BW ESS Hams Hall BESS Enters Commercial Operation at 350 MW / 1,243 MWh

BW ESS put the first phase of its Hams Hall battery energy storage system (BESS) in the West Midlands into commercial operation on Nov. 2, 2026, rated 350 MW / 1,243 MWh, the company said.

The owner-operator said the project reached commercial operation 20 days after energisation, which ESS News dates to on or around Oct. 13. BW ESS says it is now the largest BESS in Europe by storage capacity in MWh. Solar Power Portal describes it as a roughly 3.5-hour system next to National Grid's Hams Hall substation, with Sungrow as technology supplier. BW ESS thanked Sungrow, Energy-IO, National Grid and the system operator NESO for the commissioning work.

CEO Erik Strømsø said the project was built and commissioned on budget and ahead of schedule. Those are the company's own claims, and no cost figure has been disclosed.

What 20 Days to Commercial Operation Means

The gap between first power and commercial operation is the number grid planners will read. Until commercial operation, a battery of this size is a commissioning project; afterwards it is a 350 MW block that can charge and discharge on command at a 400 kV substation, for roughly 3.5 hours at full power. At full capacity, BW ESS says Hams Hall could supply around 1.3 million homes for up to 3.5 hours. That is a company comparison, not a metered result.

Hams Hall BESS Specifications, Partners and Financing

ESS News reports that Sungrow was selected in 2024 to supply 280 PowerTitan 2.0 liquid-cooled BESS units, and that consent was received in May 2022. A second phase will lift the site to 400 MW / 1,424 MWh, a figure that matches the project page on BW ESS's website, which gave a fourth-quarter 2026 target for commercial operation. Hams Hall belongs to BW ESS's 2.6 GWh Ardenham portfolio, co-owned with AIP Management, according to Energy Global, which carried the company announcement.

Revenue is underpinned by a 10-year floor and optimisation agreement with EDF, announced in April 2026. ESS News reports that EDF will optimise its longest-duration battery contracted to date through its PowerShift platform. The terms of the agreement were not disclosed.

The operating milestone follows the debt package, which BW ESS announced on Oct. 21, 2026, from OCBC, Rabobank and Societe Generale. Voltgrid's Oct. 22 report on the Hams Hall debt financing gave 400 MW / 1,424 MWh, the full-project size that phase 2 will reach, and noted that the loan amount was not disclosed. Energy Global and Solar Power Portal both note that the financing came only weeks before the project reached operation.

What BW ESS Has Not Confirmed Yet

BW ESS has not given a date for the second phase, and it has not said when the remaining 50 MW / 181 MWh will be energised. Sources differ on rounding: Solar Power Portal writes 1,240 MWh, while the company figure carried by Energy Global is 1,243 MWh, which this article uses. ESS News gives the energisation date as approximate, and BW ESS has not published the exact day. Revenue performance in the first weeks of trading has not been reported.