【未來能源研究所】充電：美國公用事業(yè)規(guī)模的電力儲存狀況-2025.4

ChargingUp:TheState

ofUtility-ScaleElectricityStorageintheUnitedStates

MollyRobertson,OmidMirzapour,andKarenPalmer

Report25-09April2025

AbouttheAuthors

MollyRobertsonisanassociatefellowatResourcesfortheFuture(RFF)working

ontopicsrelatedtotheelectricpowersector,includinggriddecarbonization,

electrification,andelectricitymarketdesign.ShehasalsocontributedtoRFF’sgrowing

workonequitablecommunitytransitionandenvironmentaljustice.Sheholdsa

master’sinpublicpolicyfromtheUniversityofMichigan’sFordSchool.

OmidMirzapourisaPhDcandidateatDepartmentofElectricalandComputer

EngineeringatUniversityofUtah.Hisresearchfocusesontheefficientdeploymentofflexibletransmissiontechnologies.In2024asaninternatRFF,hefocusedongridscale

energystorageusesanddeployment.

KarenPalmerisaseniorfellowatRFFandanexpertontheeconomicsof

environmental,climateandpublicutilityregulationoftheelectricpowersector.Her

workseekstoimprovethedesignofenvironmentalandtechnologyregulationsinthe

sectorandthedevelopmentofnewinstitutionstohelpguidetheongoingtransition

oftheelectricitysector.Totheseends,sheexploresclimatepolicydesign,analyzes

efficientwaystopromoteuseofrenewableandothercleansourcesofelectricity,andinvestigatesnewmarketdesigns,newapproachestoelectricitypricingandregulatory

reformstopavethewayforlong-termdecarbonizationofelectricitysupplyand

electrificationoftheenergyeconomy.

Acknowledgements

ThisreportwasmadepossiblebythosewhogenerouslysupportRFF.WewouldliketothankBenjaminHobbs,JamesBushnell,JesseBuchsbaum,andMcKennaPeplinskifor

theirhelpfulcomments.Anyerrorsareourown.

ResourcesfortheFuturei

ChargingUp:TheStateofUtility-ScaleElectricityStorageintheUnitedStatesii

AboutRFF

ResourcesfortheFuture(RFF)isanindependent,nonprofitresearchinstitutionin

Washington,DC.Itsmissionistoimproveenvironmental,energy,andnaturalresourcedecisionsthroughimpartialeconomicresearchandpolicyengagement.RFFis

committedtobeingthemostwidelytrustedsourceofresearchinsightsandpolicysolutionsleadingtoahealthyenvironmentandathrivingeconomy.

TheviewsexpressedherearethoseoftheindividualauthorsandmaydifferfromthoseofotherRFFexperts,itsofficers,oritsdirectors.

SharingOurWork

OurworkisavailableforsharingandadaptationunderanAttribution-

NonCommercial-NoDerivatives4.0International(CCBY-NC-ND4.0)license.Youcancopyandredistributeourmaterialinanymediumorformat;youmustgive

appropriatecredit,providealinktothelicense,andindicateifchangesweremade,andyoumaynotapplyadditionalrestrictions.Youmaydosoinanyreasonable

manner,butnotinanywaythatsuggeststhelicensorendorsesyouoryouruse.Youmaynotusethematerialforcommercialpurposes.Ifyouremix,transform,orbuilduponthematerial,youmaynotdistributethemodifiedmaterial.Formoreinformation,visit

/licenses/by-nc-nd/4.0/

.

ResourcesfortheFutureiii

Abstract

Grid-scalestoragecanplayanimportantroleinprovidingreliableelectricitysupply,

particularlyonasystemwithincreasingvariableresourceslikewindandsolar.

Economics,publicpolicies,andmarketrulesallplayaroleinshapingthelandscapeforstoragedevelopment.Inthisreport,weofferanoverviewofthesefactors,drawingontherelevantliteratureandongoingpolicydialogue.WeexplorethepotentialrolethesefactorshaveplayedinshapingthegrowthofstorageacrosstheUnitedStates.

