Neoen and RTE sign a contract to trial grid forming battery services

Paris, 13 January 2026

Neoen and RTE sign a contract to trial grid forming battery services

• Neoen’s Breizh Big Battery (BBB) will provide the French electricity transmission network with a grid forming function for the first time as part of a trial conducted with Réseau de Transport d’Electricité (RTE) to retrofit inverters.
• With a capacity of 92 MW/183 MWh, BBB is Neoen’s first large-scale battery in France and the largest in Brittany.
• The battery is currently under construction and the trial will start in the second half of 2026.

Neoen, the leading French independent producer of exclusively renewable energy and one of the world’s largest battery operators, has signed a contract with French grid operator RTE to strengthen the stability of the French power grid. With the Breizh Big Battery (BBB), Neoen will provide RTE with an innovative grid forming service.

In France, current battery storage facilities operate in grid following mode, in which inverters synchronise with the grid’s frequency. As ‘followers’ by design, these systems offer a slower and more limited response to fluctuations in electricity supply and demand.

By switching the inverters synchronisation mode through a retrofit, batteries can autonomously stabilise voltage and frequency by actively compensating for grid variations — this is known as grid forming. Without depending on an external reference source, grid forming enables an instantaneous response to grid disturbances, ensuring a more rapid stabilising effect on the power system.

To assess the benefits of this approach, RTE and Neoen have launched an experiment to convert an inverter from grid following to grid forming mode, which will run for at least one year. Once deployed, BBB will then become the first battery in France to offer these enhanced capabilities.

With a capacity of 92 MW/183 MWh, the BBB will be one of France’s biggest batteries and the largest in the Brittany region. The lithium-ion battery will be located in the village of Pleyber-Christ in Finistère. Currently under construction, the battery is expected to start operating over the summer of 2026.

Since 2017, the company has developed a battery portfolio with capacity in operation or under construction currently standing at 2.8 GW / 8.1GWh. It includes some of the largest batteries in the world, such as Collie Battery (560 MW / 2,240 MWh), the largest battery in operation in Australia, as well as Isbillen Power Reserve (93.9 MW/93.9 MWh) in Sweden and Yllikkälä Power Reserve (86.4 MW/142.9 MWh) in Finland, which are the largest in the Nordic countries.

Contact
Neoen
communication@neoen.com

Press
Fabrice Baron
+33 6 14 08 29 81
fabrice.baron@omc.com
Aurélie Bozza
+33 6 21 54 38 11
aurelie.bozza@omc.com

Guillaume Decaen, CEO of Neoen France said: “We’re extremely proud to launch this one-of-a-kind pilot project in France. With this innovation, we’re demonstrating that our assets can contribute to the electricity system not only by generating and storing electricity, but also by providing the critical services grids need to operate.”

Gabriel Bareux, R&D director from RTE commented: “I am delighted with this experiment, which aims to test cutting-edge technological advances capable of enhancing grid stability. It marks a first in France and represents the culmination of research in which RTE is at the forefront at the European level. Our ambition is to turn the rise of power electronics into an opportunity for the electricity system’s operation.”

Xavier Barbaro, CEO du Groupe Neoen concluded: “With a proud history of expertise in battery storage in Australia and the Nordic countries, we’re delighted to be bringing our storage know-how to the French electricity grid. The project reinforces Neoen’s pioneering role in storage technology and our commitment to delivering smart, reliable, and sustainable energy solutions to our customers in France and around the world.”

About Neoen

Founded in 2008, Neoen is one of the world’s leading renewable energy companies, with expertise in solar, onshore wind power and battery storage. Neoen plays an active role in accelerating the energy transition of the countries where it operates by delivering clean, competitively priced local energy. Neoen’s total global capacity in operation or under construction stands at 8.3 GW. A high-growth company, Neoen intends to install another 10 GW by 2030. Neoen is managed by an international team of experts led by Xavier Barbaro, Director of BRHL UK Holdings Ltd and BRHL UK Midco Ltd, President of Cartusia S.A.S., Group CEO.

Neoen operates close to 200 assets across three continents. Its flagship assets include Western Downs Green Power Hub in Australia, comprised of the country’s largest solar farm (460 MWp) and Western Downs Battery (540 MW / 1,080 MWh); Collie Battery (560 MW / 2,240 MWh) one of the world’s most powerful large-scale storage systems; France’s most powerful solar farm (300 MWp) in Cestas; and Finland’s largest wind farm (404 MW) in Mutkalampi.

For more information: www.neoen.com