Berlin’s municipal heat planning is providing a more detailed picture of where geothermal systems could contribute to future urban heating and cooling, including larger borehole fields coupled with heat pumps and heat networks.
Rüdiger Grimm, CEO of German geothermal engineering and consulting company geoENERGIE Konzept GmbH, presented the Berlin work at the European Geothermal Heating & Cooling Days in Dublin last week. His presentation focused on how geothermal potential can be assessed alongside heat demand, available land, existing networks and project economics at city scale.
The approach does not concern conventional deep hydrothermal geothermal development. Instead, it examines borehole heat exchanger systems extending to depths of up to several hundred metres, with heat pumps used to raise temperatures to useful levels.
For ThinkGeoEnergy, the relevance lies particularly in applications where these systems move beyond individual buildings towards larger developments, campuses, neighbourhoods and heat networks.
From geothermal potential to usable urban heat
Germany’s municipal heat-planning framework requires cities to assess existing heat demand and infrastructure, identify potential renewable heat sources and develop pathways towards climate-neutral heat supply.
Berlin adopted its city-wide heat plan in June 2026. The plan assesses renewable heat and waste-heat resources and identifies areas where heat networks or decentralised solutions may be more suitable.
Grimm said geothermal assessments need to make an important distinction between theoretical, technically accessible and economically viable potential.
A large theoretical geothermal resource does not automatically translate into heat that can realistically be developed.
Buildings, land ownership, protected areas, groundwater restrictions and the space available for drilling all reduce the technical resource. Economics then further determine which part of that potential can become an actual project.
For the Berlin work presented by Grimm, the analysis was carried out across approximately 26,000 city blocks.
Data on geology and hydrogeology were combined with buildings, available open space, heat demand and existing energy infrastructure. The resulting modelling can estimate how many borehole heat exchangers could be accommodated and how much of the local heat requirement they could supply.
The final step brings costs into the assessment.
“Even if we can do it, it doesn’t mean that it’s economical,” Grimm said.
Moving towards larger geothermal systems
The Berlin analysis includes borehole heat exchangers at depths ranging from around 100 metres towards 200, 300 and in some cases 400 metres.
While these remain within Germany’s classification of near-surface geothermal energy, increasing borehole depth and combining multiple wells can allow significantly more heat to be accessed from a constrained urban site.
That makes the approach potentially relevant for larger buildings, neighbourhood developments and low-temperature heat networks rather than solely individual residential heating systems.
The distinction is important.
Individual ground-source heat pumps for houses form a mature heating market in several European countries, but are not the primary focus of ThinkGeoEnergy’s geothermal heating coverage. Of greater interest are systems that access meaningful volumes of subsurface heat and integrate them into larger heating and cooling infrastructure.
Berlin’s heat-planning work provides one example of how such opportunities can be identified before individual projects are developed.
Cooling improves the geothermal equation
One of the more significant findings presented by Grimm concerned the combination of heating and cooling.
A borehole field used only to extract heat gradually cools the surrounding ground. If excess heat from building cooling is returned to the subsurface during warmer months, the geothermal resource can be regenerated before the following heating season.
A balanced system seeks to return approximately as much heat to the subsurface as it extracts over the course of the year.
Grimm described this as both technically and economically preferable.
Modelling presented for Berlin showed indicative levelised heat costs clustering at roughly EUR 0.35/kWh for heating-only operation under the assumptions used in the study.
Adding thermal regeneration reduced the modelled cost towards approximately EUR 0.27-0.28/kWh, while balanced heating and cooling brought it towards approximately EUR 0.26/kWh and reduced the variation between sites.
The figures are specific to the Berlin modelling and its assumptions, including Germany’s relatively high electricity prices. They should therefore not be interpreted as general geothermal heat-cost benchmarks.
The more significant finding is the change in how the geothermal resource is used.
“Our price of heating goes down when we include cooling,” Grimm said.
He argued that this means the subsurface should increasingly be considered as part of a thermal storage system rather than simply a source from which heat is extracted.
“We have to see our underground geothermal system not as a deliverer of heat. We have to see it as storage.”
Connecting geothermal with heat networks
This thermal balancing becomes particularly relevant when geothermal is integrated into larger heating and cooling systems.
Grimm’s Berlin analysis considers existing energy networks as another layer in determining where geothermal development could make sense.
This can help identify areas where borehole fields and heat pumps could contribute to existing networks or future low-temperature and fifth-generation district heating and cooling systems.
Such networks can connect multiple buildings with different heating and cooling profiles. Excess heat from one user can potentially become an input elsewhere in the system or be stored in the ground for later use.
That expands the role of geothermal beyond supplying heat from an individual borehole field.
It also aligns with Berlin’s wider heat-planning approach, which identifies areas suitable for heat networks based on heat density, existing infrastructure and proximity to renewable or waste-heat resources.
Planning could create a deployment challenge
The work also raises a different question: what happens if municipal heat planning identifies large volumes of economically attractive geothermal potential?
Grimm said Germany could again face questions around drilling capacity as more municipalities move from preparing heat plans towards implementation.
Germany requires cities with more than 100,000 inhabitants to prepare municipal heat plans, with smaller municipalities following by 2028.
If geothermal emerges as a viable option across a significant number of those plans, sufficient drilling equipment, specialist contractors and technical expertise will be needed to convert mapped potential into operating systems.
Grimm said the methodology used for Berlin can be applied to other cities where sufficient geological, heat-demand and infrastructure data are available.
The opportunity highlighted by the Berlin work is therefore less about individual ground-source installations and more about integrating geothermal into long-term urban infrastructure planning.
For larger borehole fields coupled with heat pumps, cooling and heat networks, the ability to model technical potential, heat demand and economics together could help identify where geothermal can make a meaningful contribution to city-scale heating and cooling.
