Short-duration battery energy storage (BESS) deployment has scaled rapidly in the UK. However, making meaningful progress towards grid decarbonisation requires the concurrent deployment of storage capable of discharging for 8 hours or more - Long Duration Energy Storage (LDES).

In 2025 alone, an estimated 10TWh of renewable generation was curtailed - simply switched off when the grid couldn't absorb it - costing consumers between £1.4bn and £1.8bn. As renewable capacity grows from 46GW to the over 115GW estimated by 2030, this problem will worsen without storage capable of capturing that surplus and releasing it when generation is low. That's the core case for LDES.

The UK currently has just under 3GW of LDES capacity, almost entirely from pumped hydro built decades ago. NESO forecasts that requirement growing to 10.5GW by 2035 and 16.5GW by 2050.

The Ofgem Cap and Floor scheme is the government's mechanism to unlock private investment. By guaranteeing a minimum revenue floor while capping upside returns, it de-risks the long-term capital commitments that LDES projects require. Of 171 projects that applied in Window 1, 77 passed initial eligibility - with Ofgem's shortlist expected by end of May 2026 and final licence awards before August 2026.

The Energy Storage Association (UK) representing 26+ members across the storage sector, is calling on Ofgem to, among other things:

📌 Publish a predictable long-term LDES procurement roadmap

📌 Deploy a diverse LDES technology mix from the outset - variety drives competition, accelerates cost reductions and avoids over-concentration of supply chain risk

📌 Ensure local content commitments are met through procurement decisions - a well-managed 500MW, 8hr+ LDES project creates ~700 jobs over a 3-year construction period, plus ~40 direct jobs across a 50-year operating life

Getting the detail right on issues like procurement and technology diversity will determine whether the scheme delivers at the scale the grid actually needs.