Envision Energy and European renewable energy producer Kallista Energy have commenced construction on a large-scale battery energy storage system in the Hauts-de-France region, marking the second major collaboration between the two companies as France moves to strengthen its electricity grid infrastructure.

Project Scale and Timeline

The Neuilly-en-Thelle battery energy storage system, rated at 193 MW and 386 MWh, began construction in early July 2026. Commercial operation is expected before spring 2028. The project is located in the Hauts-de-France region of northern France and represents a significant expansion of grid-scale storage capacity in the country.

The system's storage capacity is described as equivalent to the daily electricity consumption of 30,000 households. Once operational, it will provide frequency regulation services to the French grid through RTE's reserve markets, contributing to the balancing of electricity supply and demand across the national network.

A Second Chapter in an Established Partnership

The Neuilly-en-Thelle project follows the Saleux project, which Envision Energy identified as its first battery energy storage system project in France, breaking ground in 2025. Both companies described the new development as building directly on the experience and working relationship established through that earlier initiative.

Johann Tardy, CEO of the Kallista Energy Group, said that the companies were leveraging the collaboration built through the Saleux project to deliver new storage infrastructure.

He framed battery energy storage as a key driver for electrification and the expansion of renewable energy capacity, both of which he described as essential to reaching a low-carbon economy.

Henry Peng, Senior Vice President at Envision Energy and President of its EU and LATAM Regions, said the second project with Kallista Energy reflected continued growth in a partnership built on shared ambitions for Europe's energy transition.

He described Envision's role as extending beyond the delivery of storage technology to encompass comprehensive lifecycle support aimed at maximising long-term asset value.

Technology and Local Manufacturing

The project will be powered by lithium iron phosphate cells supplied by Envision AESC, Envision Energy's battery manufacturing affiliate. Those cells will be produced at a 10 GWh gigafactory located in Hauts-de-France, the same region where the storage project is being developed. That facility has been operational since June 2025.

The use of locally manufactured cells is presented by the companies as a deliberate effort to combine battery production with system integration in a way that strengthens regional industrial capacity.

Envision Energy will take responsibility for the project's full lifecycle management, covering site maintenance through to battery recycling at the conclusion of the system's operational life. The project is designed for 25 years of operation.

Grid Services and Renewable Integration

The primary function of the Neuilly-en-Thelle system will be to provide flexibility services to the French electricity grid. Frequency regulation through RTE's reserve markets is cited as a core service the project will deliver, addressing the need to match electricity supply with fluctuating demand in real time.

The companies also described the storage system as a mechanism for enabling greater integration of renewable energy into the grid, a function that becomes increasingly important as France expands its wind and solar capacity.

Energy storage is widely recognised within the industry as a means of smoothing out the intermittency that characterises renewable generation, allowing surplus power to be captured and dispatched when needed.

Tardy's comments underscored this rationale, describing battery energy storage as central to the massive expansion of renewables that the transition to a low-carbon economy requires.

A Blueprint for Broader European Deployment

Beyond its immediate function in the French grid, the Neuilly-en-Thelle project is described by Envision Energy and Kallista Energy as providing a scalable model for energy storage deployment across Europe.

The companies used the phrase "Future Energy System" to characterise the broader strategic framework within which both this project and the earlier Saleux development sit.

Peng said that the integrated approach adopted for the project, combining technology delivery with long-term asset support, was intended to strengthen grid resilience, accelerate renewable energy integration, and support sustainable industrial development across the European continent.

The presence of Envision AESC's Hauts-de-France gigafactory within the same region as the project adds a dimension of supply chain proximity that the companies suggested enhances both the reliability of the development and the regional economic case for large-scale energy storage infrastructure.

Envision Energy described itself as a global leader in green technology, while Kallista Energy is identified as a European renewable energy producer. The two companies did not disclose the financial value of the Neuilly-en-Thelle contract in their announcement.

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