoveries Collected	200	600	500	800
Ending Balance	145,600	116,300	145,600	116,300
Hardship Accounts | NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	31,100	38,500	39,700	43,900
Uncollectible Expense	0	0	0	0
Uncollectible Costs Deferred	4,900	(3,700)	(3,500)	(7,100)
Write-Offs	(100)	(200)	(300)	(600)
Recoveries Collected	0	0	0	0
Ending Balance	35,900	34,600	35,900	34,600
Retail (Non-Hardship), Wholesale, and Other Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	194,400	89,900	164,100	81,500
Uncollectible Expense	11,400	9,200	27,700	20,600
Uncollectible Costs Deferred	24,500	8,500	51,600	17,000
Write-Offs	(18,100)	(16,600)	(34,800)	(33,400)
Recoveries Collected	2,900	3,500	6,500	6,600
Ending Balance	215,100	94,500	215,100	94,500
Retail (Non-Hardship), Wholesale, and Other Receivables | CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	36,700	20,200	28,300	17,200
Uncollectible Expense	2,800	3,000	6,600	6,200
Uncollectible Costs Deferred	8,300	1,600	15,700	3,400
Write-Offs	(5,400)	(6,000)	(9,300)	(9,500)
Recoveries Collected	800	1,600	1,900	2,200
Ending Balance	43,200	20,400	43,200	20,400
Retail (Non-Hardship), Wholesale, and Other Receivables | NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	58,200	32,600	51,900	31,500
Uncollectible Expense	3,500	3,100	7,400	6,800
Uncollectible Costs Deferred	6,900	3,500	15,200	6,900
Write-Offs	(7,700)	(6,200)	(15,200)	(14,200)
Recoveries Collected	1,200	1,100	2,800	2,800
Ending Balance	$ 62,100	$ 34,100	$ 62,100	34,100
Restatement Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance				23,800
Restatement Adjustment | CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance				22,200
Restatement Adjustment | NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance				(1,300)
Restatement Adjustment | PSNH
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance				300
Restatement Adjustment | Hardship Accounts
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance				21,600
Restatement Adjustment | Hardship Accounts | CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance				21,300
Restatement Adjustment | Hardship Accounts | NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance				(1,600)
Restatement Adjustment | Retail (Non-Hardship), Wholesale, and Other Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance				2,200
Restatement Adjustment | Retail (Non-Hardship), Wholesale, and Other Receivables | CL&P
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance				900
Restatement Adjustment | Retail (Non-Hardship), Wholesale, and Other Receivables | NSTAR Electric
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance				$ 300

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Components of Other Income, Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Summary of Accounting Policies [Line Items]
Other income, net	$ 46,619	$ 30,243	$ 80,820	$ 54,347
Pension, SERP and PBOP Non-Service   Income Components
Summary of Accounting Policies [Line Items]
Other income, net	22,100	10,700	42,200	23,400
AFUDC Equity
Summary of Accounting Policies [Line Items]
Other income, net	9,200	10,800	18,400	21,400
Equity in Earnings of Unconsolidated Affiliates (1)
Summary of Accounting Policies [Line Items]
Other income, net	4,700	5,900	8,400	9,800
Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other income, net	1,900	1,800	1,300	(2,500)
Interest Income
Summary of Accounting Policies [Line Items]
Other income, net	8,400	1,000	9,900	1,800
Other
Summary of Accounting Policies [Line Items]
Other income, net	300	0	600	400
Equity In Earnings
Summary of Accounting Policies [Line Items]
Unrealized gain associated with investment	2,100	2,400	2,100	2,400
CL&P
Summary of Accounting Policies [Line Items]
Other income, net	9,879	8,459	14,787	10,357
CL&P | Pension, SERP and PBOP Non-Service   Income Components
Summary of Accounting Policies [Line Items]
Other income, net	4,300	900	7,000	2,100
CL&P | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other income, net	1,700	3,900	3,400	7,900
CL&P | Equity in Earnings of Unconsolidated Affiliates (1)
Summary of Accounting Policies [Line Items]
Other income, net	0	0	0	0
CL&P | Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other income, net	1,200	2,200	1,500	(1,300)
CL&P | Interest Income
Summary of Accounting Policies [Line Items]
Other income, net	2,700	1,400	2,800	1,600
CL&P | Other
Summary of Accounting Policies [Line Items]
Other income, net	0	100	100	100
NSTAR Electric
Summary of Accounting Policies [Line Items]
Other income, net	21,915	13,112	38,727	25,350
NSTAR Electric | Pension, SERP and PBOP Non-Service   Income Components
Summary of Accounting Policies [Line Items]
Other income, net	10,200	7,100	20,200	15,000
NSTAR Electric | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other income, net	6,200	5,300	12,400	10,300
NSTAR Electric | Equity in Earnings of Unconsolidated Affiliates (1)
Summary of Accounting Policies [Line Items]
Other income, net	100	100	200	200
NSTAR Electric | Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other income, net	600	0	800	(1,300)
NSTAR Electric | Interest Income
Summary of Accounting Policies [Line Items]
Other income, net	4,800	500	4,900	700
NSTAR Electric | Other
Summary of Accounting Policies [Line Items]
Other income, net	0	100	200	500
PSNH
Summary of Accounting Policies [Line Items]
Other income, net	4,260	3,626	8,427	6,817
PSNH | Pension, SERP and PBOP Non-Service   Income Components
Summary of Accounting Policies [Line Items]
Other income, net	2,700	1,600	5,400	3,500
PSNH | AFUDC Equity
Summary of Accounting Policies [Line Items]
Other income, net	300	1,200	900	2,600
PSNH | Equity in Earnings of Unconsolidated Affiliates (1)
Summary of Accounting Policies [Line Items]
Other income, net	0	0	0	0
PSNH | Investment Income/(Loss)
Summary of Accounting Policies [Line Items]
Other income, net	300	300	400	(200)
PSNH | Interest Income
Summary of Accounting Policies [Line Items]
Other income, net	900	500	1,600	800
PSNH | Other
Summary of Accounting Policies [Line Items]
Other income, net	$ 100	$ 0	$ 100	$ 100

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Schedule of Gross Tax Receipts [Line Items]
Gross receipts taxes	$ 39.9	$ 37.6	$ 88.5	$ 80.7
CL&P
Schedule of Gross Tax Receipts [Line Items]
Gross receipts taxes	$ 35.4	$ 33.1	$ 74.6	$ 68.6

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Non-cash Investing Activities (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Schedule of Supplemental Cash Flow [Line Items]
Plant additions included in accounts payable	$ 344.8	$ 336.1
CL&P
Schedule of Supplemental Cash Flow [Line Items]
Plant additions included in accounts payable	66.4	95
NSTAR Electric
Schedule of Supplemental Cash Flow [Line Items]
Plant additions included in accounts payable	103.8	75.5
PSNH
Schedule of Supplemental Cash Flow [Line Items]
Plant additions included in accounts payable	$ 33.9	$ 48.3

SUMMARY OF SIGNIFICANT ACCOUN_9

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Reconciliation of Cash Balances to Cash and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Restricted Cash and Cash Equivalents Items [Line Items]
Cash as reported on the Balance Sheets	$ 217,397	$ 106,599
Cash and Restricted Cash as reported on the Statements of Cash Flows	368,011	264,950	$ 176,920	$ 117,063
Special Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	71,800	73,600
Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	34,100	41,200
Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	44,700	43,600
CL&P
Restricted Cash and Cash Equivalents Items [Line Items]
Cash as reported on the Balance Sheets	198,390	90,801
Cash and Restricted Cash as reported on the Statements of Cash Flows	207,441	99,809	15,998	4,971
CL&P | Special Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	8,600	8,700
CL&P | Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	400	300
CL&P | Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	0	0
NSTAR Electric
Restricted Cash and Cash Equivalents Items [Line Items]
Cash as reported on the Balance Sheets	577	102
Cash and Restricted Cash as reported on the Statements of Cash Flows	17,898	17,410	13,482	6,312
NSTAR Electric | Special Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	17,200	17,200
NSTAR Electric | Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	100	100
NSTAR Electric | Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	0	0
PSNH
Restricted Cash and Cash Equivalents Items [Line Items]
Cash as reported on the Balance Sheets	279	141
Cash and Restricted Cash as reported on the Statements of Cash Flows	39,226	39,555	$ 34,870	$ 36,688
PSNH | Special Deposits
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	35,100	36,800
PSNH | Marketable Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	600	600
PSNH | Other Long-Term Assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 3,200	$ 2,100

