- The UK government has allocated £28m to technologies capable of discharging electricity for at least 100 continuous hours.
- An initial £3m battery competition will fund development studies, with at least £10m earmarked for demonstrators from 2027.
- The programme addresses a genuine gap between short-duration batteries and seasonal storage, but it is innovation funding rather than a commitment to deploy commercial capacity.
The UK government has launched a £28m programme to develop batteries and underground hydrogen systems capable of storing renewable energy for more than four days, as policymakers seek alternatives to gas-fired generation during prolonged periods of low wind and solar output.
The Ultra-Long Duration Energy Storage Challenge, administered through UK Research and Innovation, will support electrochemical storage technologies and systems that store hydrogen underground for later use.
A qualifying battery system must be capable of supplying the electricity grid for at least 100 continuous hours and operating for at least 25 years. The 100-hour requirement is a duration threshold, however, not a commitment to install enough capacity to power the entire country for four days.
Energy minister Michael Shanks said: “Homegrown clean energy is our route to more affordable bills and energy security and storing it for when we need it most is critical.”
Ministers estimate that underground hydrogen storage could reduce total energy system costs by between £14bn and £50bn over 2035-50, although the assumptions and allocation of funding between the hydrogen and battery strands were not detailed in the government announcement.
Funding targets project development
The money immediately available is considerably smaller than the £28m headline. Innovate UK has opened a £3m first-phase competition for battery project development studies, offering individual grants of between £350,000 and £700,000.
Successful applicants must examine technology performance, engineering design, costs, manufacturing, supply chains and the practical route to a UK demonstration site. Projects must run for between three and nine months.
A second competition, expected in mid-2027, has been allocated at least £10m for large-scale demonstrators. The government wants at least two demonstrators operating by 2030, according to the competition documentation. Details of how the balance of the £28m will be distributed have not yet been published.
The technical hurdle is formidable. Innovate UK cites modelling suggesting that electrochemical ultra-long-duration storage would need an installed cost of about $15/kWh and an annual financial return exceeding 6% to compete with gas-fired reserve. The agency acknowledges that existing technologies are neither mature nor cost-competitive on that basis.
The initiative complements, rather than replaces, the cap-and-floor regime being developed for established long-duration technologies. Ofgem has provisionally selected 16 projects using pumped hydro, compressed air, lithium-ion and vanadium-flow batteries for support. Those projects meet an eight-hour definition of long-duration storage, compared with the challenge’s 100-hour requirement.
Britain currently has 2.8 GW of long-duration capacity across four pumped-hydro plants, according to Ofgem.
Eight-hour storage can move renewable electricity from one part of the day to another. Storage lasting 100 hours could cover multi-day weather systems, reducing the need to maintain large volumes of rarely used gas capacity. Hydrogen may ultimately address even longer seasonal gaps, albeit with lower round-trip efficiency.
UK Energy Research Centre co-director Jamie Speirs said flexibility across hours, days and seasons would help reduce curtailment and strengthen security of supply. Its underlying assessment nevertheless identified unresolved commercial, technical and system-integration barriers, reinforcing the point that the new money is intended to create options rather than purchase firm capacity.
For developers, the immediate opportunity lies in paid project development and building credible demonstration pipelines. The larger test will come after 2027: whether government can connect successful technologies to bankable revenue arrangements and turn relatively modest research grants into assets that materially displace gas.