ChargingUp:TheStateofUtility-ScaleElectricityStorageintheUnitedStatesiv

Contents

1.Introduction1

2.TheRoleforEnergyStorageinthePowerSectorTodayandTomorrow1

2.1.CurrentUsesofEnergyStorage1

2.1.1.Arbitrage1

2.1.2.AncillaryServices3

2.1.3.CapacityandResourceAdequacy4

2.1.4.StorageasTransmission-OnlyAssets4

2.1.5.StorageinVerticallyIntegratedUtilities5

2.2.RoleofStorageinaHigh-RenewablesFuture6

2.3.PotentialforLong-DurationEnergyStorage9

3.PoliciesSupportingStorage10

4.CompetitiveMarketRulesforStorage14

4.1.Interconnection14

4.2.CompensationforResourceAdequacy15

4.3.BiddingRules18

4.4.StateofChargeRequirements20

5.EvidenceonStorageDeploymentintheUS22

5.1.RegionalVariationinGrowth22

5.2.StorageandVariableGeneration23

5.3.StorageCapacitybyProductClass24

5.4.DriversofAdoption27

6.Conclusions27

References29

ChargingUp:TheStateofUtility-ScaleElectricityStorageintheUnitedStates1

1.Introduction

Astheelectricitysectorreliesmoreonvariableenergysourceslikewindandsolar,grid-connectedenergystoragewillbecomeincreasinglyimportanttosupport

reliableelectricitysupply.Storagecantransferelectricitygeneratedduringhourswhenrenewableenergyisplentifultomeetdemandatothertimesoftheday.Grid-scalestoragespecificallycanalsoprovidekeygridservices,suchasreservepower,frequencyresponse,andflexibleramping,tosupportgridstability.

Astheneedsofthegridevolve,storagecanprovideeffectivesolutions,butitdoes

notalwaysfitneatlyintothemarketdesignsandoperatingpracticesintheelectricitysector.Itremainsunclearwhattypesofmarketdesignsandincentivesareneeded

toelicitoptimalstoragedeploymentwithoutoverprocuringstoragerelativetomoreefficientoptions.Thisreportreviewsdriversofgrid-scalestoragedeploymentintheUnitedStates,identifyingprogressandbarrierstoarobuststoragelandscape,withafocusontheeconomicsofandmarketsforstand-alonestoragetechnologies.WeprovideareviewinSection2ofwhattheliteraturehastosayaboutthepotential

economicvalueofstoragenowandunderdifferentfuturescenarios.InSection3,

wedescribepoliciesinplaceandunderdiscussionthatcouldhaveanimpacton

grid-scalestoragedeployment.Section4highlightsmarketstructuresandrulesthataffectstorageoperationsandincentives,andSection5discusseshowthesefactorscontributetothecurrenttrendsingrid-scalestoragedeploymentacrosstheUnitedStates.Section6concludes.

2.TheRoleforEnergyStorageinthePowerSectorTodayandTomorrow

Grid-scaleenergystoragehasbeengrowinginthepowersectorforoveradecade,

spurredbyvariablewholesaleenergyprices,technologydevelopments,andstate

andfederalpolicies.Inthissection,weidentifyseveraldifferentpotentialrolesfor

energystorageinthemoderngrid.Thenwediscusshowahigh-renewablesfuturemayexpandthevalueofenergystoragesolutions.

2.1.CurrentUsesofEnergyStorage

2.1.1.Arbitrage

Oneofthemainrolesforstorageinthepowersystemisenergypricearbitrage.Simplyput,batteriescanactasdemandwhenenergypricesarelowandassupplywhen

pricesarehigh,takingadvantageofpricefluctuations.Asanincreasingnumberoflow-marginal-costrenewablesparticipateinthemarket,arbitragecaneffectivelyextend

theavailabilityofthatlow-costenergyacrossmorehoursintheday.

ResourcesfortheFuture2

Differentmodelingeffortshaveattemptedtocapturethepotentialimpactofadding

energystoragetowholesaleenergymarketstoengageinarbitrage.Qinetal.(2023)

studytheimpactofshort-durationbatterystoragecapacityandmarketparticipationstrategyoncarbonemissions,generationcost,andconsumercosts.Theyfindthat

storageimpactonelectricitymarketsdependsonseveralfactors:renewableenergy

deployment,storagecapacity,andparticipationinreal-timeversusday-aheadmarkets.