REGULATORY ACCOUNTING - Compone

REGULATORY ACCOUNTING - Components of Regulatory Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 6,433,300	$ 6,569,900
Less:  Current Portion	1,186,851	1,076,556
Total Long-Term Regulatory Assets	5,246,381	5,493,330
Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	2,625,100	2,794,200
Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	755,400	747,100
Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	500,500	522,100
Storm Restoration Costs, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	745,900	765,600
Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	950,900	850,500
Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	279,700	296,300
Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	306,200	314,700
Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	118,200	118,400
Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	151,400	161,000
CL&P
Regulatory Assets [Line Items]
Total Regulatory Assets	2,204,400	2,211,800
Less:  Current Portion	458,609	345,622
Total Long-Term Regulatory Assets	1,745,793	1,866,152
CL&P | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	551,700	632,300
CL&P | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	460,500	458,900
CL&P | Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
CL&P | Storm Restoration Costs, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	500,200	515,100
CL&P | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	347,500	246,600
CL&P | Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	279,700	293,100
CL&P | Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
CL&P | Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	33,200	32,100
CL&P | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	31,600	33,700
NSTAR Electric
Regulatory Assets [Line Items]
Total Regulatory Assets	1,684,400	1,703,900
Less:  Current Portion	448,030	399,882
Total Long-Term Regulatory Assets	1,236,379	1,304,019
NSTAR Electric | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	653,900	690,000
NSTAR Electric | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	112,200	110,400
NSTAR Electric | Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
NSTAR Electric | Storm Restoration Costs, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	169,500	186,400
NSTAR Electric | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	378,800	332,200
NSTAR Electric | Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
NSTAR Electric | Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	262,900	270,200
NSTAR Electric | Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	55,800	58,600
NSTAR Electric | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	51,300	56,100
PSNH
Regulatory Assets [Line Items]
Total Regulatory Assets	950,400	989,100
Less:  Current Portion	99,474	115,852
Total Long-Term Regulatory Assets	850,912	873,203
PSNH | Benefit Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	255,100	267,600
PSNH | Income Taxes, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	17,400	15,200
PSNH | Securitized Stranded Costs
Regulatory Assets [Line Items]
Total Regulatory Assets	500,500	522,100
PSNH | Storm Restoration Costs, Net
Regulatory Assets [Line Items]
Total Regulatory Assets	76,200	64,100
PSNH | Regulatory Tracker Mechanisms
Regulatory Assets [Line Items]
Total Regulatory Assets	79,100	95,300
PSNH | Derivative Liabilities
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
PSNH | Goodwill-related
Regulatory Assets [Line Items]
Total Regulatory Assets	0	0
PSNH | Asset Retirement Obligations
Regulatory Assets [Line Items]
Total Regulatory Assets	4,000	3,900
PSNH | Other Regulatory Assets
Regulatory Assets [Line Items]
Total Regulatory Assets	$ 18,100	$ 20,900

REGULATORY ACCOUNTING - Narrati

REGULATORY ACCOUNTING - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	$ 255.6	$ 196.9
Regulatory costs	6,433.3	6,569.9
Storm Restoration Costs, Net
Regulatory Assets [Line Items]
Regulatory costs	745.9	765.6
COVID-19
Regulatory Assets [Line Items]
Net incremental deferred costs related to non-tracked uncollectible expense	39.1	15.8
Net incremental deferred costs	45.8	24
Tropical Storm Isaias | Storm Restoration Costs, Net
Regulatory Assets [Line Items]
Regulatory costs	243
CL&P
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	115.5	84.1
Regulatory costs	2,204.4	2,211.8
CL&P | Storm Restoration Costs, Net
Regulatory Assets [Line Items]
Regulatory costs	500.2	515.1
CL&P | COVID-19
Regulatory Assets [Line Items]
Net incremental deferred costs	13.2	4.7
CL&P | Tropical Storm Isaias | Storm Restoration Costs, Net
Regulatory Assets [Line Items]
Regulatory costs	225
NSTAR Electric
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	77.1	69.8
Regulatory costs	1,684.4	1,703.9
NSTAR Electric | Storm Restoration Costs, Net
Regulatory Assets [Line Items]
Regulatory costs	169.5	186.4
NSTAR Electric | COVID-19
Regulatory Assets [Line Items]
Net incremental deferred costs	15.8	11.9
PSNH
Regulatory Assets [Line Items]
Amount of regulatory costs not yet approved	3.1	4.3
Regulatory costs	950.4	989.1
PSNH | Storm Restoration Costs, Net
Regulatory Assets [Line Items]
Regulatory costs	$ 76.2	$ 64.1

REGULATORY ACCOUNTING - Compo_2

REGULATORY ACCOUNTING - Components of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 4,412,600	$ 4,240,200
Less:  Current Portion	532,467	389,430
Total Long-Term Regulatory Liabilities	3,880,131	3,850,781
EDIT due to Tax Cuts and Jobs Act of 2017
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	2,748,600	2,778,600
Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	657,100	624,800
Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	70,400	83,600
Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	474,700	366,500
AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	78,700	76,800
Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	383,100	309,900
CL&P
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,427,100	1,342,100
Less:  Current Portion	219,813	137,166
Total Long-Term Regulatory Liabilities	1,207,289	1,204,942
CL&P | EDIT due to Tax Cuts and Jobs Act of 2017
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,005,400	1,010,700
CL&P | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	108,700	98,400
CL&P | Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
CL&P | Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	190,300	148,900
CL&P | AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	43,900	44,600
CL&P | Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	78,800	39,500
NSTAR Electric
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,725,100	1,715,200
Less:  Current Portion	172,988	164,761
Total Long-Term Regulatory Liabilities	1,552,053	1,550,390
NSTAR Electric | EDIT due to Tax Cuts and Jobs Act of 2017
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	1,030,500	1,044,000
NSTAR Electric | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	374,400	363,600
NSTAR Electric | Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	60,200	72,500
NSTAR Electric | Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	147,700	139,700
NSTAR Electric | AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	34,800	32,200
NSTAR Electric | Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	77,500	63,200
PSNH
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	446,600	442,000
Less:  Current Portion	61,891	58,756
Total Long-Term Regulatory Liabilities	384,675	383,183
PSNH | EDIT due to Tax Cuts and Jobs Act of 2017
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	364,200	371,500
PSNH | Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	17,100	12,900
PSNH | Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
PSNH | Regulatory Tracker Mechanisms
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	51,000	47,800
PSNH | AFUDC - Transmission
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	0	0
PSNH | Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 14,300	$ 9,800

