Press release
Paris, Thursday 29 July 2026.
For this project, Kallista Energy has selected Omexom Conversion & Storage (VINCI Energies) for the construction and is renewing its partnership with Envision Energy for the supply of the BESS equipment. Kallista Energy is supported by Landesbank Saar (SaarLB) and BNP Paribas for bank financing. Battery optimisation will be provided by Agregio Solutions (EDF Group).
Following an initial battery storage project that has been under construction in Saleux since 2025, Kallista Energy is cementing its presence in the Hauts-de-France region with a new project in Neuilly-en-Thelle, a town situated between Paris and Beauvais, in the Oise department. Construction of the Neuilly-en-Thelle BESS (Battery Energy Storage System) began in early July 2026 and will be completed by spring 2028.
The Neuilly-en-Thelle battery energy storage system will help support the electricity grid, for example by providing frequency regulation services on RTE’s reserve markets. A battery-based electricity storage system can also help manage peaks in consumption by storing electricity when generation is abundant, then releasing it when demand rises, thereby avoiding the need to use thermal power stations. For example, a typical cycle might involve charging the battery during an afternoon peak in solar generation, then discharging it in the evening, when household consumption is at its highest.
The storage capacity of the Neuilly-en-Thelle site is equivalent to the energy needed to power 30,000 households¹ for a whole day, or the equivalent of 330 train journeys between Amiens and Paris².
The Neuilly-en-Thelle project has been developed entirely by Kallista Energy, with bank financing provided by its long-standing partners, Landesbank Saar (SaarLB) and BNP Paribas. The lithium iron phosphate (LFP) battery cells will be supplied by Envision AESC, a leading company in the field of battery technology³. Envision will also be responsible for site maintenance once the facility is operational and for recycling the batteries at the end of the site’s operational life, which is expected to be 25 years.
Battery optimisation will be carried out by Agregio Solutions, a subsidiary of the EDF Group, as part of its 10-year contract with Kallista Energy.
“The electrification of end-uses will only be able to realise its full potential if it is accompanied by a massive expansion of renewable energy. Battery-based electricity storage is a key driver in making this dual transformation possible and contributing to a low-carbon electricity system. The battery-based electricity storage facility at Neuilly-en-Thelle represents an investment of nearly 100 million euros and was built without any public funding,” Johann Tardy, Group CEO of Kallista Energy.
“Batteries only create value if they are optimized as closely as possible to market signals. Through a ten-year long-term contract, Agregio Solutions optimises and operates the Neuilly-en-Thelle battery and provides Kallista Energy with its full expertise in maximising the value of flexibility. In practical terms, we continuously balance the energy, reserve and system services markets in order to maximise the asset’s market value throughout its operational life,” Vincent de Rul, Chairman of Agregio Solutions.
Kallista Energy: Nishal Ramdoo | 06 07 07 13 55 | nramdoo@KallistaEnergy.com
Founded in 2005, Kallista Energy is an independent renewable energy producer whose mission is to generate electricity at the lowest possible cost – both economically and environmentally – to support the energy transition and electric mobility. With a team of over 110 employees, the company’s activities cover the entire value chain of renewable energy projects: development, financing, construction in collaboration with specialist partners, operation and maintenance of wind farms, as well as the decommissioning and renewal of facilities. Kallista Energy operates in onshore wind, solar power, electric mobility (with its YAWAY ultra-high-power charging network) and battery-based electricity storage. The group has a presence in France, Germany and the Netherlands. It owns and operates 43 energy facilities (including 434 MW of wind and solar power). The group is currently completing the construction of a battery storage facility in Saleux in the Somme and is working on other storage projects in France and across Europe.
1 Estimate based on 4,500 kWh per household per year for everyday uses excluding electric heating. Sources: RTE / ADEME.
2 Estimate based on 10 kWh per km for a train travelling at 100 km/h. Sources: Objectif Carbone.
3 Envision AESC commissioned a 10 GWh battery Gigafactory in the Hauts-de-France region in June 2025.