Qinetal.considerdifferentmarketopportunitiesforstoragearbitrageinamodeloftheNewEnglandgrid.Themodelingestimatesthatstorageparticipationwilllowerelectricitypricesandemissions,particularlywithahighpenetrationofrenewables.

Electricitypricesdropthemostwhenstorageparticipatesinthereal-timemarket,whileemissionsdecreasethemostwhenstorageparticipatesintheday-ahead

market.However,Qinetal.alsofindthatastotalstoragecapacityincreasesfrom

1to5gigawatts(GW),themarginalpriceandemissionsimpactsdiminish.Figure1

showsthediminishingprofitsacrossdifferentmarketparticipationstrategies(real-time,day-ahead,anddualparticipation)asstoragecapacityincreases.Storage

profitsdiminishsignificantlyasstoragecapacityincreasesbecauseeachadditionalunitofstoragecapacityreducesthearbitrageopportunityforotherstorageowner/operators.Anygivenamountofstoragecapacityismoreprofitablewithahigherlevelofrenewablesinthesystem(seepanelC).Intheiranalysis,Qinetal.findthegreatestprofitopportunitiesinthereal-timemarket,inpartbecausetheyassumestorage

operatorsbidphysicalcostsandparametersintheday-aheadmarket,andbidto

maximizearbitrageprofitsinreal-time(usingday-aheadpriceforecasts).Underdualparticipation,storageoperatorsmayloseoutonreal-timepricevolatilitybecause

ofhowtheywerescheduleddayahead,particularlyiftheycan’tforeseereal-timearbitrageopportunities.

Figure1.StorageProfitUnderDifferentLevelsofWindPenetration

Source:Qinetal.(2023).

Note:Storageprofitunder(A)low(6.5GW),(B)medium(13GW),and(C)high(26GW)windpenetration.RT=participationinthereal-timemarketonly;DA=participationintheday-aheadmarketonly;DA+RT=dualparticipation.Theper-unitprofitsareperMWhofstoragecapacityperday.

ChargingUp:TheStateofUtility-ScaleElectricityStorageintheUnitedStates3

Overall,theopportunityforstoragetooperateasarbitragedependsonpricevolatility,whichmayincreasewiththepenetrationofrenewablesorhigh-costpeakingresources.Thereisalimitontheamountofstoragecapacitythatcanbeprofitable,particularlyifotherarbitrageprovidersareconsidered.Forexample,greaterdemandresponseandincreasedtransmissionbetweenregionscouldhelpstabilizepricesandlimitprofitsforadditionalenergystoragecapacity.Manypowersectorexpertsagreethattransmissioniscurrentlyunderbuilt(DOEGDO2023)andthatmanagedloadprograms,demand-

responseprograms,orvariable-pricingpoliciesthattakeadvantageoftheflexibility

ofthedemandsideoftheelectricitymarketareunderused.Ifpolicyeffortsto

expandtransmissionandactivedemand-sideparticipationinelectricitymarketsaresuccessful,profitablestorageopportunitiesmaybefewer.Forexample,intheNationalTransmissionPlanningStudy(DOEGDO2024),storagepenetrationvariednoticeablyacrossdifferenttransmissionexpansionscenarios.Thescenarioswiththegreatest

transmissionexpansionhadlessstorage(asapercentageoftotalcapacity)thanthescenarioswithmoderatetransmissionexpansion,reflectingthefactthatstorageandtransmissionmaybesubstitutesinsomecases(Biancardietal.2024;Bustosetal.

2018;Neetzowetal.2018).

2.1.2.AncillaryServices

Ancillaryservicesareaclassofproductsintendedtomaintainstableoperationofthegridratherthanserveelectricitydemanddirectly.Forexample,generatorsmaybe

paidtohelpmaintainaconsistentfrequencyonthegridthroughsmalladjustments

inoperationandtomakesurethesystemhassufficientresourcestoabsorbsudden

lossesoflargecomponents,suchasmajortransmissionlinesorlargegenerators.

