00000727412020FYfalse000002342600003152560000013372us-gaap:AccountingStandardsUpdate201613Memberus-gaap:AccountingStandardsUpdate201613Memberus-gaap:AccountingStandardsUpdate201613Memberus-gaap:AccountingStandardsUpdate201613Memberus-gaap:AccountingStandardsUpdate201613Memberus-gaap:OtherLiabilitiesCurrentus-gaap:OtherLiabilitiesNoncurrentus-gaap:OtherLiabilitiesCurrentus-gaap:OtherLiabilitiesNoncurrentus-gaap:OtherLiabilitiesCurrentus-gaap:OtherLiabilitiesNoncurrentus-gaap:OtherLiabilitiesCurrentus-gaap:OtherLiabilitiesNoncurrentus-gaap:OtherAssetsNoncurrentus-gaap:OtherAssetsNoncurrentus-gaap:PublicUtilitiesPropertyPlantAndEquipmentNetus-gaap:PublicUtilitiesPropertyPlantAndEquipmentNet00000727412020-01-012020-12-310000072741es:NstarElectricCompanyMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-31iso4217:USD00000727412020-06-30xbrli:shares00000727412021-01-310000072741es:TheConnecticutLightAndPowerCompanyMember2021-01-310000072741es:NstarElectricCompanyMember2021-01-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMember2021-01-3100000727412020-12-3100000727412019-12-3100000727412019-01-012019-12-3100000727412018-01-012018-12-31iso4217:USDxbrli:shares0000072741us-gaap:CommonStockMember2017-12-310000072741us-gaap:AdditionalPaidInCapitalMember2017-12-310000072741us-gaap:RetainedEarningsMember2017-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-310000072741us-gaap:TreasuryStockMember2017-12-3100000727412017-12-310000072741us-gaap:RetainedEarningsMember2018-01-012018-12-310000072741us-gaap:AdditionalPaidInCapitalMember2018-01-012018-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310000072741us-gaap:CommonStockMember2018-12-310000072741us-gaap:AdditionalPaidInCapitalMember2018-12-310000072741us-gaap:RetainedEarningsMember2018-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMember2018-12-310000072741us-gaap:TreasuryStockMember2018-12-3100000727412018-12-310000072741us-gaap:RetainedEarningsMember2019-01-012019-12-310000072741us-gaap:CommonStockMember2019-01-012019-12-310000072741us-gaap:AdditionalPaidInCapitalMember2019-01-012019-12-310000072741us-gaap:TreasuryStockMember2019-01-012019-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000072741us-gaap:CommonStockMember2019-12-310000072741us-gaap:AdditionalPaidInCapitalMember2019-12-310000072741us-gaap:RetainedEarningsMember2019-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMember2019-12-310000072741us-gaap:TreasuryStockMember2019-12-310000072741us-gaap:RetainedEarningsMember2020-01-012020-12-310000072741us-gaap:CommonStockMember2020-01-012020-12-310000072741us-gaap:AdditionalPaidInCapitalMember2020-01-012020-12-310000072741us-gaap:TreasuryStockMember2020-01-012020-12-310000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:RetainedEarningsMember2019-12-310000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMember2019-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000072741us-gaap:CommonStockMember2020-12-310000072741us-gaap:AdditionalPaidInCapitalMember2020-12-310000072741us-gaap:RetainedEarningsMember2020-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMember2020-12-310000072741us-gaap:TreasuryStockMember2020-12-310000072741es:HinghamWaterSystemMember2020-01-012020-12-310000072741es:HinghamWaterSystemMember2019-01-012019-12-310000072741es:HinghamWaterSystemMember2018-01-012018-12-310000072741es:PSNHGenerationAssetsMember2020-01-012020-12-310000072741es:PSNHGenerationAssetsMember2019-01-012019-12-310000072741es:PSNHGenerationAssetsMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:CommonStockMember2017-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AdditionalPaidInCapitalMember2017-12-310000072741us-gaap:RetainedEarningsMemberes:TheConnecticutLightAndPowerCompanyMember2017-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-310000072741es:TheConnecticutLightAndPowerCompanyMember2017-12-310000072741us-gaap:RetainedEarningsMemberes:TheConnecticutLightAndPowerCompanyMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AdditionalPaidInCapitalMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:CommonStockMember2018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AdditionalPaidInCapitalMember2018-12-310000072741us-gaap:RetainedEarningsMemberes:TheConnecticutLightAndPowerCompanyMember2018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2018-12-310000072741es:TheConnecticutLightAndPowerCompanyMember2018-12-310000072741us-gaap:RetainedEarningsMemberes:TheConnecticutLightAndPowerCompanyMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AdditionalPaidInCapitalMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:CommonStockMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AdditionalPaidInCapitalMember2019-12-310000072741us-gaap:RetainedEarningsMemberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2019-12-310000072741us-gaap:RetainedEarningsMemberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AdditionalPaidInCapitalMember2020-01-012020-12-310000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:RetainedEarningsMemberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:CommonStockMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AdditionalPaidInCapitalMember2020-12-310000072741us-gaap:RetainedEarningsMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2020-12-310000072741es:NstarElectricCompanyMember2020-12-310000072741es:NstarElectricCompanyMember2019-12-310000072741es:NstarElectricCompanyMember2019-01-012019-12-310000072741es:NstarElectricCompanyMember2018-01-012018-12-310000072741us-gaap:CommonStockMemberes:NstarElectricCompanyMember2017-12-310000072741us-gaap:AdditionalPaidInCapitalMemberes:NstarElectricCompanyMember2017-12-310000072741us-gaap:RetainedEarningsMemberes:NstarElectricCompanyMember2017-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMemberes:NstarElectricCompanyMember2017-12-310000072741es:NstarElectricCompanyMember2017-12-310000072741us-gaap:RetainedEarningsMemberes:NstarElectricCompanyMember2018-01-012018-12-310000072741us-gaap:AdditionalPaidInCapitalMemberes:NstarElectricCompanyMember2018-01-012018-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMemberes:NstarElectricCompanyMember2018-01-012018-12-310000072741us-gaap:CommonStockMemberes:NstarElectricCompanyMember2018-12-310000072741us-gaap:AdditionalPaidInCapitalMemberes:NstarElectricCompanyMember2018-12-310000072741us-gaap:RetainedEarningsMemberes:NstarElectricCompanyMember2018-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMemberes:NstarElectricCompanyMember2018-12-310000072741es:NstarElectricCompanyMember2018-12-310000072741us-gaap:RetainedEarningsMemberes:NstarElectricCompanyMember2019-01-012019-12-310000072741us-gaap:AdditionalPaidInCapitalMemberes:NstarElectricCompanyMember2019-01-012019-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMemberes:NstarElectricCompanyMember2019-01-012019-12-310000072741us-gaap:CommonStockMemberes:NstarElectricCompanyMember2019-12-310000072741us-gaap:AdditionalPaidInCapitalMemberes:NstarElectricCompanyMember2019-12-310000072741us-gaap:RetainedEarningsMemberes:NstarElectricCompanyMember2019-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMemberes:NstarElectricCompanyMember2019-12-310000072741us-gaap:RetainedEarningsMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741us-gaap:AdditionalPaidInCapitalMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:RetainedEarningsMemberes:NstarElectricCompanyMember2019-12-310000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberes:NstarElectricCompanyMember2019-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741us-gaap:CommonStockMemberes:NstarElectricCompanyMember2020-12-310000072741us-gaap:AdditionalPaidInCapitalMemberes:NstarElectricCompanyMember2020-12-310000072741us-gaap:RetainedEarningsMemberes:NstarElectricCompanyMember2020-12-310000072741us-gaap:AccumulatedOtherComprehensiveIncomeMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:CommonStockMember2017-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AdditionalPaidInCapitalMember2017-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:RetainedEarningsMember2017-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMember2017-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:RetainedEarningsMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AdditionalPaidInCapitalMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:CommonStockMember2018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AdditionalPaidInCapitalMember2018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:RetainedEarningsMember2018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMember2018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:RetainedEarningsMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AdditionalPaidInCapitalMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:CommonStockMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AdditionalPaidInCapitalMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:RetainedEarningsMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:RetainedEarningsMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AdditionalPaidInCapitalMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMembersrt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:RetainedEarningsMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMembersrt:CumulativeEffectPeriodOfAdoptionAdjustmentMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:CommonStockMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AdditionalPaidInCapitalMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:RetainedEarningsMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2020-12-31es:customeres:utility0000072741es:ConnecticutMassachusettsandNewHampshireMember2020-01-012020-12-310000072741es:ColumbiaGasOfMassachusettsCMAMember2020-10-092020-10-090000072741es:ColumbiaGasOfMassachusettsCMAMember2020-10-090000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberes:RetailNonHardshipWholesaleandOtherReceivablesMember2020-01-010000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberes:TheConnecticutLightAndPowerCompanyMemberes:RetailNonHardshipWholesaleandOtherReceivablesMember2020-01-010000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberes:RetailNonHardshipWholesaleandOtherReceivablesMemberes:NstarElectricCompanyMember2020-01-010000072741es:PublicServiceCompanyOfNewHampshirePSNHMembersrt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberes:RetailNonHardshipWholesaleandOtherReceivablesMember2020-01-010000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:RetainedEarningsMember2020-01-010000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:RetainedEarningsMemberes:TheConnecticutLightAndPowerCompanyMember2020-01-010000072741srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:RetainedEarningsMemberes:NstarElectricCompanyMember2020-01-010000072741es:PublicServiceCompanyOfNewHampshirePSNHMembersrt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:RetainedEarningsMember2020-01-010000072741srt:RestatementAdjustmentMemberes:HardshipAccountsAndOtherLowIncomeAssistanceProgramsMember2020-12-310000072741srt:RestatementAdjustmentMemberes:TheConnecticutLightAndPowerCompanyMemberes:HardshipAccountsAndOtherLowIncomeAssistanceProgramsMember2020-12-310000072741srt:RestatementAdjustmentMemberes:HardshipAccountsAndOtherLowIncomeAssistanceProgramsMemberes:NstarElectricCompanyMember2020-12-31utr:MW0000072741es:NorthernPassMember2020-01-012020-12-310000072741es:NorthernPassMember2019-12-310000072741es:EGMAMember2020-01-012020-12-310000072741es:COVID19Member2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:COVID19Member2020-01-012020-12-310000072741es:NstarElectricCompanyMemberes:COVID19Member2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:COVID19Member2020-01-012020-12-310000072741es:NaturalGasBusinessesMemberes:COVID19Member2020-01-012020-12-310000072741es:YankeeGasServicesCompanyMember2020-01-012020-12-310000072741es:HardshipAccountsMember2019-12-310000072741es:RetailNonHardshipWholesaleandOtherReceivablesMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:HardshipAccountsMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:RetailNonHardshipWholesaleandOtherReceivablesMember2019-12-310000072741es:HardshipAccountsMemberes:NstarElectricCompanyMember2019-12-310000072741es:RetailNonHardshipWholesaleandOtherReceivablesMemberes:NstarElectricCompanyMember2019-12-310000072741srt:RestatementAdjustmentMemberes:HardshipAccountsMember2019-12-310000072741srt:RestatementAdjustmentMemberes:RetailNonHardshipWholesaleandOtherReceivablesMember2019-12-310000072741srt:RestatementAdjustmentMember2019-12-310000072741srt:RestatementAdjustmentMemberes:TheConnecticutLightAndPowerCompanyMemberes:HardshipAccountsMember2019-12-310000072741srt:RestatementAdjustmentMemberes:TheConnecticutLightAndPowerCompanyMemberes:RetailNonHardshipWholesaleandOtherReceivablesMember2019-12-310000072741srt:RestatementAdjustmentMemberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741srt:RestatementAdjustmentMemberes:HardshipAccountsMemberes:NstarElectricCompanyMember2019-12-310000072741srt:RestatementAdjustmentMemberes:RetailNonHardshipWholesaleandOtherReceivablesMemberes:NstarElectricCompanyMember2019-12-310000072741srt:RestatementAdjustmentMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMembersrt:RestatementAdjustmentMember2019-12-310000072741es:HardshipAccountsMember2020-01-012020-12-310000072741es:RetailNonHardshipWholesaleandOtherReceivablesMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:HardshipAccountsMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:RetailNonHardshipWholesaleandOtherReceivablesMember2020-01-012020-12-310000072741es:HardshipAccountsMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:RetailNonHardshipWholesaleandOtherReceivablesMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:HardshipAccountsMember2020-12-310000072741es:RetailNonHardshipWholesaleandOtherReceivablesMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:HardshipAccountsMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:RetailNonHardshipWholesaleandOtherReceivablesMember2020-12-310000072741es:HardshipAccountsMemberes:NstarElectricCompanyMember2020-12-310000072741es:RetailNonHardshipWholesaleandOtherReceivablesMemberes:NstarElectricCompanyMember2020-12-310000072741us-gaap:PublicUtilitiesInventoryFuelMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PublicUtilitiesInventoryFuelMember2020-12-310000072741us-gaap:PublicUtilitiesInventoryFuelMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PublicUtilitiesInventoryFuelMember2020-12-310000072741us-gaap:PublicUtilitiesInventoryFuelMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PublicUtilitiesInventoryFuelMember2019-12-310000072741us-gaap:PublicUtilitiesInventoryFuelMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PublicUtilitiesInventoryFuelMember2019-12-310000072741es:MaterialsandSuppliesMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:MaterialsandSuppliesMember2020-12-310000072741es:NstarElectricCompanyMemberes:MaterialsandSuppliesMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:MaterialsandSuppliesMember2020-12-310000072741es:MaterialsandSuppliesMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:MaterialsandSuppliesMember2019-12-310000072741es:NstarElectricCompanyMemberes:MaterialsandSuppliesMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:MaterialsandSuppliesMember2019-12-310000072741es:RecsMemberMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:RecsMemberMember2020-12-310000072741es:RecsMemberMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RecsMemberMember2020-12-310000072741es:RecsMemberMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:RecsMemberMember2019-12-310000072741es:RecsMemberMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RecsMemberMember2019-12-31xbrli:pure0000072741es:NonServiceCostBenefitsMember2020-01-012020-12-310000072741