France’s largest battery goes online

TagEnergy has inaugurated a 240 MW/480 MWh battery energy storage system (BESS) at Cernay-lès-Reims in northeastern France, making it the country’s largest operational battery storage project.

The project was inaugurated on Oct. 1 after four months of operation and is TagEnergy’s first operational storage asset in France. Since its founding in 2019, the Portuguese company has built a portfolio of more than 10 GW of solar, wind and battery storage capacity across the United Kingdom, France, Germany, Japan and Australia, with more than 2 GW currently operational.

Connected to transmission system operator RTE’s 225 kV grid, the project comprises 140 Tesla Megapack battery containers across just over 3 hectares. It entered operation after completing the simulations, tests and certifications required to provide frequency containment reserve, automatic frequency restoration reserve and voltage regulation services.

French construction and engineering group Eiffage carried out civil and electrical works, while Alsace-based photovoltaic and high-voltage engineering company Tewa Solar provided project management assistance from development through commissioning.

TagEnergy CEO Franck Woitiez said the Cernay-lès-Reims project shows that large-scale electricity storage has become an industrial reality in France. According to the company, the facility fed 70.5 GWh back into the grid during its first four months of operation and completed 145 full cycles over 125 days.

A banking consortium comprising ABN AMRO, NORD/LB and Caisse d’Épargne CEPAC provided financing for the project. TagEnergy jointly owns the facility with Banque des Territoires, which acquired a 49% stake in 2025, leaving TagEnergy as the majority shareholder.

The investment is the first under a three-year partnership between TagEnergy and Banque des Territoires aimed at financing several large-scale battery projects in France.

Banque des Territoires has invested in electricity storage since 2021 and currently has more than 250 MW of battery capacity in operation, 150 MW under construction and several hundred megawatts in development.

The financial institution said it plans to increase its involvement in the sector, which is expected to play a growing role in France’s decarbonized electricity system but continues to face challenges in securing bank financing due to the relative immaturity of battery storage business models.