BW ESS, a global developer, owner and operator of Battery Energy Storage Systems (BESS), has entered into a 10-year floor agreement with EDF for the first phase of the Hams Hall BESS in North Warwickshire, central England.
The first phase of the Hams Hall project will provide 350 MW of power output and 1,243 MWh of storage capacity. A second phase will add 50 MW, increasing the total site capacity to 400 MW/1,424 MWh. Currently under construction on the northeastern fringe of Birmingham, the project benefits from its proximity to major demand centres and a connection to the nearby Hams Hall 400 kV National Grid substation, with commercial operation expected in Q4 2026.
Under the agreement, whose details were not disclosed, EDF will optimise the battery – its longest-duration contracted battery to date – using its PowerShift platform. This will enable the asset to enhance electricity system flexibility, balance supply and demand, support grid stability, and facilitate the integration of more renewable generation.
A floor agreement guarantees a minimum income level to the asset owner, offering downside protection and bridging the gap between investor demand for revenue certainty and the merchant nature of battery storage, often with a profit-sharing mechanism for revenues exceeding the agreed floor.
The Hams Hall project is a key part of BW ESS’s UK portfolio and is co-owned with infrastructure investor AIP Management, which acquired a stake in BW ESS’s 2.4 GWh UK battery portfolio in September 2025. China’s Sungrow is supplying 280 sets of grid-forming PowerTitan 2.0 liquid-cooled energy storage systems to the project under a September 2024 deal.
Upon completion, Hams Hall will become BW ESS’s largest global project, around four times the size of the 100 MW/331 MWh Bramley BESS – the UK’s largest battery when commissioned in February 2025. The Bramley project made headlines in August 2024 as Great Britain’s first single BESS asset to secure a long-term tolling agreement, a seven-year fixed-price contract signed by BW ESS, partner Penso Power and Shell Energy Europe Limited.
