BW ESS breaks ground on Germany’s largest battery storage project

BW ESS has started construction on its first German BESS, breaking ground on a 1 GW/5.7 GWh asset after taking full ownership of the project earlier in 2026.

The Klostermansfeld BESS in central Germany is being developed as a single project and a BW ESS spokesperson told ESS News that the battery is expected to enter commercial operations in 2028.

Located in the Mansfeld-Südharz region, Saxony-Anhalt, the Klostermansfeld BESS was initially developed by Zelos Energy Developments. BW ESS first invested in the project in 2024 before taking full ownership of the project earlier in 2026. Zelos is expected to provide targeted support on local site matters until later in 2026, when further construction progress has been made.

BW ESS told ESS News it had taken Klostermansfeld BESS into construction without external finance to date, and the company’s revenue strategy for the project is currently under review.

With 1 GW power output and 5.7 GWh of energy storage capacity, Klostermansfeld BESS is thought to be the largest BESS project to enter construction in Germany and would provide more than four hours of deployment capacity.

In a press release, BW ESS executive director Roberto Jiménez said the developer has made a long-term commitment to realizing the potential of energy storage in Germany.

“Klostermansfeld BESS will be our first German asset to enter construction. We will continue to take an active approach to knowledge transfer across out portfolio, leveraging our extensive experience in global markets.”

Part of the BW Group – a multinational maritime company involved in shipping, floating gas infrastructure and deep-water oil and gas production – BW ESS has been ramping up its energy storage portfolio and is active in United Kingdom, Australia, Italy, Germany, Spain and Sweden.

The developer has more than 540 MWh of operating BESS capacity with around 11 GWh of assets under construction. BW ESS previously announced a partnership with Munich-based energy storage developer MIRAI Power to develop 1 GW of projects in the southern Germany. The developer was also party to the first publicly announced tolling agreement in the UK BESS market.