{"url_path":"/sec/cik-0000100122/10-k/2026/cover-page","section_key":"cover-page","section_title":"Cover Page","topic":"sec","document":{"doc_type":"10-K","doc_date":"2026-02-12","source_url":"https://www.sec.gov/Archives/edgar/data/100122/0000100122-26-000006-index.html","accession_number":"0000100122-26-000006","cik":"0000100122","ticker":null,"issuer_name":"TUCSON ELECTRIC POWER CO","edgar_url":"https://www.sec.gov/Archives/edgar/data/100122/0000100122-26-000006-index.html","primary_entity_key":"0000100122","primary_entity_name":"TUCSON ELECTRIC POWER CO"},"word_count":2882,"has_tables":true,"body_markdown":"tep-20251231\nfalse2025FY0000100122P3Yhttp://fasb.org/us-gaap/2025#OtherAssetsNoncurrenthttp://fasb.org/us-gaap/2025#OtherAssetsNoncurrenthttp://fasb.org/us-gaap/2025#OtherLiabilitiesCurrenthttp://fasb.org/us-gaap/2025#OtherLiabilitiesCurrenthttp://fasb.org/us-gaap/2025#OtherLiabilitiesNoncurrenthttp://fasb.org/us-gaap/2025#OtherLiabilitiesNoncurrentP3Yiso4217:USDxbrli:sharestep:customerutr:sqmitep:operatingSegmentxbrli:pureutr:MWutr:MWhtep:extension_optiontep:sustainability_targettep:plantep:defined_benefit_planutr:GWhutr:Btu00001001222025-01-012025-12-3100001001222025-06-3000001001222026-02-1100001001222024-01-012024-12-3100001001222023-01-012023-12-3100001001222024-12-3100001001222023-12-3100001001222022-12-3100001001222025-12-310000100122us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember2022-12-310000100122tep:CapitalStockExpenseMember2022-12-310000100122us-gaap:RetainedEarningsMember2022-12-310000100122us-gaap:AccumulatedOtherComprehensiveIncomeMember2022-12-310000100122us-gaap:RetainedEarningsMember2023-01-012023-12-310000100122us-gaap:AccumulatedOtherComprehensiveIncomeMember2023-01-012023-12-310000100122us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember2023-12-310000100122tep:CapitalStockExpenseMember2023-12-310000100122us-gaap:RetainedEarningsMember2023-12-310000100122us-gaap:AccumulatedOtherComprehensiveIncomeMember2023-12-310000100122us-gaap:RetainedEarningsMember2024-01-012024-12-310000100122us-gaap:AccumulatedOtherComprehensiveIncomeMember2024-01-012024-12-310000100122us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember2024-01-012024-12-310000100122us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember2024-12-310000100122tep:CapitalStockExpenseMember2024-12-310000100122us-gaap:RetainedEarningsMember2024-12-310000100122us-gaap:AccumulatedOtherComprehensiveIncomeMember2024-12-310000100122us-gaap:RetainedEarningsMember2025-01-012025-12-310000100122us-gaap:AccumulatedOtherComprehensiveIncomeMember2025-01-012025-12-310000100122us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember2025-01-012025-12-310000100122us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember2025-12-310000100122tep:CapitalStockExpenseMember2025-12-310000100122us-gaap:RetainedEarningsMember2025-12-310000100122us-gaap:AccumulatedOtherComprehensiveIncomeMember2025-12-310000100122tep:InvestmentsinOtherPropertyMember2025-12-310000100122tep:InvestmentsinOtherPropertyMember2024-12-310000100122tep:InvestmentsinOtherPropertyMember2023-12-310000100122us-gaap:OtherCurrentAssetsMember2025-12-310000100122us-gaap:OtherCurrentAssetsMember2024-12-310000100122us-gaap:OtherCurrentAssetsMember2023-12-310000100122srt:MinimumMembertep:CloudComputingMember2025-12-310000100122srt:MaximumMembertep:CloudComputingMember2025-12-310000100122srt:MinimumMember2025-01-012025-12-310000100122srt:MaximumMember2025-01-012025-12-310000100122tep:RoadrunnerReserveIMember2025-01-012025-12-310000100122tep:RetailRevenuesMembertep:ArizonaCorporationCommissionMember2025-06-012025-06-300000100122tep:NonFuelRetailRevenuesMembertep:ArizonaCorporationCommissionMember2025-06-012025-06-300000100122tep:FuelRelatedRetailRevenuesMembertep:ArizonaCorporationCommissionMember2025-06-012025-06-300000100122tep:RevenueFromContractWithCustomer1Membertep:ArizonaCorporationCommissionMember2025-06-012025-06-300000100122tep:ArizonaCorporationCommissionMember2025-06-300000100122tep:ArizonaCorporationCommissionMember2025-06-012025-06-300000100122tep:PurchasedPowerandFuelAdjustmentClauseMember2025-01-012025-12-310000100122tep:PurchasedPowerandFuelAdjustmentClauseMember2024-12-310000100122tep:PurchasedPowerandFuelAdjustmentClauseMember2023-12-310000100122tep:PurchasedPowerandFuelAdjustmentClauseMember2024-01-012024-12-310000100122tep:PurchasedPowerandFuelAdjustmentClauseMember2025-12-310000100122us-gaap:RenewableEnergyProgramMember2025-01-012025-12-310000100122us-gaap:RenewableEnergyProgramMember2024-05-012024-05-310000100122us-gaap:RenewableEnergyProgramMember2024-05-310000100122tep:Effective11202412312026Member2023-01-012023-12-310000100122tep:Effective11202412312026Membertep:EnergyEfficiencyStandardsMember2023-01-012023-12-310000100122tep:EnergyEfficiencyStandardsMember2022-12-310000100122tep:LostFixedCostRecoveryMechanismMember2025-01-012025-12-310000100122us-gaap:PensionAndOtherPostretirementPlansCostsMember2025-12-310000100122us-gaap:PensionAndOtherPostretirementPlansCostsMember2024-12-310000100122tep:EarlyGenerationRetirementCostsMember2025-12-310000100122tep:EarlyGenerationRetirementCostsMember2024-12-310000100122tep:LostFixedCostRecoveryMechanismMember2025-12-310000100122tep:LostFixedCostRecoveryMechanismMember2024-12-310000100122tep:PropertyTaxDeferralsMember2025-12-310000100122tep:PropertyTaxDeferralsMember2024-12-310000100122tep:TransmissionBalancingAccountsMember2025-12-310000100122tep:TransmissionBalancingAccountsMember2024-12-310000100122us-gaap:DerivativeMember2025-12-310000100122us-gaap:DerivativeMember2024-12-310000100122tep:RoadrunnerReserveIAccountingOrderMember2025-12-310000100122tep:RoadrunnerReserveIAccountingOrderMember2024-12-310000100122tep:SelfInsuredMedicalShortTermDisabilityMember2025-12-310000100122tep:SelfInsuredMedicalShortTermDisabilityMember2024-12-310000100122us-gaap:DeferredIncomeTaxChargesMember2025-12-310000100122us-gaap:DeferredIncomeTaxChargesMember2024-12-310000100122tep:FinalMineReclamationMember2025-12-310000100122tep:FinalMineReclamationMember2024-12-310000100122tep:UnamortizedLossOnReacquiredDebtMember2025-12-310000100122tep:UnamortizedLossOnReacquiredDebtMember2024-12-310000100122us-gaap:OtherRegulatoryAssetsLiabilitiesMember2025-12-310000100122us-gaap:OtherRegulatoryAssetsLiabilitiesMember2024-12-310000100122us-gaap:DeferredIncomeTaxChargesMember2025-12-310000100122us-gaap:DeferredIncomeTaxChargesMember2024-12-310000100122us-gaap:RenewableEnergyProgramMember2025-12-310000100122us-gaap:RenewableEnergyProgramMember2024-12-310000100122tep:DeferredInvestmentTaxCreditMember2025-12-310000100122tep:DeferredInvestmentTaxCreditMember2024-12-310000100122us-gaap:RemovalCostsMember2025-12-310000100122us-gaap:RemovalCostsMember2024-12-310000100122us-gaap:PensionAndOtherPostretirementPlansCostsMember2025-12-310000100122us-gaap:PensionAndOtherPostretirementPlansCostsMember2024-12-310000100122tep:OverRecoveredFuelAndPurchasedEnergyCostsMember2025-12-310000100122tep:OverRecoveredFuelAndPurchasedEnergyCostsMember2024-12-310000100122us-gaap:DerivativeMember2025-12-310000100122us-gaap:DerivativeMember2024-12-310000100122tep:DemandSideManagementMember2025-12-310000100122tep:DemandSideManagementMember2024-12-310000100122us-gaap:ElectricityGenerationPlantNonNuclearMember2025-01-012025-12-310000100122us-gaap:ElectricityGenerationPlantNonNuclearMember2025-12-310000100122us-gaap:ElectricityGenerationPlantNonNuclearMember2024-12-310000100122us-gaap:ElectricDistributionMember2025-01-012025-12-310000100122us-gaap:ElectricDistributionMember2025-12-310000100122us-gaap:ElectricDistributionMember2024-12-310000100122us-gaap:ElectricTransmissionMember2025-01-012025-12-310000100122us-gaap:ElectricTransmissionMember2025-12-310000100122us-gaap:ElectricTransmissionMember2024-12-310000100122tep:EnergyStorageMember2025-01-012025-12-310000100122tep:EnergyStorageMember2025-12-310000100122tep:EnergyStorageMember2024-12-310000100122tep:GeneralPlantMember2025-01-012025-12-310000100122tep:GeneralPlantMember2025-12-310000100122tep:GeneralPlantMember2024-12-310000100122us-gaap:ComputerSoftwareIntangibleAssetMember2025-12-310000100122us-gaap:ComputerSoftwareIntangibleAssetMember2024-12-310000100122tep:ElectricPlantHeldForFutureUseMember2025-12-310000100122tep:ElectricPlantHeldForFutureUseMember2024-12-310000100122srt:MinimumMembertep:ComputerSoftwareSmallerApplicationMember2025-12-310000100122srt:MaximumMembertep:ComputerSoftwareSmallerApplicationMember2025-12-310000100122tep:ComputerSoftwareLargeEnterpriseMember2025-12-310000100122us-gaap:ComputerSoftwareIntangibleAssetMember2025-01-012025-12-310000100122tep:RoadrunnerReserveIMember2025-07-310000100122tep:RoadrunnerReserveIMember2025-12-310000100122tep:FourCornersUnitsFourAndFiveMember2025-12-310000100122tep:LunaNettingMember2025-12-310000100122tep:GIlaRiverUnit3Member2025-12-310000100122tep:GilaRiverCommonFacilitiesMember2025-12-310000100122tep:SpringervilleCoalHandlingFacilitiesMember2025-12-310000100122tep:SpringervilleCommonFacilitiesMember2025-12-310000100122tep:TransmissionFacilitiesMember2025-12-310000100122us-gaap:RetailMember2025-01-012025-12-310000100122us-gaap:RetailMember2024-01-012024-12-310000100122us-gaap:RetailMember2023-01-012023-12-310000100122tep:WholesaleRevenueMember2025-01-012025-12-310000100122tep:WholesaleRevenueMember2024-01-012024-12-310000100122tep:WholesaleRevenueMember2023-01-012023-12-310000100122tep:OtherServicesMember2025-01-012025-12-310000100122tep:OtherServicesMember2024-01-012024-12-310000100122tep:OtherServicesMember2023-01-012023-12-310000100122us-gaap:RetailMemberus-gaap:BilledRevenuesMemberus-gaap:TradeAccountsReceivableMember2025-12-310000100122us-gaap:RetailMemberus-gaap:BilledRevenuesMemberus-gaap:TradeAccountsReceivableMember2024-12-310000100122us-gaap:RetailMemberus-gaap:UnbilledRevenuesMemberus-gaap:TradeAccountsReceivableMember2025-12-310000100122us-gaap:RetailMemberus-gaap:UnbilledRevenuesMemberus-gaap:TradeAccountsReceivableMember2024-12-310000100122us-gaap:RetailMemberus-gaap:TradeAccountsReceivableMember2025-12-310000100122us-gaap:RetailMemberus-gaap:TradeAccountsReceivableMember2024-12-310000100122tep:WholesaleMemberus-gaap:TradeAccountsReceivableMember2025-12-310000100122tep:WholesaleMemberus-gaap:TradeAccountsReceivableMember2024-12-310000100122tep:DueFromAffiliatesMember2025-12-310000100122tep:DueFromAffiliatesMember2024-12-310000100122tep:OtherReceivableMember2025-12-310000100122tep:OtherReceivableMember2024-12-310000100122tep:WholesaleMemberus-gaap:DerivativeMember2025-12-310000100122tep:WholesaleMemberus-gaap:DerivativeMember2024-12-310000100122tep:UnsElectricMemberus-gaap:RelatedPartyMember2025-12-310000100122tep:UnsElectricMemberus-gaap:RelatedPartyMember2024-12-310000100122tep:UnsGasMemberus-gaap:RelatedPartyMember2025-12-310000100122tep:UnsGasMemberus-gaap:RelatedPartyMember2024-12-310000100122tep:UnsEnergyMemberus-gaap:RelatedPartyMember2025-12-310000100122tep:UnsEnergyMemberus-gaap:RelatedPartyMember2024-12-310000100122us-gaap:RelatedPartyMember2025-12-310000100122us-gaap:RelatedPartyMember2024-12-310000100122tep:TEPtoUNSEnergyAffiliatesMemberus-gaap:RelatedPartyMember2025-01-012025-12-310000100122tep:TEPtoUNSEnergyAffiliatesMemberus-gaap:RelatedPartyMember2024-01-012024-12-310000100122tep:TEPtoUNSEnergyAffiliatesMemberus-gaap:RelatedPartyMember2023-01-012023-12-310000100122tep:TransmissionSalesToUNSElectricMemberus-gaap:RelatedPartyMember2025-01-012025-12-310000100122tep:TransmissionSalesToUNSElectricMemberus-gaap:RelatedPartyMember2024-01-012024-12-310000100122tep:TransmissionSalesToUNSElectricMemberus-gaap:RelatedPartyMember2023-01-012023-12-310000100122tep:WholesaleRevenuesUNSElectricMemberus-gaap:RelatedPartyMember2025-01-012025-12-310000100122tep:WholesaleRevenuesUNSElectricMemberus-gaap:RelatedPartyMember2024-01-012024-12-310000100122tep:WholesaleRevenuesUNSElectricMemberus-gaap:RelatedPartyMember2023-01-012023-12-310000100122tep:TucsonElectricPowerCompanyToUnsElectricMemberus-gaap:RelatedPartyMember2025-01-012025-12-310000100122tep:TucsonElectricPowerCompanyToUnsElectricMemberus-gaap:RelatedPartyMember2024-01-012024-12-310000100122tep:TucsonElectricPowerCompanyToUnsElectricMemberus-gaap:RelatedPartyMember2023-01-012023-12-310000100122tep:UNSEnergytoTEPMemberus-gaap:RelatedPartyMember2025-01-012025-12-310000100122tep:UNSEnergytoTEPMemberus-gaap:RelatedPartyMember2024-01-012024-12-310000100122tep:UNSEnergytoTEPMemberus-gaap:RelatedPartyMember2023-01-012023-12-310000100122tep:PurchasedPowerUNSElectricMemberus-gaap:RelatedPartyMember2025-01-012025-12-310000100122tep:PurchasedPowerUNSElectricMemberus-gaap:RelatedPartyMember2024-01-012024-12-310000100122tep:PurchasedPowerUNSElectricMemberus-gaap:RelatedPartyMember2023-01-012023-12-310000100122tep:UNSEnergyAffiliatestoTEPMemberus-gaap:RelatedPartyMember2025-01-012025-12-310000100122tep:UNSEnergyAffiliatestoTEPMemberus-gaap:RelatedPartyMember2024-01-012024-12-310000100122tep:UNSEnergyAffiliatestoTEPMemberus-gaap:RelatedPartyMember2023-01-012023-12-310000100122tep:UNSGastoTEPMemberus-gaap:RelatedPartyMember2025-01-012025-12-310000100122tep:UNSGastoTEPMemberus-gaap:RelatedPartyMember2024-01-012024-12-310000100122tep:UNSGastoTEPMemberus-gaap:RelatedPartyMember2023-01-012023-12-310000100122tep:OnePointFiveZeroPercentSeniorNotesDue2030Memberus-gaap:UnsecuredDebtMember2025-12-310000100122tep:OnePointFiveZeroPercentSeniorNotesDue2030Memberus-gaap:UnsecuredDebtMember2024-12-310000100122tep:ThreePointTwoFivePercentSeniorNotesDue2032Memberus-gaap:UnsecuredDebtMember2025-12-310000100122tep:ThreePointTwoFivePercentSeniorNotesDue2032Memberus-gaap:UnsecuredDebtMember2024-12-310000100122tep:FivePointTwoZeroSeniorNotesDue2034Memberus-gaap:UnsecuredDebtMember2025-12-310000100122tep:FivePointTwoZeroSeniorNotesDue2034Memberus-gaap:UnsecuredDebtMember2024-12-310000100122tep:FivePointZeroZeroPercentSeniorNotesDue2044Memberus-gaap:UnsecuredDebtMember2025-12-310000100122tep:FivePointZeroZeroPercentSeniorNotesDue2044Memberus-gaap:UnsecuredDebtMember2024-12-310000100122tep:FourPointEightFivePercentSeniorNotesDue2048Memberus-gaap:UnsecuredDebtMember2025-12-310000100122tep:FourPointEightFivePercentSeniorNotesDue2048Memberus-gaap:UnsecuredDebtMember2024-12-310000100122tep:FourPointZeroZeroPercentSeniorNotesDue2050Memberus-gaap:UnsecuredDebtMember2025-12-310000100122tep:FourPointZeroZeroPercentSeniorNotesDue2050Memberus-gaap:UnsecuredDebtMember2024-12-310000100122tep:ThreePointTwoFivePercentSeniorNotesDue2051Memberus-gaap:UnsecuredDebtMember2025-12-310000100122tep:ThreePointTwoFivePercentSeniorNotesDue2051Memberus-gaap:UnsecuredDebtMember2024-12-310000100122tep:FivePointFiveZeroPercentSeniorUnsecuredNotesDueApril2053Memberus-gaap:UnsecuredDebtMember2025-12-310000100122tep:FivePointFiveZeroPercentSeniorUnsecuredNotesDueApril2053Memberus-gaap:UnsecuredDebtMember2024-12-310000100122tep:FivePointNineZeroPercentSeniorUnsecuredNotesDue2055Memberus-gaap:UnsecuredDebtMember2025-12-310000100122tep:FivePointNineZeroPercentSeniorUnsecuredNotesDue2055Memberus-gaap:UnsecuredDebtMember2024-12-310000100122tep:FivePointNineZeroPercentSeniorUnsecuredNotesDue2055Memberus-gaap:UnsecuredDebtMember2025-02-280000100122tep:FivePointNineZeroPercentSeniorUnsecuredNotesDue2055Memberus-gaap:UnsecuredDebtMember2025-02-012025-02-280000100122tep:FivePointTwoZeroSeniorNotesDue2034Memberus-gaap:UnsecuredDebtMember2024-08-310000100122tep:FivePointTwoZeroSeniorNotesDue2034Memberus-gaap:UnsecuredDebtMember2024-08-012024-08-310000100122tep:ThreePointZeroFivePercentSeniorNotesDue2025Memberus-gaap:UnsecuredDebtMember2024-12-012024-12-310000100122tep:ThreePointZeroFivePercentSeniorNotesDue2025Memberus-gaap:UnsecuredDebtMember2024-12-310000100122us-gaap:RevolvingCreditFacilityMemberus-gaap:LineOfCreditMembertep:A2021AgreementMember2025-10-310000100122us-gaap:RevolvingCreditFacilityMemberus-gaap:LineOfCreditMembertep:A2021AgreementMember2025-10-012025-10-310000100122us-gaap:RevolvingCreditFacilityMemberus-gaap:LineOfCreditMembertep:A2021AgreementMember2025-12-310000100122tep:SubLimitSwinglineMemberus-gaap:LineOfCreditMembertep:A2021AgreementMember2025-12-310000100122us-gaap:LetterOfCreditMemberus-gaap:LineOfCreditMembertep:A2021AgreementMember2025-12-310000100122us-gaap:RevolvingCreditFacilityMemberus-gaap:LineOfCreditMemberus-gaap:BaseRateMembertep:A2021AgreementMember2025-01-012025-12-310000100122us-gaap:RevolvingCreditFacilityMemberus-gaap:LineOfCreditMemberus-gaap:SecuredOvernightFinancingRateSofrMembertep:A2021AgreementMember2025-01-012025-12-310000100122us-gaap:RevolvingCreditFacilityMemberus-gaap:LineOfCreditMembertep:A2021AgreementMember2024-12-310000100122tep:SubLimitSwinglineMemberus-gaap:LineOfCreditMembertep:A2021AgreementMember2024-12-310000100122us-gaap:LetterOfCreditMemberus-gaap:LineOfCreditMembertep:A2021AgreementMember2024-12-310000100122us-gaap:RevolvingCreditFacilityMemberus-gaap:LineOfCreditMemberus-gaap:BaseRateMembertep:A2021AgreementMember2024-01-012024-12-310000100122us-gaap:RevolvingCreditFacilityMemberus-gaap:LineOfCreditMemberus-gaap:SecuredOvernightFinancingRateSofrMembertep:A2021AgreementMember2024-01-012024-12-310000100122us-gaap:LetterOfCreditMemberus-gaap:LineOfCreditMembertep:A2021AgreementMembertep:IssuedBetweenOctober2024AndMay2025Member2025-12-310000100122us-gaap:LetterOfCreditMemberus-gaap:LineOfCreditMembertep:A2021AgreementMember2025-10-012025-10-310000100122us-gaap:RevolvingCreditFacilityMemberus-gaap:LineOfCreditMembertep:A2021AgreementMember2025-01-012025-12-310000100122srt:FuelMember2025-12-310000100122tep:TransmissionFacilitiesMember2025-12-310000100122tep:RenewablePPAsAndOtherCommerciallyOperableMember2025-12-310000100122tep:RenewablePPAsAndOtherNonCommerciallyOperableMember2025-12-310000100122tep:RESPerformanceBasedIncentivesMinimumCommitmentMember2025-12-310000100122tep:TransmissionFacilitiesMemberus-gaap:SubsequentEventMember2026-02-080000100122tep:RenewableEnergyPowerPurchaseAgreementMember2025-12-310000100122tep:RoadrunnerReserveIIMemberus-gaap:CapitalAdditionsMember2024-08-012024-08-310000100122tep:RoadrunnerReserveIIMemberus-gaap:CapitalAdditionsMember2025-01-012025-12-310000100122tep:RoadrunnerReserveIIMemberus-gaap:CapitalAdditionsMember2024-08-310000100122tep:RoadrunnerReserveIIMemberus-gaap:CapitalAdditionsMember2025-12-310000100122tep:RoadrunnerReserveIIMemberus-gaap:CapitalAdditionsMember2024-12-310000100122tep:FourCornersMember2024-12-310000100122tep:FourCornersMember2025-12-310000100122tep:SanJuanMember2025-12-310000100122tep:SanJuanMember2024-12-310000100122tep:LunaNettingMemberus-gaap:PerformanceGuaranteeMember2025-12-310000100122tep:FourCornersMemberus-gaap:PerformanceGuaranteeMember2025-12-310000100122us-gaap:PerformanceGuaranteeMember2025-12-310000100122us-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2024-12-310000100122us-gaap:PensionPlansDefinedBenefitMember2023-12-310000100122us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2023-12-310000100122us-gaap:PensionPlansDefinedBenefitMember2025-01-012025-12-310000100122us-gaap:PensionPlansDefinedBenefitMember2024-01-012024-12-310000100122us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-01-012025-12-310000100122us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2024-01-012024-12-310000100122us-gaap:PensionPlansDefinedBenefitMember2023-01-012023-12-310000100122us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2023-01-012023-12-310000100122us-gaap:PensionPlansDefinedBenefitMembertep:RegulatoryAssetMember2025-01-012025-12-310000100122us-gaap:PensionPlansDefinedBenefitMembertep:RegulatoryAssetMember2024-01-012024-12-310000100122us-gaap:PensionPlansDefinedBenefitMembertep:RegulatoryAssetMember2023-01-012023-12-310000100122us-gaap:PensionPlansDefinedBenefitMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2025-01-012025-12-310000100122us-gaap:PensionPlansDefinedBenefitMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2024-01-012024-12-310000100122us-gaap:PensionPlansDefinedBenefitMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2023-01-012023-12-310000100122us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembertep:RegulatoryAssetLiabilityMember2025-01-012025-12-310000100122us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembertep:RegulatoryAssetLiabilityMember2024-01-012024-12-310000100122us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembertep:RegulatoryAssetLiabilityMember2023-01-012023-12-310000100122srt:MinimumMember2025-12-310000100122srt:MaximumMember2025-12-310000100122tep:ServicecostMemberus-gaap:PensionPlansDefinedBenefitMember2025-01-012025-12-310000100122tep:ServicecostMemberus-gaap:PensionPlansDefinedBenefitMember2024-01-012024-12-310000100122tep:ServicecostMemberus-gaap:PensionPlansDefinedBenefitMember2023-01-012023-12-310000100122tep:ServicecostMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-01-012025-12-310000100122tep:ServicecostMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2024-01-012024-12-310000100122tep:ServicecostMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2023-01-012023-12-310000100122tep:InterestCostMemberMemberus-gaap:PensionPlansDefinedBenefitMember2025-01-012025-12-310000100122tep:InterestCostMemberMemberus-gaap:PensionPlansDefinedBenefitMember2024-01-012024-12-310000100122tep:InterestCostMemberMemberus-gaap:PensionPlansDefinedBenefitMember2023-01-012023-12-310000100122tep:InterestCostMemberMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-01-012025-12-310000100122tep:InterestCostMemberMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2024-01-012024-12-310000100122tep:InterestCostMemberMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2023-01-012023-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2024-12-310000100122us-gaap:FixedIncomeSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:FixedIncomeSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:FixedIncomeSecuritiesMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122us-gaap:FixedIncomeSecuritiesMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2024-12-310000100122us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2024-12-310000100122us-gaap:OtherInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:OtherInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:OtherInvestmentsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122us-gaap:OtherInvestmentsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2024-12-310000100122tep:FairValueInputsLevel1AndLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122tep:FairValueInputsLevel1AndLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FixedIncomeFundsMember2025-12-310000100122tep:FairValueInputsLevel1AndLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMember2025-12-310000100122tep:FairValueInputsLevel1AndLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2024-12-310000100122tep:FairValueInputsLevel1AndLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FixedIncomeFundsMember2024-12-310000100122tep:FairValueInputsLevel1AndLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesMember2024-12-310000100122tep:FairValueInputsLevel1AndLevel2Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembertep:CashAndShortTermInvestmentsMember2024-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2025-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2025-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2025-12-310000100122us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMember2025-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMember2025-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMember2025-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsSmallCapMember2025-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsSmallCapMember2025-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsSmallCapMember2025-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesUsSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2025-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2025-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2025-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMembertep:DefinedBenefitPlanEquitySecuritiesGlobalMember2025-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMembertep:DefinedBenefitPlanEquitySecuritiesGlobalMember2025-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMembertep:DefinedBenefitPlanEquitySecuritiesGlobalMember2025-12-310000100122tep:DefinedBenefitPlanEquitySecuritiesGlobalMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:FixedIncomeSecuritiesMember2025-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:FixedIncomeSecuritiesMember2025-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:FixedIncomeSecuritiesMember2025-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMember2025-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMember2025-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMember2025-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMember2025-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMember2025-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMember2025-12-310000100122us-gaap:PrivateEquityFundsMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2024-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2024-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanCashAndCashEquivalentsMember2024-12-310000100122us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMember2024-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMember2024-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMember2024-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsSmallCapMember2024-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsSmallCapMember2024-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsSmallCapMember2024-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesUsSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2024-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2024-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMember2024-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesNonUsMemberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMembertep:DefinedBenefitPlanEquitySecuritiesGlobalMember2024-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMembertep:DefinedBenefitPlanEquitySecuritiesGlobalMember2024-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMembertep:DefinedBenefitPlanEquitySecuritiesGlobalMember2024-12-310000100122tep:DefinedBenefitPlanEquitySecuritiesGlobalMemberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:FixedIncomeSecuritiesMember2024-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:FixedIncomeSecuritiesMember2024-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:FixedIncomeSecuritiesMember2024-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMember2024-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMember2024-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:DefinedBenefitPlanRealEstateMember2024-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMember2024-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMember2024-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberus-gaap:PrivateEquityFundsMember2024-12-310000100122us-gaap:PrivateEquityFundsMemberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2024-12-310000100122us-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2025-01-012025-12-310000100122us-gaap:PrivateEquityFundsMemberus-gaap:FairValueInputsLevel3Member2023-12-310000100122us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel3Member2023-12-310000100122us-gaap:FairValueInputsLevel3Member2023-12-310000100122us-gaap:PrivateEquityFundsMemberus-gaap:FairValueInputsLevel3Member2024-01-012024-12-310000100122us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel3Member2024-01-012024-12-310000100122us-gaap:FairValueInputsLevel3Member2024-01-012024-12-310000100122us-gaap:PrivateEquityFundsMemberus-gaap:FairValueInputsLevel3Member2024-12-310000100122us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel3Member2024-12-310000100122us-gaap:FairValueInputsLevel3Member2024-12-310000100122us-gaap:PrivateEquityFundsMemberus-gaap:FairValueInputsLevel3Member2025-01-012025-12-310000100122us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel3Member2025-01-012025-12-310000100122us-gaap:FairValueInputsLevel3Member2025-01-012025-12-310000100122us-gaap:PrivateEquityFundsMemberus-gaap:FairValueInputsLevel3Member2025-12-310000100122us-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel3Member2025-12-310000100122us-gaap:FairValueInputsLevel3Member2025-12-310000100122us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesUsMidCapMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesUsMidCapMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122us-gaap:DefinedBenefitPlanEquitySecuritiesUsSmallCapMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122tep:DefinedBenefitPlanEquitySecuritiesNonUSDevelopedMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122tep:DefinedBenefitPlanEquitySecuritiesNonUSDevelopedMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122tep:DefinedBenefitPlanEquitySecuritiesNonUSEmergingMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122tep:DefinedBenefitPlanEquitySecuritiesNonUSEmergingMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122tep:DefinedBenefitPlanEquitySecuritiesGlobalMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122tep:DefinedBenefitPlanEquitySecuritiesGlobalInfrastructureMemberus-gaap:PensionPlansDefinedBenefitMember2025-12-310000100122tep:DefinedBenefitPlanEquitySecuritiesGlobalInfrastructureMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122us-gaap:PrivateEquityFundsMemberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2025-12-310000100122tep:A2024FortisShareUnitPlanMember2025-01-012025-12-310000100122tep:A2024FortisShareUnitPlanMemberus-gaap:PerformanceSharesMember2025-01-012025-12-310000100122tep:A2024FortisShareUnitPlanMemberus-gaap:PerformanceSharesMember2024-01-012024-12-310000100122tep:A2024FortisShareUnitPlanMemberus-gaap:RestrictedStockUnitsRSUMember2025-01-012025-12-310000100122tep:A2024FortisShareUnitPlanMemberus-gaap:RestrictedStockUnitsRSUMember2024-01-012024-12-310000100122tep:A2024FortisShareUnitPlanMember2025-12-310000100122tep:A2024FortisShareUnitPlanMember2024-12-310000100122tep:A2024FortisShareUnitPlanMember2024-01-012024-12-310000100122tep:A2020FORTISRESTRICTEDSTOCKUNITPLANMember2025-01-012025-12-310000100122tep:A2020FORTISRESTRICTEDSTOCKUNITPLANMemberus-gaap:RestrictedStockUnitsRSUMember2025-01-012025-12-310000100122tep:A2020FORTISRESTRICTEDSTOCKUNITPLANMemberus-gaap:RestrictedStockUnitsRSUMember2024-01-012024-12-310000100122tep:A2020FORTISRESTRICTEDSTOCKUNITPLANMemberus-gaap:RestrictedStockUnitsRSUMember2023-01-012023-12-310000100122tep:A2020FORTISRESTRICTEDSTOCKUNITPLANMember2025-12-310000100122tep:A2020FORTISRESTRICTEDSTOCKUNITPLANMember2024-12-310000100122tep:A2020FORTISRESTRICTEDSTOCKUNITPLANMember2024-01-012024-12-310000100122tep:A2020FORTISRESTRICTEDSTOCKUNITPLANMember2023-01-012023-12-310000100122tep:A2015ShareUnitPlanMember2025-01-012025-12-310000100122tep:A2015ShareUnitPlanMemberus-gaap:PerformanceSharesMember2025-01-012025-12-310000100122tep:A2015ShareUnitPlanMemberus-gaap:PerformanceSharesMember2024-01-012024-12-310000100122tep:A2015ShareUnitPlanMemberus-gaap:PerformanceSharesMember2023-01-012023-12-310000100122tep:A2015ShareUnitPlanMemberus-gaap:RestrictedStockUnitsRSUMember2025-01-012025-12-310000100122tep:A2015ShareUnitPlanMemberus-gaap:RestrictedStockUnitsRSUMember2024-01-012024-12-310000100122tep:A2015ShareUnitPlanMemberus-gaap:RestrictedStockUnitsRSUMember2023-01-012023-12-310000100122tep:A2015ShareUnitPlanMember2025-12-310000100122tep:A2015ShareUnitPlanMember2024-12-310000100122tep:A2015ShareUnitPlanMember2024-01-012024-12-310000100122tep:A2015ShareUnitPlanMember2023-01-012023-12-310000100122tep:RoadrunnerReserveIMember2025-12-012025-12-310000100122stpr:NM2025-01-012025-12-310000100122stpr:NM2024-01-012024-12-310000100122stpr:NM2023-01-012023-12-310000100122us-gaap:FairValueInputsLevel1Member2025-12-310000100122us-gaap:FairValueInputsLevel2Member2025-12-310000100122us-gaap:FairValueInputsLevel1Member2024-12-310000100122us-gaap:FairValueInputsLevel2Member2024-12-310000100122us-gaap:EnergyRelatedDerivativeMember2025-12-310000100122us-gaap:EnergyRelatedDerivativeMember2024-12-310000100122us-gaap:EnergyRelatedDerivativeMemberus-gaap:NondesignatedMember2025-01-012025-12-310000100122us-gaap:EnergyRelatedDerivativeMemberus-gaap:NondesignatedMember2024-01-012024-12-310000100122us-gaap:EnergyRelatedDerivativeMemberus-gaap:NondesignatedMember2023-01-012023-12-310000100122tep:PowerContractsMember2025-01-012025-12-310000100122tep:PowerContractsMember2024-01-012024-12-310000100122tep:GasContractsMember2025-01-012025-12-310000100122tep:GasContractsMember2024-01-012024-12-310000100122us-gaap:CarryingReportedAmountFairValueDisclosureMemberus-gaap:FairValueInputsLevel2Member2025-12-310000100122us-gaap:CarryingReportedAmountFairValueDisclosureMemberus-gaap:FairValueInputsLevel2Member2024-12-310000100122us-gaap:EstimateOfFairValueFairValueDisclosureMemberus-gaap:FairValueInputsLevel2Member2025-12-310000100122us-gaap:EstimateOfFairValueFairValueDisclosureMemberus-gaap:FairValueInputsLevel2Member2024-12-310000100122us-gaap:StateAndLocalJurisdictionMember2025-12-310000100122us-gaap:DomesticCountryMember2025-12-310000100122tep:RoadrunnerReserveIMember2025-07-012025-07-310000100122tep:OtherIncomeTaxCreditMember2025-12-310000100122tep:OtherIncomeTaxCreditMember2024-12-31\n\nUNITED STATES\n\nSECURITIES AND EXCHANGE COMMISSION\n\nWashington, D.C. 20549\n\nFORM 10-K\n\n(Mark One)\n\n☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934\n\nFor the fiscal year ended December 31, 2025\n\nOR\n\n☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934\n\nFor the transition period from                    to                    . \n\nCommission File Number 1-5924\n\nTUCSON ELECTRIC POWER COMPANY\n\n(Exact name of registrant as specified in its charter)\n\nArizona86-0062700\n\n(State or other jurisdiction of incorporation or organization)(I.R.S. Employer Identification No.)\n\n88 East Broadway Boulevard, Tucson, AZ 85701\n\n(Address of principal executive offices) (Zip Code)\n\nRegistrant's telephone number, including area code: (520) 571-4000\n\nSecurities registered pursuant to Section 12(b) of the Exchange Act: None\n\nSecurities registered pursuant to Section 12(g) of the Exchange Act: Common Stock, No Par Value (Title of Class)\n\nIndicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes x No o\n\nIndicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes o No x\n\nIndicate by check mark whether the registrant (1) has 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 registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes x No o\n\nIndicate by check mark whether the registrant has 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 registrant was required to submit such files). Yes x No o\n\nIndicate 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.\n\nLarge Accelerated Filer ☐\n\nAccelerated Filer ☐\n\nNon-Accelerated Filer x\n\nSmaller Reporting Company ☐\n\nEmerging Growth Company ☐\n\nIf 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. o\n\nIndicate 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.o \n\nIf securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. o\n\nIndicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b). o\n\nIndicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No x\n\nState the aggregate market value of the voting and non-voting common equity 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 the registrant’s most recently completed second fiscal quarter: None\n\nAs of February 11, 2026, Tucson Electric Power Company had 32,139,434 shares of common stock, no par value, outstanding, all of which were held by UNS Energy Corporation, an indirect wholly-owned subsidiary of Fortis Inc.\n\nDocuments incorporated by reference: None\n\nTucson Electric Power Company meets the conditions set forth in General Instruction I(1)(a) and (b) of Form 10-K and is, therefore, filing portions of this Form 10-K with the reduced disclosure format specified in General Instruction I(2) of Form 10-K.