Envision Energy, Kallista Energy start 386 MWh BESS project in France

Envision Energy and Kallista Energy said they have started construction on a 193 MW/386 MWh battery energy storage system (BESS) in Neuilly-en-Thelle, in France’s Hauts-de-France region, with commercial operation targeted before spring 2028, according to the companies.

The companies said the project is their second BESS collaboration in France, following the 120 MW/240 MWh Saleux project in Somme, which they said broke ground in June 2025 and is due for completion by the end of 2026. Construction on Neuilly-en-Thelle began in early July 2026.

Envision Energy said it will provide the BESS technology and manage the project’s lifecycle, including maintenance and battery recycling, over a planned 25-year operating period. The companies said the project will be powered by lithium iron phosphate (LFP) cells from Envision AESC’s gigafactory in Hauts-de-France, which the company says has 10 GWh of annual production capacity and has been operating since June 2025.

According to the companies, the project will provide frequency regulation services to grid operator RTE’s reserve markets, helping balance electricity supply and demand and supporting greater integration of renewable energy onto the French grid. The companies said the storage capacity is equivalent to roughly one day’s electricity consumption for 30,000 households.

“For the battery energy storage system in Neuilly-en-Thelle, we are leveraging the strong collaboration built with Envision Energy on our previous project in Saleux to deliver a new high-quality storage infrastructure to further support the energy transition,” said Johann Tardy, CEO of Kallista Energy Group.

The Saleux project marked Envision Energy’s entry into France’s battery storage market when construction began in June 2025.