Envision Energy and Kallista Energy have expanded their partnership with the development of a 193 MW / 386 MWh battery energy storage system in northern France, designed to provide additional flexibility to the electricity grid as renewable generation and electrification increase.
Construction of the Neuilly-en-Thelle BESS project, located in the Hauts-de-France region, began in early July 2026. Commercial operations are expected to start before spring 2028.
The development is the second French battery storage project involving Envision Energy and European renewable energy producer Kallista Energy. Their earlier Saleux project, described as Envision’s first BESS development in France, entered construction in 2025.
Under the latest project, Envision Energy will provide its battery storage technology and support the facility throughout its lifecycle. Its responsibilities will extend from site maintenance during operations to battery recycling after the project’s planned 25-year operating period.
The storage system will use lithium iron phosphate (LFP) battery cells from Envision AESC. The companies are also linking the project to local battery manufacturing: Envision AESC operates a 10 GWh gigafactory in Hauts-de-France, which has been in operation since June 2025.
Once commissioned, the Neuilly-en-Thelle facility will participate in the French electricity system by providing flexibility and frequency regulation services through RTE’s reserve markets. By storing electricity and releasing it when required, large-scale batteries can help balance short-term differences between electricity generation and consumption.
According to the companies, the project’s storage capacity is equivalent to the daily electricity consumption of approximately 30,000 households.
The development comes as battery storage takes on a growing role in electricity systems with increasing amounts of wind and solar generation. Unlike conventional generation, renewable output varies with weather conditions, increasing the need for technologies capable of rapidly responding to changes in supply and demand.
For Kallista Energy, the new project builds on experience gained through the companies’ existing cooperation at Saleux.
“Battery energy storage is a key driver to achieve electrification of energy consumption and massive expansion of renewable energies, which aim at reaching a low-carbon economy,” said Johann Tardy, CEO of Kallista Energy Group.
Envision Energy said the partnership also demonstrates its approach of combining battery technology with long-term operational support and recycling.
The 193 MW / 386 MWh Neuilly-en-Thelle project will add substantial grid-scale storage capacity in France and provides another example of investment shifting toward the infrastructure required to integrate larger volumes of renewable electricity into Europe’s power system.