Envision Energy and Kallista Energy have started construction of a 193 MW, 386 MWh battery energy storage project at Neuilly-en-Thelle in Hauts-de-France. Commercial operation is expected before spring 2028. At two hours of energy capacity at full rated power, the installation is designed less as a long-duration substitute for generation than as a fast, flexible grid asset.
The companies say the system will participate in reserve markets operated by French transmission group RTE, including frequency regulation. That role is central to the project’s business case. Batteries can react quickly when supply and demand diverge, absorb electricity when the system has excess production and release it when additional power is valuable.
The second project matters more than the first announcement
Neuilly-en-Thelle follows the Saleux project, Envision’s first battery installation with Kallista in France, which broke ground in 2025. Repetition suggests that the partnership is moving beyond a demonstration. Developers, equipment providers, lenders and grid operators learn from standardised designs, procurement and operating data. A second project can therefore reduce risk for a third more effectively than a single flagship site.
Envision is set to provide the battery system and support the project through maintenance and eventual recycling after 25 years of operation, according to its announcement. That lifecycle responsibility is commercially significant. A storage asset’s value depends on degradation, software controls, availability and safe operation over many years. The original purchase price is only one part of the economics.
The system will use lithium iron phosphate cells from Envision AESC. LFP chemistry is widely used in stationary storage because it avoids nickel and cobalt and offers a strong safety and cycle-life profile, although project-level fire prevention and emergency planning remain essential. Envision also points to its 10 GWh battery factory in Hauts-de-France, operational since June 2025, as the local manufacturing base supporting the project.
Local content meets a global supply chain
Combining regional cell production with a French project supports the industrial-policy case for storage. Europe wants more control over battery manufacturing while electrification increases demand from vehicles and grids. A nearby factory can shorten logistics and improve coordination between cell production and system integration.
Local assembly does not make the supply chain entirely French or European. Battery materials, processing equipment and upstream components remain globally traded. Envision is a Chinese-headquartered green-technology group, while Kallista is a European renewable-energy producer. The project illustrates a practical form of industrial sovereignty: building domestic capacity through international technology and capital rather than attempting complete self-sufficiency.
That model brings scrutiny as well as benefits. Customers and regulators will care about cybersecurity, control software, data access, procurement resilience and recycling. Grid batteries are connected infrastructure, not passive boxes. Contracts must define who can update systems, how remote access is secured and what happens if a supplier relationship changes over the asset’s life.
What 386 MWh can and cannot do
Envision says the capacity is equivalent to the daily consumption of 30,000 households. Such comparisons help readers understand scale but do not describe grid function precisely. The project could deliver 193 MW for about two hours before losses and operating limits. It cannot carry a region through a prolonged winter shortage.
Its strength is speed and repetition. A battery can deliver frequency response, trade across intraday price spreads and help manage short renewable fluctuations. Revenue stacking can improve returns, but it also creates forecasting and dispatch complexity. If too many batteries pursue the same service, prices can fall. The asset must be flexible enough to shift toward whichever grid services remain valuable.
France’s low-carbon nuclear fleet changes the context compared with power systems dominated by fossil generation. Storage can still help handle ramping, renewable output and electrification, but its emissions impact depends on when it charges and discharges. A battery charged during a high-carbon import period may not deliver the same climate benefit as one absorbing surplus low-carbon production.
The real innovation is bankable integration
None of the project’s individual elements is novel on its own. LFP cells, two-hour systems and frequency markets are established. The innovation lies in combining manufacturing, project development, grid-market access, maintenance and end-of-life planning into infrastructure that investors can finance and operators can trust.
The commissioning timetable will now matter more than the launch. Construction performance, grid connection, safety approvals and commercial operation before spring 2028 are the milestones to watch. After that, availability and degradation data will show whether the promised 25-year lifecycle is economically credible.
If Neuilly-en-Thelle performs as expected, it can help normalise storage in France as a standard grid investment rather than an experimental renewable add-on. That transition is necessary because electrification increases both electricity demand and the value of flexibility. The project is large enough to be consequential, but its broader value will come from making the next deployments easier to build.