es:NonServiceCostBenefitsMember2019-01-012019-12-310000072741es:NonServiceCostBenefitsMember2018-01-012018-12-310000072741es:AFUDCEquityMember2020-01-012020-12-310000072741es:AFUDCEquityMember2019-01-012019-12-310000072741es:AFUDCEquityMember2018-01-012018-12-310000072741es:EquityinEarningsMember2020-01-012020-12-310000072741es:EquityinEarningsMember2019-01-012019-12-310000072741es:EquityinEarningsMember2018-01-012018-12-310000072741es:InvestmentIncomeLossMember2020-01-012020-12-310000072741es:InvestmentIncomeLossMember2019-01-012019-12-310000072741es:InvestmentIncomeLossMember2018-01-012018-12-310000072741us-gaap:InterestIncomeMember2020-01-012020-12-310000072741us-gaap:InterestIncomeMember2019-01-012019-12-310000072741us-gaap:InterestIncomeMember2018-01-012018-12-310000072741us-gaap:PropertyPlantAndEquipmentMember2020-01-012020-12-310000072741us-gaap:PropertyPlantAndEquipmentMember2019-01-012019-12-310000072741us-gaap:PropertyPlantAndEquipmentMember2018-01-012018-12-310000072741es:OtherMember2020-01-012020-12-310000072741es:OtherMember2019-01-012019-12-310000072741es:OtherMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:NonServiceCostBenefitsMember2020-01-012020-12-310000072741es:NonServiceCostBenefitsMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:NonServiceCostBenefitsMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:NonServiceCostBenefitsMember2019-01-012019-12-310000072741es:NonServiceCostBenefitsMemberes:NstarElectricCompanyMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:NonServiceCostBenefitsMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:NonServiceCostBenefitsMember2018-01-012018-12-310000072741es:NonServiceCostBenefitsMemberes:NstarElectricCompanyMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:NonServiceCostBenefitsMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:AFUDCEquityMember2020-01-012020-12-310000072741es:NstarElectricCompanyMemberes:AFUDCEquityMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:AFUDCEquityMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:AFUDCEquityMember2019-01-012019-12-310000072741es:NstarElectricCompanyMemberes:AFUDCEquityMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:AFUDCEquityMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:AFUDCEquityMember2018-01-012018-12-310000072741es:NstarElectricCompanyMemberes:AFUDCEquityMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:AFUDCEquityMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:EquityinEarningsMember2020-01-012020-12-310000072741es:EquityinEarningsMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:EquityinEarningsMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:EquityinEarningsMember2019-01-012019-12-310000072741es:EquityinEarningsMemberes:NstarElectricCompanyMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:EquityinEarningsMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:EquityinEarningsMember2018-01-012018-12-310000072741es:EquityinEarningsMemberes:NstarElectricCompanyMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:EquityinEarningsMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:InvestmentIncomeLossMember2020-01-012020-12-310000072741es:InvestmentIncomeLossMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:InvestmentIncomeLossMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:InvestmentIncomeLossMember2019-01-012019-12-310000072741es:InvestmentIncomeLossMemberes:NstarElectricCompanyMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:InvestmentIncomeLossMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:InvestmentIncomeLossMember2018-01-012018-12-310000072741es:InvestmentIncomeLossMemberes:NstarElectricCompanyMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:InvestmentIncomeLossMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:InterestIncomeMember2020-01-012020-12-310000072741es:NstarElectricCompanyMemberus-gaap:InterestIncomeMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:InterestIncomeMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:InterestIncomeMember2019-01-012019-12-310000072741es:NstarElectricCompanyMemberus-gaap:InterestIncomeMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:InterestIncomeMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:InterestIncomeMember2018-01-012018-12-310000072741es:NstarElectricCompanyMemberus-gaap:InterestIncomeMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:InterestIncomeMember2018-01-012018-12-310000072741us-gaap:PropertyPlantAndEquipmentMemberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741us-gaap:PropertyPlantAndEquipmentMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PropertyPlantAndEquipmentMember2020-01-012020-12-310000072741us-gaap:PropertyPlantAndEquipmentMemberes:TheConnecticutLightAndPowerCompanyMember2019-01-012019-12-310000072741us-gaap:PropertyPlantAndEquipmentMemberes:NstarElectricCompanyMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PropertyPlantAndEquipmentMember2019-01-012019-12-310000072741us-gaap:PropertyPlantAndEquipmentMemberes:TheConnecticutLightAndPowerCompanyMember2018-01-012018-12-310000072741us-gaap:PropertyPlantAndEquipmentMemberes:NstarElectricCompanyMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PropertyPlantAndEquipmentMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:OtherMember2020-01-012020-12-310000072741es:OtherMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:OtherMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:OtherMember2019-01-012019-12-310000072741es:OtherMemberes:NstarElectricCompanyMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:OtherMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:OtherMember2018-01-012018-12-310000072741es:OtherMemberes:NstarElectricCompanyMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:OtherMember2018-01-012018-12-310000072741es:RenewableEnergyFundInvestmentMember2018-01-012018-12-310000072741es:AccessNortheastProjectMember2018-01-012018-12-310000072741us-gaap:PrepaidExpensesAndOtherCurrentAssetsMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PrepaidExpensesAndOtherCurrentAssetsMember2020-12-310000072741us-gaap:PrepaidExpensesAndOtherCurrentAssetsMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PrepaidExpensesAndOtherCurrentAssetsMember2020-12-310000072741us-gaap:PrepaidExpensesAndOtherCurrentAssetsMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PrepaidExpensesAndOtherCurrentAssetsMember2019-12-310000072741us-gaap:PrepaidExpensesAndOtherCurrentAssetsMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PrepaidExpensesAndOtherCurrentAssetsMember2019-12-310000072741es:MarketableSecuritiesMember2020-12-310000072741es:MarketableSecuritiesMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:MarketableSecuritiesMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:MarketableSecuritiesMember2020-12-310000072741es:MarketableSecuritiesMember2019-12-310000072741es:MarketableSecuritiesMemberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:MarketableSecuritiesMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:MarketableSecuritiesMember2019-12-310000072741us-gaap:OtherNoncurrentAssetsMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OtherNoncurrentAssetsMember2020-12-310000072741us-gaap:OtherNoncurrentAssetsMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMemberus-gaap:OtherNoncurrentAssetsMember2020-12-310000072741us-gaap:OtherNoncurrentAssetsMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OtherNoncurrentAssetsMember2019-12-310000072741us-gaap:OtherNoncurrentAssetsMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:OtherNoncurrentAssetsMember2019-12-310000072741es:EnergyReliefFundMerrimackValleyProgramsMember2020-12-310000072741es:BenefitCostsMember2020-12-310000072741es:BenefitCostsMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:BenefitCostsMemberes:NstarElectricCompanyMember2020-12-310000072741es:BenefitCostsMemberes:PublicServiceCompanyOfNewHampshirePSNHMember2020-12-310000072741es:BenefitCostsMember2019-12-310000072741es:BenefitCostsMemberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:BenefitCostsMemberes:NstarElectricCompanyMember2019-12-310000072741es:BenefitCostsMemberes:PublicServiceCompanyOfNewHampshirePSNHMember2019-12-310000072741us-gaap:DeferredIncomeTaxChargesMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:DeferredIncomeTaxChargesMember2020-12-310000072741us-gaap:DeferredIncomeTaxChargesMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:DeferredIncomeTaxChargesMember2020-12-310000072741us-gaap:DeferredIncomeTaxChargesMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:DeferredIncomeTaxChargesMember2019-12-310000072741us-gaap:DeferredIncomeTaxChargesMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:DeferredIncomeTaxChargesMember2019-12-310000072741us-gaap:StrandedCostsMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:StrandedCostsMember2020-12-310000072741us-gaap:StrandedCostsMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:StrandedCostsMember2020-12-310000072741us-gaap:StrandedCostsMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:StrandedCostsMember2019-12-310000072741us-gaap:StrandedCostsMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:StrandedCostsMember2019-12-310000072741es:StormRestorationCostsMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:StormRestorationCostsMember2020-12-310000072741es:StormRestorationCostsMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:StormRestorationCostsMember2020-12-310000072741es:StormRestorationCostsMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:StormRestorationCostsMember2019-12-310000072741es:StormRestorationCostsMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:StormRestorationCostsMember2019-12-310000072741es:RegulatoryTrackerDeferralsRegulatoryAssetsMember2020-12-310000072741es:RegulatoryTrackerDeferralsRegulatoryAssetsMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:RegulatoryTrackerDeferralsRegulatoryAssetsMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RegulatoryTrackerDeferralsRegulatoryAssetsMember2020-12-310000072741es:RegulatoryTrackerDeferralsRegulatoryAssetsMember2019-12-310000072741es:RegulatoryTrackerDeferralsRegulatoryAssetsMemberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:RegulatoryTrackerDeferralsRegulatoryAssetsMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RegulatoryTrackerDeferralsRegulatoryAssetsMember2019-12-310000072741es:RegulatoryAssetsOffsettingDerivativeLiabilitiesMember2020-12-310000072741es:RegulatoryAssetsOffsettingDerivativeLiabilitiesMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:RegulatoryAssetsOffsettingDerivativeLiabilitiesMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RegulatoryAssetsOffsettingDerivativeLiabilitiesMember2020-12-310000072741es:RegulatoryAssetsOffsettingDerivativeLiabilitiesMember2019-12-310000072741es:RegulatoryAssetsOffsettingDerivativeLiabilitiesMemberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:RegulatoryAssetsOffsettingDerivativeLiabilitiesMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RegulatoryAssetsOffsettingDerivativeLiabilitiesMember2019-12-310000072741es:GoodwillRegulatoryAssetMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:GoodwillRegulatoryAssetMember2020-12-310000072741es:NstarElectricCompanyMemberes:GoodwillRegulatoryAssetMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:GoodwillRegulatoryAssetMember2020-12-310000072741es:GoodwillRegulatoryAssetMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:GoodwillRegulatoryAssetMember2019-12-310000072741es:NstarElectricCompanyMemberes:GoodwillRegulatoryAssetMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:GoodwillRegulatoryAssetMember2019-12-310000072741es:AssetRetirementObligationsMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:AssetRetirementObligationsMember2020-12-310000072741es:NstarElectricCompanyMemberes:AssetRetirementObligationsMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:AssetRetirementObligationsMember2020-12-310000072741es:AssetRetirementObligationsMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:AssetRetirementObligationsMember2019-12-310000072741es:NstarElectricCompanyMemberes:AssetRetirementObligationsMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:AssetRetirementObligationsMember2019-12-310000072741es:OtherRegulatoryAssetsMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:OtherRegulatoryAssetsMember2020-12-310000072741es:OtherRegulatoryAssetsMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:OtherRegulatoryAssetsMember2020-12-310000072741es:OtherRegulatoryAssetsMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:OtherRegulatoryAssetsMember2019-12-310000072741es:OtherRegulatoryAssetsMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:OtherRegulatoryAssetsMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RateReductionBondsMember2018-05-080000072741es:DeferredStormRestorationCostsMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:DeferredStormRestorationCostsMember2020-12-310000072741es:DeferredStormRestorationCostsMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:DeferredStormRestorationCostsMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:StormRestorationCostsMemberes:TropicalStormIsaiasMember2020-12-310000072741es:StormRestorationCostsMemberes:TropicalStormIsaiasMember2020-12-310000072741es:GoodwillRegulatoryAssetMember2020-01-012020-12-310000072741es:COVID19Member2020-12-310000072741es:ExcessADITduetotaxCutsandJobsActMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:ExcessADITduetotaxCutsandJobsActMember2020-12-310000072741es:NstarElectricCompanyMemberes:ExcessADITduetotaxCutsandJobsActMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:ExcessADITduetotaxCutsandJobsActMember2020-12-310000072741es:ExcessADITduetotaxCutsandJobsActMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:ExcessADITduetotaxCutsandJobsActMember2019-12-310000072741es:NstarElectricCompanyMemberes:ExcessADITduetotaxCutsandJobsActMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:ExcessADITduetotaxCutsandJobsActMember2019-12-310000072741es:CostOfRemovalMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:CostOfRemovalMember2020-12-310000072741es:NstarElectricCompanyMemberes:CostOfRemovalMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:CostOfRemovalMember2020-12-310000072741es:CostOfRemovalMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:CostOfRemovalMember2019-12-310000072741es:NstarElectricCompanyMemberes:CostOfRemovalMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:CostOfRemovalMember2019-12-310000072741es:BenefitCostsMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:BenefitCostsMember2020-12-310000072741es:BenefitCostsMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:BenefitCostsMember2020-12-310000072741es:BenefitCostsMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:BenefitCostsMember2019-12-310000072741es:BenefitCostsMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:BenefitCostsMember2019-12-310000072741es:RegulatoryTrackerDeferralsRegulatoryLiabilitiesMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:RegulatoryTrackerDeferralsRegulatoryLiabilitiesMember2020-12-310000072741es:NstarElectricCompanyMemberes:RegulatoryTrackerDeferralsRegulatoryLiabilitiesMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RegulatoryTrackerDeferralsRegulatoryLiabilitiesMember2020-12-310000072741es:RegulatoryTrackerDeferralsRegulatoryLiabilitiesMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:RegulatoryTrackerDeferralsRegulatoryLiabilitiesMember2019-12-310000072741es:NstarElectricCompanyMemberes:RegulatoryTrackerDeferralsRegulatoryLiabilitiesMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RegulatoryTrackerDeferralsRegulatoryLiabilitiesMember2019-12-310000072741es:AfudcTransmissionIncentiveMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:AfudcTransmissionIncentiveMember2020-12-310000072741es:AfudcTransmissionIncentiveMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:AfudcTransmissionIncentiveMember2020-12-310000072741es:AfudcTransmissionIncentiveMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:AfudcTransmissionIncentiveMember2019-12-310000072741es:AfudcTransmissionIncentiveMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:AfudcTransmissionIncentiveMember2019-12-310000072741es:OtherRegulatoryLiabilitiesMember2020-12-310000072741es:OtherRegulatoryLiabilitiesMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:OtherRegulatoryLiabilitiesMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:OtherRegulatoryLiabilitiesMember2020-12-310000072741es:OtherRegulatoryLiabilitiesMember2019-12-310000072741es:OtherRegulatoryLiabilitiesMemberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:OtherRegulatoryLiabilitiesMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:OtherRegulatoryLiabilitiesMember2019-12-310000072741es:FERCROEFirstandSecondComplaintsMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:FERCROEFirstandSecondComplaintsMember2020-01-012020-12-310000072741es:FERCROEFirstandSecondComplaintsMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:FERCROEFirstandSecondComplaintsMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:NewHampshirePublicUtilitiesCommissionNHPUCMember2020-12-152020-12-150000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:NewHampshirePublicUtilitiesCommissionNHPUCMember2020-12-232020-12-230000072741es:NewHampshirePublicUtilitiesCommissionNHPUCMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:NewHampshirePublicUtilitiesCommissionNHPUCMember2020-01-012020-12-310000072741es:NewHampshirePublicUtilitiesCommissionNHPUCMember2019-09-012019-09-300000072741es:NewHampshirePublicUtilitiesCommissionNHPUCMember2020-09-300000072741es:NewHampshirePublicUtilitiesCommissionNHPUCMember2020-12-172020-12-170000072741es:NewHampshirePublicUtilitiesCommissionNHPUCMemberes:RegulatoryAssetMember2020-12-310000072741es:NewHampshirePublicUtilitiesCommissionNHPUCMemberus-gaap:OtherNoncurrentAssetsMember2020-12-310000072741es:NSTARGasCompanyMemberes:MassachusettsDepartmentOfPublicUtilitiesDPUMember2020-10-302020-10-300000072741es:HinghamWaterSystemMemberus-gaap:DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember2020-07-310000072741es:HinghamWaterSystemMemberus-gaap:DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember2020-07-312020-07-310000072741es:HinghamWaterSystemMemberus-gaap:DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember2020-01-012020-12-310000072741es:ComputerSoftwareHardwareAndEquipmentMembersrt:MinimumMember2020-01-012020-12-310000072741srt:MaximumMemberes:ComputerSoftwareHardwareAndEquipmentMember2020-01-012020-12-310000072741us-gaap:BuildingMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PrepaidExpensesAndOtherCurrentAssetsMemberus-gaap:FairValueInputsLevel3Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PrepaidExpensesAndOtherCurrentAssetsMemberus-gaap:FairValueInputsLevel3Member2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OtherNoncurrentAssetsMemberus-gaap:FairValueInputsLevel3Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OtherNoncurrentAssetsMemberus-gaap:FairValueInputsLevel3Member2019-12-310000072741us-gaap:OtherCurrentLiabilitiesMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FairValueInputsLevel3Member2020-12-310000072741us-gaap:OtherCurrentLiabilitiesMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FairValueInputsLevel3Member2019-12-310000072741us-gaap:OtherCurrentLiabilitiesMemberus-gaap:FairValueInputsLevel2Member2020-12-310000072741us-gaap:OtherCurrentLiabilitiesMemberus-gaap:FairValueInputsLevel2Member2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OtherNoncurrentLiabilitiesMemberus-gaap:FairValueInputsLevel3Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OtherNoncurrentLiabilitiesMemberus-gaap:FairValueInputsLevel3Member2019-12-310000072741us-gaap:OtherNoncurrentLiabilitiesMemberus-gaap:FairValueInputsLevel2Member2020-12-310000072741us-gaap:OtherNoncurrentLiabilitiesMemberus-gaap:FairValueInputsLevel2Member2019-12-31utr:MWhutr:MMBTUiso4217:USDes:KWmo0000072741es:TheConnecticutLightAndPowerCompanyMembersrt:MinimumMemberes:MeasurementInputCapacityPricesMemberus-gaap:FairValueInputsLevel3Member2020-12-310000072741srt:MaximumMemberes:TheConnecticutLightAndPowerCompanyMemberes:MeasurementInputCapacityPricesMemberus-gaap:FairValueInputsLevel3Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMembersrt:MinimumMemberes:MeasurementInputCapacityPricesMemberus-gaap:FairValueInputsLevel3Member2019-12-310000072741srt:MaximumMemberes:TheConnecticutLightAndPowerCompanyMemberes:MeasurementInputCapacityPricesMemberus-gaap:FairValueInputsLevel3Member2019-12-310000072741es:MeasurementInputForwardReserveMemberes:TheConnecticutLightAndPowerCompanyMembersrt:MinimumMemberus-gaap:FairValueInputsLevel3Member2020-12-310000072741es:MeasurementInputForwardReserveMembersrt:MaximumMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FairValueInputsLevel3Member2020-12-310000072741es:MeasurementInputForwardReserveMemberes:TheConnecticutLightAndPowerCompanyMembersrt:MinimumMemberus-gaap:FairValueInputsLevel3Member2019-12-310000072741es:MeasurementInputForwardReserveMembersrt:MaximumMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FairValueInputsLevel3Member2019-12-310000072741srt:MinimumMemberus-gaap:FairValueInputsLevel3Member2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMembersrt:MinimumMemberus-gaap:FairValueInputsLevel3Member2020-01-012020-12-310000072741srt:WeightedAverageMemberus-gaap:FairValueInputsLevel3Member2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:FairValueInputsLevel3Member2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:FairValueInputsLevel3Member2018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:FairValueInputsLevel3Member2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:FairValueInputsLevel3Member2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:FairValueInputsLevel3Member2020-12-310000072741us-gaap:AccountingStandardsUpdate201601Member2020-01-012020-12-310000072741us-gaap:AccountingStandardsUpdate201601Member2019-01-012019-12-310000072741es:CyapcAndYaecMember2020-12-310000072741es:CyapcAndYaecMember2019-12-310000072741us-gaap:FairValueInputsLevel1Memberes:MutualFundsMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberes:MutualFundsMember2019-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:CashAndCashEquivalentsMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:CashAndCashEquivalentsMember2019-12-310000072741us-gaap:FairValueInputsLevel1Member2020-12-310000072741us-gaap:FairValueInputsLevel1Member2019-12-310000072741us-gaap:USGovernmentDebtSecuritiesMemberus-gaap:FairValueInputsLevel2Member2020-12-310000072741us-gaap:USGovernmentDebtSecuritiesMemberus-gaap:FairValueInputsLevel2Member2019-12-310000072741us-gaap:CorporateBondSecuritiesMemberus-gaap:FairValueInputsLevel2Member2020-12-310000072741us-gaap:CorporateBondSecuritiesMemberus-gaap:FairValueInputsLevel2Member2019-12-310000072741us-gaap:FairValueInputsLevel2Memberus-gaap:AssetBackedSecuritiesMember2020-12-310000072741us-gaap:FairValueInputsLevel2Memberus-gaap:AssetBackedSecuritiesMember2019-12-310000072741us-gaap:MunicipalBondsMemberus-gaap:FairValueInputsLevel2Member2020-12-310000072741us-gaap:MunicipalBondsMemberus-gaap:FairValueInputsLevel2Member2019-12-310000072741us-gaap:FairValueInputsLevel2Memberus-gaap:OtherDebtSecuritiesMember2020-12-310000072741us-gaap:FairValueInputsLevel2Memberus-gaap:OtherDebtSecuritiesMember2019-12-310000072741us-gaap:FairValueInputsLevel2Member2020-12-310000072741us-gaap:FairValueInputsLevel2Member2019-12-310000072741es:OffshoreWindBusinessNorthEastOffshoreAndBayStateWindMember2020-12-310000072741es:OffshoreWindBusinessNorthEastOffshoreAndBayStateWindMember2019-12-310000072741es:NaturalGasInfrastructurePipelineOwnedByEnbridgeInc.Member2020-12-310000072741es:NaturalGasInfrastructurePipelineOwnedByEnbridgeInc.Member2019-12-310000072741es:RenewableEnergyInvestmentFundMember2020-12-310000072741es:RenewableEnergyInvestmentFundMember2019-12-310000072741es:OtherEquityMethodInvestmentsMember2020-12-310000072741es:OtherEquityMethodInvestmentsMember2019-12-310000072741es:RevolutionWindAndSouthForkWindMember2019-02-08utr:sqmi0000072741es:BayStateWindMember2019-02-080000072741es:HydroQuebecSystemMember2020-12-31es:company0000072741es:HydroQuebecSystemMember2020-01-012020-12-310000072741es:HydroQuebecSystemMember2019-01-012019-12-310000072741us-gaap:OtherCurrentLiabilitiesMemberes:EversourceAndNSTARElectricMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMember2019-10-250000072741es:NstarElectricCompanyMember2019-12-180000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:ShortTermDebtAuthorizationCalculationMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:UnsecuredDebtMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741us-gaap:CommercialPaperMembersrt:ParentCompanyMember2020-12-310000072741us-gaap:LineOfCreditMembersrt:ParentCompanyMember2020-01-012020-12-310000072741us-gaap:LineOfCreditMembersrt:ParentCompanyMember2020-12-310000072741us-gaap:RevolvingCreditFacilityMember2020-10-210000072741us-gaap:CommercialPaperMemberes:NstarElectricCompanyMember2020-12-310000072741us-gaap:LineOfCreditMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741us-gaap:LineOfCreditMemberes:NstarElectricCompanyMember2020-12-310000072741us-gaap:CommercialPaperMembersrt:ParentCompanyMember2019-12-310000072741us-gaap:CommercialPaperMemberes:NstarElectricCompanyMember2020-12-310000072741us-gaap:CommercialPaperMemberes:NstarElectricCompanyMember2019-12-310000072741us-gaap:LineOfCreditMember2019-01-012019-12-310000072741us-gaap:LineOfCreditMember2020-01-012020-12-310000072741us-gaap:LineOfCreditMemberes:TheConnecticutLightAndPowerCompanyMember2020-05-150000072741us-gaap:LineOfCreditMemberes:PublicServiceCompanyOfNewHampshirePSNHMember2020-05-150000072741us-gaap:LineOfCreditMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesD1994NotesDue2024Memberus-gaap:FirstMortgageMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesD1994NotesDue2024Memberus-gaap:FirstMortgageMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesB2004NotesDue2034Memberus-gaap:FirstMortgageMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesB2004NotesDue2034Memberus-gaap:FirstMortgageMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesB2005NotesDue2035Memberus-gaap:FirstMortgageMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesB2005NotesDue2035Memberus-gaap:FirstMortgageMember2019-12-310000072741es:SeriesA2006NotesDue2036Memberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FirstMortgageMember2020-12-310000072741es:SeriesA2006NotesDue2036Memberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FirstMortgageMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesB2007NotesDue2037Memberus-gaap:FirstMortgageMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesB2007NotesDue2037Memberus-gaap:FirstMortgageMember2019-12-310000072741es:SeriesD2007NotesDue2037Memberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FirstMortgageMember2020-12-310000072741es:SeriesD2007NotesDue2037Memberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FirstMortgageMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesA2013NotesDue2023Memberus-gaap:FirstMortgageMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesA2013NotesDue2023Memberus-gaap:FirstMortgageMember2019-12-310000072741es:SeriesA2014NotesDue2044Memberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FirstMortgageMember2020-12-310000072741es:SeriesA2014NotesDue2044Memberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FirstMortgageMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesA2015NotesDue2045Memberus-gaap:FirstMortgageMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesA2015NotesDue2045Memberus-gaap:FirstMortgageMember2019-12-310000072741es:SeriesA2017NotesDue2027Memberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FirstMortgageMember2020-12-310000072741es:SeriesA2017NotesDue2027Memberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:FirstMortgageMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesA2018NotesDue2048Memberus-gaap:FirstMortgageMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesA2018NotesDue2048Memberus-gaap:FirstMortgageMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesA2020NotesDue2025Memberus-gaap:FirstMortgageMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesA2020NotesDue2025Memberus-gaap:FirstMortgageMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:FirstMortgageMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:FirstMortgageMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:FixedrateTaxExemptDue2028Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:FixedrateTaxExemptDue2028Member2019-12-310000072741es:UnsecuredNotesDue2036Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741es:UnsecuredNotesDue2036Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2019-12-310000072741es:UnsecuredNotesDue2040Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741es:UnsecuredNotesDue2040Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2019-12-310000072741es:UnsecuredNotesDue2022Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741es:UnsecuredNotesDue2022Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2019-12-310000072741es:NstarElectricCompanyMemberes:UnsecuredNotesDue2044Memberus-gaap:UnsecuredDebtMember2020-12-310000072741es:NstarElectricCompanyMemberes:UnsecuredNotesDue2044Memberus-gaap:UnsecuredDebtMember2019-12-310000072741es:UnsecuredNotesDue2025Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741es:UnsecuredNotesDue2025Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2019-12-310000072741es:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMemberes:UnsecuredNotesDue2026Member2020-12-310000072741es:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMemberes:UnsecuredNotesDue2026Member2019-12-310000072741es:UnsecuredNotesDue2027Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741es:UnsecuredNotesDue2027Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2019-12-310000072741es:UnsecuredNotesDue2029Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741es:UnsecuredNotesDue2029Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2019-12-310000072741es:A3950NotesDue2030Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741es:A3950NotesDue2030Memberes:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2019-12-310000072741es:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741es:NstarElectricCompanyMemberus-gaap:UnsecuredDebtMember2019-12-310000072741es:SeriesBNotesDue2034Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2020-12-310000072741es:SeriesBNotesDue2034Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2019-12-310000072741es:SeriesDNotesDue2037Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2020-12-310000072741es:SeriesDNotesDue2037Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2019-12-310000072741es:A510SeriesESeniorNotesMemberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2020-03-310000072741es:SeriesENotesDue2020Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2020-12-310000072741es:SeriesENotesDue2020Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2019-12-310000072741es:SeriesFNotesDue2021Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2020-12-310000072741es:SeriesFNotesDue2021Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2019-12-310000072741es:SeriesGNotesDue2023Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2020-12-310000072741es:SeriesGNotesDue2023Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2019-12-310000072741es:SeriesHNotesDue2026Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2020-12-310000072741es