Geothermal Energy

Geothermal energy is a renewable, local and eco-friendly source of energy that is simultaneously efficient and economical. It offers considerable potential for heat and power generation. ENGIE sees it as an energy with high potential for developing an energy mix that will help achieve zero carbon.

How does geothermal energy work?

Onshore geothermal energy 

The term geothermal energy (i.e. “heat from the earth”) encompasses all the applications that make it possible to recover the heat contained in the subsoil or groundwater (steam or hot water reservoirs or hot rocks). The temperature of the earth and groundwater increases with depth, by 3° C every 100 meters. When the geothermal reservoir is at a moderate temperature, this resource is exploited to produce heat that is then distributed by way of a heating network.


Marine geothermal energy

Marine geothermal energy makes use of  the difference in temperature between warm surface water and cold water found on the seabed, pumped through pipes 1 km long to coastal facilities, where heat exchangers and heat pumps are used to meet heating or cooling needs. The water can then be piped to individual buildings requiring heating or air-conditioning.


Géothermie marine


Key figures

The strengths of a promising source of energy 


  • A continuous resource 
    This basic form of energy is available and usable 24/7. The heat generated from thermal energy requires no specific storage, since the subsoil itself serves this function. 
  • A renewable resource 
    The resources delivered as geothermal energy cannot be exhausted. They are naturally renewed by the flow of surface water or, in some cases, by artificial injection. The heat into the rock that constitute 90% or more of this reserve.
  • A universally available resource 
    Subterranean heat is present on every continent. Technologies now exist to enable its development in areas with suitable geological formations and/or rock composition

Geothermal energy around the world

The main producing countries are Japan, China, Russia, Central and Eastern European countries and the United States. 
France has nevertheless played a pioneering role in the development of geothermal energy, largely as a result of the doublet drilling technique (two wells, the first referred to as the production well, and the second as the re-injection well), and the Dogger aquifer in the Paris Region, which has the largest density of ongoing geothermal operations in the world. 

Geothermal: integral to government thinking on sustainable development

Around the world 

It was at the Rio Earth Summit in 1992 that world leaders expressed their awareness and concern about the advanced stage of environmental damage being caused worldwide (depletion of natural resources, sea and land pollution, the greenhouse effect, acid rain, etc.). Acutely aware of the need to reverse or at least slow this trend, most countries – including the member states of the European Union – are now putting sustainable development concepts into practice as part of their wider policies. As a result, geothermal is seen as an extremely promising option for sustainable development.


In France

Commitments made at the Grenelle Environment Round Table (to reduce greenhouse gas emissions by a factor of 4 by 2020) are encouraging the development of geothermal energy: by 2020, the contribution of geothermal heat to the energy mix should have increased sixfold. To achieve this target, the government is considering, among other things, the development of geothermal heating in office buildings, public facilities and collective housing, in regions where the resource is plentiful, particularly in the Paris Region.


Read about some examples of ENGIE’s geothermal solutions around the world 

Thassalia: the first marine geothermal power plant in Marseille 

The Thassalia marine geothermal project was specially designed to meet the needs of Marseille's Euroméditerranée eco-city business center, the largest urban regeneration program in Southern Europe. It is the first project of its kind to generate heating, hot water and air conditioning on such a scale. The Thassalia power plant transforms the Mediterranean Sea into a sustainable source of energy for an area of nearly 500,000 m2 of buildings in Marseilles. 
A partnership associating the Euroméditerranée development agency, local and regional authorities and private companies, the project is a true example of innovation driving energy transition and efficiency. Cofely Services has contributed its expertise in thermal engineering and Climespace, the ENGIE Group's expert in urban cooling networks, its expertise in refrigeration.

Paris Region: 100 GWh of green heat for 10,000 homes

ENGIE is supplying 100 GWh of green heat for homes in the towns of Champs-sur-Marne and Noisiel . Powered by more than 80% geothermal energy, this is a 25-year public service delegation to the Paris - Vallée de la Marne conurbation community (CAPVM) for the creation and operation of a 20 kilometer-long geothermal heating network. This new network will contribute to the decarbonization of this estate, and will give green credentials to future buildings to be built in the area. In addition, this network will help to combat fuel poverty by guaranteeing affordable and stable rates for future users.

Key figures:


  • 80% of geothermal energy in the network 
  • 100 GWh of green heat, equivalent to the needs of 10,000 homes 
  • Approx. 96 GWh of energy consumption by 2030

Indonesia: first power plant commissioned in December 2019

ENGIE is also developing geothermal technologies for power generation. Initial experiments are under way in Indonesia, a country which, with 140 active volcanoes, offers the highest level of geothermal potential on the planet and 40% of the world’s reserves.


The first drilling operations undertaken in 2012 and 2013 by PT Supreme Energy Muara Laboh (SEML), a company jointly owned by ENGIE and Sumitomo Corporation, in Muaralaboh, in Western Sumatra, confirmed the existence of a high-temperature reservoir (above 200° C). 


ENGIE is currently operating the Muara Laboh plant, which was commissioned in December 2019. It has en energy capacity of 85 MW. ENGIE is also conducting a geothermal exploration project at Rantau Dedap, 225 km from the South Sumatran provincial capital of Palembang. The concession was awarded to a consortium consisting of ENGIE, PT Supreme Energy and Marubeni. With a target capacity of 240 MW, the project is expected to generate geothermal electricity for more than 30 years, supplying about 480,000 homes and reducing carbon dioxide emissions by 1.1 million tonnes per year. The plant is expected to be operational in late 2020.