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PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Schedule of Aggregate Composite Depreciation Rates (Details) | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Property, Plant and Equipment [Line Items] |  |  |
Composite depreciation rate for plant in service | 3.10% | 3.00% | 3.00%
The Connecticut Light and Power Company |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Composite depreciation rate for plant in service | 2.80% | 2.80% | 2.80%
NSTAR Electric Company |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Composite depreciation rate for plant in service | 2.80% | 2.80% | 2.80%
Public Service Company of New Hampshire |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Composite depreciation rate for plant in service | 3.10% | 2.80% | 2.80%

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- Definition Composite depreciation rate for public utility plants in service. + References No definition available. + Details
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