:SeriesHNotesDue2026Memberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2019-12-310000072741es:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2020-12-310000072741es:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:SeriesMNotesDue2035Memberus-gaap:FirstMortgageMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:SeriesMNotesDue2035Memberus-gaap:FirstMortgageMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:SeriesQNotesDue2021Memberus-gaap:FirstMortgageMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:SeriesQNotesDue2021Memberus-gaap:FirstMortgageMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:SeriesRNotesDue2021Memberus-gaap:FirstMortgageMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:SeriesRNotesDue2021Memberus-gaap:FirstMortgageMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:SeriesSNotesDue2023Memberus-gaap:FirstMortgageMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:SeriesSNotesDue2023Memberus-gaap:FirstMortgageMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:SeriesTNotesDue2049Memberus-gaap:FirstMortgageMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:SeriesTNotesDue2049Memberus-gaap:FirstMortgageMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:A240SeriesUFirstMortgageBondsMemberus-gaap:SeniorNotesMember2020-08-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:A2400SeriesUDue2050Memberus-gaap:FirstMortgageMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:A2400SeriesUDue2050Memberus-gaap:FirstMortgageMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:FirstMortgageMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:FirstMortgageMember2019-12-310000072741srt:MinimumMemberes:UnsecuredNotesDue20182044Memberus-gaap:FirstMortgageMemberes:YankeeGasMember2020-12-310000072741srt:MaximumMemberes:UnsecuredNotesDue20182044Memberus-gaap:FirstMortgageMemberes:YankeeGasMember2020-12-310000072741es:UnsecuredNotesDue20182044Memberus-gaap:FirstMortgageMemberes:YankeeGasMember2020-12-310000072741es:UnsecuredNotesDue20182044Memberus-gaap:FirstMortgageMemberes:YankeeGasMember2019-12-310000072741es:UnsecuredNotesDue20202045Membersrt:MinimumMemberes:NSTARGasCompanyMemberus-gaap:FirstMortgageMember2020-12-310000072741es:UnsecuredNotesDue20202045Membersrt:MaximumMemberes:NSTARGasCompanyMemberus-gaap:FirstMortgageMember2020-12-310000072741es:UnsecuredNotesDue20202045Memberes:NSTARGasCompanyMemberus-gaap:FirstMortgageMember2020-12-310000072741es:UnsecuredNotesDue20202045Memberes:NSTARGasCompanyMemberus-gaap:FirstMortgageMember2019-12-310000072741es:AquarionMemberes:SeniorNotesDue2024Memberus-gaap:UnsecuredDebtMember2020-12-310000072741es:AquarionMemberes:SeniorNotesDue2024Memberus-gaap:UnsecuredDebtMember2019-12-310000072741es:AquarionMembersrt:MinimumMemberus-gaap:UnsecuredDebtMemberes:UnsecuredNotesDue20212037Member2020-12-310000072741srt:MaximumMemberes:AquarionMemberus-gaap:UnsecuredDebtMemberes:UnsecuredNotesDue20212037Member2020-12-310000072741es:AquarionMemberus-gaap:UnsecuredDebtMemberes:UnsecuredNotesDue20212037Member2020-12-310000072741es:AquarionMemberus-gaap:UnsecuredDebtMemberes:UnsecuredNotesDue20212037Member2019-12-310000072741es:AquarionMemberes:SecuredDebtNotesDue20212035Memberus-gaap:SecuredDebtMembersrt:MinimumMember2020-12-310000072741srt:MaximumMemberes:AquarionMemberes:SecuredDebtNotesDue20212035Memberus-gaap:SecuredDebtMember2020-12-310000072741es:AquarionMemberes:SecuredDebtNotesDue20212035Memberus-gaap:SecuredDebtMember2020-12-310000072741es:AquarionMemberes:SecuredDebtNotesDue20212035Memberus-gaap:SecuredDebtMember2019-12-310000072741es:EversourceParentSeniorNotesDue20212050Membersrt:MinimumMembersrt:ParentCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741srt:MaximumMemberes:EversourceParentSeniorNotesDue20212050Membersrt:ParentCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741es:EversourceParentSeniorNotesDue20212050Membersrt:ParentCompanyMemberus-gaap:UnsecuredDebtMember2020-12-310000072741es:EversourceParentSeniorNotesDue20212050Membersrt:ParentCompanyMemberus-gaap:UnsecuredDebtMember2019-12-310000072741es:SpentNuclearFuelObilgationCyMember2020-12-310000072741es:SpentNuclearFuelObilgationCyMember2019-12-310000072741es:FairValueAdjustmentMember2020-12-310000072741es:FairValueAdjustmentMember2019-12-310000072741es:FairvalueadjustmentmembercurrentportionMember2020-12-310000072741es:FairvalueadjustmentmembercurrentportionMember2019-12-310000072741us-gaap:LoansPayableMember2020-12-310000072741us-gaap:LoansPayableMember2019-12-310000072741us-gaap:SeniorNotesMember2020-12-310000072741us-gaap:SeniorNotesMember2019-12-310000072741es:TotalOtherLongTermDebtMember2020-12-310000072741es:TotalOtherLongTermDebtMember2019-12-310000072741es:NSTARGasCompanyMember2020-01-270000072741es:PublicServiceCompanyOfNewHampshirePSNHMember2020-07-310000072741es:NstarElectricCompanyMember2020-12-140000072741es:AquarionWaterCompanyMember2020-12-160000072741es:TheConnecticutLightAndPowerCompanyMemberes:A075SeriesAFirstMortgageBondsMemberus-gaap:SeniorNotesMember2020-12-012020-12-310000072741es:A3952020DebenturesMemberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2020-03-310000072741es:A3952020DebenturesMemberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2020-03-012020-03-310000072741es:A510SeriesESeniorNotesMemberes:NstarElectricCompanyMemberus-gaap:SeniorNotesMember2020-03-012020-03-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:A240SeriesUFirstMortgageBondsMemberus-gaap:SeniorNotesMember2020-08-012020-08-310000072741es:EversourceParent345SeriesPSeniorNotesMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2020-01-310000072741es:EversourceParent345SeriesPSeniorNotesMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2020-01-012020-01-310000072741es:EversourceParent345SeriesPSeniorNotesMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2020-08-310000072741es:EversourceParent345SeriesPSeniorNotesMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2020-08-012020-08-310000072741es:EversourceParent080SeriesQSeniorNotesMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2020-08-310000072741es:EversourceParent080SeriesQSeniorNotesMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2020-08-012020-08-310000072741es:EversourceParent165SeriesRSeniorNotesMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2020-08-310000072741es:EversourceParent165SeriesRSeniorNotesMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2020-08-012020-08-310000072741es:EversourceParentSeriesISeniorNotesMemberes:NSTARGasCompanyMemberus-gaap:SeniorNotesMember2020-01-310000072741es:EversourceParentSeriesISeniorNotesMemberes:NSTARGasCompanyMemberus-gaap:SeniorNotesMember2020-01-012020-01-310000072741es:NSTARGasCompanyMemberes:NSTARGas446SeriesNFirstMortgageBondsMemberus-gaap:SeniorNotesMember2020-01-310000072741es:NSTARGasCompanyMemberes:NSTARGas446SeriesNFirstMortgageBondsMemberus-gaap:SeniorNotesMember2020-01-012020-01-310000072741es:NSTARGasCompanyMemberes:NSTARGas233SeriesRFirstMortgageBondsMemberus-gaap:SeniorNotesMember2020-05-310000072741es:NSTARGasCompanyMemberes:NSTARGas233SeriesRFirstMortgageBondsMemberus-gaap:SeniorNotesMember2020-05-012020-05-310000072741es:NSTARGasCompanyMemberus-gaap:SeniorNotesMemberes:NSTARGas315SeriesSFirstMortgageBondsMember2020-05-310000072741es:NSTARGasCompanyMemberus-gaap:SeniorNotesMemberes:NSTARGas315SeriesSFirstMortgageBondsMember2020-05-012020-05-310000072741es:NSTARGasCompanyMemberes:NSTARGas995SeriesJFirstMortgageBondsMemberus-gaap:SeniorNotesMember2020-12-310000072741es:NSTARGasCompanyMemberes:NSTARGas995SeriesJFirstMortgageBondsMemberus-gaap:SeniorNotesMember2020-12-012020-12-310000072741es:YankeeGas487SeriesKFirstMortgageBondsMemberus-gaap:SeniorNotesMemberes:YankeeGasMember2020-04-300000072741es:YankeeGas487SeriesKFirstMortgageBondsMemberus-gaap:SeniorNotesMemberes:YankeeGasMember2020-04-012020-04-300000072741es:YankeeGas3.30SeriesQFirstMortgageBondsMemberus-gaap:SeniorNotesMemberes:YankeeGasMember2020-09-300000072741es:YankeeGas3.30SeriesQFirstMortgageBondsMemberus-gaap:SeniorNotesMemberes:YankeeGasMember2020-09-012020-09-300000072741es:AquarionMemberes:Aquarion3.54SeniorNotesMemberus-gaap:SeniorNotesMember2020-07-012020-07-300000072741es:A2018SeriesAFirstMortgageBondsDue2048Memberes:TheConnecticutLightAndPowerCompanyMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:SubsequentEventMemberes:SeriesQNotesDue2021Memberus-gaap:FirstMortgageMember2021-01-3100000727412019-12-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMemberus-gaap:PrepaidExpensesAndOtherCurrentAssetsMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMemberus-gaap:PrepaidExpensesAndOtherCurrentAssetsMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMemberus-gaap:OtherNoncurrentAssetsMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMemberus-gaap:StrandedCostsMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMemberus-gaap:StrandedCostsMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMemberes:OtherRegulatoryAssetsMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMemberes:OtherRegulatoryAssetsMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RateReductionBondsMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RateReductionBondsMemberus-gaap:VariableInterestEntityPrimaryBeneficiaryMember2019-01-012019-12-310000072741us-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741es:NstarElectricCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:PensionPlansDefinedBenefitMember2018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2018-12-310000072741es:NstarElectricCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PensionPlansDefinedBenefitMember2018-12-310000072741us-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000072741es:NstarElectricCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000072741us-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000072741es:NstarElectricCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000072741us-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741es:NstarElectricCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:PensionPlansDefinedBenefitMember2020-12-312020-12-310000072741us-gaap:OtherCurrentLiabilitiesMember2020-12-310000072741us-gaap:OtherCurrentLiabilitiesMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:NstarElectricCompanyMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:PublicServiceCompanyOfNewHampshirePSNHMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2018-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:TheConnecticutLightAndPowerCompanyMember2018-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:NstarElectricCompanyMember2018-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:PublicServiceCompanyOfNewHampshirePSNHMember2018-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-01-012020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:PublicServiceCompanyOfNewHampshirePSNHMember2020-01-012020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-01-012019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:TheConnecticutLightAndPowerCompanyMember2019-01-012019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:NstarElectricCompanyMember2019-01-012019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:PublicServiceCompanyOfNewHampshirePSNHMember2019-01-012019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:NstarElectricCompanyMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:PublicServiceCompanyOfNewHampshirePSNHMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:OtherNoncurrentAssetsMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:OtherNoncurrentAssetsMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:AccruedPensionSERPandPBOPMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:AccruedPensionSERPandPBOPMember2019-12-310000072741srt:MinimumMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741srt:MaximumMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741srt:MinimumMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741srt:MaximumMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MinimumMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MaximumMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MinimumMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MaximumMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:Pre65PlanMember2020-01-012020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:Pre65PlanMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:Post65PlanMember2020-12-310000072741us-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000072741es:NstarElectricCompanyMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2018-01-012018-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:TheConnecticutLightAndPowerCompanyMember2018-01-012018-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:NstarElectricCompanyMember2018-01-012018-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:PublicServiceCompanyOfNewHampshirePSNHMember2018-01-012018-12-310000072741srt:MinimumMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000072741srt:MaximumMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000072741srt:MinimumMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000072741srt:MaximumMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000072741srt:MinimumMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000072741srt:MaximumMemberus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MinimumMember2020-01-012020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MaximumMember2020-01-012020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MinimumMember2019-01-012019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MaximumMember2019-01-012019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MinimumMember2018-01-012018-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MaximumMember2018-01-012018-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:AquarionMembersrt:MinimumMemberes:Pre65PlanMember2020-01-012020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MaximumMemberes:AquarionMemberes:Pre65PlanMember2020-01-012020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:AquarionMembersrt:MinimumMemberes:Pre65PlanMember2019-01-012019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembersrt:MaximumMemberes:AquarionMemberes:Pre65PlanMember2019-01-012019-12-310000072741es:EversourceServicePensionAndPBOPPlansMember2020-01-012020-12-310000072741es:AquarionPlansMember2020-01-012020-12-310000072741us-gaap:DefinedBenefitPlanEquitySecuritiesUsMember2020-12-310000072741us-gaap:DefinedBenefitPlanEquitySecuritiesUsMember2019-12-310000072741es:DefinedBenefitPlanEquitySecuritiesGlobalMember2020-12-310000072741es:DefinedBenefitPlanEquitySecuritiesGlobalMember2019-12-310000072741us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2020-12-310000072741us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2019-12-310000072741es:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMember2020-12-310000072741es:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMember2019-12-310000072741us-gaap:FixedIncomeSecuritiesMember2020-12-310000072741us-gaap:FixedIncomeSecuritiesMember2019-12-310000072741es:DefinedBenefitPlanDebtSecurityPublicHighYieldFixedIncomeMember2020-12-310000072741es:DefinedBenefitPlanDebtSecurityPublicHighYieldFixedIncomeMember2019-12-310000072741es:DefinedBenefitPlanDebtSecurityPrivateDebtMember2020-12-310000072741es:DefinedBenefitPlanDebtSecurityPrivateDebtMember2019-12-310000072741us-gaap:PrivateEquityFundsMember2020-12-310000072741us-gaap:PrivateEquityFundsMember2019-12-310000072741us-gaap:RealEstateMember2020-12-310000072741us-gaap:RealEstateMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:EversourcePBOPPlanMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:EversourcePBOPPlanMemberes:DefinedBenefitPlanFixedIncomeSecuritiesMember2020-12-310000072741us-gaap:DefinedBenefitPlanEquitySecuritiesMemberes:AquarionPensionPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:DefinedBenefitPlanDebtSecurityMemberes:AquarionPensionPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741es:DefinedBenefitPlanOtherSecuritiesMemberes:AquarionPensionPlanMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMemberes:AquarionPBOPPlanMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanDebtSecurityMemberes:AquarionPBOPPlanMember2020-12-310000072741es:DefinedBenefitPlanOtherSecuritiesMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:AquarionPBOPPlanMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:FixedIncomeFundsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:FairValueInputsLevel2Memberus-gaap:FixedIncomeFundsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:FixedIncomeFundsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:FixedIncomeFundsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:FairValueInputsLevel2Memberus-gaap:FixedIncomeFundsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:FixedIncomeFundsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:PrivateEquityFundsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:PrivateEquityFundsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:PrivateEquityFundsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:PrivateEquityFundsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:PrivateEquityFundsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:PrivateEquityFundsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741es:TotalAssetsBefore401hMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741es:TotalAssetsBefore401hMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741es:Assetsrelatedto401hMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000072741es:Assetsrelatedto401hMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:FairValueInputsLevel2Member2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:FairValueInputsLevel2Member2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMember2019-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FixedIncomeFundsMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel2Memberus-gaap:FixedIncomeFundsMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FixedIncomeFundsMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FixedIncomeFundsMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel2Memberus-gaap:FixedIncomeFundsMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FixedIncomeFundsMember2019-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMemberus-gaap:FairValueInputsLevel2Member2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMemberus-gaap:FairValueInputsLevel2Member2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMember2019-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel2Member2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel2Member2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMember2019-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel2Member2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:TotalAssetsBefore401hMember2020-12-310000072741us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel2Member2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:TotalAssetsBefore401hMember2019-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:Assetsrelatedto401hMember2020-12-310000072741us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberes:Assetsrelatedto401hMember2019-12-310000072741es:DefinedContributionPlan401KMember2020-01-012020-12-310000072741es:DefinedContributionPlanAlternateContribution401KMember2020-01-012020-12-310000072741es:EmployeesMember2020-01-012020-12-310000072741es:BoardMembersMember2020-01-012020-12-310000072741us-gaap:RestrictedStockUnitsRSUMember2019-12-310000072741us-gaap:RestrictedStockUnitsRSUMember2020-01-012020-12-310000072741us-gaap:RestrictedStockUnitsRSUMember2020-12-310000072741us-gaap:RestrictedStockUnitsRSUMember2019-01-012019-12-310000072741us-gaap:RestrictedStockUnitsRSUMember2018-01-012018-12-310000072741us-gaap:PerformanceSharesMember2019-12-310000072741us-gaap:PerformanceSharesMember2020-01-012020-12-310000072741us-gaap:PerformanceSharesMember2020-12-310000072741us-gaap:PerformanceSharesMember2019-01-012019-12-310000072741us-gaap:PerformanceSharesMember2018-01-012018-12-310000072741us-gaap:InternalRevenueServiceIRSMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:InternalRevenueServiceIRSMember2020-12-310000072741us-gaap:InternalRevenueServiceIRSMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:InternalRevenueServiceIRSMember2020-12-310000072741us-gaap:InternalRevenueServiceIRSMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:InternalRevenueServiceIRSMember2019-12-310000072741us-gaap:InternalRevenueServiceIRSMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:InternalRevenueServiceIRSMember2019-12-310000072741us-gaap:StateAndLocalJurisdictionMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:StateAndLocalJurisdictionMember2020-12-310000072741us-gaap:StateAndLocalJurisdictionMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:StateAndLocalJurisdictionMember2020-12-310000072741us-gaap:StateAndLocalJurisdictionMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:StateAndLocalJurisdictionMember2019-12-310000072741us-gaap:StateAndLocalJurisdictionMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:StateAndLocalJurisdictionMember2019-12-310000072741us-gaap:StateAndLocalJurisdictionMembersrt:ParentCompanyMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:StateAndLocalJurisdictionMember2019-01-012019-12-310000072741us-gaap:StateAndLocalJurisdictionMembersrt:ParentCompanyMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:StateAndLocalJurisdictionMember2018-01-012018-12-310000072741us-gaap:StateAndLocalJurisdictionMember2018-12-31es:sitees:gasSite0000072741es:MgpSiteAccrualMember2020-12-310000072741es:MgpSiteAccrualMember2019-12-310000072741es:EnvironmentalSitesforWhichaRangeofLossExistsMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:EnvironmentalSitesforWhichaRangeofLossExistsMember2020-01-012020-12-310000072741es:EnvironmentalSitesforWhichaRangeofLossExistsMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:EnvironmentalSitesforWhichaRangeofLossExistsMember2020-12-310000072741es:EnvironmentalSiteforWhichaRangeisTooEarlytoDetermineMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:EnvironmentalSiteforWhichaRangeisTooEarlytoDetermineMember2020-01-012020-12-310000072741es:EnvironmentalSiteforWhichaRangeisTooEarlytoDetermineMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:EnvironmentalSiteforWhichaRangeisTooEarlytoDetermineMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:EnvironmentalSiteforWhichaRangeisTooEarlytoDetermineMember2020-12-310000072741es:EnvironmentalSiteforWhichaRangeisTooEarlytoDetermineMemberes:NstarElectricCompanyMember2020-12-310000072741es:EvironmentalSiteswithBestEstimateMember2020-01-012020-12-310000072741es:EvironmentalSiteswithBestEstimateMemberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741es:EvironmentalSiteswithBestEstimateMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:EvironmentalSiteswithBestEstimateMember2020-01-012020-12-310000072741es:EvironmentalSiteswithBestEstimateMember2020-12-310000072741es:EvironmentalSiteswithBestEstimateMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:EvironmentalSiteswithBestEstimateMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:EvironmentalSiteswithBestEstimateMember2020-12-310000072741es:RenewableEnergyContractsMember2020-12-310000072741es:NaturalGasProcurementContractsMember2020-12-310000072741es:SupplyAndStrandedCostObligationsMember2020-12-310000072741es:PeakerContractsForDifferencesMember2020-12-310000072741es:TransmissionSupportCommitmentsMember2020-12-310000072741es:RenewableEnergyContractsMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:SupplyAndStrandedCostObligationsMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:PeakerContractsForDifferencesMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:TransmissionSupportCommitmentsMember2020-12-310000072741es:RenewableEnergyContractsMemberes:NstarElectricCompanyMember2020-12-310000072741es:SupplyAndStrandedCostObligationsMemberes:NstarElectricCompanyMember2020-12-310000072741es:TransmissionSupportCommitmentsMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:RenewableEnergyContractsMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:SupplyAndStrandedCostObligationsMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:TransmissionSupportCommitmentsMember2020-12-310000072741es:MilestoneNuclearPowerStationMemberes:TheConnecticutLightAndPowerCompanyMember2018-12-282018-12-280000072741es:MilestoneNuclearPowerStationMemberes:UIMember2018-12-282018-12-280000072741es:MilestoneNuclearPowerStationMember2018-12-282018-12-280000072741es:MilestoneNuclearPowerStationMemberes:UIMember2019-03-152019-03-150000072741es:MilestoneNuclearPowerStationMemberes:TheConnecticutLightAndPowerCompanyMember2019-03-152019-03-150000072741es:MilestoneNuclearPowerStationMember2019-03-152019-03-15es:megawatt0000072741es:SeabrookNuclearPowerPlantMemberes:UIMember2018-12-282018-12-280000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeabrookNuclearPowerPlantMember2018-12-282018-12-280000072741es:SeabrookNuclearPowerPlantMember2019-11-222019-11-220000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeabrookNuclearPowerPlantMember2019-11-222019-11-220000072741es:SeabrookNuclearPowerPlantMemberes:UIMember2019-11-222019-11-220000072741es:MillstoneNuclearPowerStationAndSeabrookNuclearPowerPlantMember2020-12-310000072741srt:MinimumMember2020-12-310000072741srt:MaximumMember2020-12-310000072741us-gaap:ConstructionInProgressMember2020-12-31es:contractes:project0000072741es:PeakerContractsForDifferencesMemberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741es:PeakerContractsForDifferencesMember2020-01-012020-12-310000072741es:CLPNSTARElectricandPSNHMemberes:TransmissionSupportCommitmentsMember2020-01-012020-12-310000072741es:CLPNSTARElectricandPSNHMemberes:TransmissionSupportCommitmentsMember2020-10-312020-10-310000072741es:YankeeCompaniesMember2017-05-222017-05-220000072741es:CYAPCYAECAndMYAPCMember2019-02-212019-02-210000072741es:CYAPCMember2019-02-212019-02-210000072741es:YAECMember2019-02-212019-02-210000072741es:MyapcMember2019-02-212019-02-2100000727412019-06-122019-06-1200000727412019-07-012019-07-310000072741es:YAECMember2019-12-012019-12-310000072741es:MyapcMember2019-12-012019-12-310000072741es:NortheastOffshoreLLCMemberes:PurchaseGuaranteeMember2020-12-310000072741us-gaap:IndemnificationGuaranteeMemberes:EversourceInvestmentLLCMember2020-12-310000072741es:CapacityProductionGuaranteeMemberes:SunriseWindLLCMember2020-12-310000072741es:TransmissionInterconnectionGuaranteeMemberes:SouthForkWindLLCMember2020-12-310000072741es:RealEstatePurchaseGuaranteeMemberes:BayStateWindLLCMember2020-12-310000072741es:VariousEntitiesMemberus-gaap:SuretyBondMember2020-12-310000072741es:RockyRiverRealtyCompanyAndEversourceServiceMemberus-gaap:PropertyLeaseGuaranteeMember2020-12-310000072741es:NortheastOffshoreLLCMember2020-12-010000072741es:NortheastOffshoreLLCMemberus-gaap:PerformanceGuaranteeMember2020-12-310000072741es:NortheastOffshoreLLCMemberus-gaap:PaymentGuaranteeMember2020-12-310000072741es:NortheastOffshoreLLCMemberes:EversourceInvestmentLLCMember2020-12-010000072741us-gaap:IndemnificationGuaranteeMemberes:NortheastOffshoreLLCMemberes:EversourceInvestmentLLCMember2020-12-310000072741es:SunriseWindLLCMember2019-10-250000072741us-gaap:LetterOfCreditMemberes:EversourceInvestmentLLCMember2020-09-16es:complaint0000072741es:FERCROEComplaintsMember2016-04-290000072741es:FERCROEFirstSecondandThirdComplaintsMember2014-07-310000072741es:FERCROEFirstSecondandThirdComplaintsMember2020-01-012020-12-310000072741es:FERCROEComplaintsMember2020-01-012020-12-310000072741es:FERCROEFourthComplaintMember2016-04-292016-04-290000072741srt:MinimumMemberes:FERCROEFirstSecondandThirdComplaintsMember2011-10-012014-10-150000072741srt:MaximumMemberes:FERCROEFirstSecondandThirdComplaintsMember2011-10-012014-10-150000072741es:FERCROESecondComplaintMember2014-10-162017-04-140000072741es:FERCROEFirstComplaintMember2014-10-162017-04-140000072741es:FERCROEFirstComplaintMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:FERCROEFirstComplaintMember2020-01-012020-12-310000072741es:FERCROEFirstComplaintMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:FERCROEFirstComplaintMember2020-01-012020-12-310000072741es:FERCROESecondComplaintMember2020-12-310000072741es:FERCROESecondComplaintMember2020-01-012020-12-310000072741es:FERCROESecondComplaintMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:FERCROESecondComplaintMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:FERCROESecondComplaintMember2020-12-310000072741es:FERCROEComplaintsMember2018-10-1600000727412018-10-162018-10-160000072741es:FERCROEFirstSecondandThirdComplaintsMember2018-10-162018-10-160000072741es:FERCROEFourthComplaintMember2017-10-062017-10-060000072741es:FERCROEComplaintsMember2020-12-31es:kV00000727412016-07-152016-07-150000072741us-gaap:OtherNoncurrentLiabilitiesMember2019-12-310000072741srt:MinimumMember2020-01-012020-12-310000072741srt:MinimumMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMembersrt:MinimumMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMembersrt:MinimumMember2020-01-012020-12-310000072741srt:MaximumMember2020-01-012020-12-310000072741srt:MaximumMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741srt:MaximumMemberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMembersrt:MaximumMember2020-01-012020-12-310000072741es:ColumbiaGasOfMassachusettsCMAMember2020-01-012020-12-310000072741us-gaap:CarryingReportedAmountFairValueDisclosureMember2020-12-310000072741us-gaap:EstimateOfFairValueFairValueDisclosureMember2020-12-310000072741us-gaap:CarryingReportedAmountFairValueDisclosureMemberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:EstimateOfFairValueFairValueDisclosureMember2020-12-310000072741us-gaap:CarryingReportedAmountFairValueDisclosureMemberes:NstarElectricCompanyMember2020-12-310000072741us-gaap:EstimateOfFairValueFairValueDisclosureMemberes:NstarElectricCompanyMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:CarryingReportedAmountFairValueDisclosureMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:EstimateOfFairValueFairValueDisclosureMember2020-12-310000072741us-gaap:CarryingReportedAmountFairValueDisclosureMember2019-12-310000072741us-gaap:EstimateOfFairValueFairValueDisclosureMember2019-12-310000072741us-gaap:CarryingReportedAmountFairValueDisclosureMemberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:EstimateOfFairValueFairValueDisclosureMember2019-12-310000072741us-gaap:CarryingReportedAmountFairValueDisclosureMemberes:NstarElectricCompanyMember2019-12-310000072741us-gaap:EstimateOfFairValueFairValueDisclosureMemberes:NstarElectricCompanyMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:CarryingReportedAmountFairValueDisclosureMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:EstimateOfFairValueFairValueDisclosureMember2019-12-310000072741us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-12-310000072741us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2019-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2019-12-310000072741us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2018-12-310000072741us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2018-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2018-12-310000072741us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-01-012020-12-310000072741us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2020-01-012020-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2020-01-012020-12-310000072741us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-01-012019-12-310000072741us