Historically,theseserviceshavebeenprovidedbyfossilfuelgeneratorsbecauseof

theirabilitytoadjustoutputrelativelyquicklyondemand,butbatterieshavebecomeanincreasinglycompetitiveplayerinthesemarketsbecauseoftheirinstantaneous

rampingcapability.Someancillaryservices,suchasthefrequencyregulationjust

described,aredeployedonamuchshortertimeframe,secondtosecond,andtypicallyforsmall-megawatt(MW)quantities.Asaresult,storagedevicesdonotneedlong

durationstotakeadvantageofcertainancillaryservicemarkets.Asdiscussedin

Section5,ancillaryservicesmakeupamajorpartofthecurrentstoragerevenuestack.

Marketexpertshaveestimatedthatinsomemarkets,suchastheElectricReliabilityCouncilofTexas(ERCOT)andtheCaliforniaIndependentSystemOperator(CAISO),storageisnearlysaturatingtheancillaryservicemarkets,meaningsufficientcapacityisavailablethatprices,andcorrespondingrevenuesaredeclining(Vermillion2023b;AscendAnalytics2023).Forinstance,whenbatterystorageenteredtheCalifornia

market,itsmainrevenuesourcewasup-anddown-regulationservices.Sincethatmarketwassmall,onlyseveralhundredMWofeachofthoseproducts,themarketquicklybecamesaturatedasbatteriesexceeded10GWin2024(CAISO2024).Thepaceanddegreeofsaturationintherelevantancillaryservicemarketsdependongrowthofstoragecapacityandopportunitiesforarbitrageintheenergymarkets,whichmaydecreasetheamountofstoragecapacitysetasideforancillaryservices.

ResourcesfortheFuture4

Operatorsofstoragedevicesdonotnecessarilyexclusivelychargeatthelowest

energypriceswhentheysellinancillaryservicemarkets,andtheremaybesome

unanticipatedconsequences.Forexample,batteriesmayneedtobechargedduringarelativelyhigh-priceperiodintheenergymarkettomaintainstateofcharge

requirements(eeSection4.4)(MansfieldandKonet2023).Researchindicatesthat

untilthereissufficientrenewableenergyinthegenerationmix,batteryoperationin

ancillaryservicemarketsmayalsoleadtoanincreaseinemissionsduetospillover

effectsintheenergymarketsasfossilgeneratorsaltertheiroperationstomeet

battery-chargingneedsforenergy(Buchsbaumetal.2024;Ryanetal.2018;MansfieldandKonet2023).

2.1.3.CapacityandResourceAdequacy

Energystoragecanalsosupportresourceadequacybycountingtowardasystem’s

totalinstalledcapacity.Throughcapacitymarketsorotherresourceadequacy

constructs,storageprovidersarecompensatedfortheirpotentialtoprovideenergy

inthefuture,particularlywhentheexpectationisthatdemandwillbehighorsupplylow.Thetreatmentofstorageincapacitymarketsvariesbyregion(seeSection4.2),butgenerally,longer-durationstorageproviderscanreceivemorecompensationthantheirshort-durationcounterpartsbecausethestoragetheyprovideismorelikelyto

beavailablewhenneeded.Asvariablegenerationincreasesandenergypricesfall,

generatorsmayincreasinglyturntocapacitypaymentstocovertheirgoing-forwardcosts(LoPreteetal.2024).Generatorretirementscanalsoincreasecapacitypaymentopportunitiesfornewgenerators.Thesummer2024capacityauctioninthePJM

regionaltransmissionorganization(RTO)sawrecordhighpricesafteraseriesofgeneratorretirementsleftitwithdiminishedsupplyofcapacity(PJM2024).

Capacitypaymentscanalsoencouragetheexpansionofhybridresourceswhere

storageisco-locatedwithgenerationlikewindorsolarplants.Variableresourceshaverelativelylow-capacityvalueontheirown,becausetheyareintermittentandcan’t

alwaysprovideenergyondemand.Byaddingon-sitestorage,variablegeneratorscanextendtheiravailabilityandsecuregreatercapacitypayments(Stencliketal.2022).

