Find your Local
We're a national brand with a local team in your area.
Select the location below that's closest to you:
The Next Million Powerwall Rebate - you can get up to £750 back for your Tesla Powerwall installation: Find out more
When most people think about home energy storage, they picture bulky hot water cylinders, or sleek lithium batteries tucked away in a utility room. There’s another technology quietly transforming how we store and use energy: introducing phase change materials (PCMs). These advanced materials are at the heart of modern heat batteries like Sunamp, helping homes cut carbon, save space, and save money on their energy bills.
Phase change materials are substances that can store and release large amounts of energy as they change state, typically from solid to liquid and back again. It’s the same basic principle as ice melting and freezing, but PCMs are engineered to melt and solidify at higher, precisely controlled temperatures.
When the material melts, it releases stores energy as heat. This solidifying and melting process can be repeated lots of times with minimal degradation, allowing for long-lasting and efficient thermal storage.
In our Sunamp heat batteries, the PCM sits inside a highly insulated unit. Electricity, often from solar panels or off-peak tariffs, charges the unit and stores this energy until it’s needed. When hot water is needed, the stored energy is used to heat your water quickly and efficiently, delivering hot water on demand without the standby losses of a conventional cylinder.
Traditional hot water systems rely on storing large volumes of water and keeping them hot. That constant reheating wastes energy – and money – and can lead to heat loss, even in well-insulated tanks. Phase change materials work differently, as they store energy with very low losses over time.
Because the PCM only changes temperature when charged or discharged, the stored energy stays locked in until it’s needed. This makes PCM based systems exceptionally efficient, compact, and safe. For homeowners, it means more usable space, faster hot water delivery, and lower running costs.
As the UK moves away from gas heating, new technologies like heat pumps, solar PV, and electric heating will dominate the home energy landscape. The challenge is balancing when energy is generated with when it’s actually used.
This is where phase change materials can be used. A Sunamp heat battery can charge when electricity is cheap, or from renewable sources, and release that energy later when needed in the form of heat.
By smoothing out energy demand and reducing strain on the grid, PCMs make it easier for households to rely entirely on renewable energy for hot water. They also help maximise the value of solar installations, by storing surplus generation that would otherwise be exported for little financial return.
For many homeowners, the appeal of PCM technology isn’t just its energy efficiency, it’s the practicality. A Sunamp heat battery can replace a large 300L cylinder with a compact unit that’s up to four times smaller. There’s almost no risk of leaks or Legionella bacteria as the units don’t store water, and there’s no mandatory annual maintenance.
That makes it a particularly attractive option for smaller homes, apartments, and retrofit projects where space is limited.
Phase change materials may sound like cutting-edge science, but they’ve actually been used for decades in aerospace, refrigeration, and temperature-control applications. What’s changed is their refinement for everyday domestic use, thanks to companies like Sunamp, who have developed reliable, non-toxic PCMs that can last over 50 years without losing capacity.
As manufacturing scales up and integration with solar and smart home systems improves, Sunamp heat batteries are likely to become as common as electric boilers or battery storage units. They represent a key step towards fully electric, zero-carbon homes that use energy far more intelligently than before.
Phase change materials are redefining how we think about heat storage. Compact, efficient, and long-lasting, they’re enabling households to use clean energy when it’s most available, not just when it’s generated. As the UK accelerates its move towards net zero, technologies like Sunamp’s PCM based heat batteries will play a crucial role in making home energy smarter, greener, and more sustainable.
