BW ESS signed a 10-year optimization agreement with EDF for the first phase of its Hams Hall BESS project in North Warwickshire, UK. The 350 MW/1,243 MWh battery system, expected online in Q4 2026, will support grid flexibility, renewable integration and energy security. A second phase will expand total capacity to 400 MW/1,424 MWh.
PROJECT SNAPSHOT
Companies: BW ESS, EDF
Project: Hams Hall BESS
Location: North Warwickshire, UK
Phase 1 Capacity: 350 MW / 1,243 MWh
Total Capacity: 400 MW / 1,424 MWh
Agreement: 10-year optimisation (floor) agreement
Commissioning: Expected Q4 2026
Key Role: Grid flexibility and renewable integration
BW ESS, the global energy storage developer, the owner and operator has partnered with EDF with a 10-year floor agreement to optimize the first phase of its Hams Hall BESS in North Warwickshire. A 350MW / 1,243MWh grid scale battery project, which is the longest-duration battery, where EDF has ever been contracted. This is the longest-duration battery project EDF has contracted to date, with a discharge capacity of up to 3.5 hours. In supporting more flexible and resilient UK electricity system with growing renewable energy supply, this project aims to create a more stable and adaptable power grid. EDF will manage the asset's trading and dispatch into UK power markets using its PowerShift platform.
This deal marks a significant expansion of the partnership between BW ESS and EDF. Hams Hall is their most prominent joint venture. It follows BW ESS's rapid growth in the UK market including the opening of its 100MW Bramley BESS in February 2025. The Hams Hall project is co-owned by BW ESS and AIP Management, which acquired a 49% stake in BW ESS’s 2.4GWh UK portfolio in September 2025. The site's location near the Hams Hall 400kV National Grid substation and major load centers was a key factor in EDF's interest for providing balancing and arbitrage services.
The "floor agreement" provides BW ESS with downside protection by guaranteeing a minimum income level while allowing for profit-sharing when revenues exceed that floor. Located on the outskirts of Birmingham, the facility is currently being built and is expected to begin commercial operations by final quarter of 2026. The site will start with 350MW capacity, followed by a second phase that adds 50MW to reach a total output of 400MW (1,424 MWh).
As a centerpiece of BW ESS’s UK portfolio, the Hams Hall project is co-owned by AIP Management. Once finished, it will be the company's largest global asset—surpassing the Bramley facility (the UK’s leader as of early 2025 with 100 MW / 331 MWh) by four times the capacity. When finished, the facility will power roughly 1.3 million homes for up to 3.5 hours, strengthening the UK’s energy security and grid flexibility. Its location near major demand centers and its connection to the Hams Hall 400kV substation will help minimize grid congestion while allowing the site to fully participate in energy trading and balancing services.
Stuart Fenner of EDF noted that Hams Hall represents the longest-duration battery the company has ever contracted. He explained that using their PowerShift platform to optimize the site will provide the flexibility necessary to integrate more renewable energy and support EDF’s goal of electrifying Britain.
BW ESS Executive Director Kilian Leykam expressed enthusiasm about partnering with EDF, noting that the collaboration creates a revenue framework intended to maximize the project's commercial value. He added that by blending BW ESS's development experience with EDF’s technical expertise, they will ensure the facility provides significant utility-scale value and serves as a vital flexible asset for the UK power grid.
This facility contributes to EDF’s expanding storage portfolio, supporting the increasing part of grid-scale batteries in stabilizing the power system as wind and solar energy production grows throughout the UK.