Havingstorageonthesystemalsointroducesanewtypeofelectricitydemandthat

couldaffectsystem-widecapacityneeds.Unlikegenerators,storagealsoactsas

demandforelectricity,andthatsideofthestorageoperationneedstobeconsideredintheloadforecaststoensureresourceadequacy.Whilestorageengaginginarbitrageisunlikelytoconsumeelectricitywhenpricesarehigh,batteriesobligatedtoprovideancillaryservicescouldstillstrainthesystemattimesofhighenergydemand.

2.1.4.StorageasTransmission-OnlyAssets

Storagecanalsocontributetotransmissioncongestionreliefbyshiftingpeakdemandtooff-peaktimeperiodsatconstrainedlocationsonthegrid.Inmanymarkets,energystoragecanactinthiswayasatransmissionasset,remuneratedwitharegulatedrateinsteadofthroughsalesofamarketproduct.Aftera2016technicalconference,the

FederalEnergyRegulatoryCommission(FERC)releasedapolicystatementproviding

ChargingUp:TheStateofUtility-ScaleElectricityStorageintheUnitedStates5

guidelinesforthecost-basedregulatedpricingofstorageastransmission-onlyassets(SATOAs).FollowingthereleaseofFERC’spolicystatement,severalindependent

systemoperators(ISOs)andRTOssubmittedtheirSATOAintegrationproposalsto

FERC.SATOAiscurrentlyimplementedbytheMidcontinentIndependentSystem

Operator(MISO),theIndependentSystemOperatorofNewEngland(ISO-NE),andtheSouthwestPowerPool(SPP).TheNewYorkIndependentSystemOperator(NYISO)

andthePennsylvania-NewJersey-MarylandInterconnection(PJM)proposalsarestillunderdevelopment,andCAISOandERCOTdonotcurrentlysupportstorageasa

transmission-onlyassetdespiteongoingdiscussionshighlightingthevalueofsuchaservice.

InapresentationonconsideringstorageastransmissioninNYISO(Zoellmer2023),severalchallengesandconsiderationswereidentified:

?integratingenergystorageintransmission-planningprocesses,includinglocaltransmissionplanning,reliabilitystudies,economicstudies,andpublicpolicystudies

?evaluatingSATOAagainstothertransmissionsolutions,includinglinebuildoutanddeploymentofgrid-enhancingtechnologies,intermsofefficiency,cost-effectiveness,andidentificationofuniqueattributesofSATOA

?incorporatingSATOAintheinterconnectionprocess

?establishingcapacityanddurationrequirements,includingassetmodelingof

installedreservemarginandlocationalminimuminstalledcapacityrequirements

?definingownershiprequirementsandoperationandmaintenanceresponsibilities

?consideringpotentialuseincontingencymanagement

FERChaspubliclystatedthatstoragecouldbeusedasadual-useasset,actingas

bothatransmissionandagenerationresource,inaccordancewithestablishedrules(FERC2017).However,noderegulatedmarketcurrentlypermitsdualuse,although

Californiahasconsideredpossiblemechanismsfordoingso.Themainconcernsare

cross-subsidizationandadverseimpactsinthecompetitivemarketsandmanagementofthestateofchargeacrossthedifferentproductcategories.

2.1.5.StorageinVerticallyIntegratedUtilities

Verticallyintegratedutilitiesowngeneration,transmission,anddistributionsystemsintheirgeographicserviceterritories.Theseutilitiesreceiveafixedrateofreturn

oncapitalinvestments,asregulatedbytherelevantpublicutilitycommission,and

regulatorsapproveinvestmentsandcoststhatincludethisrateofreturnonthose

investmentsinsettingelectricityratesdesignedtorecoverthosecosts.Thisrate-

makingstructureofferssomepotentialbenefitstobatteriesandotherformsofgrid-scalestorage.Becauseasingleutilityownsthegridandgenerationinfrastructure,

storageassetsownedbyverticallyintegratedutilitiescanbeusedtosupportenergy,transmission,andgridservicesallatthesametime.Onechallengeforenergystorageproliferationinverticallyintegratedutilitiesisthelackofanhourlypricesignalina

competitivewholesaleenergymarket.Energyarbitrageopportunitiesbecomeclear

ResourcesfortheFuture6

whentherearelargeswingsinday-aheadandreal-timepricesthatstoragedevices

cancapitalizeon.Withoutthoselargeswings,verticallyintegratedutilitiesthatoperateoutsideoforganizedwholesalemarketsmaybeslowertoseethevalueoropportunityinbuildingnewstoragedevices.