\n\nii\n\nTable of Contents\n\n[Definitions](#iaa4bfb93949147c689d89e1563a40f0a_10)\n\n[v](#iaa4bfb93949147c689d89e1563a40f0a_10)\n\n[Forward-Looking Information](#iaa4bfb93949147c689d89e1563a40f0a_13)\n\n[viii](#iaa4bfb93949147c689d89e1563a40f0a_13)\n\nPART I\n\n[Item 1. Business](#iaa4bfb93949147c689d89e1563a40f0a_19)\n\n[1](#iaa4bfb93949147c689d89e1563a40f0a_19)\n\n[Overview of Business](#iaa4bfb93949147c689d89e1563a40f0a_22)\n\n[1](#iaa4bfb93949147c689d89e1563a40f0a_22)\n\n[Environmental Matters](#iaa4bfb93949147c689d89e1563a40f0a_28)\n\n[9](#iaa4bfb93949147c689d89e1563a40f0a_28)\n\n[Human Capital](#iaa4bfb93949147c689d89e1563a40f0a_31)\n\n[9](#iaa4bfb93949147c689d89e1563a40f0a_31)\n\n[Information about our Executive Officers](#iaa4bfb93949147c689d89e1563a40f0a_34)\n\n[11](#iaa4bfb93949147c689d89e1563a40f0a_34)\n\n[SEC Reports Available](#iaa4bfb93949147c689d89e1563a40f0a_40)\n\n[11](#iaa4bfb93949147c689d89e1563a40f0a_40)\n\n[Item 1A. Risk Factors](#iaa4bfb93949147c689d89e1563a40f0a_43)\n\n[11](#iaa4bfb93949147c689d89e1563a40f0a_43)\n\n[Item 1B. Unresolved Staff Comments](#iaa4bfb93949147c689d89e1563a40f0a_49)\n\n[17](#iaa4bfb93949147c689d89e1563a40f0a_49)\n\n[Item 1C. Cybersecurity](#iaa4bfb93949147c689d89e1563a40f0a_52)\n\n[17](#iaa4bfb93949147c689d89e1563a40f0a_52)\n\n[Item 2. Properties](#iaa4bfb93949147c689d89e1563a40f0a_58)\n\n[18](#iaa4bfb93949147c689d89e1563a40f0a_58)\n\n[Item 3. Legal Proceedings](#iaa4bfb93949147c689d89e1563a40f0a_64)\n\n[19](#iaa4bfb93949147c689d89e1563a40f0a_64)\n\n[Item 4. Mine Safety Disclosures](#iaa4bfb93949147c689d89e1563a40f0a_67)\n\n[19](#iaa4bfb93949147c689d89e1563a40f0a_67)\n\nPART II\n\n[Item 5. Market for Registrant's Common Equity, Related Stockholder Matters, and Issuer Purchases of Equity Securities](#iaa4bfb93949147c689d89e1563a40f0a_73)\n\n[20](#iaa4bfb93949147c689d89e1563a40f0a_73)\n\n[Item 6. [Reserved]](#iaa4bfb93949147c689d89e1563a40f0a_76)\n\n[20](#iaa4bfb93949147c689d89e1563a40f0a_76)\n\n[Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations](#iaa4bfb93949147c689d89e1563a40f0a_79)\n\n[21](#iaa4bfb93949147c689d89e1563a40f0a_79)\n\n[Critical Accounting Estimates](#iaa4bfb93949147c689d89e1563a40f0a_112)\n\n[35](#iaa4bfb93949147c689d89e1563a40f0a_112)\n\n[New Accounting Standards Issued and Adopted or Not Yet Adopted](#iaa4bfb93949147c689d89e1563a40f0a_118)\n\n[38](#iaa4bfb93949147c689d89e1563a40f0a_118)\n\n[Item 7A. Quantitative and Qualitative Disclosures about Market Risk](#iaa4bfb93949147c689d89e1563a40f0a_121)\n\n[39](#iaa4bfb93949147c689d89e1563a40f0a_121)\n\n[Item 8. Consolidated Financial Statements and Supplementary Data](#iaa4bfb93949147c689d89e1563a40f0a_124)\n\n[41](#iaa4bfb93949147c689d89e1563a40f0a_124)\n\n[Report of Independent Registered Public Accounting Firm](#iaa4bfb93949147c689d89e1563a40f0a_127)\n\n[41](#iaa4bfb93949147c689d89e1563a40f0a_127)\n\n[Consolidated Statements of Income](#iaa4bfb93949147c689d89e1563a40f0a_130)\n\n[43](#iaa4bfb93949147c689d89e1563a40f0a_130)\n\n[Consolidated Statements of Cash Flows](#iaa4bfb93949147c689d89e1563a40f0a_136)\n\n[44](#iaa4bfb93949147c689d89e1563a40f0a_136)\n\n[Consolidated Balance Sheets](#iaa4bfb93949147c689d89e1563a40f0a_139)\n\n[45](#iaa4bfb93949147c689d89e1563a40f0a_139)\n\n[Consolidated Statements of Changes in Stockholder's Equity](#iaa4bfb93949147c689d89e1563a40f0a_142)\n\n[47](#iaa4bfb93949147c689d89e1563a40f0a_142)\n\n[Notes to Consolidated Financial Statements](#iaa4bfb93949147c689d89e1563a40f0a_145)\n\n[48](#iaa4bfb93949147c689d89e1563a40f0a_145)\n\n[Note 1. Nature of Operations and Summary of Significant Accounting Policies](#iaa4bfb93949147c689d89e1563a40f0a_148)\n\n[48](#iaa4bfb93949147c689d89e1563a40f0a_148)\n\n[Note 2. Regulatory Matters](#iaa4bfb93949147c689d89e1563a40f0a_154)\n\n[55](#iaa4bfb93949147c689d89e1563a40f0a_154)\n\n[Note](#iaa4bfb93949147c689d89e1563a40f0a_163)[3](#iaa4bfb93949147c689d89e1563a40f0a_163)[. Utility Plant and Jointly-Owned Facilities](#iaa4bfb93949147c689d89e1563a40f0a_163)\n\n[59](#iaa4bfb93949147c689d89e1563a40f0a_163)\n\n[Note](#iaa4bfb93949147c689d89e1563a40f0a_169)[4](#iaa4bfb93949147c689d89e1563a40f0a_169)[. Revenue](#iaa4bfb93949147c689d89e1563a40f0a_169)\n\n[60](#iaa4bfb93949147c689d89e1563a40f0a_169)\n\n[Note](#iaa4bfb93949147c689d89e1563a40f0a_172)[5](#iaa4bfb93949147c689d89e1563a40f0a_172)[. Accounts Receivable](#iaa4bfb93949147c689d89e1563a40f0a_172)\n\n[62](#iaa4bfb93949147c689d89e1563a40f0a_172)\n\n[Note](#iaa4bfb93949147c689d89e1563a40f0a_178)[6](#iaa4bfb93949147c689d89e1563a40f0a_178)[. Related Party Transactions](#iaa4bfb93949147c689d89e1563a40f0a_178)\n\n[62](#iaa4bfb93949147c689d89e1563a40f0a_178)\n\n[Note](#iaa4bfb93949147c689d89e1563a40f0a_184)[7](#iaa4bfb93949147c689d89e1563a40f0a_184)[. Debt and Credit Agreement](#iaa4bfb93949147c689d89e1563a40f0a_184)\n\n[64](#iaa4bfb93949147c689d89e1563a40f0a_184)\n\n[Note](#iaa4bfb93949147c689d89e1563a40f0a_190)[8](#iaa4bfb93949147c689d89e1563a40f0a_190)[. Commitments and Contingencies](#iaa4bfb93949147c689d89e1563a40f0a_190)\n\n[65](#iaa4bfb93949147c689d89e1563a40f0a_190)\n\n[Note](#iaa4bfb93949147c689d89e1563a40f0a_196)[9](#iaa4bfb93949147c689d89e1563a40f0a_196)[. Employee Benefits Plans](#iaa4bfb93949147c689d89e1563a40f0a_196)\n\n[67](#iaa4bfb93949147c689d89e1563a40f0a_196)\n\n[Note 1](#iaa4bfb93949147c689d89e1563a40f0a_202)[0](#iaa4bfb93949147c689d89e1563a40f0a_202)[. Share-Based Compensation](#iaa4bfb93949147c689d89e1563a40f0a_202)\n\n[73](#iaa4bfb93949147c689d89e1563a40f0a_202)\n\n[Note 1](#iaa4bfb93949147c689d89e1563a40f0a_208)[1](#iaa4bfb93949147c689d89e1563a40f0a_208)[. Supplemental Cash Flow Information](#iaa4bfb93949147c689d89e1563a40f0a_208)\n\n[75](#iaa4bfb93949147c689d89e1563a40f0a_208)\n\n[Note 1](#iaa4bfb93949147c689d89e1563a40f0a_211)[2](#iaa4bfb93949147c689d89e1563a40f0a_211)[. Fair Value Measurements and Derivative Instruments](#iaa4bfb93949147c689d89e1563a40f0a_211)\n\n[76](#iaa4bfb93949147c689d89e1563a40f0a_211)\n\n[Note 1](#iaa4bfb93949147c689d89e1563a40f0a_214)[3](#iaa4bfb93949147c689d89e1563a40f0a_214)[. Income Taxes](#iaa4bfb93949147c689d89e1563a40f0a_214)\n\n[79](#iaa4bfb93949147c689d89e1563a40f0a_214)\n\n[Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure](#iaa4bfb93949147c689d89e1563a40f0a_223)\n\n[81](#iaa4bfb93949147c689d89e1563a40f0a_223)\n\n[Item 9A. Controls and Procedures](#iaa4bfb93949147c689d89e1563a40f0a_226)\n\n[81](#iaa4bfb93949147c689d89e1563a40f0a_226)\n\niii\n\n[Item 9B. Other Information](#iaa4bfb93949147c689d89e1563a40f0a_229)\n\n[81](#iaa4bfb93949147c689d89e1563a40f0a_229)\n\n[Item 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspections](#iaa4bfb93949147c689d89e1563a40f0a_232)\n\n[81](#iaa4bfb93949147c689d89e1563a40f0a_229)\n\nPART III\n\n[Item 10. Directors, Executive Officers, and Corporate Governance](#iaa4bfb93949147c689d89e1563a40f0a_235)\n\n[82](#iaa4bfb93949147c689d89e1563a40f0a_235)\n\n[Item 11. Executive Compensation](#iaa4bfb93949147c689d89e1563a40f0a_238)\n\n[82](#iaa4bfb93949147c689d89e1563a40f0a_238)\n\n[Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters](#iaa4bfb93949147c689d89e1563a40f0a_241)\n\n[82](#iaa4bfb93949147c689d89e1563a40f0a_241)\n\n[Item 13. Certain Relationships and Related Transactions and Director Independence](#iaa4bfb93949147c689d89e1563a40f0a_244)\n\n[82](#iaa4bfb93949147c689d89e1563a40f0a_244)\n\n[Item 14. Principal Accountant Fees and