Geothermal Energy in District Heating

Why geothermal heat matters

Geothermal district heating offers something few other renewable technologies can: constant, base-load energy that works every hour of every day, regardless of the season or weather. Once a system is in place, it can provide decades of stable, low-carbon heat without relying on imported fuels.

For cities and utilities aiming to cut CO₂ emissions and improve energy security, geothermal is a valuable addition to the energy mix. It complements other renewable heat sources, such as solar thermal or industrial waste heat, and reduces the need for fossil-based backup systems.
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How it works

A geothermal district heating system begins with exploration. Geological surveys and seismic studies identify promising underground reservoirs. Then two or more wells are drilled: at least one production well is needed to bring hot water to the surface, and one or more injection wells are needed to return the cooled water to the same underground formation from which it came.

At the surface, the geothermal water passes through a heat exchanger that transfers as much energy as possible to the district heating network without mixing the two water streams.

More energy can be extracted from the geothermal loop using heat pumps, which can, at the same time, increase the flow temperature to match the network’s supply requirements, in case the reservoir temperature is not high enough on its own. The cooled geothermal water is then reinjected underground, maintaining reservoir pressure and ensuring the system’s long-term sustainability.
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The advantages in practice

For district heating operators, geothermal heat offers several clear advantages. It is renewable, with a constant resource that does not fluctuate like solar or wind. It has a high efficiency due to the relatively high reservoir temperature. It is local, reducing dependence on fuel imports and shielding heat prices from global market swings. And it is environmentally friendly, producing extremely low or even no emissions once operational.

Just as importantly, geothermal plants have long lifespans. With proper maintenance, the wells and surface systems can operate for decades, making them a sound long-term investment for municipalities and energy companies committed to the green transition.
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Challenges to overcome

Despite its many strengths, geothermal district heating requires the right conditions to succeed. The geology must be suitable – deep, water-bearing layers with good permeability and the right temperature are essential.

There must be a local heat demand of sufficient size to ensure a relatively high number of full-load hours. And finally, a suitable plot for the drilling, construction, and operation of the surface facilities must be found.

The upfront investment is significant, as drilling and exploration are costly, and there is always some degree of uncertainty about the exact yield until the first well has been tested.

This exploration risk can be reduced through a portfolio approach, insurance schemes, public support programmes, or partnerships. Project timelines are also relatively long, often taking several years from feasibility studies to commissioning.
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Proven examples in Denmark, Germany, and France

In Denmark, the town of Thisted has operated one of Europe’s first such plants since 1984, supplying the community with stable renewable heat for more than 4 decades. New large-scale projects are under development in Aarhus and Greater Copenhagen (Virum), aiming to deliver significant shares of local heating demand.

Elsewhere in Europe, geothermal is scaling rapidly. Munich, Germany, has committed to covering a large share of its district heating with geothermal energy by 2040. In Paris, France, more than 40 geothermal plants have been in operation since the 1970s, serving hundreds of thousands of residents.
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Where it makes the most sense

Geothermal district heating is best suited for areas with both the right geology and a stable and relatively high heat demand. Urban areas, large towns, and industrial clusters are particularly attractive locations, especially when local governments and district heating companies have clear decarbonisation strategies and are willing to support long-term renewable energy projects.
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A key role in the green transition

As district heating networks around the world work to replace fossil fuels with renewable sources, geothermal heat is emerging as a dependable foundation for the future. Its ability to provide constant, local, low- or no-carbon energy makes it an ideal accelerator of the green heat transition – especially when combined with other renewable and recovered heat sources.

In short, when the conditions are right, geothermal district heating is more than just a technology — it is a long-term commitment to clean, stable, and affordable heat for generations to come.