# Caldera

> Caldera is a UK clean-energy company decarbonizing industrial heat with Warmstone, a thermal battery built from recycled aluminium and volcanic rock inside vacuum-insulated heat cells. Its electric Storage Boiler converts cheap off-peak renewable electricity into industrial steam and hot water up to roughly 200C, offering factories a zero-emissions alternative to gas boilers. Founded in 2017 in Fareham, England, Caldera closed a 10M pound Series A led by Germany's GEA Group in 2025 and landed its first commercial order from the NHS.

- **Founded:** 2017
- **Headquarters:** Fareham, England, United Kingdom
- **Founders:** James Macnaghten (Co-founder & CEO), Guy Winstanley (Co-founder & COO)
- **Team size:** ~35 employees
- **Products:** Warmstone, Industrial Storage Boiler, Domestic Warmstone heat battery
- **Notable:** First in the world to create a heat-storage material from volcanic rock and recycled aluminium (2018)., Closed a 10M pound Series A led by GEA Group in March 2025., Won its first commercial order, a 10 MWh Storage Boiler, from an NHS hospital.

## Products & services

- **Warmstone** — Proprietary thermal storage material made from recycled aluminium and volcanic rock, charged by electric resistive heating and held in vacuum-insulated double-walled heat cells with minimal standby loss.
- **Industrial Storage Boiler** — Modular electric heat battery storing 5 to 100 MWh, charging in about 2.5 hours from off-peak or renewable electricity, delivering hot water and steam up to roughly 200C as a drop-in replacement for gas boilers.
- **Domestic Warmstone heat battery** — Earlier ~100 kWh home unit providing heating and hot water for a four-bedroom house for a full winter day, trialled in the Energy Systems Catapult Living Lab.

## Achievements

- First in the world to create a heat-storage material from volcanic rock and recycled aluminium (2018).
- Closed a 10M pound Series A led by GEA Group in March 2025.
- Won its first commercial order, a 10 MWh Storage Boiler, from an NHS hospital.
- Awarded 4.3M pounds from UK DESNZ to build a full-scale industrial demonstrator in Fareham.
- Industrial demonstrator reached 1 MWe charging capacity (2024).
- Exhibited at Hannover Messe 2025 and spoke at ESS Expo 2025.
- Featured by BBC, Sky News and The Times.

## Latest updates

- **2026-04** — Industry coverage on rising demand for gas-to-electric steam as inquiries for large heat batteries grow.
- **2025-03** — Announced 10M pound Series A led by GEA Group, which took a minority stake.
- **2025** — Secured first commercial order - a 10 MWh Storage Boiler for an NHS hospital.
- **2025-04** — Exhibited at Hannover Messe and presented at ESS Expo on decarbonizing industrial heat.

## Links

- Website: https://caldera.co.uk
- LinkedIn: https://www.linkedin.com/company/caldera-energy/
- YouTube: https://www.youtube.com/channel/UCuNf48NrptX8Hds5l5rbYTw

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Profile page: https://yespress.io/caldera
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Last updated: 2026-06-15