zero carbon heat batteries
We are the makers of Warmstone™, the world’s most efficient and technologically advanced zero carbon heat battery for household use.

I want to buy

If you’re on oil or LPG, our Zero-Carbon Warmstone Heat Battery is going to save you thousands of pounds in heating bills – as well as significantly reduce your family’s carbon footprint. Our solution is cheaper and easier to install than air source heat pumps with no disruption to your home.

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Is Warmstone for me?

I live in the UK and want to reduce my carbon footprint
My home and hot water is currently heated by oil or LPG
I have or will soon install a smart meter

cheaper and easier to install than air source heat pumps

Lifetime heating costs vs ASHP
Lifetime heating costs vs ASHP

Worked Example: 153 m2 detached home using 25,236 kWh per annum for heating and hot water. The home currently uses oil for heating and generates 7.75 tonnes CO2 per annum. A comparison of Warmstone annuals costs versus an air source heat pump plus retrofit.

Source Gemserv Analysis

*Installed cost subject to T&Cs


WarmstoneTM is our patented solid storage material that is made from a combination of recycled and natural materials.

We use cheap nighttime electricity to heat the solid core of the Caldera. We then use the stored heat to provide a supply of hot water and heating to your home during the day when you need it.

If you live in a house that uses heating oil or LPG, has solid walls (built pre-1930) and normal radiators, then you will almost certainly be better off with a heat battery.


We are excited to be shareholders in Caldera and look forward to supporting their vision to help decarbonise home heating.
Nina Zwiebelhofer
Owner and managing director of the König Metall Group
Caldera has created a potentially game-changing technology with Warmstone, and we are working hard to help them to bring it to market.
Guy Newey
Strategy and Performance Director at Energy Systems Catapult
The Warmstone heat battery is a simple, innovative technology and a game changing step forward.
Hans-Jörg Leuze
Executive Board Member of the König Metall Group

I want to buy