The Paris Basin stands as a proven model for large-scale urban geothermal heating. With the right geological conditions, strong policy backing, and careful integration into the wider energy system, cities around the world can replicate its success.
A unique geological resource beneath Paris
Beneath the streets of Paris lies one of Europe’s most important geothermal resources: the Dogger aquifer, a deep limestone formation rich in warm water. This aquifer lies between 1,500 and 2,000 metres below the surface and delivers water at 55–85°C – ideal for district heating.
The Paris Basin’s geology combines sufficient permeability for water flow with enough depth to reach useful temperatures, making it perfectly suited for large-scale geothermal use.
Four decades of continuous operation
Geothermal district heating in the Paris Basin began in the late 1970s and early 1980s, when France sought to reduce oil dependency following the global energy crisis. The first systems proved highly reliable, and the model quickly spread across the region.
Today, more than 40 geothermal plants are in operation around the Greater Paris area, supplying heat to over 250,000 households, as well as schools, hospitals, and public buildings. Many of these plants have been operating for decades with minimal decline in performance thanks to careful reservoir management and reinjection.
How the Paris Basin systems work
Most Paris Basin geothermal installations use a doublet system:
- A production well pumps hot water from the Dogger aquifer.
- A reinjection well returns the cooled water to the same formation to maintain reservoir pressure and sustainability.
- Heat exchangers transfer the geothermal heat to the district heating network without mixing the geothermal water with the network water.
Where higher temperatures are needed, large-scale heat pumps are often installed to boost the output to the required supply levels.
Integration into the urban energy mix
Geothermal energy in the Paris Basin is typically used as a base-load supply, covering the majority of annual heat demand. In colder months or during peak periods, it is supplemented by other sources such as biomass, natural gas, or heat from waste-to-energy plants. This hybrid approach ensures both reliability and low carbon intensity.
Environmental and economic benefits
The Paris Basin geothermal network collectively avoids hundreds of thousands of tons of CO₂ emissions each year compared to fossil fuel heating. The systems provide long-term price stability for customers, as operating costs are largely independent of global fuel markets.
Furthermore, most geothermal plants in the region are municipally owned or operated in partnership with public utilities, meaning the economic benefits are retained within the community.
Lessons for other cities
The success of the Paris Basin offers several lessons for urban planners and energy providers worldwide:
- Geological mapping is key – Early investment in detailed surveys reduces exploration risk.
- Long-term policy support matters – French government incentives and risk insurance schemes encouraged private investment.
- Hybrid systems increase resilience – Pairing geothermal with other heat sources ensures stable supply and optimised carbon reductions.