EDF has partnered with BW ESS to initiate the first phase of the 350MW/1.24GW-hour (GWh) Hams Hall battery energy storage system (BESS) in north Warwickshire, UK.

This grid-scale battery project is the longest-duration battery that EDF has contracted to date.

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It will improve the flexibility and resilience of the UK’s electricity system while supporting the continued growth of renewable energy generation.

Once completed, Hams Hall phase one will support the electricity needs of approximately 1.3 million homes during peak periods, with the capacity to sustain power for up to 3.5 hours.

EDF wholesale market services director Stuart Fenner said: “Hams Hall will be the longest-duration battery EDF has contracted to date.

“By optimising it through our PowerShift platform, we can unlock the flexibility needed to support more renewable power and help deliver EDF’s purpose of electrifying Britain.”

EDF will manage the project under a ten-year floor agreement and will use its PowerShift platform to optimise operations.

The arrangement aims to help the battery support the electricity system by matching supply with demand, maintaining grid stability and enabling the integration of higher levels of renewable generation.

The project is currently under development on the north-eastern outskirts of Birmingham and is expected to become operational by the fourth quarter of 2026 (Q4 2026).

A second phase is planned to add a further 50MW, bringing the project total to 400MW/1.42GWh.

Hams Hall forms part of BW ESS’s UK portfolio and is co-owned by BW ESS and AIP Management, an energy and decarbonisation investor.

BW ESS expects Hams Hall to become its largest project by capacity once completed, four-times the size of the Bramley BESS (100MW/331MW-hours), which held the UK’s largest designation when it opened in February 2025.

BW ESS revenue executive director Kilian Leykam said: “We are very pleased to welcome EDF as our optimisation partner on the Hams Hall project. This collaboration enables a revenue structure designed to maximise the commercial potential of this strategically important UK asset.

“By combining BW ESS’s experience in developing and operating utility-scale battery storage projects with EDF’s optimisation expertise, we will ensure that Hams Hall delivers exceptional value while fulfilling its role as a key flexibility asset in the UK electricity system.”

The project’s location near major demand centres and its connection to the Hams Hall 400kV National Grid substation support access to arbitrage and balancing services, and aim to limit congestion risk.

The development adds to EDF’s expanding battery storage portfolio and reflects the growing use of grid-scale batteries to help balance the electricity system as wind and solar generation increase across the UK.

Last month, Matrix Renewables signed a long-term battery optimisation agreement with EDF for a 500MW/1GWh BESS currently under construction in Eccles, Scotland.