The ambition of the upcoming Multiannual Energy Programming (PPE) is to phase out fossil fuels by 2050, relying on low-carbon electricity production. It is notably expected that electricity’s share in final energy consumption will increase from 27% today to 54% by 2050. In other words, by the same deadline, heat will account for 46%, with a growing share of renewable and recovered heat. In this context, three energy sources are gaining momentum at different stages: geothermal energy (revival), waste heat from industry and data centers (acceleration), and thalassothermal energy (emergence).

Heat is essential for heating buildings, domestic hot water (DHW) production, and industrial processes, but it is still largely produced from fossil sources. To address this decarbonization challenge, the PPE3 sets a target of 276 TWh of renewable heat consumption by 2030 (compared to 173.5 TWh in 2023—see box) and at least 330 TWh by 2035. Notably, the strategic committee for the “New Energy Systems” sector made renewable and low-carbon heat one of the four pillars of its new strategic sector contract in February.

The geothermal revival

Geothermal energy harnesses underground heat at various depths (i.e., shallow or deep geothermal energy). It can be used for heating, cooling, air conditioning, energy storage, or steam production.

For shallow geothermal (or very low-energy geothermal), France has 210,000 heat pumps (HPs) that generated 4.7 TWh of heat in 2023: 3.78 TWh for individual use, 0.54 TWh for the tertiary sector, 0.18 TWh for collective residential housing, and 0.15 TWh for agriculture and industry.

Deep geothermal involves aquifers over 800 meters deep, where water temperatures can reach 30°C to 250°C, allowing direct heating of buildings or industrial sites, or via a district heating network. By the end of 2023, France had 73 deep geothermal installations (55 in the Paris Basin, 16 in the Aquitaine Basin), producing a total of 2.3 TWh of renewable heat, representing 0.4% of the country’s final heat consumption.

In 2023, the Ministry of Ecology launched a comprehensive action plan to “make France a European leader in geothermal energy in terms of both renewable energy production and industrial development.” The third PPE, to be finalized by summer 2025, sets targets of 6 TWh by 2030 and 8–10 TWh by 2035 for shallow geothermal energy, and 10 TWh by 2030 and 15–18 TWh by 2035 for deep geothermal. The plan also includes regulatory simplifications and a guarantee fund to reduce risks associated with deep geothermal.

During the 6th Geothermal Days held on June 19–20 in Biarritz, the Prime Minister announced that the permit exemption threshold for projects would be raised from 0.5 MW to 2 MW. New measures related to the Heat Fund were also mentioned.

Early 2025 saw new geothermal-powered heating networks launched in Villetaneuse (93), Garges-lès-Gonesse (95), and Bordeaux Airport (33). In May, Bpifrance invested in Arverne Group, a geothermal specialist that recently partnered with Dalkia to install a plant at Safran Aircraft Engines’ Villaroche site (94). Arverne is also launching France’s first direct lithium extraction geothermal pilot in Alsace.

This growing momentum is also reflected in new industry events, such as the first European Geothermal Summit organized by EGEC (European Geothermal Energy Council) on June 17 in Brussels.

Industrial Waste Heat: The Ultimate Recovered Energy

Some activities or facilities produce heat as a by-product—this is known as waste heat. Major sources include thermal discharges from smoke, boilers, or dryers at industrial or energy production sites, wastewater treatment plants, or municipal waste incineration units. Another fast-growing source is data centers, such as Equinix, which heats the Olympic pool in Saint-Denis by recovering 28°C hot water and boosting it to 65°C via heat pumps.

ADEME estimates France’s recoverable waste heat potential at 118 TWh/year, with 110 TWh from industrial sites: agri-food (29%), chemicals/plastics (20%), paper/cardboard (12%), metals (11%), cement and glass (10%). However, only 18.3 TWh was recovered in 2021—just 15.5% of the national potential.

Waste heat can be recovered on-site using direct or storage-based heat exchangers (e.g., in steel or glass). There are also energy conversion systems (engines, turbines, absorption units) that turn heat into electricity, cooling, or compressed air. Alternatively, waste heat can be utilized off-site via district heating networks (low-to-medium temps) or for electricity production (high temps).

France supports waste heat recovery through mechanisms like the Heat Fund, the Industry Decarbonization Fund, and Energy Saving Certificates (CEE).

Thalassothermal Energy: An Endless Resource for Coastal Cities

Some systems already use lake, river, or canal water for thermal comfort in cities. For instance, the Idex water loop in Annecy provides heating, DHW, and cooling for a hotel and senior residence. Similarly, Paris’s urban cooling network is powered by Seine river water.

In tropical zones, Ocean Thermal Energy Conversion (OTEC) systems harness temperature differences between ocean surface and depths to generate electricity. Others focus on osmotic energy using salinity gradients (e.g., Statkraft’s 2009 pilot in Norway). SWAC (Sea Water Air Conditioning) systems use deep or cold surface sea currents to supply chilled water networks.

Thalassothermal energy—now growing—uses shallow coastal seawater to produce heating or cooling for seaside cities. Water is pumped from near the shore.

A recent Cerema study reviewed technologies in 30 operational projects along the French coastline as of late 2023. One key method is the seawater loop producing hot and/or cold water in centralized or decentralized setups, involving water intake and discharge without fluid exchange.

Another is hydromarethery, which uses solar-heated sea surface layers, thermal inertia, convection, and salinity via submerged probes or those placed under sand, functioning in closed circuits with no seawater discharge.

A third is the Enerplage system, an optimized version of Ecoplage’s drainage system that simultaneously combats erosion and recovers seawater via drains beneath the beach—used in places like Les Sables d’Olonne.

The study’s authors highlighted project criteria: year-round demand for both heating and cooling, and a mix of residential and tertiary uses to enable resource pooling. They propose an analysis method to identify potential sites across France’s Mediterranean coast, identifying over 580 potential locations in 108 ports.

1) The Multiannual Energy Programming (PPE) defines France’s energy policy and fossil fuel exit strategy. It sets a 10-year trajectory, updated halfway through. The third edition (2025–2030, 2031–2035) is expected by the end of summer.

2) With intermediate targets of 34% by 2030 and 39% by 2035.

3) Study Report: Evaluation of Thalassothermal Development Potential in the Mediterranean – Existing Projects and Site Identification, Hélène Mayot and Myriam Lorcet, Cerema, March 2025, 86 pages.

4) Like OTEC, hydromarethery is part of marine renewable energy (MRE).