Largest battery in France commissioned in 2026

The large battery installed by TagEnergy in Cernay-lès-Reims, in the Marne, is currently the most powerful in service in France. Although it was commissioned as early as May 2026, its official inauguration took place on October 1st of last year.

Joint ownership and technical specifications

The project is jointly owned by TagEnergy, which holds 51%, and the Banque des Territoires, which owns 49%. The installation serves the power grid and has a power of 240 MW and a storage capacity of 480 MWh. At full power, it can supply electricity for two hours, enough to cover the consumption of 450,000 households for that duration, according to its operators.

Previous record and comparison

The previous record was held by the site in Cheviré, on the port of Nantes-Saint-Nazaire, which was energized in August 2025 by Harmony Energy and also equipped with Tesla Megapack batteries. With 100 MW for 200 MWh, it is less than half the size of the Marne battery.

Installation details and performance

The Cernay-lès-Reims site covers a little more than three hectares and consists of 140 battery Megapack containers supplied by Tesla, which also coordinated the construction site and manages the interface with the electricity markets. Connected to the RTE electricity transmission network at a voltage of 225 kV and commercially operated since the end of May 2026, the power plant had already injected 70.5 GWh of electricity and completed 145 full cycles in 125 days by September 23.

Grid balancing and renewable integration

The power plant contributes to grid balancing by providing frequency and voltage regulation services. In Europe, the power grid frequency must be maintained around 50 Hz. This frequency varies when electricity production and consumption are no longer balanced. The plant can then absorb production surpluses and supply stored electricity when the grid needs it, thus helping to maintain its stability.

Support for renewable energy

The system especially supports the integration of solar and wind energy, whose production varies depending on weather conditions. "This flexibility is gradually becoming essential to the electricity system and allows for more renewable energy to be integrated into our energy mix," explains Christophe Léonard, associate director of TagEnergy for France.

Consumer impact and energy cost management

For consumers, the effect is indirect. As France Renouvelables recalls, batteries charge when electricity is abundant and cheap, then return it when demand rises. They thus limit periods of negative prices and reduce the use of costly and polluting peak gas plants during consumption peaks.

Battery storage growth in France

Battery storage is expanding in France. The French energy roadmap (the Multi-Year Energy Programming) highlights the importance and urgency of providing more flexibility means, including batteries, to ensure the continuity of supply. Large-scale projects are therefore beginning to multiply across the country.

Future projects and current capacity

The Cernay-lès-Reims installation will not hold its title for long, as Neoen has launched a 248 MW battery for 496 MWh in Vernou-la-Celle-sur-Seine, in Seine-et-Marne, with commissioning expected for 2028. Battery storage in France has progressed relatively quickly in recent years, even though the country is lagging in this area.

Growth trajectory and European context

According to RTE, France had only about 316 MW of batteries in 2021. By mid-2026, the park had reached 2 GW, according to France Renouvelables. This park is expected to grow significantly, even though not all announced projects will be realized, or not immediately. In its latest electricity report, RTE listed 14 GW of battery projects whose access to the grid has already been contracted by the end of 2025.

European comparison and future goals

The French delay is measured on a European scale. According to France Renouvelables, which relies on data from SolarPower Europe, Europe installed an additional 36 GW of batteries in 2025, for a total park of more than 100 GW. The third Multi-Year Energy Programming does not set any numerical targets for storage, while the industry demands 10 GW of batteries by 2030, then 15 GW by 2035.

Limitations of battery storage

Batteries suitable for short-term storage. Batteries, however, have a size limit, as they are only suitable for short-term storage. They can absorb production surpluses and return them a few hours later, but cannot cover storage needs over several days.

Hydroelectric storage as an alternative

To meet these longer-term needs, France can rely on its pumped storage hydroelectric power stations (STEP), totaling 5 GW of power. This hydroelectric storage technology, developed in France since the 1970s, is more proven than batteries, but its expansion is hindered by environmental, geographic, and economic constraints.