The largest battery storage facility in France was officially inaugurated on Thursday near Reims, but it is expected to be quickly surpassed, given the rapid deployment of these systems that allow, among other things, the optimization of the share of renewable energies. The Cernay-lès-Reims installation consists of 140 battery containers from the American company Tesla, spread over more than three hectares. In service since May, the site is capable of injecting 240 MW of power into the electrical grid for two hours (equivalent to 480 MWh). Today, this installation, which cost more than 100 million euros, "is the largest in France," but "there are others that are coming, and that is very good for the French electrical grid," said Franck Woitiez, the general manager of TagEnergy, the operator of the site, in partnership with the Banque des Territoires, on Thursday. The previous largest battery storage park in France was that of Cheviré, near Nantes, put into service at the end of 2025 by the British company Harmony Energy. These mega-batteries first serve to regulate the frequency of the electrical grid to keep it stable, absorbing real-time variations in energy production. They also allow to rebalance the gaps between electricity production and consumption, charging when there is excess production, such as during the day with solar power, and then re-injecting electricity into the grid during consumption peaks in the evening. The installed power of the French battery storage park reached more than 1.5 gigawatts by the end of 2025, an increase of 42% over one year, according to the Observatoire des batteries stationnaires, a study led by several actors including the Commission de régulation de l'énergie (CRE), the manager of the electricity transmission network RTE, and the Ademe, the agency for ecological transition. There are approximately 13 GW of projects currently in the pipeline, according to the association France Renouvelables. France started later than other European countries to equip itself with large battery storage sites, notably because renewable energies took "more time" to develop in the Hexagon, partly due to the predominance of nuclear power. The drastic decrease in battery costs also contributes greatly to this growth. "The price of battery cells, in the space of five years, has been divided by three," according to Christophe Desplats-Redier, general manager of France at Neoen, interviewed by AFP on Thursday. However, for now, it is China that overwhelmingly dominates the stationary battery market, as well as those for electric vehicles. "We would very much like to buy French equipment, the difficulty is that this production is not on the territory today," lamented Franck Woitiez of TagEnergy. But there too, the lines are beginning to move: the batteries of the future large storage site of Neoen in Seine-et-Marne will thus be built in France by Nidec ASI, in a new factory of this Japanese group near Saint-Etienne. A sign of the current effervescence in this industry, the company Neoen is also set to inaugurate a battery storage site in the Finistère in a few days. Neoen has also recently launched the construction of the next largest installation of this kind in France, in Seine-et-Marne, with a start of service planned for 2028.