Alpiq has acquired from ECO STOR one of Germany’s largest operational battery energy storage systems (BESS). The facility, located in Bollingstedt in the federal state of Schleswig-Holstein, has an output of 103.5 MW and a storage capacity of 238 MWh.

The transaction adds Alpiq’s first operational large-scale battery storage system in Germany to its infrastructure portfolio, expanding the company’s presence in one of Europe’s key markets for flexibility solutions. The financial terms of the transaction were not disclosed.

The Bollingstedt BESS was developed and built by ECO STOR, a German-Norwegian company specialising in battery storage systems, and has been operational since June 2025.

“With BESS Bollingstedt, we are strengthening our ability to provide flexibility where it delivers the greatest value for the electricity system,” said Amédée Murisier, Head of the Assets business division and member of Alpiq’s Executive Board.

The company also said that, alongside its existing project pipeline, it will explore further opportunities in Germany involving battery storage systems that are already operational.

Alpiq’s largest operational BESS

Bollingstedt becomes the third and currently largest operational battery storage system in Alpiq’s portfolio. The company also operates BESS Cheviré in Nantes Saint-Nazaire, France, with 100 MW, and BESS Valkeakoski in Finland, with 30 MW.

Alpiq also has BESS projects with a combined installed capacity of more than 250 MW currently under construction or close to commissioning. Additional projects in Italy and Switzerland are in the development phase.

The transaction follows Alpiq’s acquisition in early July of a 90% majority stake in Harmony Energy, a pan-European BESS developer and operator with a multi-gigawatt project pipeline across the United Kingdom, France, Germany and Poland.

According to Alpiq, the Bollingstedt acquisition complements this pipeline with an operational asset that contributes directly to earnings while giving the company direct access to the German battery storage market.

Alpiq expands partnership with ECO STOR

The acquisition also strengthens the existing relationship between Alpiq and ECO STOR. In November 2025, the companies signed a long-term tolling agreement for the Schuby battery storage system in northern Germany, which was also built and is operated by ECO STOR.

Alpiq sees BESS, alongside pumped-storage hydropower plants, as part of its strategy to expand its portfolio of flexible energy assets. These technologies can help balance electricity supply and demand and support the integration of increasing volumes of renewable energy into the power system.