Germany’s ‘Largest’ BESS Project Begins Construction At 1 GW

BW ESS, the global energy storage projects developer and operator, has broken ground on the 1,000 MW/5,700 MWh Klostermansfeld battery energy storage system (BESS). This marks the start of construction on what the company says is Germany’s largest battery storage project and one of the biggest in Europe. 

The project is located near the Klostermansfeld substation in the Mansfeld-Südharz district of Saxony-Anhalt. Once operational, it will be capable of supplying electricity to around 3 million German households for at least 4 hours.  

Part of BW Group, Switzerland-headquartered BW ESS first invested in the project in 2024 and acquired full ownership earlier this year. The original developer, Zelos Energy Developments, will continue supporting local site activities until the project reaches a later stage of construction, expected by the end of 2026. 

The battery system is designed to improve Germany’s energy security and grid stability by supporting the Klostermansfeld substation, a key node in the country's electricity network, said BW ESS. It will help absorb larger volumes of renewable electricity and improve the grid’s ability to manage periods of peak demand.   

Roberto Jiménez, Executive Director of BW ESS, said the project reflects the company's long-term commitment to Germany's energy storage market. He added that Klostermansfeld will be BW ESS’s first energy storage asset to enter construction in the country. He added, “We will continue to take an active approach to knowledge transfer across our portfolio, leveraging our extensive experience from the mature global markets.” 

BW ESS says it operates over 540 MWh of BESS and has around 11 GWh under construction along with a development pipeline of several GWs. 

Saxony-Anhalt's Minister for Science, Energy, Climate Protection and the Environment and Deputy Prime Minister, Prof. Dr. Armin Willingmann, stressed the need for large-scale battery storage for stabilizing power grids as renewable energy capacity expands. He said the project would help store surplus renewable electricity, strengthen grid flexibility and support secure electricity supply. 

According to the German solar industry association BSW-Solar, Germany has approximately 30 GWh of battery storage capacity, of which nearly 6 GWh are large-scale storage systems. Another 58 GWh capacity is in planning stages, but its implementation is subject to ‘considerable uncertainties’.  

Nevertheless, Germany retained the top slot as Europe’s largest battery storage market, according to SolarPower Europe (see Europe’s Battery Storage Capacity Exceeds 100 GWh).