In an innovative approach that transforms an environmental problem into a sustainable solution, Denmark is repurposing excess heat from data centers to warm thousands of homes. Instead of wasting energy, projects led by tech giants like Microsoft and Meta are channeling this heat through advanced heat pumps into local district heating networks — reducing carbon emissions and providing stable home heating.

In a world of relentless digital expansion, where the demand for data centers is growing at an astonishing pace, a pressing question arises: what do we do with all the wasted heat? Data centers — the hidden arteries of the internet, AI, and cloud services — consume enormous amounts of energy to run and cool thousands of servers around the clock. As a byproduct, these servers generate large quantities of low-grade heat, which is often expelled outdoors, much like running heaters in the middle of a desert.

Denmark, a country long known for environmental innovation, refused to accept this waste. Instead of letting this energy dissipate into the air, the country decided to give it a second life — in people’s homes. In a nation blanketed by cold weather, the government and its industrial partners introduced an idea that seems simple on the surface but is revolutionary in practice: using excess heat from data centers to warm residential neighborhoods.

This is more than just a lofty ambition on paper. In the Danish cities of Høje Taastrup and Odense, thanks to pioneering projects by Microsoft and Meta (formerly Facebook), this idea has become a tangible reality, providing warmth to thousands of homes each year.

In Høje Taastrup, Microsoft is building a new data center designed to redirect excess heat to nearly 6,000 homes, in partnership with two local heating utilities. In Odense, Meta’s data center has been operational since 2020, recovering approximately 100,000 megawatt-hours of energy annually — enough to heat around 6,900 homes through the local district heating system.

What makes this approach unique and transformative is that it treats excess heat not as a problem, but as an opportunity. Energy once wasted into the atmosphere — sometimes contributing to local heat islands — is now improving residents’ quality of life while cutting carbon emissions.

Turning this vision into reality, however, was far from straightforward. The main technical challenge lay in the nature of data center heat itself: it is “low-grade” heat, not hot enough on its own to heat buildings. Here, technology had to step in. Advanced heat pumps were installed to raise the temperature of collected hot water, making it suitable for district heating networks. Additionally, data center locations had to be carefully chosen near existing heating infrastructure, minimizing the need for costly distribution investments. This has been successfully implemented in Høje Taastrup through the advanced VEKS network, and in Odense via the Fjernvarme Fyn system.

Economically, the equation is even more complex. Building data centers designed for heat recovery and upgrading heating networks to handle this new energy source require meticulous planning and tight cooperation between stakeholders. Public-private partnerships played a crucial role: tech companies financed much of the retrofitting and infrastructure integration, while municipal authorities coordinated and executed the broader plan.

At Meta’s Odense center, hot air from the servers is captured and passed over pipes filled with water, heating it up. This water is then transferred to heat pumps — themselves powered by renewable energy — which raise its temperature to a level suitable for household heating before it is pumped into the city’s district heating grid. In Microsoft’s project, the design was integrated from the earliest planning stages to align seamlessly with VEKS, ensuring heat recovery with minimal losses and lower infrastructure costs.
Beyond the technical aspects, both companies have committed to operating their data centers using 100% renewable energy. This means the resulting heat is not just recycled but is also fully green, aligning each step of the process with Denmark’s sustainability goals — from electricity source to the warmth felt inside living rooms.

These outcomes are not theoretical. Environmentally, the projects have significantly reduced CO₂ emissions and eased reliance on fossil fuel-based heating. Economically, residents enjoy more stable — and potentially lower — heating bills in the long term.

The success of Denmark’s experiment offers valuable lessons in merging technology with sustainability. Chief among them: the importance of proximity between data centers and heating infrastructure, the need to involve local communities early, and the power of collaborative planning from day one. On a social level, this approach has built a new bridge between digital infrastructure and everyday life. Ordinary residents now feel the effects of “digital transformation” in a tangible way — this time, as comforting warmth during harsh winter nights.

References:
• https://local.microsoft.com/blog/datacenter_heat_repurposed/
• https://sustainability.atmeta.com/wp-content/uploads/2020/12/FB_Denmark-Data-Center-to-Warm-Local-Community.pdf