Not Every Battery Is a Box of Lithium. What Is Long-Duration Energy Storage?
Ask somebody to picture an energy storage project and they'll probably imagine a shipping container full of lithium-ion batteries. That's understandable - it's also a little like describing transport by pointing at a delivery van.
Britain is now supporting storage designed to discharge over much longer periods, through a mechanism called the cap-and-floor regime, specifically built to make that kind of investment viable.
What duration actually means
A storage asset's power rating (MW) tells you how fast it can charge or discharge. Its energy capacity (MWh) tells you how much it can store. Duration is simply energy capacity divided by power - how long the asset can sustain its rated output before it's empty. A typical short-duration battery might run for one to four hours; the projects being supported under this scheme run considerably longer than that.
Why short-duration batteries are useful
Rapid response, shifting demand within a day, supporting solar self-consumption, managing peaks, some resilience benefit, and various system services are all things a short-duration battery does well, and does relatively cheaply per unit of power.
Why longer storage is also needed
Extended renewable shortfalls, sustained high demand, prolonged surplus generation and some network constraints aren't always economically solvable by simply installing more two-hour batteries. Longer-duration storage addresses a genuinely different part of the system's needs.
What Ofgem is actually supporting
Ofgem's cap-and-floor regime for long-duration electricity storage is designed to make longer-duration projects investable by reducing revenue risk: a floor protects investors against very low returns, and a cap limits how much they can earn, protecting consumers from excessive returns on the same asset. Ofgem published its provisional ("minded-to") selection for the first application window in mid-2026 - a portfolio spanning several gigawatts of power capacity and well over 100GWh of storage, with discharge durations broadly in the range of eight to twenty-two hours. A consultation on those provisional decisions is open before final awards, expected later in 2026.
The technology mix may surprise you
The provisional portfolio isn't dominated by an exotic single technology - it includes a meaningful number of extended-duration lithium-ion battery projects alongside pumped-storage hydro and other approaches. The real distinction this scheme is drawing isn't "lithium versus everything else." It's short-duration versus long-duration, and multiple technologies - including lithium-ion built for longer discharge - can compete on that basis.
What it means for ordinary businesses
Almost certainly not a pumped-hydro scheme behind the warehouse. What it does signal is a more diverse, more resilient national storage mix developing above and beyond the short-duration batteries most commercial sites would ever consider - and a useful reminder that storage, at any scale, should be sized around the actual problem it's solving rather than a default duration.
The facilities-management angle
Before assuming electricity needs to be stored at all, it's worth asking whether the underlying need is really for stored heat or stored cooling instead. Hot water, chilled water, refrigeration and space or process heat can sometimes be served more cost-effectively by thermal storage than by storing and reconverting electricity.
The best storage technology isn't the one that holds energy longest or responds fastest - it's the one designed around the service actually required. Occasionally that's a lithium battery. Occasionally it's a much longer-duration asset. And sometimes the better answer is to store heat instead of electricity in the first place. If you're weighing up storage for a site, get in touch.