PROPERTY, PLANT AND EQUIPMENT_3

PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Summary of Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	$ 17,104,800	$ 16,703,200
Distribution - Natural Gas	6,227,800	6,111,200
Transmission - Electric	12,296,800	11,954,000
Distribution - Water	1,772,700	1,743,100
Solar	200,400	201,500
Utility	37,602,500	36,713,000
Other	1,386,900	1,269,000
Property, Plant and Equipment, Gross	38,989,400	37,982,000
Less:  Accumulated Depreciation
Utility	(8,756,600)	(8,476,300)
Other	(525,800)	(477,600)
Total Accumulated Depreciation	(9,282,400)	(8,953,900)
Property, Plant and Equipment, Net	29,707,000	29,028,100
Construction Work in Progress	2,171,600	1,854,400
Total Property, Plant and Equipment, Net	31,878,551	30,882,523
CL&P
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	6,989,400	6,820,700
Transmission - Electric	5,653,400	5,512,000
Solar	0	0
Property, Plant and Equipment, Gross	12,642,800	12,332,700
Less:  Accumulated Depreciation
Total Accumulated Depreciation	(2,559,400)	(2,475,400)
Property, Plant and Equipment, Net	10,083,400	9,857,300
Construction Work in Progress	395,800	377,300
Total Property, Plant and Equipment, Net	10,479,192	10,234,556
NSTAR Electric
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	7,716,500	7,544,400
Transmission - Electric	4,866,500	4,701,300
Solar	200,400	201,500
Property, Plant and Equipment, Gross	12,783,400	12,447,200
Less:  Accumulated Depreciation
Total Accumulated Depreciation	(3,182,800)	(3,074,100)
Property, Plant and Equipment, Net	9,600,600	9,373,100
Construction Work in Progress	836,600	750,000
Total Property, Plant and Equipment, Net	10,437,198	10,123,062
PSNH
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	2,439,200	2,378,400
Transmission - Electric	1,778,600	1,742,400
Solar	0	0
Property, Plant and Equipment, Gross	4,217,800	4,120,800
Less:  Accumulated Depreciation
Total Accumulated Depreciation	(879,900)	(848,900)
Property, Plant and Equipment, Net	3,337,900	3,271,900
Construction Work in Progress	129,900	102,400
Total Property, Plant and Equipment, Net	$ 3,467,810	$ 3,374,270

DERIVATIVE INSTRUMENTS - Gross

DERIVATIVE INSTRUMENTS - Gross Fair Values and Net Amounts of Contracts (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Current Derivative Assets | CL&P | Level 3
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	$ 14.1	$ 13.7
Netting	(0.4)	(0.4)
Net Amount Recorded as a Derivative	13.7	13.3
Other Long-Term Assets | CL&P | Level 3
Derivative Assets (Liabilities), at Fair Value, Net, by Balance Sheet Classification [Abstract]
Commodity Supply and Price Risk Management	55	58.7
Netting	(1.7)	(1.8)
Net Amount Recorded as a Derivative	53.3	56.9
Current Derivative Liabilities | CL&P | Level 3
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(70.9)	(68.8)
Netting	0	0
Net Amount Recorded as a Derivative	(70.9)	(68.8)
Current Derivative Liabilities | Other | Level 2
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	0	(3.3)
Netting	0	0.1
Net Amount Recorded as a Derivative	0	(3.2)
Long-Term Derivative Liabilities | CL&P | Level 3
Current and Long-Term Derivative Liabilities
Commodity Supply and Price Risk Management	(275.8)	(294.5)
Netting	0	0
Net Amount Recorded as a Derivative	$ (275.8)	$ (294.5)

DERIVATIVE INSTRUMENTS - Narrat

DERIVATIVE INSTRUMENTS - Narrative (Details) MMBTU in Millions, $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021USD ($)MW	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)MW	Jun. 30, 2020USD ($)	Dec. 31, 2020MMBTUMW
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of costs or benefits borne under capacity-related contracts by United Illuminated Company			20.00%
Amount of power to be purchased under capacity-related contract (in MW) | MW	675		675		675
Amount of natural gas to be purchased under futures contracts | MMBTU					8.9
Gains (losses) on deferred as regulatory costs | $	$ 0.9	$ (0.1)	$ (10.2)	$ (18)
Level 3 | Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts			6.00%
Level 3 | Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts			10.40%
Level 3 | Weighted Average
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of exit price premiums related to derivative contracts			9.30%
CL&P
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Percentage of costs or benefits borne under capacity-related contracts			80.00%

DERIVATIVE INSTRUMENTS - Summar

DERIVATIVE INSTRUMENTS - Summary of Level 3 Derivative Contracts and Significant Unobservable Inputs Used (Details) - CL&P - Level 3 - $ / KWmo	Jun. 30, 2021	Dec. 31, 2020
Capacity Prices
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	2.61
Capacity Prices | Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input		4.30
Capacity Prices | Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input		5.30
Capacity Prices | Weighted Average
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	2.61	4.63
Forward Reserve Prices | Minimum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	0.54	0.54
Forward Reserve Prices | Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	0.90	0.90
Forward Reserve Prices | Weighted Average
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative measurement input	0.72	0.72

DERIVATIVE INSTRUMENTS - Change

DERIVATIVE INSTRUMENTS - Changes in the Level 3 Category of Derivative Assets Measured at Fair Value on a Recurring Basis (Details) - CL&P - Level 3 - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivatives, Net [Rollforward]
Fair Value as of Beginning of Period	$ (293.1)	$ (333.8)	$ (293.1)	$ (329.2)
Net Realized/Unrealized Gains/(Losses) Included in Regulatory Assets	0.9	(1.3)	(11.5)	(17.6)
Settlements	12.5	13.1	24.9	24.8
Fair Value as of End of Period	$ (279.7)	$ (322)	$ (279.7)	$ (322)

MARKETABLE SECURITIES - Narrati

MARKETABLE SECURITIES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Available-for-sale equity securities	$ 39.9		$ 39.9		$ 40.9
Unrealized gain (loss) recorded in other income	1.9	$ 6.6	3	$ (2.5)
CYAPC and YAEC
Debt Securities, Available-for-sale [Line Items]
Available-for-sale equity securities	207.3		207.3		205.1
Marketable securities held in nuclear decommissioning trust	$ 198.4		$ 198.4		$ 192.5

MARKETABLE SECURITIES - Summary

MARKETABLE SECURITIES - Summary of Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Amortized Cost	$ 224	$ 213.1
Pre-Tax Unrealized Gains	7	11.2
Pre-Tax Unrealized Losses	(0.1)	(0.1)
Fair Value	$ 230.9	$ 224.2

MARKETABLE SECURITIES - Contrac

MARKETABLE SECURITIES - Contractual Maturities of Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Amortized Cost
Less than one year	$ 36.5
One to five years	67.5
Six to ten years	49.7
Greater than ten years	70.3
Amortized Cost	224	$ 213.1
Fair Value
Less than one year	36.5
One to five years	69.4
Six to ten years	51.4
Greater than ten years	73.6
Fair Value	$ 230.9	$ 224.2

MARKETABLE SECURITIES - Marketa

MARKETABLE SECURITIES - Marketable Securities Recorded at Fair Value on a Recurring Basis by Level (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 478.1	$ 470.2
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	281.3	287.2
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	196.8	183
Mutual Funds and Equities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	247.2	246
Money Market Funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	34.1	41.2
U.S. Government Issued Debt Securities (Agency and Treasury) | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	100.8	72.9
Corporate Debt Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	62.8	63.8
Asset-Backed Debt Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	13.6	11.9
Municipal Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	6.4	24
Other Fixed Income Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 13.2	$ 10.4

SHORT-TERM AND LONG-TERM DEBT -

SHORT-TERM AND LONG-TERM DEBT - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2021	Jul. 31, 2021	May 18, 2021	Mar. 31, 2021	Dec. 31, 2020
NSTAR Electric
Line of Credit Facility [Line Items]
Notes payable to Eversource parent	$ 21,500,000				$ 21,300,000
Amount of long-term debt requested for issuance				$ 1,600,000,000
CL&P | Bonds | Subsequent Event
Line of Credit Facility [Line Items]
Interest rate, stated percentage		4.375%
Face amount		$ 120,500,000
PSNH
Line of Credit Facility [Line Items]
Notes payable to Eversource parent	48,600,000				46,300,000
Massachusetts Department of Public Utilities
Line of Credit Facility [Line Items]
Amount of long-term debt requested for issuance			$ 725,000,000
Line of Credit | CL&P
Line of Credit Facility [Line Items]
Maximum borrowing capacity	450,000,000
Amount outstanding under line of credit	0
Line of Credit | PSNH
Line of Credit Facility [Line Items]
Maximum borrowing capacity	300,000,000
Amount outstanding under line of credit	0
Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	550,000,000
Commercial Paper | NSTAR Electric
Line of Credit Facility [Line Items]
Maximum borrowing capacity	650,000,000
Line of Credit
Line of Credit Facility [Line Items]
Amount outstanding under line of credit	0				$ 0
Line of Credit | NSTAR Electric
Line of Credit Facility [Line Items]
Maximum borrowing capacity	650,000,000
Eversource Parent | Commercial Paper
Line of Credit Facility [Line Items]
Maximum borrowing capacity	2,000,000,000
Eversource Parent | Line of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 1,450,000,000
Debt instrument term	5 years
NSTAR Electric | Line of Credit | NSTAR Electric
Line of Credit Facility [Line Items]
Debt instrument term	5 years

