Energy bills are set to rise next month. But one innovative solution could help homeowners save money — by using the heat from computers to warm tap water.
How It Works
At the heart of the system is a small computer server, attached to a home’s hot water cylinder.
When the server runs, it generates heat. This heat is transferred directly to the water tank through thermal contact.
The system works only with vented, unpressurised water tanks — those typically wrapped in blue insulation.
Installation Process
- Engineers cut a hole in the tank’s insulation.
- A container with the server is glued to the front of the tank.
- The unit is connected to a power and fibre broadband source.
- No plumbing changes are needed.
Installation takes about two hours. The homeowner pays only for broadband. The company covers electricity costs.
Key Facts
The Surrey-based company heata has installed its units in homes.
There are 3,000 people on a waiting list for installation.
heata’s units provide about 80% of the heat needed for domestic hot water.
Homeowners still use gas boilers during peak times — such as when taking a bath.
Cost and Savings
heata pays for electricity. Homeowners pay for broadband only.
Giles Gibson, a user in south-east London, estimates his monthly water bills have dropped by £10 to £15 since installation.
Over a year, this adds up to significant savings.
Another Domestic Project
In Essex, a separate project is testing a mini datacentre made of nearly 500 matchbox-sized computers.
The unit, called HeatHub, is made by thermify in Wales.
Computers generate heat, which warms mineral oil. This heat is passed through a heat exchanger to warm water in a radiator.
HeatHub units are designed for different home sizes:
- Three to four-bedroom homes: unit about the size of a washing machine.
- Flats: unit about the size of a microwave.
Thermify says the system could one day replace gas boilers entirely.
Cost and Performance
Monthly costs range from £90 for average homes. Larger homes pay more; smaller ones less.
The cost includes installation, leasing, and repairs. Contracts last a minimum of 10 years.
Thermify claims a 14% reduction in energy bills for homes with gas boilers. That jumps to 34% for homes with heat pumps.
These savings come from avoiding the cost of installing a boiler or heat pump.
Why It Matters
Large datacentres waste heat — a major environmental concern.
Domestic systems like heata and thermify aim to redirect that waste heat into useful home heating.
They offer a low-cost, scalable way to reduce energy bills and carbon emissions.
Limitations and Open Questions
The system does not work with combi boilers.
Units for unvented water tanks are in development.
Long-term performance and reliability data are still emerging.
While the concept is promising, it is not yet a mainstream solution.
For more on this topic, see the original report from The Guardian.
Sources & further reading
Featured image: How the Wikimedia Foundation can help you close the gaps… by Larasabri401, CC BY 4.0, via Wikimedia Commons. Image source · License