Services](#iaa4bfb93949147c689d89e1563a40f0a_247)\n\n[82](#iaa4bfb93949147c689d89e1563a40f0a_247)\n\nPART IV\n\n[Item 15. Exhibits and Financial Statement Schedules](#iaa4bfb93949147c689d89e1563a40f0a_253)\n\n[84](#iaa4bfb93949147c689d89e1563a40f0a_253)\n\n[Item 16. Form 10-K Summary](#iaa4bfb93949147c689d89e1563a40f0a_256)\n\n[84](#iaa4bfb93949147c689d89e1563a40f0a_256)\n\n[Exhibits](#iaa4bfb93949147c689d89e1563a40f0a_259)\n\n[85](#iaa4bfb93949147c689d89e1563a40f0a_259)\n\n[Signatures](#iaa4bfb93949147c689d89e1563a40f0a_262)\n\n[87](#iaa4bfb93949147c689d89e1563a40f0a_262)\n\niv\n\n[Table of Contents](#iaa4bfb93949147c689d89e1563a40f0a_7)\n\nDEFINITIONS\n\nThe abbreviations and acronyms used in the 2025 Form 10-K are defined below:\n\nINDUSTRY ACRONYMS AND CERTAIN DEFINITIONS\n\n2020 IRPTEP's 2020 Integrated Resource Plan\n\n2021 Credit AgreementThe unsecured 2021 Credit Agreement, as amended in June 2023 and extended in October 2025, provides for $250 million of revolving credit commitments with swingline and LOC sublimits of $15 million and $50 million, respectively, and a maturity date of October 2028\n\n2022 Final FERC Rate OrderOrder issued by the FERC in 2022 approving the settlement agreement filed in conjunction with TEP's 2019 transmission rate case\n\n2023 IRPTEP's 2023 Integrated Resource Plan which outlines TEP's aspirational goal to reach net zero direct greenhouse gas emissions by 2050\n\n2023 Rate OrderOrder issued by the ACC resulting in a new rate structure for TEP, effective on September 1, 2023\n\n2025 Rate CaseTEP's June 2025 general rate case filed with the ACC based on a test year ended December 31, 2024\n\nABRAlternate Base Rate\n\nACCArizona Corporation Commission\n\nADEQArizona Department of Environmental Quality\n\nADJSOFR Rate Spread Adjustment\n\nAFUDCAllowance for Funds Used During Construction\n\nAIArtificial Intelligence\n\nAOCIAccumulated Other Comprehensive Income\n\nAOCLAccumulated Other Comprehensive Loss\n\nARAMAnnual Rate Adjustment Mechanism\n\nAROAsset Retirement Obligation\n\nASCAccounting Standards Codification\n\nASRFPAll-Source Request for Proposal\n\nBESSBattery Energy Storage System\n\nBRGBusiness Resource Group\n\nCCRCoal Combustion Residuals\n\nCCRMUCCR Management Units\n\nCCSCarbon Capture and Sequestration\n\nCEMCustomer Energy Management\n\nCISSPCertified Information Systems Security Professional\n\nCO2\nCarbon Dioxide\n\nCODMChief Operating Decision Maker\n\nCOVID-19Coronavirus Disease 2019\n\nCustomer RatesRates designed to allow a regulated utility recovery of its costs of providing services and an opportunity to earn a reasonable return on its investment\n\nDGDistributed Generation\n\nDSMDemand Side Management\n\nECAEnvironmental Compliance Adjustor\n\nEDITExcess Deferred Income Taxes\n\nEE StandardsEnergy Efficiency Standards\n\nEGUsElectric Generating Units\n\nEIMEnergy Imbalance Market\n\nEPAEnvironmental Protection Agency\n\nEPCEngineering, Procurement, and Construction\n\nv\n\n[Table of Contents](#iaa4bfb93949147c689d89e1563a40f0a_7)\n\nERMEnterprise Risk Management\n\nESAEnergy Supply Agreement\n\nFASBFinancial Accounting Standards Board\n\nFERCFederal Energy Regulatory Commission\n\nFIPFederal Implementation Plan\n\nGAAPGenerally Accepted Accounting Principles in the United States of America\n\nGHGGreenhouse Gas\n\nGICSPGlobal Industrial Cyber Security Professional\n\nIBEWInternational Brotherhood of Electrical Workers Local No. 1116\n\nIRAInflation Reduction Act of 2022, signed into law on August 16, 2022\n\nIRSInternal Revenue Service\n\nITCInvestment Tax Credit\n\nLFCRLost Fixed Cost Recovery\n\nLIRALimited Income Rate Adjustment\n\nLOCLetter(s) of Credit\n\nMarkets+Southwest Power Pool Markets+\n\nNAAQSNational Ambient Air Quality Standard\n\nNERCNorth American Electric Reliability Corporation\n\nNOx\nNitrogen Oxide\n\nNOPRNotice of Proposed Rulemaking\n\nOATTOpen Access Transmission Tariff\n\nOBBBAOne Big Beautiful Bill Act, signed into law on July 4, 2025\n\nPBIPerformance Based Incentives\n\nPPAPower Purchase Agreement\n\nPPFACPurchased Power and Fuel Adjustment Clause\n\nPSUPerformance Based Share Units\n\nPTC\nProduction Tax Credit\n\nPVPhotovoltaic\n\nRECRenewable Energy Credit\n\nRESRenewable Energy Standard\n\nRMCRisk Management Committee\n\nRSURestricted Share Units\n\nSERPSupplemental Executive Retirement Plan\n\nSIPState Implementation Plan\n\nSO2\nSulfur Dioxide\n\nSOFRSecured Overnight Financing Rate\n\nSRBSystem Resource Benefit\n\nTCATransmission Cost Adjustor\n\nTEAMTax Expense Adjustor Mechanism\n\nVEBAVoluntary Employee Beneficiary Association\n\nVIEVariable Interest Entity\n\nENTITIES AND GENERATING STATIONS\n\nAPSArizona Public Service Company\n\nFortisFortis Inc., a corporation incorporated under the Corporations Act of Newfoundland and Labrador, Canada, whose principal executive offices are located at Fortis Place, Suite 1100, 5 Springdale Street, St. John's, NL A1E 0E4\n\nFortisUSFortis intermediate holding company\n\nvi\n\n[Table of Contents](#iaa4bfb93949147c689d89e1563a40f0a_7)\n\nFour CornersFour Corners Power Plant\n\nGila RiverGila River Generating Station\n\nLunaLuna Generating Station\n\nNavajoNavajo Generating Station\n\nOso GrandeA 250 MW nominal capacity wind-powered electric generation facility, located in southeastern New Mexico\n\nPNMPublic Service Company of New Mexico\n\nRoadrunner Reserve IA standalone battery energy storage system facility with a nominal capacity rating of 200 MW and energy capacity of 800 MWh, located in southeast Tucson\n\nRoadrunner Reserve IIA standalone battery energy storage system facility with a nominal capacity rating of 200 MW and energy capacity of 800 MWh, located in southeast Tucson, expected to be placed in service in 2026\n\nSan JuanSan Juan Generating Station\n\nSpringervilleSpringerville Generating Station\n\nSpringerville Common FacilitiesPortion of the facilities at Springerville used in common with Springerville Units 1-4.\n\nSRPSalt River Project Agricultural Improvement and Power District\n\nSundtH. Wilson Sundt Generating Station\n\nTEPTucson Electric Power Company, the principal subsidiary of UNS Energy Corporation\n\nTri-StateTri-State Generation and Transmission Association, Inc.\n\nUASTPUniversity of Arizona Science and Technology Park\n\nUNS ElectricUNS Electric, Inc., an indirect wholly-owned subsidiary of UNS Energy Corporation\n\nUNS EnergyUNS Energy Corporation, the parent company of TEP, whose principal executive offices are located at 88 East Broadway Boulevard, Tucson, Arizona 85701\n\nUNS Energy AffiliatesAffiliated subsidiaries of UNS Energy Corporation including UniSource Energy Services, Inc., UNS Electric, Inc., UNS Gas, Inc., and Millennium Energy Holdings, Inc.