SHORT-TERM AND LONG-TERM DEBT_2

SHORT-TERM AND LONG-TERM DEBT - Borrowings Outstanding and Available under the Commercial Paper Programs (Details) - Commercial Paper - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Borrowings outstanding	$ 1,447	$ 1,054.3
Available borrowing capacity	$ 553	$ 945.7
Weighted-average interest rate	0.19%	0.25%
NSTAR Electric
Debt Instrument [Line Items]
Borrowings outstanding	$ 555.5	$ 195
Available borrowing capacity	$ 94.5	$ 455
Weighted-average interest rate	0.11%	0.16%

SHORT-TERM AND LONG-TERM DEBT_3

SHORT-TERM AND LONG-TERM DEBT - Summary of Long-Term Debt Issuance and Repayments (Details) - USD ($) $ in Thousands	1 Months Ended					6 Months Ended
	Jun. 30, 2021	May 31, 2021	Apr. 30, 2021	Mar. 31, 2021	Feb. 28, 2021	Jun. 30, 2021	Jun. 30, 2020
Debt Instrument [Line Items]
Repayments						$ (1,022,000)	$ (270,456)
Senior Notes | Eversource Parent 2.50% Series I Senior Notes | Eversource Parent
Debt Instrument [Line Items]
Interest rate, stated percentage					2.50%
Repayments					$ (450,000)
Senior Notes | Eversource Parent 2.55% Series S Senior Notes | Eversource Parent
Debt Instrument [Line Items]
Interest rate, stated percentage				2.55%
Issuances				$ 350,000
CL&P | Senior Notes | 2.05% Series A First Mortgage Bonds
Debt Instrument [Line Items]
Interest rate, stated percentage	2.05%					2.05%
Issuances	$ 425,000
NSTAR Electric
Debt Instrument [Line Items]
Repayments						$ (250,000)	(95,000)
NSTAR Electric | Senior Notes | 3.10% 2021 Debentures
Debt Instrument [Line Items]
Interest rate, stated percentage		3.10%
Issuances		$ 300,000
NSTAR Electric | Senior Notes | 3.50% Series F Senior Notes
Debt Instrument [Line Items]
Interest rate, stated percentage	3.50%					3.50%
Repayments	$ (250,000)
PSNH
Debt Instrument [Line Items]
Repayments						$ (282,000)	$ 0
PSNH | Senior Notes | 4.05% Series Q First Mortgage Bonds
Debt Instrument [Line Items]
Interest rate, stated percentage				4.05%
Repayments				$ (122,000)
PSNH | Senior Notes | 3.20% Series R First Mortgage Bonds
Debt Instrument [Line Items]
Interest rate, stated percentage	3.20%					3.20%
Repayments	$ (160,000)
PSNH | Senior Notes | 2.20% Series V First Mortgage Bonds
Debt Instrument [Line Items]
Interest rate, stated percentage	2.20%					2.20%
Issuances	$ 350,000
Aquarion | Senior Notes | Aquarion Water Company of Connecticut 3.31% Senior Notes
Debt Instrument [Line Items]
Interest rate, stated percentage			3.31%
Issuances			$ 100,000
Aquarion | Senior Notes | Aquarion Water Company of Connecticut 5.50% Notes
Debt Instrument [Line Items]
Interest rate, stated percentage			5.50%
Repayments			$ (40,000)

RATE REDUCTION BONDS AND VARI_3

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Narrative (Details) - PSNH - Rate Reduction Bonds	May 31, 2018USD ($)
Debt Instrument [Line Items]
Amount of securitized rate reduction bonds issued	$ 635,700,000
Weighted average interest rate	3.66%

RATE REDUCTION BONDS AND VARI_4

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Summary of the Impact of Funding on the Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	$ 6,433,300	$ 6,569,900
Regulatory Liabilities	3,880,131	3,850,781
Accrued Interest (included in Other Current Liabilities)	665,424	809,214
Rate Reduction Bonds - Current Portion	43,210	43,210
Rate Reduction Bonds - Long-Term Portion	475,307	496,912
Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	500,500	522,100
Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	151,400	161,000
Current Derivative Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	71,800	73,600
Other Long-Term Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	44,700	43,600
PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	950,400	989,100
Regulatory Liabilities	384,675	383,183
Accrued Interest (included in Other Current Liabilities)	46,984	58,487
Rate Reduction Bonds - Current Portion	43,210	43,210
Rate Reduction Bonds - Long-Term Portion	475,307	496,912
PSNH | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Rate Reduction Bonds - Current Portion	43,200	43,200
Rate Reduction Bonds - Long-Term Portion	475,300	496,900
PSNH | Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	500,500	522,100
PSNH | Securitized Stranded Costs | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	500,500	522,100
PSNH | Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	18,100	20,900
PSNH | Other Regulatory Assets | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory Liabilities	8,900	9,100
Accrued Interest (included in Other Current Liabilities)	7,700	8,000
PSNH | Current Derivative Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	35,100	36,800
PSNH | Current Derivative Assets | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	34,900	36,800
PSNH | Other Long-Term Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	3,200	2,100
PSNH | Other Long-Term Assets | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	$ 3,200	$ 2,100

RATE REDUCTION BONDS AND VARI_5

RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Summary of the Impact of Funding on the Income Statements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Condensed Income Statements, Captions [Line Items]
Interest Expense on RRB Principal (included in Interest Expense)	$ 145,435	$ 134,285	$ 283,201	$ 269,000
PSNH
Condensed Income Statements, Captions [Line Items]
Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net)	(26,274)	(11,563)	(44,821)	(31,673)
Interest Expense on RRB Principal (included in Interest Expense)	13,821	14,607	28,452	29,087
PSNH | VIE | Rate Reduction Bonds
Condensed Income Statements, Captions [Line Items]
Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net)	10,800	10,800	21,600	21,600
Interest Expense on RRB Principal (included in Interest Expense)	$ 4,600	$ 5,000	$ 9,300	$ 10,000

