Storage: Harmony Energy inaugurates France's largest BESS plant at the port of Nantes (Loire-Atlantique)

100 MW/200 MWh: this is the capacity of the battery storage plant inaugurated by Harmony Energy at the port of Nantes Saint-Nazaire (Loire-Atlantique) on 16/12/2025.

This is the largest French storage plant to date, and the first plant with the capacity to store two hours of energy. "This battery will increase the installed capacity of battery storage on the French grid by around 15%," said Clément Girard, Managing Director and Chief Operating Officer of Harmony Energy France.

The Cheviré plant is located on the site of a former EDF thermal power station (1954-1986), which at the time was fuelled by coal, gas and oil. "We're delighted to be giving it a new lease of life, symbolising the transformation of the grid towards an increasingly low-carbon mix," continued Clément Girard. Launched at the end of 2022, the project took three years to develop and 12 months to build. "The thermal power station was the main challenge on the site, because all the foundations for the power station are still there underground. So we had to adapt, relocate equipment and adapt construction techniques,…