UK’s Harmony Energy to build France’s largest BESS

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Developer Harmony Energy is set to build a 100MW/200MWh battery energy storage system (BESS) project in France, the country’s largest.

The company will deploy Tesla Megapacks for the 2-hour ‘Cheviré’ project in Nantes Saint-Nazaire Harbour, western France, the first large-scale 2-hour system in the country, Harmony said. The project will also utilise Tesla’s Autobidder energy management system (EMS) platform.

The project site was previously occupied by the Cheviré oil, coal and gas power station which operated until 1986. Retired legacy power plants make ideal locations for clean energy projects thanks to their existing grid infrastructure.

Harmony Energy COO for France Clément Girard said: “It’s an exciting location given the historical importance of the fossil fuel coal power station, but looking ahead, the delivery of the Cheviré BESS will transform the site into exactly the opposite, facilitating the green electrification of the French energy system, whilst offsetting several hundred thousand tonnes of CO2.”

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The firm didn’t give an expected commercial operation date (COD) for the French project.

Harmony Energy is a developer and investment advisor to the Harmony Energy Income Trust (HEIT), a UK-listed fund which owns and operates BESS projects in the UK/GB market, including the two largest operational units in Europe, sized similarly to the Cheviré project. Harmony Energy is a separate entity that develops projects which can be sold to HEIT or to other owner-operators, and its team manages HEIT.

Like other UK BESS owner-operators, it has sought to diversify internationally as revenues on home soil plummet. In February, Harmony Energy chief investment officer Paul Mason told an audience at Solar Media’s Energy Storage Summit 2024 in London that it had a ready-to-build portfolio in France, Germany and Poland. Its Poland head discussed that market with us a year ago although it has yet to announce major projects there.

The market outlook in the UK has become so negative – rightly or wrongly – that HEIT said it was considering selling its portfolio entirely.

13 October 2026
London, UK
Now in its second edition, the Summit provides a dedicated platform for UK & Ireland’s BESS community to share practical insights on performance, degradation, safety, market design and optimisation strategies. As storage deployment accelerates towards 2030 targets, attendees gain the tools needed to enhance returns and operate resilient, efficient assets.

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