PENSION BENEFITS AND POSTRETI_3

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION - Components of Net Periodic Benefit Expense/(Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	$ 18.4	$ 18.7	$ 39.7	$ 38.3
Interest Cost	27.1	44.3	59.7	88.6
Expected Return on Plan Assets	(87.4)	(99.3)	(196.3)	(199.6)
Actuarial Loss	47.8	50.7	109.4	100
Prior Service Cost/(Credit)	0.3	0.3	0.6	0.6
Total Net Periodic Benefit Plan Expense/(Income)	6.2	14.7	13.1	27.9
PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	3.3	2	6.8	4.9
Interest Cost	4.2	6.4	8.6	12.2
Expected Return on Plan Assets	(19.8)	(18.7)	(39.5)	(36.8)
Actuarial Loss	1.3	2	3.9	4.1
Prior Service Cost/(Credit)	(5.3)	(5.2)	(10.6)	(10.6)
Total Net Periodic Benefit Plan Expense/(Income)	(16.3)	(13.5)	(30.8)	(26.2)
CL&P | Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	5.5	5.4	11.8	11.1
Interest Cost	6.7	9.3	14	18.8
Expected Return on Plan Assets	(21.7)	(19.8)	(43.3)	(39.8)
Actuarial Loss	10.8	9.7	23.8	19.7
Prior Service Cost/(Credit)	0	0	0	0
Total Net Periodic Benefit Plan Expense/(Income)	1.3	4.6	6.3	9.8
Intercompany Expense/(Income) Allocations	2.3	2.4	3.6	4.3
CL&P | PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.6	0.4	1.2	0.9
Interest Cost	0.8	1	1.6	2.2
Expected Return on Plan Assets	(2.6)	(2.5)	(5.2)	(4.9)
Actuarial Loss	0.4	0.2	0.8	0.6
Prior Service Cost/(Credit)	0.3	0.2	0.5	0.4
Total Net Periodic Benefit Plan Expense/(Income)	(0.5)	(0.7)	(1.1)	(0.8)
Intercompany Expense/(Income) Allocations	(0.6)	(0.2)	(0.9)	(0.6)
NSTAR Electric | Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	3.9	3.8	7.9	7.6
Interest Cost	6.7	9.7	13.4	19.3
Expected Return on Plan Assets	(27.1)	(25.7)	(54)	(51.5)
Actuarial Loss	15.3	14	30.8	27.3
Prior Service Cost/(Credit)	0.1	0.1	0.2	0.2
Total Net Periodic Benefit Plan Expense/(Income)	(1.1)	1.9	(1.7)	2.9
Intercompany Expense/(Income) Allocations	2.5	2.3	4	4.2
NSTAR Electric | PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.6	0.5	1.2	1.1
Interest Cost	1.1	1.6	2.2	3.3
Expected Return on Plan Assets	(9.2)	(8.5)	(18.5)	(17)
Actuarial Loss	0.5	0.5	1.1	1.2
Prior Service Cost/(Credit)	(4.2)	(4.3)	(8.4)	(8.5)
Total Net Periodic Benefit Plan Expense/(Income)	(11.2)	(10.2)	(22.4)	(19.9)
Intercompany Expense/(Income) Allocations	(0.6)	(0.2)	(1)	(0.6)
PSNH | Pension and SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	2.2	2	4.4	4.2
Interest Cost	3.6	4.8	7.2	9.7
Expected Return on Plan Assets	(11.8)	(11.1)	(23.7)	(22.4)
Actuarial Loss	5.2	3.9	10.1	8
Prior Service Cost/(Credit)	0	0	0	0
Total Net Periodic Benefit Plan Expense/(Income)	(0.8)	(0.4)	(2)	(0.5)
Intercompany Expense/(Income) Allocations	0.7	0.8	1.2	1.4
PSNH | PBOP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0.3	0.2	0.6	0.4
Interest Cost	0.4	0.8	0.9	1.4
Expected Return on Plan Assets	(1.5)	(1.4)	(3)	(2.8)
Actuarial Loss	0.1	0.3	0.3	0.4
Prior Service Cost/(Credit)	0.1	0.1	0.2	0.2
Total Net Periodic Benefit Plan Expense/(Income)	(0.6)	0	(1)	(0.4)
Intercompany Expense/(Income) Allocations	$ (0.2)	$ (0.1)	$ (0.3)	$ (0.3)

PENSION BENEFITS AND POSTRETI_4

PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION - Narrative (Details) $ in Millions	Jun. 30, 2021USD ($)
Defined Benefit Plan Disclosure [Line Items]
Expected pension plan contributions	$ 180
CL&P
Defined Benefit Plan Disclosure [Line Items]
Expected pension plan contributions	99
NSTAR Electric
Defined Benefit Plan Disclosure [Line Items]
Expected pension plan contributions	$ 30

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Environmental Sites and Related Reserves (Details) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2021USD ($)site	Dec. 31, 2020USD ($)site
Site Contingency [Line Items]
Number of Sites | site	62	63
Reserve | $	$ 108.8	$ 102.4
CL&P
Site Contingency [Line Items]
Number of Sites | site	14	15
Reserve | $	$ 10.7	$ 12.3
NSTAR Electric
Site Contingency [Line Items]
Number of Sites | site	12	12
Reserve | $	$ 3.9	$ 4.7
PSNH
Site Contingency [Line Items]
Number of Sites | site	9	9
Reserve | $	$ 6.6	$ 7.1

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Environmental Matters (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Site Contingency [Line Items]
Reserve balance	$ 108.8	$ 102.4
MGP Sites
Site Contingency [Line Items]
Reserve balance	$ 101	$ 92.2

COMMITMENTS AND CONTINGENCIES_3

COMMITMENTS AND CONTINGENCIES - Non-Cancellable Commitments under Purchase Commitment Contracts (Details) - Renewable Energy - NSTAR Electric $ in Millions	6 Months Ended
	Jun. 30, 2021USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]
2021	$ 48.1
2022	103.6
2023	229.3
2024	339.4
2025	346.2
Thereafter	6,527.7
Total	7,594.3
Massachusetts Clean Energy 83D Contract
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	$ 6,700
Contract term	20 years
Minimum | Massachusetts Clean Energy 83D Contract
Unrecorded Unconditional Purchase Obligation [Line Items]
Estimated costs	$ 150
Maximum | Massachusetts Clean Energy 83D Contract
Unrecorded Unconditional Purchase Obligation [Line Items]
Estimated costs	$ 415

COMMITMENTS AND CONTINGENCIES_4

COMMITMENTS AND CONTINGENCIES - Guarantees and Obligations Narrative (Details) - USD ($)	Jun. 30, 2021	Sep. 16, 2020
Loss Contingencies [Line Items]
Fair value of guarantees	$ 500,000
Letter of Credit | Eversource Investment LLC
Loss Contingencies [Line Items]
Maximum borrowing capacity		$ 25,000,000

COMMITMENTS AND CONTINGENCIES_5

COMMITMENTS AND CONTINGENCIES - Guarantees and Indemnifications (Details) $ in Millions	Jun. 30, 2021USD ($)
North East Offshore LLC
Guarantor Obligations [Line Items]
Ownership interest	50.00%
Sunrise Wind LLC
Guarantor Obligations [Line Items]
Maximum exposure (up to)	$ 15.4
Ownership interest	50.00%
Eversource Investment LLC | North East Offshore LLC
Guarantor Obligations [Line Items]
Ownership interest	50.00%
Construction-related purchase agreements with third-party contractors | North East Offshore LLC
Guarantor Obligations [Line Items]
Maximum exposure (up to)	$ 29.7
Funding and indemnification obligations of North East Offshore LLC | Eversource Investment LLC
Guarantor Obligations [Line Items]
Maximum exposure (up to)	0
Funding and indemnification obligations of North East Offshore LLC | Eversource Investment LLC | North East Offshore LLC
Guarantor Obligations [Line Items]
Maximum exposure (up to)	910
OREC capacity production | Sunrise Wind LLC
Guarantor Obligations [Line Items]
Maximum exposure (up to)	2.2
Transmission interconnection | South Fork Wind, LLC
Guarantor Obligations [Line Items]
Maximum exposure (up to)	1.6
Real estate purchase | Bay State Wind LLC
Guarantor Obligations [Line Items]
Maximum exposure (up to)	2.5
Surety bonds | Various
Guarantor Obligations [Line Items]
Maximum exposure (up to)	59.5
Lease payments for real estate | Rocky River Realty Company and Eversource Service
Guarantor Obligations [Line Items]
Maximum exposure (up to)	4.4
Performance guarantee | North East Offshore LLC
Guarantor Obligations [Line Items]
Maximum exposure (up to)	$ 1,300
Percent of obligations guaranteed	50.00%
Payment guarantee | North East Offshore LLC
Guarantor Obligations [Line Items]
Maximum exposure (up to)	$ 62.5
Percent of obligations guaranteed	50.00%

