Domestic datacentres are using the waste heat generated by computer servers to warm household hot water, potentially reducing energy bills and the environmental impact of larger datacentres. One London homeowner says a Heata server attached to his water cylinder has cut his hot-water costs by £10–£15 a month.

Heata’s units run cloud-computing jobs and aim to provide about 80% of a home’s hot-water heating, with the company covering the server’s electricity costs. They require a vented, unpressurised cylinder and fibre broadband, and are unsuitable for combi boilers; 100 homes currently have the system, with 3,000 people awaiting installation. A separate Essex trial is testing nearly 500 small computers grouped into a freezer-sized unit that converts their heat into energy.