French energy technology startup Epyr has raised €15 million (USD 16.8 million) in a Series A round to scale thermal energy storage for industry, with the first deployment a 35 MWh unit set to replace all natural gas consumption at paper manufacturer Papeco's Orval-sur-Sienne site in France.

SlateVC led the round. Existing investors AENU, Daphni, OVNI, WEPA Ventures and Aurum Impact also participated. The company, founded in 2024 by Léa Dardenne and Bastien Oggeri and based in Paris, will direct the capital toward accelerating new thermal storage projects, starting with Papeco.

Why industrial heat matters to the material stream

Industrial heat accounts for roughly 20% of global energy consumption and still runs largely on fossil fuels, above all natural gas in Europe. The EU has made electrifying that heat a priority, targeting both emissions cuts and reduced dependence on imported fossil gas.

Epyr's answer is a storage-and-service package rather than a box sale. The company combines its thermal storage technology with system integration, energy management and financing under a Heat-as-a-Service model. The material at the core is deliberately mundane: firebrick.

How the technology works

The system draws electricity when prices are low, using it to power electric heating elements that heat air. The air in turn heats firebricks, which store the energy at high temperature. The stored heat is released on demand for industrial processes.

That sequence does two things at once. It cuts energy costs and emissions for the host plant, and it gives the electricity grid a flexible load that can absorb power nobody else wants.

The founders point to a market signal that keeps strengthening. Dardenne and Oggeri said: "In France, there have already been more hours of near-zero or negative power prices this year than in 2025. That electricity is the cheapest, cleanest energy source European industry has. Our mission is to harness it, and this Series A lets us do it at scale."

Built versus announced: the Papeco project

Capacity today consists of the announced Papeco installation. Epyr expects it to be France's largest thermal energy storage installation, with the 35 MWh unit designed to replace the site's entire natural gas consumption. Papeco, a French hygiene paper manufacturer, hosts the project at its Orval-sur-Sienne facility.

Beyond Papeco, the round funds a pipeline rather than delivered megawatt-hours. The company describes the rollout as acceleration, not completion. The distinction matters for anyone counting decarbonised process heat in France this decade.

The scale of the prize is not small. Sébastien Léger, co-founder and general partner at SlateVC, said: "Epyr has the potential to become a European leader in electrifying the €100bn industrial heat market. We are delighted to enable their growth in France and beyond."

What decides what happens next

Two milestones will determine whether the Series A buys momentum or merely runway. The first is commissioning at Orval-sur-Sienne: a 35 MWh unit replacing a full site's gas consumption is a claim best settled by an operating plant. The second is contract count, because Heat-as-a-Service lives or dies on repeat customers signing on to flexible heat.

Watch the Papeco commissioning date.