COMMITMENTS AND CONTINGENCIES_6

COMMITMENTS AND CONTINGENCIES - FERC ROE Complaints (Details) - USD ($) $ in Millions	Apr. 29, 2016	Oct. 16, 2014	Jun. 30, 2021	Oct. 15, 2014	Dec. 31, 2020
Loss Contingencies [Line Items]
Percentage of base ROE reasonably justified			10.41%
Percentage of incentive cap on total ROE			13.08%
FERC ROE First, Second and Third Complaints
Loss Contingencies [Line Items]
Base ROE subsequently authorized			11.14%
FERC ROE First, Second and Third Complaints | Minimum
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project				11.14%
FERC ROE First, Second and Third Complaints | Maximum
Loss Contingencies [Line Items]
Percentage of maximum ROE for any incentive project				13.10%
FERC ROE Complaints
Loss Contingencies [Line Items]
Period of complaint			15 months
Basis point change			0.10%
Estimate of possible loss for each 10 basis point change to base ROE			$ 3
FERC ROE Fourth Complaint
Loss Contingencies [Line Items]
Base ROE percentage of complaint period	10.57%
Maximum percentage cap of ROE for incentive projects	11.74%
FERC ROE First Complaint
Loss Contingencies [Line Items]
Base ROE subsequently authorized		10.57%
Percentage of maximum ROE for any incentive project		11.74%
Amounts associated with first complaint refunded			38.9
FERC ROE First Complaint | CL&P
Loss Contingencies [Line Items]
Amounts associated with first complaint refunded			22.4
FERC ROE First Complaint | NSTAR Electric
Loss Contingencies [Line Items]
Amounts associated with first complaint refunded			13.7
FERC ROE First Complaint | PSNH
Loss Contingencies [Line Items]
Amounts associated with first complaint refunded			$ 2.8
FERC ROE Second Complaint
Loss Contingencies [Line Items]
Base ROE percentage of complaint period			10.57%
Percentage of maximum ROE for any incentive project			11.74%
Loss contingency, estimate of possible earnings impact			$ 39.1		$ 39.1
FERC ROE Second Complaint | CL&P
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			21.4		21.4
FERC ROE Second Complaint | NSTAR Electric
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			14.6		14.6
FERC ROE Second Complaint | PSNH
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			$ 3.1		$ 3.1

COMMITMENTS AND CONTINGENCIES_7

COMMITMENTS AND CONTINGENCIES - Eversource and NSTAR Electric Boston Harbor Civil Action (Details)	Jul. 15, 2016kV
Commitments and Contingencies Disclosure [Abstract]
Amount of capacity required for installation of distribution cable (in kV)	115

COMMITMENTS AND CONTINGENCIES_8

COMMITMENTS AND CONTINGENCIES - CL&P Tropical Storm Isaias Response Investigation (Details) - USD ($) $ / shares in Units, $ in Millions	May 07, 2021	Jul. 14, 2021	May 06, 2021	Apr. 28, 2021
Loss Contingencies [Line Items]
Loss contingency, allowed rate of ROE				9.25%
Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact			$ 30
Loss contingency, estimate of possible earnings impact, non-compliance with performance standards			28.4
Loss contingency, estimate of possible earnings impact, accident reporting violation fines			$ 1.6
Loss contingency, penalty rate as a percent of distribution revenues	2.50%
Decrease in future annual revenues as a result of a 90 basis point ROE reduction	$ 31
Increase in future earnings as a result of a 90 basis point ROE reduction	$ 21
Unfavorable Regulatory Action | Subsequent Event
Loss Contingencies [Line Items]
Non-compliance fine		$ 28.6
Loss contingency, accident reporting violation fines		$ 0.2
Loss contingency, after-tax earnings impact per share		$ 0.07

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	$ 155,570	$ 155,570
Rate Reduction Bonds	475,307	496,912
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	155,600	155,600
Long-Term Debt	16,651,200	16,179,100
Rate Reduction Bonds	518,500	540,100
Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	166,400	169,100
Long-Term Debt	18,364,000	18,420,100
Rate Reduction Bonds	579,600	603,400
CL&P
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	116,200	116,200
CL&P | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	116,200	116,200
Long-Term Debt	4,335,600	3,914,800
Rate Reduction Bonds	0	0
CL&P | Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	122,200	123,400
Long-Term Debt	5,049,800	4,800,900
Rate Reduction Bonds	0	0
NSTAR Electric
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	43,000	43,000
NSTAR Electric | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	43,000	43,000
Long-Term Debt	3,688,300	3,643,200
Rate Reduction Bonds	0	0
NSTAR Electric | Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	44,200	45,700
Long-Term Debt	4,208,400	4,294,000
Rate Reduction Bonds	0	0
PSNH
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Rate Reduction Bonds	475,307	496,912
PSNH | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	0	0
Long-Term Debt	1,163,700	1,099,100
Rate Reduction Bonds	518,500	540,100
PSNH | Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred Stock Not Subject to Mandatory Redemption	0	0
Long-Term Debt	1,239,000	1,207,000
Rate Reduction Bonds	$ 579,600	$ 603,400

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Attributable to Parent [Roll Forward]
OCI Before Reclassifications					$ (2,900)	$ (1,200)
Amounts Reclassified from AOCI					5,000	3,700
Net OCI	$ 881	$ 1,188	$ 553	$ 1,948	2,069	2,501
Total
AOCI Attributable to Parent [Roll Forward]
Beginning balance		(76,400)		(65,100)	(76,400)	(65,100)
Net OCI	881	1,188	553	1,948
Ending balance	(74,300)		(62,600)		(74,300)	(62,600)
Qualified Cash Flow Hedging Instruments
AOCI Attributable to Parent [Roll Forward]
Beginning balance		(1,400)		(3,000)	(1,400)	(3,000)
OCI Before Reclassifications					0	0
Amounts Reclassified from AOCI					900	600
Net OCI					900	600
Ending balance	(500)		(2,400)		(500)	(2,400)
Unrealized Gains/(Losses) on Marketable Securities
AOCI Attributable to Parent [Roll Forward]
Beginning balance		1,100		700	1,100	700
OCI Before Reclassifications					(500)	400
Amounts Reclassified from AOCI					0	0
Net OCI					(500)	400
Ending balance	600		1,100		600	1,100
Defined Benefit Plans
AOCI Attributable to Parent [Roll Forward]
Beginning balance		$ (76,100)		$ (62,800)	(76,100)	(62,800)
OCI Before Reclassifications					(2,400)	(1,600)
Amounts Reclassified from AOCI					4,100	3,100
Net OCI					1,700	1,500
Ending balance	$ (74,400)		$ (61,300)		$ (74,400)	$ (61,300)

COMMON SHARES - Common Shares A

COMMON SHARES - Common Shares Authorized and Issued (Details) - $ / shares	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020
Class of Stock [Line Items]
Par value (in dollars per share)	$ 5		$ 5	$ 5
Authorized (in shares)	380,000,000	380,000,000
Issued (in shares)	357,818,402	357,818,402
CL&P
Class of Stock [Line Items]
Par value (in dollars per share)	$ 10
Authorized (in shares)	24,500,000	24,500,000
Issued (in shares)	6,035,205	6,035,205
NSTAR Electric
Class of Stock [Line Items]
Par value (in dollars per share)	$ 1
Authorized (in shares)	100,000,000	100,000,000
Issued (in shares)	200	200
PSNH
Class of Stock [Line Items]
Par value (in dollars per share)	$ 1
Authorized (in shares)	100,000,000	100,000,000
Issued (in shares)	301	301

COMMON SHARES - Narrative (Deta

COMMON SHARES - Narrative (Details) - shares	Jun. 30, 2021	Dec. 31, 2020
Equity [Abstract]
Treasury stock (in shares)	14,217,299	14,864,379
Common stock outstanding (in shares)	343,601,103	342,954,023

COMMON SHAREHOLDERS' EQUITY A_2

COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Equity [Abstract]
Dividends on preferred stock	$ 1,880	$ 1,880	$ 1,880	$ 1,880	$ 3,800	$ 3,800
Noncontrolling interest attributed to preferred stock of subsidiaries	$ 155,570				$ 155,570		$ 155,570

EARNINGS PER SHARE - Narrative

EARNINGS PER SHARE - Narrative (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Antidilutive share awards excluded from the EPS computation (in shares)	0	158,242	0	79,121

EARNINGS PER SHARE - Components

EARNINGS PER SHARE - Components of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net Income Attributable to Common Shareholders	$ 264,520	$ 252,232	$ 630,663	$ 586,984
Net Income Attributable to Common Shareholders	$ 264,500	$ 252,200	$ 630,700	$ 587,000
Weighted Average Common Shares Outstanding:
Basic (in shares)	343,844,626	337,946,663	343,761,435	334,524,452
Dilutive Effect of:
Share-Based Compensation Awards and Other (in shares)	591,070	614,986	623,758	681,110
Equity Forward Sale Agreement (in shares)	0	0	0	543,842
Total Dilutive Effect (in shares)	591,070	614,986	623,758	1,224,952
Diluted (in shares)	344,435,696	338,561,649	344,385,193	335,749,404
Basic EPS (in dollars per share)	$ 0.77	$ 0.75	$ 1.83	$ 1.75
Diluted EPS (in dollars per share)	$ 0.77	$ 0.75	$ 1.83	$ 1.75