Thereislimitedevidenceofgrowingstorageinvestmentbyverticallyintegrated

utilitiescomparedwithindependentpowerproviders.TheEIAreportsgenerationbyownershipclass,butwithlimiteddetail.Theinvestor-ownedutility(IOU)category

includesverticallyintegratedutilitiesbutmayalsoincludeutilitiesthatonlyown

transmissionanddistributionassets.In2023,investor-ownedutilitiesowned

approximately36percentofelectricitycapacitybutonly13percentofstorage

capacity.TheshareofIOUownedstoragecapacityisslightlylessthaninvestor-ownedutilityownershipofwind(19percent)andsolar(18percent)resources(EIA2023b).

Thiscomparisondoesnotperfectlyrepresenttheprevalenceofstorageinverticallyintegratedutilities,butwedonotobserveanypreferentialinvestmentinstorage

comparedwithotherzero-emissionsgenerationinthesedata.

2.2.RoleofStorageinaHigh-RenewablesFuture

Muchoftheassumedvalueofenergystorageacrosstheproductsandservices

discussedinSection2.1comesfromvariableprices,particularlyovertime.Asgrid

decarbonizationeffortscontinueandlow-costrenewablesproliferate,pricevariabilityisexpectedtogrow(Armstrongetal.2022).Therefore,weexpectthevalueofstoragetoincreasewiththeexpansionofvariableresourceslikewindandsolar.Figure2,fromMallapragadaetal.(2023),showstheimpactofimposing5gramsperkilowatthour(g/kWh;98.9percentcarbonreductionfrombaseline)and1g/kWh(99.8percentcarbonreductionfrombaseline)emissionsstandardsonthegenerationcapacitymixin2050.Astheresultsshow,morestringentcarbonconstraintscausealargeportionofnaturalgascapacitytobereplacedwithincreasedvariablegeneration(yellowandgreen),

energystorage(brown),andasmallshareofgaswithcarboncapture(orange).

ChargingUp:TheStateofUtility-ScaleElectricityStorageintheUnitedStates7

Figure2.AnnualGenerationUnderVariousLevelsofCarbonConstraints

Source:Mallapragadaetal.(2023).

Note:CCGT=combinedcyclegasturbine;OCGT=open-cyclegasturbine;PHS=pumpedhydrostorage;DistrPV=distributedphotovoltaic;NSE=non-servedenergy;CCGT_CCS=combinedcyclegasturbinewithcarboncaptureandsequestration.

Figure3showspotentialdistributionsofenergypricesinERCOT(whichareequivalent

tothemarginalvalueofenergy)historicallyandacrossdifferentemissionsand

flexibletechnologyscenarios.Theemissionslimitcasesrangefrom50gCO2/kWhto1gCO2/kWhin2050.Technologieswithineachemissionsscenarioincludedifferentcombinationsofexistingstoragetechnologies(includinglithiumionandpumped

hydrostorageinthebasecase),reduxflowbatteries,thermalstorage,andhydrogenelectrolysisatdifferentprices.Astheresultsshow,thesharesofhourswithverylow($0–$5/MWh)andveryhigh(>$200/MWh)pricesinthesystemincreaseascarbon

constraintstighten,withsomevariationdependingonavailabletechnologies.This

findingisthedirectresultofrenewablegenerationdominanceunderstringentcarbon

constraints.

ResourcesfortheFuture8

Figure3.PriceVariabilityinERCOTUnderDifferentEmissionsPoliciesandStorageEnvironments

Source:Mallapragadaetal.(2023).

Note:BC=basecase;RFB=reduxflowbatteries

Verylowpricesgenerallyindicaterenewablegenerationcurtailmentduringexcess-generationperiods,andveryhighpricesreflectrelianceonscarcitypricestoattractsuppliers.Themoderatepricesinbetween(teal-coloredbands)usuallyrepresent

marginalcosts,andtheshareofhourswherethosepricesprevailgrowst