Companies are finding creative ways to use heat from data centres

When it comes to heat, data centres deliver a double whammy. These massive computing hubs generate a constant torrent of excess heat while simultaneously using vast amounts of power to get rid of it. An estimated 38% to 40% of energy used by data centres goes toward cooling. 

But instead of using energy to cool their servers, some companies are trying to recover heat and put it to use. “What we try to do,” says Sacha van Geffen, a lead engineer at Leafcloud, “is actually see if we can place some of those compute resources that generate a lot of heat really close to a place where heat is needed.”

Leafcloud is an Amsterdam-based cloud services company that turns waste heat into warm showers through a distributed network of servers, or “leaf sites.” To do this, Leafcloud uses off-the-shelf components to build heat-waste-recovery systems inside the technical rooms of facilities like large apartment complexes, swimming pools or retirement homes, van Geffen says. The heat captured from the servers is used to produce hot water for the building.

Leafcloud isn’t the only company putting heat waste to work. U.K. company Heata offers a similar service to individual homeowners. The 2025 Paris Olympics pool was partially heated from data-centre servers run by the company Equinix. In Brooklyn, Bathhouse uses waste heat from Bitcoin mining rigs to warm its spa pools. Nexalus in Ireland harnesses heat waste to improve efficiency and lower data-centre energy consumption.

Heat waste from computing workloads is considered low-grade heat, meaning anything less than 100°C. “With low temperature grades,” says Amin Mohammadi, a PhD candidate at Simon Fraser University’s Laboratory for Alternative Energy Conversion, “converting that energy to thermal energy or cooling energy would be the best option that you have.” In other words, it’s too gentle to be converted to electricity such as with steam from a boiler, but with the help of heat pumps, it’s perfect for making a hot shower or keeping interiors toasty on a cold day. 

There are data centres and centralized district heating systems working together, too, such as Stockholm Exergi or Denmark’s Fjernvarme Fyn. This application could play an important role in heat-waste recovery from the growing demand for computing capacity. A recent Leafcloud white paper outlined that different thermal outputs could be optimized for different applications: high-performance computing for higher heat-waste temperatures, such as 60°C to 80°C, could be sent to district heating, whereas standard servers that produce temperatures in the 40°C to 60°C range could be used for building heat. 

The pieces are already in place to start making a difference. Leafcloud and other companies can capture heat waste now and without complex infrastructure that would otherwise take years to build out, such as constructing a data centre or retrofitting pipe systems for larger-scale municipal heating. By placing the heat source close to where it will be used, overall efficiency is improved, because it avoids the energy loss that occurs when heat has to move through a large system, Mohammadi says. 

In addition to heat-waste recovery, van Geffen says that Leafcloud’s distributed server system has other benefits. Using residual heat onsite not only reduces the reliance on other energy sources needed to heat water, such as natural gas; it also reduces costs. In a world where our data is so often controlled by secretive corporations, installing local servers in basements in Europe offers security and control, van Geffen says: “What we are offering is sovereign data storage, where the heat is also put to a good use.”