REVENUES (Details)

REVENUES (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	$ 2,142,900	$ 1,947,200	$ 4,915,500	$ 4,241,700
Alternative Revenue Programs	(21,400)	4,900	30,300	79,400
Other Revenues	1,000	1,000	2,600	5,800
Operating Revenues	$ 2,122,538	$ 1,953,128	4,948,378	4,326,854
Operating Lease, Income, Comprehensive Income [Extensible Enumeration]	Operating Revenues	Operating Revenues
Lease revenue	$ 1,000	$ 1,100	2,700	2,200
CL&P
Disaggregation of Revenue [Line Items]
Operating Revenues	$ 829,597	$ 817,421	1,816,871	1,717,124
Operating Lease, Income, Comprehensive Income [Extensible Enumeration]	Operating Revenues	Operating Revenues
Lease revenue	$ 200	$ 200	400	400
NSTAR Electric
Disaggregation of Revenue [Line Items]
Operating Revenues	$ 687,375	$ 660,971	1,424,418	1,394,804
Operating Lease, Income, Comprehensive Income [Extensible Enumeration]	Operating Revenues	Operating Revenues
Lease revenue	$ 700	$ 700	1,800	1,400
PSNH
Disaggregation of Revenue [Line Items]
Operating Revenues	$ 278,849	$ 255,224	572,284	531,592
Operating Lease, Income, Comprehensive Income [Extensible Enumeration]	Operating Revenues	Operating Revenues
Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	$ 1,092,300	$ 1,071,800	2,652,900	2,301,300
Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	698,500	608,400	1,478,500	1,363,700
Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	113,500	96,600	250,000	202,700
Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,904,300	1,776,800	4,381,400	3,867,700
Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	91,300	70,400	183,800	140,500
Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	113,900	71,500	290,100	176,500
Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	33,400	28,500	60,200	57,000
Operating Segments | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	958,200	940,700	2,060,900	1,916,300
Alternative Revenue Programs	(1,100)	(7,500)	7,800	37,100
Other Revenues	(200)	200	100	1,900
Operating Segments | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	824,200	764,100	1,662,700	1,583,600
Alternative Revenue Programs	(15,300)	3,600	(1,500)	23,000
Other Revenues	700	700	1,800	2,100
Operating Segments | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	319,600	284,300	653,300	592,900
Alternative Revenue Programs	2,300	7,900	5,300	12,600
Other Revenues	500	0	500	600
Operating Segments | Residential | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	440,800	469,300	986,600	959,200
Operating Segments | Residential | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	304,700	311,500	667,100	642,400
Operating Segments | Residential | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	136,600	135,200	294,400	278,100
Operating Segments | Commercial | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	215,700	199,300	429,900	425,600
Operating Segments | Commercial | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	296,100	261,000	564,400	562,900
Operating Segments | Commercial | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	82,800	66,100	160,600	145,300
Operating Segments | Industrial | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	28,400	33,300	65,200	67,300
Operating Segments | Industrial | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	29,100	24,800	53,600	51,600
Operating Segments | Industrial | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	24,500	19,600	46,200	38,600
Operating Segments | Total Retail Tariff Sales Revenues | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	684,900	701,900	1,481,700	1,452,100
Operating Segments | Total Retail Tariff Sales Revenues | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	629,900	597,300	1,285,100	1,256,900
Operating Segments | Total Retail Tariff Sales Revenues | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	243,900	220,900	501,200	462,000
Operating Segments | Wholesale Transmission Revenues | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	195,700	191,400	384,600	343,200
Operating Segments | Wholesale Transmission Revenues | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	160,100	142,500	307,200	277,300
Operating Segments | Wholesale Transmission Revenues | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	61,100	49,500	119,400	99,200
Operating Segments | Wholesale Market Sales Revenues | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	68,100	39,300	177,800	104,000
Operating Segments | Wholesale Market Sales Revenues | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	18,900	13,200	43,400	27,600
Operating Segments | Wholesale Market Sales Revenues | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	10,200	8,000	25,100	19,900
Operating Segments | Other Revenues from Contracts with Customers | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	9,500	8,100	16,800	17,000
Operating Segments | Other Revenues from Contracts with Customers | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	15,300	11,100	27,000	21,800
Operating Segments | Other Revenues from Contracts with Customers | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	4,400	5,900	7,600	11,800
Other
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	330,000	283,800	673,000	578,500
Alternative Revenue Programs	0	0	0	0
Other Revenues	0	0	0	0
Operating Revenues	330,000	283,800	673,000	578,500
Other | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	20,300	19,200	39,500	36,600
Other | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	309,700	264,600	633,500	541,900
Eliminations
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(658,600)	(599,700)	(1,305,900)	(1,163,600)
Alternative Revenue Programs	(1,200)	9,400	1,000	(18,100)
Other Revenues	0	0	0	0
Operating Revenues	(659,800)	(590,300)	(1,304,900)	(1,181,700)
Eliminations | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Eliminations | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(1,300)	(1,300)	(2,700)	(2,300)
Eliminations | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(4,400)	(3,400)	(8,000)	(6,600)
Eliminations | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(5,700)	(4,700)	(10,700)	(8,900)
Eliminations | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(345,900)	(332,200)	(666,900)	(615,800)
Eliminations | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Eliminations | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(307,000)	(262,800)	(628,300)	(538,900)
Eliminations | CL&P
Disaggregation of Revenue [Line Items]
Operating Revenues	(127,300)	(116,000)	(251,900)	(238,200)
Eliminations | NSTAR Electric
Disaggregation of Revenue [Line Items]
Operating Revenues	(122,200)	(107,400)	(238,600)	(213,900)
Eliminations | PSNH
Disaggregation of Revenue [Line Items]
Operating Revenues	(43,600)	(37,000)	(86,800)	(74,500)
Electric Distribution | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,680,500	1,601,300	3,556,800	3,364,300
Alternative Revenue Programs	(4,800)	14,200	18,200	53,100
Other Revenues	800	700	1,900	4,200
Operating Revenues	1,676,500	1,616,200	3,576,900	3,421,600
Electric Distribution | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	882,100	916,000	1,948,100	1,879,700
Electric Distribution | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	594,100	526,000	1,154,000	1,133,000
Electric Distribution | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	82,000	77,700	165,000	157,500
Electric Distribution | Operating Segments | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,558,200	1,519,700	3,267,100	3,170,200
Electric Distribution | Operating Segments | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Distribution | Operating Segments | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	97,200	60,500	246,300	151,500
Electric Distribution | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	25,100	21,100	43,400	42,600
Natural Gas Distribution | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	315,300	216,500	1,073,700	632,000
Alternative Revenue Programs	(3,400)	(5,300)	18,600	26,900
Other Revenues	(100)	0	0	900
Operating Revenues	311,800	211,200	1,092,300	659,800
Natural Gas Distribution | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	174,200	116,100	641,100	354,100
Natural Gas Distribution | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	89,600	67,800	297,400	202,400
Natural Gas Distribution | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	34,800	21,100	90,800	49,500
Natural Gas Distribution | Operating Segments | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	298,600	205,000	1,029,300	606,000
Natural Gas Distribution | Operating Segments | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Natural Gas Distribution | Operating Segments | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	15,700	10,100	42,000	23,200
Natural Gas Distribution | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,000	1,400	2,400	2,800
Electric Transmission | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	420,300	386,700	818,000	726,300
Alternative Revenue Programs	(9,300)	(10,200)	(6,600)	19,600
Other Revenues	200	200	500	400
Operating Revenues	411,200	376,700	811,900	746,300
Electric Transmission | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	416,900	383,400	811,200	719,700
Electric Transmission | Operating Segments | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	3,400	3,300	6,800	6,600
Water Distribution | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	55,400	58,600	99,900	104,200
Alternative Revenue Programs	(2,700)	(3,200)	(900)	(2,100)
Other Revenues	100	100	200	300
Operating Revenues	52,800	55,500	99,200	102,400
Water Distribution | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	36,000	39,700	63,700	67,500
Water Distribution | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	16,100	15,900	29,800	30,600
Water Distribution | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,100	1,200	2,200	2,300
Water Distribution | Operating Segments | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	53,200	56,800	95,700	100,400
Water Distribution | Operating Segments | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Water Distribution | Operating Segments | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,000	900	1,800	1,800
Water Distribution | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	$ 1,200	$ 900	$ 2,400	$ 2,000

