The long duration electricity storage cap and floor is a proposed UK state support mechanism to encourage the development of more long duration energy storage (LDES) on the National Grid. This aims to support future investment in LDES project, such as pumped storage hydroelectricity, which have high up-front capital cost but lower operating costs. The "cap and floor" contracts would offer a top-up when wholesale market prices are below a set "floor", but projects would have to pay back excess profits above the cap. The mechanism would be funded through electricity consumer bill, but Ofgem expect the scheme to be broadly neutral over time on energy bills.
Building more LDES is expected to lower the overall costs of electricity systems, reducing both the need to curtail renewable generation when there is too much and to turn up expensive gas fire generation at times of high electricity demand. It can also provide flexibility and resilience, such as frequency stabilisation and black-start. The cost of limited storage was highlighted during the June 2026 heatwave, when, during a period of high demand and low generation, the National Energy System Operator had to buy imported electricity at £1379/MWh — around 15 times the typical rate on the day-ahead market.
As of 2026, the GB national grid has 2.8 GW of LDES, made up of four pumped storage hydro electric schemes, two in Wales and two in Scotland. As well as more pumped-storage, projects being considered include various forms of batteries and compressed air storage. The first of these projects are expected to start operating in the early 2030s.
Ofgem’s definition for LDES is being able to provide at least eight hours at full power, which is at least 100MW for established technologies (TRL9) in Stream 1 or 50MW for less established technologies in Stream 2 at TRL8. Ofgem clarified at the Energy Storage Summit in February 2026 that the scheme was not about developing new technologies, which should be done using other funding mechanisms.
A similar scheme has operated for electricity inter-connectors since 2014. According to the Government, no floor payments have been made within this, although revenues have been capped and profits shared with consumers.
History The UK Government launched a consultation on a policy framework to enable investment in long duration electricity storage. This ran from 9 January to 5 March 2024, with the government’s response in October that year.
In October 2024, Energy Minister Michael Shanks launched the Long Duration Electricity Storage investment support scheme.
In September 2025, Ofgem shortlisted 77 projects, from 171 applications. These projects were invited to submit detailed proposals for evaluation, although four projects withdrew.
In June 2026, this shortlist was reduced to 16 projects that the government are minded to support. The final list will be announced in the Autumn following a consultation that closes on 7 August.
Long duration storage projects In the tables below, capacity refers to the maximum output and duration the longest time at full output, however they are rarely operated like this. Technology abbreviations: pumped storage hydroelectricity (PSH), compressed air energy storage (CAES); Lithium-ion battery energy storage system (Li-ion BESS), Vanadium Flow/Zinc Battery (VFB/Zn).
Operational projects
NameTechnologyLocationCapacity (MW)Duration (h)CommissionedFfestiniogPSHN Wales36041963CruachanPSHW Scotland400221965FoyersPSHN Scotland300211974DinorwigPSHN Wales180051984
Proposed projects The UK Government announced in June 2026 they were minded to support the following top 16 projects ranked projects, with a total capacity of 7645 MW. This allows for some attrition, while staying within the recommended capacity range of 2.7–7.7 GW.
+List of projects "minded to support"NameTechnologyLocationCapacity (MW)Duration (h)Expected operationLoch Kemp StoragePSHN Scotland66022.32030Coire Glas power stationPSHN Scotland1440322033TeesCAESCAESNE England50302029Earba Storage ProjectPSHN Scotland1800152033Field NethertonLi-ion BESSN Scotland40016.32030Field New DeerLi-ion BESSN Scotland40018.032030Field RigifaLi-ion BESSN Scotland20018.032030Field FyrishLi-ion BESSN Scotland20016.52030Field Long StrattonLi-ion BESSE England40016.052033East Claydon StorageLi-ion BESSE England500122030Ocker Hill BESSLi-ion BESSW Midlands14582029Sundon StorageLi-ion BESSE England50082030Drakelow (Innova)Li-ion BESSW Midlands3858.72030Frontier LegacyVFB/ZnN Wales6582029SpringwellLi-ion BESSE Midlands40011.12030Thornton BESS 2Li-ion BESSE Midlands10011.112029
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