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COMMITMENTS AND CONTINGENCIES - FERC ROE Complaints Narrative (Details) $ in Millions |  |  | 12 Months Ended | 30 Months Ended | 36 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Oct. 16, 2018 complaint | Apr. 29, 2016 complaint | Dec. 31, 2023 USD ($) | Apr. 14, 2017 | Oct. 15, 2014 | Dec. 31, 2022 USD ($) | Jul. 31, 2014 complaint
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Percentage of base ROE reasonably justified | 10.41% |  |  |  |  |  |
Percentage of incentive cap on total ROE | 13.08% |  |  |  |  |  |
FERC ROE Complaints |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss contingency, pending claims, number | complaint | 4 | 4 |  |  |  |  |
Period of complaint |  |  | 15 months |  |  |  |
Basis point change |  |  | 0.10% |  |  |  |
Estimate of possible loss for each 10 basis point change to base ROE |  |  | $ 3.0 |  |  |  |
Complaint period |  |  | 15 months |  |  |  |
FERC ROE First, Second and Third Complaints |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss contingency, pending claims, number | complaint |  |  |  |  |  |  | 3
Base ROE percentage challenged by complainants |  |  | 11.14% |  |  |  |
Percentage of ROE for any incentive project | 13.08% |  |  |  |  |  |
FERC ROE First Complaint |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Percentage of ROE for any incentive project |  |  |  | 11.74% |  |  |
Refund payments |  |  | $ 38.9 |  |  |  |
FERC ROE Second Complaint |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Percentage of base ROE of complaint period |  |  | 10.57% | 10.57% |  |  |
Percentage of ROE for any incentive project |  |  | 11.74% |  |  |  |
Loss contingency, estimate of possible earnings impact |  |  | $ 39.1 |  |  |  |
FERC ROE Fourth Complaint |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Percentage of base ROE of complaint period |  | 10.57% |  |  |  |  |
Maximum percentage cap of ROE for incentive projects |  | 11.74% |  |  |  |  |
Percentage of ROE for any incentive project |  |  | 10.57% |  |  |  |
Original base ROE authorized by FERC at time of complaint |  |  | 11.74% |  |  |  |
FERC MISO Complaints |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss contingency, pending claims, number | complaint | 2 |  |  |  |  |  |
CL&P | FERC ROE First Complaint |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Refund payments |  |  | $ 22.4 |  |  |  |
CL&P | FERC ROE Second Complaint |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss contingency, estimate of possible earnings impact |  |  | 21.4 |  |  | $ 21.4 |
NSTAR Electric | FERC ROE First Complaint |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Refund payments |  |  | 13.7 |  |  |  |
NSTAR Electric | FERC ROE Second Complaint |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss contingency, estimate of possible earnings impact |  |  | 14.6 |  |  | 14.6 |
PSNH | FERC ROE First Complaint |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Refund payments |  |  | 2.8 |  |  |  |
PSNH | FERC ROE Second Complaint |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss contingency, estimate of possible earnings impact |  |  | $ 3.1 |  |  | $ 3.1 |
Minimum | FERC ROE First, Second and Third Complaints |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Percentage of ROE for any incentive project |  |  |  |  | 11.14% |  |
Maximum | FERC ROE First, Second and Third Complaints |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Percentage of ROE for any incentive project |  |  |  |  | 13.10% |  |

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