\n\nUNS GasUNS Gas, Inc., an indirect wholly-owned subsidiary of UNS Energy Corporation\n\nWilmot IIWilmot Energy Center II\n\nWinchesterWinchester Solar I, LLC\n\nUNITS OF MEASURE\n\nACAlternating Current\n\nBBtuBillion British thermal unit(s)\n\nGWhGigawatt-hour(s)\n\nkWhKilowatt-hour(s)\n\nkVKilovolt\n\nMMBtuMillion Metric British thermal units\n\nMWMegawatt(s)\n\nMWhMegawatt-hour(s)\n\nvii\n\n[Table of Contents](#iaa4bfb93949147c689d89e1563a40f0a_7)\n\nFORWARD-LOOKING INFORMATION\n\nThis Annual Report on Form 10-K contains forward-looking statements as defined by the Private Securities Litigation Reform Act of 1995. TEP, or the Company, is including the following cautionary statements to make applicable and take advantage of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 for any forward-looking statements made by TEP in this Annual Report on Form 10-K. Forward-looking statements include statements concerning plans, objectives, goals, strategies, future events, future economic conditions, future operational or financial performance and underlying assumptions, and other statements that are not statements of historical facts. Forward-looking statements may be identified by the use of words or phrases that include \"anticipates,\" \"believes,\" \"estimates,\" \"expects,\" \"intends,\" \"continues,\" \"assumes,\" \"aspires,\" \"may,\" \"plans,\" \"predicts,\" \"projects,\" \"would,\" \"could,\" \"forecast,\" \"target,\" \"goal,\" \"potential,\" \"commitment,\" \"strategy,\" \"will,\" and similar expressions. From time to time, we may publish or otherwise make available forward-looking statements of this nature. All such forward-looking statements, whether written or oral, and whether made by or on behalf of TEP, are expressly qualified by these cautionary statements and any other cautionary statements which may accompany such forward-looking statements. In addition, TEP disclaims any obligation to update any forward-looking statements to reflect events or circumstances after the date of this report, except as may otherwise be required by the federal securities laws.\n\nForward-looking statements involve risks and uncertainties which could cause actual results or outcomes to differ materially from those expressed herein. We express our estimates, expectations, beliefs, aspirations, and projections in good faith and believe them to have a reasonable basis. However, we make no assurances that management’s estimates, expectations, beliefs, aspirations, or projections will be achieved or accomplished. We have identified the following important factors that could cause actual results to differ materially from those discussed in our forward-looking statements. These may be in addition to other factors and matters discussed in: Part I, Item 1A. Risk Factors; Part II, Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations; and other parts of this report. These factors include: voter initiatives and federal, state, and local regulatory and legislative decisions and actions, including changes in tax, tariff, and energy policies (including, among other things, data center energy use, efficiency standards, and sources of power), as they may be affected by the policies and priorities of governmental officials at the federal, state, and local levels; any change in the structure of utility service in Arizona resulting from the ACC or state legislature's examination of the state's energy policies or the City of Tucson's study of municipalization; changes in, and compliance with, environmental laws and regulatory decisions and policies that could increase operating and capital costs, reduce generation facility output, or accelerate generation facility retirements; unfavorable rulings, penalties, or findings by the FERC; regional economic and market conditions that could affect customer growth and electricity usage; potential changes in the benefits of participation in the Western Energy Imbalance Market and Markets+; changes in electricity consumption by retail customers; risks related to climate change, including shifts in weather seasonality, extreme weather events, and their increasing frequency and severity, and wildfires, affecting electricity usage of our customers, operational performance, and operating and capital costs to ensure system reliability; our forecasts of peak demand and whether existing generation capacity and PPAs are sufficient to meet the demand plus reserve margin requirements; our ability to implement successfully our business strategies, including any impediments to implementing such strategies arising from state or local opposition, and meet the growing demand for electricity, particularly in view of potential for new large customer requirements; the ability and willingness of our large customer counterparties, including counterparties to data center ESAs, to satisfy their financial and performance commitments; the cost of debt and equity capital and access to capital markets and bank markets during extended periods of volatility, which may affect our ability to raise additional capital and to use the proceeds from any capital that we do raise as originally intended; the performance of the stock market and changes in interest rates, which affect the value of our pension and other postretirement benefit plan assets and related contribution requirements and expenses; our ability to manage timelines and budgets and to access necessary materials and labor, in each case, related to capital projects, including EPC agreements to develop standalone BESS, and/or to obtain the anticipated performance or other benefits of such capital projects; the potential inability to make additions to our existing high voltage transmission system; unexpected increases in operations and maintenance expense, including increases due to inflationary pressures, tariffs, international trade policy, heightened geopolitical instability, and/or global supply chain challenges; resolution of pending litigation matters; changes in accounting standards; changes in our critical accounting estimates; the ongoing impact of mandated energy efficiency and DG initiatives and the potential repeal of such mandates; our ability to meet our aspirational goal related to reducing carbon emissions by 2050 due to load growth required by potential new large customers, and the potential impact on our financial condition; our ability to exit all ownership interests in coal-fired generation by 2032; changes to long-term contracts; the cost of fuel and power supplies; fluctuations or increases in commodity prices; the ability to obtain coal or natural gas from our suppliers; the timing and cost of generation facility decommissioning and mine reclamation activities; cyber-attacks, data breaches, or other cyberspace attacks to our information security and our operations and technology infrastructure, including attacks that may arise from heightened geopolitical instability or due to the evolution of AI or otherwise, as well as additional exposure to data breaches, algorithmic bias and legal liability resulting from the implementation of AI into our business operations; physical attacks to our electric generation, transmission, and distribution assets; the performance of generation facilities, including renewable generation resources; the extent of the impact of a global health or other crisis on our business and operations, and any economic and/or societal disruptions resulting therefrom and from\n\nviii\n\n[Table of Contents](#iaa4bfb93949147c689d89e1563a40f0a_7)\n\nthe government actions taken in response thereto; the implementation of our 2023 IRP; and our ability to obtain ACC approval of a formula rate plan with acceptable terms in response to our 2025 Rate Case.\n\nix\n\n[Table of Contents](#iaa4bfb93949147c689d89e1563a40f0a_7)\n\nPART I"}