• Envision Energy and Kallista Energy are developing a 193 MW / 386 MWh battery energy storage project in Hauts-de-France.
• The system will support French grid balancing, frequency regulation and renewable energy integration, with commercial operation expected before spring 2028.
• Envision will manage the full project lifecycle, including maintenance and battery recycling after 25 years of operation.

Envision Energy and Kallista Energy have started construction on a 193 MW / 386 MWh battery energy storage system in Hauts-de-France, expanding their collaboration in the French power market.

Construction on the Neuilly-en-Thelle project began in early July 2026. Commercial operations are expected before spring 2028.

The project follows the companies’ Saleux battery storage development, which broke ground in 2025. Together, the projects deepen their presence in a European storage market that is becoming increasingly important as renewable generation and electricity demand rise.

Storage capacity expands in northern France

Envision Energy will supply its battery energy storage system and oversee the project across its full operating lifecycle.

That responsibility includes site maintenance and battery recycling after 25 years of operation. The structure gives Kallista Energy a single technology and service partner across development, operation and end-of-life management.

The system will use lithium iron phosphate cells manufactured by Envision AESC. Envision said the project will also draw on its 10 GWh battery gigafactory in Hauts-de-France, which began operations in June 2025.

The combination of local cell production and system integration could strengthen regional supply chains while reducing reliance on imported battery components. It also links France’s energy transition more directly with domestic industrial development.

Henry Peng, Senior Vice President, Envision Energy & President of EU & LATAM Regions said: “Our second BESS project with Kallista Energy reflects the continued growth of a partnership built on shared ambitions for Europe’s energy transition. Beyond delivering safe, reliable and scalable storage technology, Envision provides comprehensive lifecycle support, helping customers maximise long-term asset value. This integrated approach further advances our Future Energy System, strengthening grid resilience, accelerating the integration of renewable energy and supporting sustainable industrial development across Europe.”

Project to provide flexibility to France’s grid

Once operational, Neuilly-en-Thelle will provide flexibility services to the French electricity system.

These services will include frequency regulation through reserve markets operated by French transmission system operator RTE. Batteries can respond quickly when electricity supply and demand diverge, helping grid operators maintain system stability.

Envision said the project’s storage capacity is equivalent to the daily electricity consumption of around 30,000 households.

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The ability to store electricity also supports greater deployment of intermittent renewable generation. Solar and wind output can fluctuate considerably, creating periods when electricity production does not align with consumption.

Large-scale battery systems can absorb surplus power and release it when required. That function is becoming more valuable as France electrifies transport, buildings and industrial processes.

“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 the Kallista Energy Group. “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”.

Battery investment moves closer to energy policy

For investors and energy executives, the project highlights how storage is moving from supporting infrastructure to a core component of European electricity markets.

Renewable deployment alone cannot provide the flexibility required by increasingly electrified economies. Grid operators also need dispatchable capacity that can respond rapidly to changing system conditions.

Battery projects can address part of that requirement while creating additional revenue opportunities through reserve and balancing markets. Their economics increasingly depend on access to those markets, effective asset management and long-term battery performance.

The Neuilly-en-Thelle development also connects energy security with industrial policy. Local manufacturing capacity can become strategically important as European governments seek stronger domestic clean technology supply chains.

France will need additional grid flexibility as renewable generation and electricity demand expand. Projects such as Neuilly-en-Thelle show how storage, manufacturing and grid services are beginning to converge within the country’s broader energy transition.

Across Europe, that convergence is likely to shape where new battery capital is deployed and which markets can integrate rising volumes of renewable power without compromising system reliability.