The commune of Rueil-Malmaison has joined forces with ENGIE Solutions to establish GéoReuil*, a company that will use geothermal drilling to provide predominantly local and renewable heating and domestic hot water for the area’s residents in 2022. Geothermal energy will drive decarbonisation in the region, and has great potential for growth in Île-de-France. Rueil-Malmaison has therefore chosen to provide its residents with clean heating derived from an immediately available resource, and has entrusted the geothermal aspects to the know-how of the ENGIE Solutions teams.


Drilling – the first key stage in geothermal energy – involves capturing heat available in the soil layers using a probe. Evaporators in heat pumps then release that heat into the homes and buildings connected to the network.


A technical operation to deliver an efficient future network

The drilling operation undertaken by the ENGIE Solutions teams will be completed in autumn, and construction of the geothermal power plant will then begin. It will undergo final testing and commissioning in 2022, in parallel with the construction of the heating network, also to be undertaken by ENGIE Solutions.

Once the drilling operation is complete (it will be undertaken in the summer of 2021 to minimise disruption to local residents), Rueil-Malmaison’s geothermal power will come from water heated to around 62°C some 1,500 metres below the ground.

Eventually, 65% of the energy fuelling the heating network will be renewable, avoiding 21,000 tonnes of CO2 emissions per year, equivalent to those of 11,600 vehicles. An excellent example of a decarbonisation project contributing to the comfort of the residents of Rueil-Malmaison.

The geothermal project and construction of the heating network represent a total investment of €71 million, €19.82 million of which will be funded by ADEME and €5.5 million by the Ile-de-France region.

All the news on the drilling operation and the construction of the geothermal plant can be found on the Rueil-Malmaison website, in the Rezomee section set up by ENGIE Solutions: 

A targeted communication campaign is planned to notify local residents of the site’s official launch.



The GéoReuil project - key figures:

  • 1,500 m: Borehole depth
  • 2,200 m: Borehole length
  • 11.3 MW: Geothermal output
  • 62°C: Temperature of the water extracted


Reuil-Malmaison heating network figures:

  • Approx. 25 km envisaged
  • 126 GWh heat commercialised per year
  • 65% renewable energy supplying the heating network
  • 21,000 tonnes of CO2 emissions avoided per year, equivalent to those of 11,600 vehicles
  • €71 million investment


* S.A.S ENR (Renewable Energy Joint-Stock Company) GéoReuil. The new company set up to deliver this major energy project is the result of a local partnership between ENGIE Solutions, which has an 88.5% stake in it, and the City of Rueil-Malmaison, which owns 11.5%.