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REVENUES - Operating Revenues Disaggregated by Revenue Source (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | $ 11,801,800 | $ 11,890,600 | $ 12,270,200
Alternative Revenue Programs | 74,900 | (6,000) | 5,300
Other Revenues | 24,100 | 26,100 | 13,800
Operating Revenues | 11,900,809 | 11,910,705 | 12,289,336
Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 6,184,300 | 6,344,300 | 6,142,700
Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 3,623,900 | 3,595,900 | 3,614,200
Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 543,800 | 524,000 | 559,200
Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 10,352,000 | 10,464,200 | 10,316,100
Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 503,100 | 467,000 | 436,000
Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 825,000 | 835,600 | 1,335,500
Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 123,600 | 119,500 | 110,600
Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (1,900) | 4,300 | 72,000
CL&P |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | 4,614,977 | 4,578,804 | 4,817,744
NSTAR Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | 3,720,877 | 3,515,539 | 3,583,070
PSNH |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | 1,294,493 | 1,447,873 | 1,474,799
Operating Segments | Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 9,018,200 | 9,007,400 | 9,409,500
Alternative Revenue Programs | 28,700 | (54,300) | (15,400)
Other Revenues | 19,600 | 20,400 | 11,200
Operating Revenues | 9,066,500 | 8,973,500 | 9,405,300
Operating Segments | Electric Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 4,904,800 | 5,054,200 | 4,796,100
Operating Segments | Electric Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 2,973,300 | 2,893,200 | 2,903,300
Operating Segments | Electric Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 389,000 | 352,400 | 374,900
Operating Segments | Electric Distribution | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 8,267,100 | 8,299,800 | 8,074,300
Operating Segments | Electric Distribution | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Distribution | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 658,900 | 625,000 | 1,190,900
Operating Segments | Electric Distribution | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 92,200 | 82,600 | 72,300
Operating Segments | Electric Distribution | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 72,000
Operating Segments | Natural Gas Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 2,056,600 | 2,182,200 | 2,199,500
Alternative Revenue Programs | 44,500 | 35,500 | 14,800
Other Revenues | 2,800 | 4,000 | 1,300
Operating Revenues | 2,103,900 | 2,221,700 | 2,215,600
Operating Segments | Natural Gas Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,129,100 | 1,145,400 | 1,204,900
Operating Segments | Natural Gas Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 588,000 | 637,700 | 648,500
Operating Segments | Natural Gas Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 172,500 | 186,800 | 199,700
Operating Segments | Natural Gas Distribution | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,889,600 | 1,969,900 | 2,053,100
Operating Segments | Natural Gas Distribution | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Natural Gas Distribution | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 161,900 | 206,700 | 140,800
Operating Segments | Natural Gas Distribution | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 5,100 | 5,600 | 5,600
Operating Segments | Natural Gas Distribution | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 2,046,300 | 1,796,400 | 1,715,300
Alternative Revenue Programs | 74,200 | 118,900 | 92,700
Other Revenues | 500 | 600 | 700
Operating Revenues | 2,121,000 | 1,915,900 | 1,808,700
Operating Segments | Electric Transmission | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Transmission | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Transmission | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Transmission | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Transmission | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 2,032,400 | 1,777,500 | 1,700,500
Operating Segments | Electric Transmission | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Electric Transmission | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 13,900 | 14,600 | 14,100
Operating Segments | Electric Transmission | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 4,300 | 700
Operating Segments | Water Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 233,400 | 231,000 | 224,400
Alternative Revenue Programs | (5,300) | 400 | (2,500)
Other Revenues | 1,200 | 1,100 | 600
Operating Revenues | 229,300 | 232,500 | 222,500
Operating Segments | Water Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 150,400 | 144,700 | 141,700
Operating Segments | Water Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 70,300 | 69,800 | 66,500
Operating Segments | Water Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 4,700 | 4,500 | 4,700
Operating Segments | Water Distribution | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 225,400 | 219,000 | 212,900
Operating Segments | Water Distribution | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | Water Distribution | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 4,200 | 3,900 | 3,800
Operating Segments | Water Distribution | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 5,700 | 8,100 | 8,400
Operating Segments | Water Distribution | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (1,900) | 0 | (700)
Operating Segments | CL&P |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 5,222,100 | 5,077,600 | 5,343,200
Alternative Revenue Programs | 45,400 | 66,800 | 56,500
Other Revenues | 9,000 | 9,600 | 1,800
Operating Segments | CL&P | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 2,493,700 | 2,597,800 | 2,397,200
Operating Segments | CL&P | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,164,800 | 1,082,100 | 1,067,900
Operating Segments | CL&P | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 164,200 | 137,200 | 146,400
Operating Segments | CL&P | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 3,822,700 | 3,817,100 | 3,611,500
Operating Segments | CL&P | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 870,800 | 794,700 | 755,100
Operating Segments | CL&P | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 491,900 | 429,100 | 873,700
Operating Segments | CL&P | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 36,700 | 32,400 | 30,200
Operating Segments | CL&P | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 4,300 | 72,700
Operating Segments | NSTAR Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 4,332,000 | 4,129,400 | 4,127,300
Alternative Revenue Programs | 36,700 | (52,000) | 700
Other Revenues | 8,500 | 8,400 | 7,200
Operating Segments | NSTAR Electric | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,771,800 | 1,691,000 | 1,601,800
Operating Segments | NSTAR Electric | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,466,700 | 1,442,300 | 1,457,400
Operating Segments | NSTAR Electric | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 118,100 | 123,200 | 135,800
Operating Segments | NSTAR Electric | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 3,356,600 | 3,256,500 | 3,195,000
Operating Segments | NSTAR Electric | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 794,100 | 692,000 | 670,400
Operating Segments | NSTAR Electric | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 131,100 | 131,800 | 215,000
Operating Segments | NSTAR Electric | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 50,200 | 49,100 | 46,900
Operating Segments | NSTAR Electric | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Operating Segments | PSNH |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,514,200 | 1,600,000 | 1,659,600
Alternative Revenue Programs | 20,800 | 49,800 | 20,100
Other Revenues | 2,600 | 3,000 | 2,900
Operating Segments | PSNH | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 639,300 | 765,400 | 797,100
Operating Segments | PSNH | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 343,600 | 369,600 | 380,800
Operating Segments | PSNH | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 106,700 | 92,000 | 92,700
Operating Segments | PSNH | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,089,600 | 1,227,000 | 1,270,600
Operating Segments | PSNH | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 367,500 | 290,800 | 275,000
Operating Segments | PSNH | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 35,900 | 64,100 | 102,200
Operating Segments | PSNH | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 21,200 | 18,100 | 11,800
Operating Segments | PSNH | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,701,300 | 1,636,600 | 1,435,500
Alternative Revenue Programs | 0 | 0 | 0
Other Revenues | 0 | 0 | 0
Operating Revenues | 1,701,300 | 1,636,600 | 1,435,500
Other | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Other | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 1,701,300 | 1,636,600 | 1,435,500
Other | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Eliminations |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (3,254,000) | (2,963,000) | (2,714,000)
Alternative Revenue Programs | (67,200) | (106,500) | (84,300)
Other Revenues | 0 | 0 | 0
Operating Revenues | (3,321,200) | (3,069,500) | (2,798,300)
Eliminations | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Eliminations | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (7,700) | (4,800) | (4,100)
Eliminations | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (22,400) | (19,700) | (20,100)
Eliminations | Total Retail Tariff Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (30,100) | (24,500) | (24,200)
Eliminations | Wholesale Transmission Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (1,529,300) | (1,310,500) | (1,264,500)
Eliminations | Wholesale Market Sales Revenues |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Eliminations | Other Revenues from Contracts with Customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | (1,694,600) | (1,628,000) | (1,425,300)
Eliminations | Reserve for Revenues Subject to Refund |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from Contracts with Customers | 0 | 0 | 0
Consolidations Eliminations | CL&P |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | (661,500) | (575,200) | (583,800)
Consolidations Eliminations | NSTAR Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | (656,300) | (570,300) | (552,100)
Consolidations Eliminations | PSNH |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating Revenues | $ (243,100) | $ (204,900) | $ (207,800)

X
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