Grid Storage Britain's first long-duration electricity storage support round now has a project list. Ofgem said on June 26 that it is minded to back 16 projects totaling 7,645 MW under the first application window of the long-duration electricity storage cap-and-floor regime. The portfolio spans pumped storage hydro, compressed air energy storage, lithium-ion batteries, and vanadium redox flow batteries. AI-generated image Ofgem's first LDES window moves 16 storage projects into consultation, with durations running from at least eight hours to more than a day. The decision is provisional, not a final award. Ofgem opened a consultation that runs through Aug. 7, 2026, and said it will review responses before confirming final cap-and-floor awards later in the year. Still, the minded-to list is enough to show what Britain's regulator thinks a useful long-duration portfolio looks like: large pumped hydro in Scotland, multi-hour lithium-ion batteries in several regions, a compressed air project in northeast England, and flow batteries for longer discharge windows. For the battery sector, the surprise is not only that lithium-ion made the list. It is the duration. Energy-Storage.news reported that the selected projects range from 8-hour to 22-hour durations, with several lithium-ion systems planned well beyond the standard four-hour design common in today's grid storage market. Ofgem's impact assessment lists lithium-ion projects including Field Netherton at 400 MW and 16.3 hours, Field Kilmarnock South at 200 MW and 18 hours, Field Auchteraw at 100 MW and 16 hours, and Eku Energy's projects at 8 to 13 hours. 7,645 MW Proposed Window 1 capacity 16 Projects selected for consultation 4 Technology families Aug. 7 Consultation close Why Cap and Floor Matters Long-duration storage has a financing problem. The grid needs assets that can shift renewable power across long evening peaks, wind lulls, and network constraints, but energy arbitrage alone often does not pay for high upfront capital costs. A cap-and-floor model tries to bridge that gap. If project revenues fall below an agreed floor, consumers top up the difference through network charges. If revenues rise above a cap, excess money flows back to consumers. That structure is familiar in Britain because regulators have used a version of it for electricity interconnectors. For storage, the goal is to give developers enough revenue certainty to finance assets that may not look attractive in merchant markets, while keeping a limit on upside if the assets earn more than expected. Ofgem says the proposed portfolio should reduce costs by easing pressure on transmission and distribution networks and cutting the need for expensive constraint management. AI-generated image Three pumped storage hydro projects dominate the energy side of the proposed portfolio, including Coire Glas, Loch Kemp, and Earba. Pumped hydro is the heavyweight in the list. The proposed portfolio includes Coire Glas at 1,440 MW and 32 hours, Loch Kemp at 660 MW and 22.3 hours, and Earba at 1,800 MW and 15 hours, according to Ofgem's assessment table. Those projects would be among Britain's first new major pumped hydro additions in decades. They also explain why the LDES window is not simply a battery procurement. It is a reliability and network planning tool. Lithium-Ion Stretches Beyond Four Hours The lithium-ion entries are the part battery buyers will watch closely. The technology is mature, bankable, and supported by a deep manufacturing base, but it becomes more expensive as developers add hours by adding more cells. That has left many analysts assuming lithium-ion would dominate the two-to-four-hour market while flow batteries, compressed air, thermal storage, iron-air systems, or pumped hydro would compete for longer durations. Ofgem's list complicates that clean split. A 16-hour or 18-hour lithium-ion system is possible, but the commercial question is whether it is the best use of capital compared with alternatives. The answer can vary by site. Lithium-ion has advantages where land is constrained, interconnection is ready, delivery speed matters, and lenders prefer familiar equipment. Flow batteries or compressed air may look stronger where energy duration can be expanded at lower marginal cost. AI-generated image Several selected lithium-ion projects are designed for far longer discharge than the four-hour systems common in many markets. That makes the UK window a real-world test of duration economics. If long-duration lithium-ion projects clear final award, raise financing, and reach operation with manageable costs, developers in other markets will use the case study. If they struggle, the result may strengthen the argument for storage chemistries built specifically for long discharge. The Regional Signal The geography is just as important as the technology. Ofgem and the National Energy System Operator are trying to build storage where it reduces system costs, not only where developers can find land. Northern Scotland has large renewable output and transmission constraints, so storage there can help absorb wind that might otherwise be curtailed. England and Wales need assets that can support demand centers, firm renewable supply, and delay network upgrades. This is why the portfolio matters more than any single project. A storage asset near a constrained generation zone does a different job than one near load. A 32-hour pumped hydro project does a different job than an 8-hour battery. Ofgem's process tries to compare these assets through cost, system modeling, economic value, financial deliverability, and strategic fit, rather than treating every megawatt as equal. AI-generated image The first window is a portfolio choice, mixing location, technology, power capacity, and duration. What Happens Next Developers are not across the finish line. Ofgem is asking for feedback on the proposed portfolio, the assessment method, capacity limits, regime requests, and future application windows. Final awards may change if consultation responses expose errors, challenge assumptions, or show that a project no longer meets the value test. The next practical milestones are financial. Winning a place on the minded-to list can support investor conversations, but projects still need supply contracts, civil works plans, grid connection progress, permits, and final cap-and-floor terms that lenders can underwrite. Pumped hydro projects face especially long development cycles. Battery projects can move faster, but long-duration designs still need careful degradation, warranty, augmentation, and safety assumptions. For policymakers outside Britain, the lesson is clear enough. Long-duration storage is moving from grant programs and demonstration awards into regulated infrastructure planning. The UK is not waiting for a single winning chemistry. It is using a revenue framework to test a mixed portfolio and asking which combination can lower system costs for consumers. The bottom line: Ofgem's first LDES shortlist gives Britain a 7.6 GW pipeline of assets designed to stretch beyond today's short-duration battery market. Pumped hydro supplies the deep storage, lithium-ion is pushing into 8-to-18-hour territory, and flow plus compressed air projects keep the door open for alternatives. The final awards will decide whether this becomes a bankable template for long-duration storage procurement. Sources: Ofgem press release , Ofgem consultation , Ofgem impact assessment , Energy-Storage.news , Renewables Now .