Alpiq (energy producer and energy services provider) has expanded its European flexibility portfolio with the acquisition of one of Germany's largest operational battery energy storage systems, purchasing the 103.5 MW facility in Bollingstedt, Schleswig-Holstein, from German-Norwegian developer ECO STOR (energy storage developer and manufacturer).

The Swiss energy company announced the deal on August 25, 2026, describing it as a further step in the implementation of its growth strategy. Financial terms of the transaction were not disclosed.

Facility Details and Operational Status

The Bollingstedt battery energy storage system, known as BESS Bollingstedt, has been operational since June 2025. With an output of 103.5 MW and a storage capacity of 238 MWh, the facility is described as one of the largest battery storage systems in Germany.

ECO STOR developed and built the system before it was acquired by Alpiq. The site is located in the northern German federal state of Schleswig-Holstein. The acquisition gives Alpiq its first operational large-scale battery storage system in Germany, which the company characterizes as one of Europe's most important markets for flexibility solutions.

Amédée Murisier, Head of the Assets business division and member of Alpiq's Executive Board, said the facility is an excellent fit with the company's existing portfolio and underlined its ambition to take a leading role in the European battery storage market.

Murisier added that Alpiq will explore further opportunities in Germany involving battery storage systems that are already operational, alongside its existing project pipeline.

Third Operational BESS in Alpiq's Portfolio

Bollingstedt represents the third and currently largest operational battery storage system in Alpiq's portfolio. The other two operational assets are BESS Cheviré, a 100 MW facility located in Nantes Saint-Nazaire, France, and BESS Valkeakoski, a 30 MW system in Finland.

Beyond these operational sites, Alpiq has further BESS projects with a combined installed capacity of more than 250 MW currently under construction or close to commissioning. Projects in Italy and Switzerland are also in the development phase.

Alpiq stated that flexible energy storage assets such as battery energy storage systems and pumped-storage hydropower plants are essential to the future energy system, supporting the integration of renewable energy and helping to balance electricity supply and demand.

The company describes such assets as central to strengthening the resilience of the electricity system, increasing security of supply, and enabling the energy transition.

Strategic Context: Harmony Energy Acquisition

The Bollingstedt acquisition follows another significant move by Alpiq in the battery storage space. In early July 2026, the company acquired a 90 percent majority stake in Harmony Energy, described as an established pan-European developer and operator of battery energy storage systems with a multi-gigawatt project pipeline in the United Kingdom, France, Germany and Poland.

Alpiq stated that the acquisition of BESS Bollingstedt complements this pipeline by adding an operational asset that contributes directly to earnings and provides direct access to the German battery storage market.

By combining a strong project portfolio with operational assets, Alpiq said it is strengthening its position along the battery storage value chain and laying the foundations for the further expansion of its flexibility platform in Europe.

Renewed Collaboration with ECO STOR

The transaction deepens an already established relationship between Alpiq and ECO STOR. In November 2025, the two companies signed a long-term tolling agreement for the Schuby battery storage system in northern Germany, another facility built and operated by ECO STOR.

Alpiq described the acquisition of BESS Bollingstedt as reflecting its confidence in ECO STOR's project development capabilities, technical expertise and understanding of economically viable storage solutions.

ECO STOR is a German-Norwegian company that develops, builds, and operates battery storage systems in Germany. Alpiq noted that the deal also underlines the two companies' shared conviction that high-performance battery storage systems are an important component of a sustainable energy system.

Broader Flexibility Strategy

Alpiq's push into battery storage is framed within a wider strategic emphasis on flexible energy infrastructure. The company, headquartered in Lausanne, Switzerland, positions large-scale storage alongside its pumped-storage hydropower assets as key components of its infrastructure portfolio.

The Bollingstedt acquisition, combined with the Harmony Energy stake and the existing operational assets in France and Finland, signals a concerted effort to establish Alpiq as a significant player in the European battery storage market across multiple geographies, including Germany, France, the United Kingdom, Poland, Italy and Switzerland.

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