SEGMENT INFORMATION - Narrative

SEGMENT INFORMATION - Narrative (Details) $ in Millions	6 Months Ended
	Jun. 30, 2021USD ($)segment
CL&P
Segment Reporting Information [Line Items]
Number of reportable segments	1
NSTAR Electric
Segment Reporting Information [Line Items]
Number of reportable segments	1
PSNH
Segment Reporting Information [Line Items]
Number of reportable segments	1
Affiliated Entity
Segment Reporting Information [Line Items]
Amount of natural gas transmission purchased | $	$ 77.7

SEGMENT INFORMATION - Summary o

SEGMENT INFORMATION - Summary of Segment Information and Segmented Total Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Operating Revenues	$ 2,122,538	$ 1,953,128	$ 4,948,378	$ 4,326,854
Depreciation and Amortization	(280,200)	(263,900)	(659,000)	(549,900)
Other Operating Expenses	(1,390,700)	(1,255,600)	(3,252,200)	(2,804,200)
Operating Income, Net	451,605	433,655	1,037,173	972,775
Interest Expense	(145,435)	(134,285)	(283,201)	(269,000)
Other Income, Net	46,619	30,243	80,820	54,347
Net Income Attributable to Common Shareholders	264,520	252,232	630,663	586,984
Cash Flows Used for Investments in Plant			1,423,223	1,400,198
Assets	47,234,640		47,234,640		$ 46,099,598
Other
Segment Reporting Information [Line Items]
Operating Revenues	330,000	283,800	673,000	578,500
Depreciation and Amortization	(28,400)	(22,700)	(55,700)	(44,000)
Other Operating Expenses	(285,700)	(243,100)	(585,200)	(500,000)
Operating Income, Net	15,900	18,000	32,100	34,500
Interest Expense	(41,800)	(37,600)	(83,400)	(80,300)
Other Income, Net	309,200	303,200	733,400	686,900
Net Income Attributable to Common Shareholders	282,700	282,800	677,600	639,200
Cash Flows Used for Investments in Plant			109,900	124,600
Assets	21,669,000		21,669,000		22,089,400
Eliminations
Segment Reporting Information [Line Items]
Operating Revenues	(659,800)	(590,300)	(1,304,900)	(1,181,700)
Depreciation and Amortization	1,100	300	2,100	900
Other Operating Expenses	660,300	593,500	1,305,200	1,184,800
Operating Income, Net	1,600	3,500	2,400	4,000
Interest Expense	12,800	8,800	24,400	20,500
Other Income, Net	(304,800)	(300,400)	(725,800)	(679,100)
Net Income Attributable to Common Shareholders	(290,400)	(288,100)	(699,000)	(654,600)
Cash Flows Used for Investments in Plant			0	0
Assets	(21,641,100)		(21,641,100)		(21,492,400)
Electric Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	1,676,500	1,616,200	3,576,900	3,421,600
Depreciation and Amortization	(132,300)	(140,700)	(354,300)	(308,100)
Other Operating Expenses	(1,360,300)	(1,293,300)	(2,890,800)	(2,732,900)
Operating Income, Net	183,900	182,200	331,800	380,600
Interest Expense	(61,100)	(54,300)	(114,400)	(107,400)
Other Income, Net	29,900	16,400	50,600	28,900
Net Income Attributable to Common Shareholders	121,600	115,000	214,900	245,100
Cash Flows Used for Investments in Plant			510,400	563,200
Assets	25,904,600		25,904,600		24,981,900
Natural Gas Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	311,800	211,200	1,092,300	659,800
Depreciation and Amortization	(34,600)	(21,200)	(80,300)	(40,300)
Other Operating Expenses	(257,700)	(176,100)	(793,600)	(487,700)
Operating Income, Net	19,500	13,900	218,400	131,800
Interest Expense	(14,600)	(10,700)	(28,500)	(22,000)
Other Income, Net	4,600	400	8,500	1,800
Net Income Attributable to Common Shareholders	4,100	2,600	151,600	88,600
Cash Flows Used for Investments in Plant			305,900	205,600
Assets	6,593,200		6,593,200		6,450,500
Electric Transmission | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	411,200	376,700	811,900	746,300
Depreciation and Amortization	(74,500)	(68,800)	(148,000)	(136,200)
Other Operating Expenses	(121,900)	(111,200)	(237,300)	(218,000)
Operating Income, Net	214,800	196,700	426,600	392,100
Interest Expense	(32,600)	(32,100)	(65,300)	(62,700)
Other Income, Net	6,800	10,600	12,200	15,700
Net Income Attributable to Common Shareholders	137,600	129,500	273,000	256,200
Cash Flows Used for Investments in Plant			443,200	460,800
Assets	12,289,300		12,289,300		11,695,000
Water Distribution | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	52,800	55,500	99,200	102,400
Depreciation and Amortization	(11,500)	(10,800)	(22,800)	(22,200)
Other Operating Expenses	(25,400)	(25,400)	(50,500)	(50,400)
Operating Income, Net	15,900	19,300	25,900	29,800
Interest Expense	(8,100)	(8,400)	(16,000)	(17,100)
Other Income, Net	900	0	1,900	100
Net Income Attributable to Common Shareholders	8,900	$ 10,400	12,600	12,500
Cash Flows Used for Investments in Plant			53,800	$ 46,000
Assets	$ 2,419,600		$ 2,419,600		$ 2,375,200

ACQUISITION OF ASSETS OF COLU_3

ACQUISITION OF ASSETS OF COLUMBIA GAS OF MASSACHUSETTS - Narrative (Details) - CMA $ in Millions	Oct. 09, 2020USD ($)
Business Acquisition [Line Items]
Cash purchase price	$ 1,100
Target working capital amount	$ 68.6

ACQUISITION OF ASSETS OF COLU_4

ACQUISITION OF ASSETS OF COLUMBIA GAS OF MASSACHUSETTS - Preliminary Allocation of the Cash Purchase Price (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Oct. 09, 2020
Business Acquisition [Line Items]
Goodwill	$ 4,453,618	$ 4,445,988
CMA
Business Acquisition [Line Items]
Current Assets			$ 138,000
Restricted Cash			57,000
PP&E			1,184,000
Goodwill			50,000
Other Noncurrent Assets, excluding Goodwill			131,000
Other Current Liabilities			(81,000)
Other Noncurrent Liabilities			(310,000)
Cash Purchase Price			$ 1,169,000

Uncategorized Items - es-202106

Label	Element	Value
Accounting Standards Update [Extensible Enumeration]	us-gaap_AccountingStandardsUpdateExtensibleList	Accounting Standards Update 2016-13 [Member]
Public Service Company Of New Hampshire (PSNH) [Member]
Accounting Standards Update [Extensible Enumeration]	us-gaap_AccountingStandardsUpdateExtensibleList	Accounting Standards Update 2016-13 [Member]
NSTAR Electric Company [Member]
Accounting Standards Update [Extensible Enumeration]	us-gaap_AccountingStandardsUpdateExtensibleList	Accounting Standards Update 2016-13 [Member]
The Connecticut Light And Power Company [Member]
Accounting Standards Update [Extensible Enumeration]	us-gaap_AccountingStandardsUpdateExtensibleList	Accounting Standards Update 2016-13 [Member]