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2019-01-012019-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2019-01-012019-12-310000072741us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-12-310000072741us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2020-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2020-12-310000072741us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:InterestRateContractMemberus-gaap:AccumulatedNetGainLossFromCashFlowHedgesIncludingPortionAttributableToNoncontrollingInterestMember2020-01-012020-12-310000072741us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:InterestRateContractMemberus-gaap:AccumulatedNetGainLossFromCashFlowHedgesIncludingPortionAttributableToNoncontrollingInterestMember2019-01-012019-12-310000072741us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:InterestRateContractMemberus-gaap:AccumulatedNetGainLossFromCashFlowHedgesIncludingPortionAttributableToNoncontrollingInterestMember2018-01-012018-12-310000072741us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedNetGainLossFromCashFlowHedgesIncludingPortionAttributableToNoncontrollingInterestMember2020-01-012020-12-310000072741us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedNetGainLossFromCashFlowHedgesIncludingPortionAttributableToNoncontrollingInterestMember2019-01-012019-12-310000072741us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedNetGainLossFromCashFlowHedgesIncludingPortionAttributableToNoncontrollingInterestMember2018-01-012018-12-310000072741us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000072741us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000072741us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember2020-01-012020-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember2019-01-012019-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember2018-01-012018-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember2020-01-012020-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember2019-01-012019-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember2018-01-012018-12-310000072741us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2018-01-012018-12-3100000727412020-06-152020-06-1500000727412020-06-1500000727412019-06-012019-06-3000000727412019-12-302019-12-3000000727412020-12-012020-12-3100000727412020-03-232020-03-2300000727412020-03-262020-03-2600000727412020-03-012020-03-3100000727412020-03-012020-06-1500000727412019-06-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1947PreferredStockat1.90Member2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1947PreferredStockat1.90Member2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1947PreferredStockat1.90Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1947PreferredStockat1.90Member2019-12-310000072741es:Seriesof1947PreferredStockat2.00Memberes:TheConnecticutLightAndPowerCompanyMember2019-01-012019-12-310000072741es:Seriesof1947PreferredStockat2.00Memberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741es:Seriesof1947PreferredStockat2.00Memberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:Seriesof1947PreferredStockat2.00Memberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1949PreferredStockat2.04Member2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1949PreferredStockat2.04Member2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1949PreferredStockat2.04Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1949PreferredStockat2.04Member2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1949PreferredStockat2.20Member2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1949PreferredStockat2.20Member2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1949PreferredStockat2.20Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1949PreferredStockat2.20Member2019-12-310000072741es:Seriesof1949PreferredStockat3.90Memberes:TheConnecticutLightAndPowerCompanyMember2019-01-012019-12-310000072741es:Seriesof1949PreferredStockat3.90Memberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741es:Seriesof1949PreferredStockat3.90Memberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:Seriesof1949PreferredStockat3.90Memberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesE1954PreferredStockat2.06Member2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesE1954PreferredStockat2.06Member2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesE1954PreferredStockat2.06Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesE1954PreferredStockat2.06Member2019-12-310000072741es:SeriesFof1955PreferredStockat2.09Memberes:TheConnecticutLightAndPowerCompanyMember2019-01-012019-12-310000072741es:SeriesFof1955PreferredStockat2.09Memberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741es:SeriesFof1955PreferredStockat2.09Memberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:SeriesFof1955PreferredStockat2.09Memberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1956PreferredStockat4.5Member2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1956PreferredStockat4.5Member2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1956PreferredStockat4.5Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1956PreferredStockat4.5Member2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1958PreferredStockat4.96Member2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1958PreferredStockat4.96Member2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1958PreferredStockat4.96Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:Seriesof1958PreferredStockat4.96Member2019-12-310000072741es:Seriesof1963PreferredStockat4.5Memberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741es:Seriesof1963PreferredStockat4.5Memberes:TheConnecticutLightAndPowerCompanyMember2019-01-012019-12-310000072741es:Seriesof1963PreferredStockat4.5Memberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:Seriesof1963PreferredStockat4.5Memberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:Seriesof1967PreferredStockat5.28Memberes:TheConnecticutLightAndPowerCompanyMember2019-01-012019-12-310000072741es:Seriesof1967PreferredStockat5.28Memberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741es:Seriesof1967PreferredStockat5.28Memberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:Seriesof1967PreferredStockat5.28Memberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesGof1968PreferredStockat3.24Member2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesGof1968PreferredStockat3.24Member2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesGof1968PreferredStockat3.24Member2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:SeriesGof1968PreferredStockat3.24Member2019-12-310000072741es:Seriesof1968PreferredStockat6.56Memberes:TheConnecticutLightAndPowerCompanyMember2020-01-012020-12-310000072741es:Seriesof1968PreferredStockat6.56Memberes:TheConnecticutLightAndPowerCompanyMember2019-01-012019-12-310000072741es:Seriesof1968PreferredStockat6.56Memberes:TheConnecticutLightAndPowerCompanyMember2020-12-310000072741es:Seriesof1968PreferredStockat6.56Memberes:TheConnecticutLightAndPowerCompanyMember2019-12-310000072741es:SeriesofPreferredStockat4.25Memberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:SeriesofPreferredStockat4.25Memberes:NstarElectricCompanyMember2019-01-012019-12-310000072741es:SeriesofPreferredStockat4.25Memberes:NstarElectricCompanyMember2020-12-310000072741es:SeriesofPreferredStockat4.25Memberes:NstarElectricCompanyMember2019-12-310000072741es:NstarElectricCompanyMemberes:SeriesofPreferredStockat4.78Member2019-01-012019-12-310000072741es:NstarElectricCompanyMemberes:SeriesofPreferredStockat4.78Member2020-01-012020-12-310000072741es:NstarElectricCompanyMemberes:SeriesofPreferredStockat4.78Member2020-12-310000072741es:NstarElectricCompanyMemberes:SeriesofPreferredStockat4.78Member2019-12-310000072741es:SeriesofPreferredStockat6Memberes:AquarionWaterCompanyMember2020-01-012020-12-310000072741es:SeriesofPreferredStockat6Memberes:AquarionWaterCompanyMember2020-12-310000072741es:SeriesofPreferredStockat6Memberes:AquarionWaterCompanyMember2019-12-310000072741es:ResidentialMemberes:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:ResidentialMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2020-01-012020-12-310000072741es:ResidentialMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:ResidentialMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2020-01-012020-12-310000072741es:ResidentialMemberus-gaap:CorporateNonSegmentMember2020-01-012020-12-310000072741es:ResidentialMemberus-gaap:IntersegmentEliminationMember2020-01-012020-12-310000072741es:ResidentialMember2020-01-012020-12-310000072741es:CommercialMemberes:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:CommercialMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2020-01-012020-12-310000072741es:CommercialMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:CommercialMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2020-01-012020-12-310000072741es:CommercialMemberus-gaap:CorporateNonSegmentMember2020-01-012020-12-310000072741es:CommercialMemberus-gaap:IntersegmentEliminationMember2020-01-012020-12-310000072741es:CommercialMember2020-01-012020-12-310000072741es:IndustrialMemberes:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:IndustrialMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2020-01-012020-12-310000072741es:IndustrialMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:IndustrialMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2020-01-012020-12-310000072741es:IndustrialMemberus-gaap:CorporateNonSegmentMember2020-01-012020-12-310000072741es:IndustrialMemberus-gaap:IntersegmentEliminationMember2020-01-012020-12-310000072741es:IndustrialMember2020-01-012020-12-310000072741es:EversourceElectricDistributionMemberes:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2020-01-012020-12-310000072741es:TotalRetailSalesRevenueMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2020-01-012020-12-310000072741us-gaap:CorporateNonSegmentMemberes:TotalRetailSalesRevenueMember2020-01-012020-12-310000072741es:TotalRetailSalesRevenueMemberus-gaap:IntersegmentEliminationMember2020-01-012020-12-310000072741es:TotalRetailSalesRevenueMember2020-01-012020-12-310000072741es:EversourceElectricDistributionMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2020-01-012020-12-310000072741es:EversourceElectricTransmissionMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2020-01-012020-12-310000072741us-gaap:CorporateNonSegmentMemberes:WholesaleTransmissionRevenueMember2020-01-012020-12-310000072741us-gaap:IntersegmentEliminationMemberes:WholesaleTransmissionRevenueMember2020-01-012020-12-310000072741es:WholesaleTransmissionRevenueMember2020-01-012020-12-310000072741es:EversourceElectricDistributionMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2020-01-012020-12-310000072741es:EversourceElectricTransmissionMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2020-01-012020-12-310000072741us-gaap:CorporateNonSegmentMemberes:WholesaleMarketSalesRevenueMember2020-01-012020-12-310000072741us-gaap:IntersegmentEliminationMemberes:WholesaleMarketSalesRevenueMember2020-01-012020-12-310000072741es:WholesaleMarketSalesRevenueMember2020-01-012020-12-310000072741es:EversourceElectricDistributionMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2020-01-012020-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2020-01-012020-12-310000072741us-gaap:CorporateNonSegmentMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMember2020-01-012020-12-310000072741us-gaap:IntersegmentEliminationMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMember2020-01-012020-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMember2020-01-012020-12-310000072741es:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2020-01-012020-12-310000072741us-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2020-01-012020-12-310000072741es:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2020-01-012020-12-310000072741us-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2020-01-012020-12-310000072741us-gaap:CorporateNonSegmentMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2020-01-012020-12-310000072741us-gaap:IntersegmentEliminationMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2020-01-012020-12-310000072741es:ReserveAdjustmentforRevenueSubjecttoRefundMember2020-01-012020-12-310000072741es:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741us-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2020-01-012020-12-310000072741es:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741us-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2020-01-012020-12-310000072741us-gaap:CorporateNonSegmentMember2020-01-012020-12-310000072741us-gaap:IntersegmentEliminationMember2020-01-012020-12-310000072741es:ResidentialMemberes:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:ResidentialMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2019-01-012019-12-310000072741es:ResidentialMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:ResidentialMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2019-01-012019-12-310000072741es:ResidentialMemberus-gaap:CorporateNonSegmentMember2019-01-012019-12-310000072741es:ResidentialMemberus-gaap:IntersegmentEliminationMember2019-01-012019-12-310000072741es:ResidentialMember2019-01-012019-12-310000072741es:CommercialMemberes:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:CommercialMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2019-01-012019-12-310000072741es:CommercialMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:CommercialMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2019-01-012019-12-310000072741es:CommercialMemberus-gaap:CorporateNonSegmentMember2019-01-012019-12-310000072741es:CommercialMemberus-gaap:IntersegmentEliminationMember2019-01-012019-12-310000072741es:CommercialMember2019-01-012019-12-310000072741es:IndustrialMemberes:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:IndustrialMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2019-01-012019-12-310000072741es:IndustrialMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:IndustrialMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2019-01-012019-12-310000072741es:IndustrialMemberus-gaap:CorporateNonSegmentMember2019-01-012019-12-310000072741es:IndustrialMemberus-gaap:IntersegmentEliminationMember2019-01-012019-12-310000072741es:IndustrialMember2019-01-012019-12-310000072741es:EversourceElectricDistributionMemberes:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2019-01-012019-12-310000072741es:TotalRetailSalesRevenueMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2019-01-012019-12-310000072741us-gaap:CorporateNonSegmentMemberes:TotalRetailSalesRevenueMember2019-01-012019-12-310000072741es:TotalRetailSalesRevenueMemberus-gaap:IntersegmentEliminationMember2019-01-012019-12-310000072741es:TotalRetailSalesRevenueMember2019-01-012019-12-310000072741es:EversourceElectricDistributionMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2019-01-012019-12-310000072741es:EversourceElectricTransmissionMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2019-01-012019-12-310000072741us-gaap:CorporateNonSegmentMemberes:WholesaleTransmissionRevenueMember2019-01-012019-12-310000072741us-gaap:IntersegmentEliminationMemberes:WholesaleTransmissionRevenueMember2019-01-012019-12-310000072741es:WholesaleTransmissionRevenueMember2019-01-012019-12-310000072741es:EversourceElectricDistributionMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2019-01-012019-12-310000072741es:EversourceElectricTransmissionMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2019-01-012019-12-310000072741us-gaap:CorporateNonSegmentMemberes:WholesaleMarketSalesRevenueMember2019-01-012019-12-310000072741us-gaap:IntersegmentEliminationMemberes:WholesaleMarketSalesRevenueMember2019-01-012019-12-310000072741es:WholesaleMarketSalesRevenueMember2019-01-012019-12-310000072741es:EversourceElectricDistributionMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2019-01-012019-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2019-01-012019-12-310000072741us-gaap:CorporateNonSegmentMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMember2019-01-012019-12-310000072741us-gaap:IntersegmentEliminationMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMember2019-01-012019-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMember2019-01-012019-12-310000072741es:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2019-01-012019-12-310000072741us-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2019-01-012019-12-310000072741es:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2019-01-012019-12-310000072741us-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2019-01-012019-12-310000072741us-gaap:CorporateNonSegmentMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2019-01-012019-12-310000072741us-gaap:IntersegmentEliminationMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2019-01-012019-12-310000072741es:ReserveAdjustmentforRevenueSubjecttoRefundMember2019-01-012019-12-310000072741es:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741us-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2019-01-012019-12-310000072741es:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741us-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2019-01-012019-12-310000072741us-gaap:CorporateNonSegmentMember2019-01-012019-12-310000072741us-gaap:IntersegmentEliminationMember2019-01-012019-12-310000072741es:ResidentialMemberes:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:ResidentialMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2018-01-012018-12-310000072741es:ResidentialMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:ResidentialMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2018-01-012018-12-310000072741es:ResidentialMemberus-gaap:CorporateNonSegmentMember2018-01-012018-12-310000072741es:ResidentialMemberus-gaap:IntersegmentEliminationMember2018-01-012018-12-310000072741es:ResidentialMember2018-01-012018-12-310000072741es:CommercialMemberes:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:CommercialMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2018-01-012018-12-310000072741es:CommercialMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:CommercialMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2018-01-012018-12-310000072741es:CommercialMemberus-gaap:CorporateNonSegmentMember2018-01-012018-12-310000072741es:CommercialMemberus-gaap:IntersegmentEliminationMember2018-01-012018-12-310000072741es:CommercialMember2018-01-012018-12-310000072741es:IndustrialMemberes:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:IndustrialMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2018-01-012018-12-310000072741es:IndustrialMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:IndustrialMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2018-01-012018-12-310000072741es:IndustrialMemberus-gaap:CorporateNonSegmentMember2018-01-012018-12-310000072741es:IndustrialMemberus-gaap:IntersegmentEliminationMember2018-01-012018-12-310000072741es:IndustrialMember2018-01-012018-12-310000072741es:EversourceElectricDistributionMemberes:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2018-01-012018-12-310000072741es:TotalRetailSalesRevenueMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2018-01-012018-12-310000072741us-gaap:CorporateNonSegmentMemberes:TotalRetailSalesRevenueMember2018-01-012018-12-310000072741es:TotalRetailSalesRevenueMemberus-gaap:IntersegmentEliminationMember2018-01-012018-12-310000072741es:TotalRetailSalesRevenueMember2018-01-012018-12-310000072741es:EversourceElectricDistributionMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2018-01-012018-12-310000072741es:EversourceElectricTransmissionMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2018-01-012018-12-310000072741us-gaap:CorporateNonSegmentMemberes:WholesaleTransmissionRevenueMember2018-01-012018-12-310000072741us-gaap:IntersegmentEliminationMemberes:WholesaleTransmissionRevenueMember2018-01-012018-12-310000072741es:WholesaleTransmissionRevenueMember2018-01-012018-12-310000072741es:EversourceElectricDistributionMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2018-01-012018-12-310000072741es:EversourceElectricTransmissionMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2018-01-012018-12-310000072741us-gaap:CorporateNonSegmentMemberes:WholesaleMarketSalesRevenueMember2018-01-012018-12-310000072741us-gaap:IntersegmentEliminationMemberes:WholesaleMarketSalesRevenueMember2018-01-012018-12-310000072741es:WholesaleMarketSalesRevenueMember2018-01-012018-12-310000072741es:EversourceElectricDistributionMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2018-01-012018-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberes:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2018-01-012018-12-310000072741us-gaap:CorporateNonSegmentMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMember2018-01-012018-12-310000072741us-gaap:IntersegmentEliminationMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMember2018-01-012018-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMember2018-01-012018-12-310000072741es:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2018-01-012018-12-310000072741us-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2018-01-012018-12-310000072741es:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2018-01-012018-12-310000072741us-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2018-01-012018-12-310000072741us-gaap:CorporateNonSegmentMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2018-01-012018-12-310000072741us-gaap:IntersegmentEliminationMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2018-01-012018-12-310000072741es:ReserveAdjustmentforRevenueSubjecttoRefundMember2018-01-012018-12-310000072741es:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741us-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2018-01-012018-12-310000072741es:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741us-gaap:OperatingSegmentsMemberes:WaterDistributionSegmentMember2018-01-012018-12-310000072741us-gaap:CorporateNonSegmentMember2018-01-012018-12-310000072741us-gaap:IntersegmentEliminationMember2018-01-012018-12-310000072741es:ResidentialMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:ResidentialMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:ResidentialMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:ResidentialMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:ResidentialMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:ResidentialMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:ResidentialMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:ResidentialMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:ResidentialMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:CommercialMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:CommercialMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:CommercialMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:CommercialMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:CommercialMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:CommercialMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:CommercialMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:CommercialMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:CommercialMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:IndustrialMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:IndustrialMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:IndustrialMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:IndustrialMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:IndustrialMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:IndustrialMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:IndustrialMemberes:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:IndustrialMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:IndustrialMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:TotalRetailSalesRevenueMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:TotalRetailSalesRevenueMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:TotalRetailSalesRevenueMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:TotalRetailSalesRevenueMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:WholesaleTransmissionRevenueMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:WholesaleTransmissionRevenueMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:WholesaleTransmissionRevenueMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:WholesaleTransmissionRevenueMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:WholesaleMarketSalesRevenueMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:WholesaleMarketSalesRevenueMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:WholesaleMarketSalesRevenueMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:WholesaleMarketSalesRevenueMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:OtherRevenueAdjustmentsfromContractswithCustomersMemberes:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberes:OtherRevenueAdjustmentsfromContractswithCustomersMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2020-01-012020-12-310000072741es:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2019-01-012019-12-310000072741es:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2018-01-012018-12-310000072741es:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:OperatingSegmentsMemberes:ReserveAdjustmentforRevenueSubjecttoRefundMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:NstarElectricCompanyMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMembersrt:ConsolidationEliminationsMember2020-01-012020-12-310000072741srt:ConsolidationEliminationsMemberes:NstarElectricCompanyMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMembersrt:ConsolidationEliminationsMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMembersrt:ConsolidationEliminationsMember2019-01-012019-12-310000072741srt:ConsolidationEliminationsMemberes:NstarElectricCompanyMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMembersrt:ConsolidationEliminationsMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMembersrt:ConsolidationEliminationsMember2018-01-012018-12-310000072741srt:ConsolidationEliminationsMemberes:NstarElectricCompanyMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMembersrt:ConsolidationEliminationsMember2018-01-012018-12-310000072741es:YankeeGasNSTARGasAndEGMAMember2020-01-012020-12-31es:segment0000072741es:EversourceWaterMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000072741es:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2020-12-310000072741us-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2020-12-310000072741es:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2020-12-310000072741es:EversourceWaterMemberus-gaap:OperatingSegmentsMember2020-12-310000072741us-gaap:CorporateNonSegmentMember2020-12-310000072741us-gaap:IntersegmentEliminationMember2020-12-310000072741es:EversourceWaterMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000072741es:EversourceElectricDistributionMemberus-gaap:OperatingSegmentsMember2019-12-310000072741us-gaap:OperatingSegmentsMemberes:NaturalGasDistributionMember2019-12-310000072741es:EversourceElectricTransmissionMemberus-gaap:OperatingSegmentsMember2019-12-310000072741es:EversourceWaterMemberus-gaap:OperatingSegmentsMember2019-12-310000072741us-gaap:CorporateNonSegmentMember2019-12-310000072741us-gaap:IntersegmentEliminationMember2019-12-310000072741es:EversourceWaterMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-31utr:mi00000727412020-10-090000072741es:MassachusettsDepartmentOfPublicUtilitiesDPUMember2020-10-072020-10-070000072741es:MassachusettsDepartmentOfPublicUtilitiesDPUMember2020-10-070000072741srt:ScenarioForecastMemberes:MassachusettsDepartmentOfPublicUtilitiesDPUMember2021-11-012021-11-010000072741srt:ScenarioForecastMemberes:MassachusettsDepartmentOfPublicUtilitiesDPUMember2022-11-012022-11-01es:resetes:rateIncrease0000072741es:ColumbiaGasOfMassachusettsCMAMember2020-10-310000072741es:ColumbiaGasOfMassachusettsCMAMember2019-01-012019-12-3100000727412017-01-012017-12-310000072741es:TransitionServicesAgreementTSAMember2020-10-012020-12-310000072741es:NaturalGasDistributionMember2020-01-012020-12-310000072741es:HinghamWaterSystemMemberes:WaterDistributionSegmentMember2020-01-012020-12-3100000727412020-10-012020-10-010000072741es:EversourceElectricDistributionMember2019-12-310000072741es:EversourceElectricTransmissionMember2019-12-310000072741es:NaturalGasDistributionMember2019-12-310000072741es:WaterDistributionSegmentMember2019-12-310000072741es:EversourceElectricDistributionMember2020-01-012020-12-310000072741es:EversourceElectricTransmissionMember2020-01-012020-12-310000072741es:WaterDistributionSegmentMember2020-01-012020-12-310000072741es:EversourceElectricDistributionMember2020-12-310000072741es:EversourceElectricTransmissionMember2020-12-310000072741es:NaturalGasDistributionMember2020-12-310000072741es:WaterDistributionSegmentMember2020-12-310000072741srt:ParentCompanyMember2020-12-310000072741srt:ParentCompanyMember2019-12-310000072741srt:ParentCompanyMember2020-01-012020-12-310000072741srt:ParentCompanyMember2019-01-012019-12-310000072741srt:ParentCompanyMember2018-01-012018-12-310000072741srt:ParentCompanyMember2018-12-310000072741srt:ParentCompanyMember2017-12-310000072741us-gaap:AllowanceForCreditLossMember2019-12-310000072741us-gaap:AllowanceForCreditLossMember2020-01-012020-12-310000072741us-gaap:AllowanceForCreditLossMember2020-12-310000072741us-gaap:AllowanceForCreditLossMember2018-12-310000072741us-gaap:AllowanceForCreditLossMember2019-01-012019-12-310000072741us-gaap:AllowanceForCreditLossMember2017-12-310000072741us-gaap:AllowanceForCreditLossMember2018-01-012018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AllowanceForCreditLossMember2019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AllowanceForCreditLossMember2020-01-012020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AllowanceForCreditLossMember2020-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AllowanceForCreditLossMember2018-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AllowanceForCreditLossMember2019-01-012019-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AllowanceForCreditLossMember2017-12-310000072741es:TheConnecticutLightAndPowerCompanyMemberus-gaap:AllowanceForCreditLossMember2018-01-012018-12-310000072741es:NstarElectricCompanyMemberus-gaap:AllowanceForCreditLossMember2019-12-310000072741es:NstarElectricCompanyMemberus-gaap:AllowanceForCreditLossMember2020-01-012020-12-310000072741es:NstarElectricCompanyMemberus-gaap:AllowanceForCreditLossMember2020-12-310000072741es:NstarElectricCompanyMemberus-gaap:AllowanceForCreditLossMember2018-12-310000072741es:NstarElectricCompanyMemberus-gaap:AllowanceForCreditLossMember2019-01-012019-12-310000072741es:NstarElectricCompanyMemberus-gaap:AllowanceForCreditLossMember2017-12-310000072741es:NstarElectricCompanyMemberus-gaap:AllowanceForCreditLossMember2018-01-012018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AllowanceForCreditLossMember2019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AllowanceForCreditLossMember2020-01-012020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AllowanceForCreditLossMember2020-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AllowanceForCreditLossMember2018-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AllowanceForCreditLossMember2019-01-012019-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AllowanceForCreditLossMember2017-12-310000072741es:PublicServiceCompanyOfNewHampshirePSNHMemberus-gaap:AllowanceForCreditLossMember2018-01-012018-12-31

			UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549
			FORM			10-K
☒			ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
			For the fiscal year ended			December 31, 2020
			or
☐			TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE      SECURITIES EXCHANGE ACT OF 1934
			For the transition period from ____________ to ____________

Registrant; State of Incorporation; Address; Telephone Number;

Commission File Number; and I.R.S. Employer Identification No.

EVERSOURCE ENERGY

(a Massachusetts voluntary association)

300 Cadwell Drive, Springfield, Massachusetts 01104

Telephone: (800) 286-5000

Commission File Number: 1-5324

I.R.S. Employer Identification No. 04-2147929

THE CONNECTICUT LIGHT AND POWER COMPANY

(a Connecticut corporation)

107 Selden Street, Berlin, Connecticut 06037-1616

Telephone: (800) 286-5000

Commission File Number: 0-00404

I.R.S. Employer Identification No. 06-0303850

NSTAR ELECTRIC COMPANY

(a Massachusetts corporation)

800 Boylston Street, Boston, Massachusetts 02199

Telephone: (800) 286-5000

Commission File Number: 1-02301

I.R.S. Employer Identification No. 04-1278810

PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE

(a New Hampshire corporation)

Energy Park

780 North Commercial Street, Manchester, New Hampshire 03101-1134

Telephone: (800) 286-5000

Commission File Number: 1-6392

I.R.S. Employer Identification No. 02-0181050

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading Symbol(s)

Name of each exchange on which registered

Common Shares, $5.00 par value per share

ES

New York Stock Exchange

Indicate by check mark if the registrants are well-known seasoned issuers, as defined in Rule 405 of the Securities Act.

			Yes			No
			☒			☐

Indicate by check mark if the registrants are not required to file reports pursuant to Section 13 or Section 15(d) of the Act.

			Yes			No
			☐			☒

Indicate by check mark whether the registrants (1) have filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrants were required to file such reports), and (2) have been subject to such filing requirements for the past 90 days.

			Yes			No
			☒			☐

Indicate by check mark whether the registrants have submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrants were required to submit such files).

			Yes			No
			☒			☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☒

Indicate by check mark whether the registrants are shell companies (as defined in Rule 12b-2 of the Act):

The aggregate market value of Eversource Energy's Common Shares, $5.00 par value, held by non-affiliates, computed by reference to the price at which the common equity was last sold, or the average bid and asked price of such common equity, as of the last business day of Eversource Energy's most recently completed second fiscal quarter (June 30, 2020) was $28,496,151,703 based on a closing market price of $83.27 per share for the 342,213,903 common shares outstanding held by non-affiliates on June 30, 2020. 

Indicate the number of shares outstanding of each of the registrant's classes of common stock, as of the latest practicable date:

Eversource Energy holds all of the 6,035,205 shares, 200 shares and 301 shares of the outstanding common stock of The Connecticut Light and Power Company, NSTAR Electric Company and Public Service Company of New Hampshire, respectively.

Documents Incorporated by Reference

Portions of the Eversource Energy and Subsidiaries 2019 combined Annual Report on Form 10-K and portions of the Proxy Statement relating to the Annual Meeting of Shareholders to be held on May 5, 2021, are incorporated by reference into Parts II and III of this Report.

NSTAR Electric Company and Public Service Company of New Hampshire each meet the conditions set forth in General Instruction I(1)(a) and (b) of Form 10-K, and each is therefore filing this Form 10-K with the reduced disclosure format specified in General Instruction I(2) of Form 10‑K.  

Eversource Energy, The Connecticut Light and Power Company, NSTAR Electric Company and Public Service Company of New Hampshire each separately file this combined Form 10-K.  Information contained herein relating to any individual registrant is filed by such registrant on its own behalf.  Each registrant makes no representation as to information relating to the other registrants.

EVERSOURCE ENERGY AND SUBSIDIARIES

THE CONNECTICUT LIGHT AND POWER COMPANY

NSTAR ELECTRIC COMPANY AND SUBSIDIARY

PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE AND SUBSIDIARIES

2020 FORM 10-K ANNUAL REPORT

TABLE OF CONTENTS

						Page
PART I
Item 1.			Business			2
Item 1A.			Risk Factors			16
Item 1B.			Unresolved Staff Comments			21
Item 2.			Properties			21
Item 3.			Legal Proceedings			24
Item 4.			Mine Safety Disclosures			24
PART II
Item 5.			Market for the Registrants’ Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities			24
Item 6.			Removed and Reserved			25
Item 7.			Management’s Discussion and Analysis of Financial Condition and Results of Operations			26
Item 7A.			Quantitative and Qualitative Disclosures about Market Risk			55
Item 8.			Financial Statements and Supplementary Data			56
Item 9.			Changes in and Disagreements with Accountants on Accounting and Financial Disclosure			138
Item 9A.			Controls and Procedures			138
Item 9B.			Other Information			138
PART III
Item 10.			Directors, Executive Officers and Corporate Governance			139
Item 11.			Executive Compensation			140
Item 12.			Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters			171
Item 13.			Certain Relationships and Related Transactions, and Director Independence			172
Item 14.			Principal Accountant Fees and Services			173
PART IV
Item 15.			Exhibits and Financial Statement Schedules			174
Item 16.			Form 10-K Summary			174
Signatures						E-9

EVERSOURCE ENERGY AND SUBSIDIARIES

THE CONNECTICUT LIGHT AND POWER COMPANY

NSTAR ELECTRIC COMPANY AND SUBSIDIARY

PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE AND SUBSIDIARIES

SAFE HARBOR STATEMENT UNDER THE PRIVATE SECURITIES

LITIGATION REFORM ACT OF 1995

References in this Annual Report on Form 10-K to "Eversource," the "Company," "we," "our," and "us" refer to Eversource Energy and its consolidated subsidiaries. CL&P, NSTAR Electric, and PSNH are each doing business as Eversource Energy.  

From time to time, we make statements concerning our expectations, beliefs, plans, objectives, goals, strategies, assumptions of future events, future financial performance or growth and other statements that are not historical facts.  These statements are "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995.  You can generally identify our forward-looking statements through the use of words or phrases such as "estimate," "expect," "anticipate," "intend," "plan," "project," "believe," "forecast," "should," "could," and other similar expressions.  Forward-looking statements are based on the current expectations, estimates, assumptions or projections of management and are not guarantees of future performance.  These expectations, estimates, assumptions or projections may vary materially from actual results. Accordingly, any such statements are qualified in their entirety by reference to, and are accompanied by, the following important factors that could cause our actual results to differ materially from those contained in our forward-looking statements, including, but not limited to:

•cyberattacks or breaches, including those resulting in the compromise of the confidentiality of our proprietary information and the personal information of our customers,

•disruptions in the capital markets or other events that make our access to necessary capital more difficult or costly,

•the negative impacts of the novel coronavirus (COVID-19) pandemic on our customers, vendors, employees, regulators, and operations,

•changes in economic conditions, including impact on interest rates, tax policies, and customer demand and payment ability,

•ability or inability to commence and complete our major strategic development projects and opportunities,

•acts of war or terrorism, physical attacks or grid disturbances that may damage and disrupt our electric transmission and electric, natural gas, and water distribution systems,

•actions or inaction of local, state and federal regulatory, public policy and taxing bodies,

•substandard performance of third-party suppliers and service providers,

•fluctuations in weather patterns, including extreme weather due to climate change,

•changes in business conditions, which could include disruptive technology or development of alternative energy sources related to our current or future business model,

•contamination of, or disruption in, our water supplies,

•changes in levels or timing of capital expenditures,

•changes in laws, regulations or regulatory policy, including compliance with environmental laws and regulations,

•changes in accounting standards and financial reporting regulations,

•actions of rating agencies, and

•other presently unknown or unforeseen factors.

Other risk factors are detailed in our reports filed with the SEC and updated as necessary, and we encourage you to consult such disclosures.

All such factors are difficult to predict and contain uncertainties that may materially affect our actual results, many of which are beyond our control.  You should not place undue reliance on the forward-looking statements, as each speaks only as of the date on which such statement is made, and, except as required by federal securities laws, we undertake no obligation to update any forward-looking statement or statements to reflect events or circumstances after the date on which such statement is made or to reflect the occurrence of unanticipated events.  New factors emerge from time to time and it is not possible for us to predict all of such factors, nor can we assess the impact of each such factor on the business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements. For more information, see Item 1A, Risk Factors, included in this combined Annual Report on Form 10-K. This Annual Report on Form 10-K also describes material contingencies and critical accounting policies in the accompanying Management's Discussion and Analysis of Financial Condition and Results of Operations and Combined Notes to Financial Statements.  We encourage you to review these items.  

EVERSOURCE ENERGY AND SUBSIDIARIES

THE CONNECTICUT LIGHT AND POWER COMPANY

NSTAR ELECTRIC COMPANY AND SUBSIDIARY

PUBLIC SERVICE COMPANY OF NEW HAMPSHIRE AND SUBSIDIARIES