Eavor's geothermal plant aims to replace natural gas with clean heat in Geretsried, a Bavarian town of 25,000 people. 

To build its underground heat engine, Eavor drills straight down 4,500 meters — deep enough to reach rock simmering at 160°C. Then it makes a sideways move, branching out horizontally for another 3,000 to 3,500 meters, before looping back up through a second vertical well. The result is a massive, closed-loop circuit sealed off from the Earth around it.

Inside the loop, water flows in a constant cycle. As it goes down, it heats up from the hot rock deep underground. That hot water then rises on its own, while cooler water from above moves down to take its place. This natural flow — called a thermosiphon — keeps everything moving without the need for pumps. That makes the system more energy efficient.

At the surface, the hot water flows through a heat exchanger — a device that transfers its heat without mixing the water itself. Inside the exchanger, the heat from the geothermal water is passed on to a separate water network connected to the district heating system. When summer hits and heating demand drops, the system flips modes: some of that underground heat is diverted to a steam turbine, which converts it into electricity.

The €370mn project kicked off drilling in July 2023 and already has serious backing: €91.6mn from the EU's Innovation Fund and a €45mn loan from the European Investment Bank. Eavor aims to generate the first power from the site by the end of 2025.

“All eyes are on Geretsried,” says Sanjeev Kumar, head of policy at the European Geothermal Energy Council. “If it works, it could seriously move the needle on geothermal.”

Untapped potential

Europe has long been at the forefront of tapping heat from below our feet. The Romans first exploited geothermal energy over 2,000 years ago to warm royal villas. In Larderello, Italy, the world's first industrial geothermal power plant was switched on in 1911. Iceland, by the 1930s, had turned its superheated pools of volcanic water into a district-wide energy source. 

Yet today, geothermal only supplies 0.2% of Europe's electricity and 0.7% of its heat. That's a tiny slice compared to wind and solar. But geothermal energy offers something those renewables cannot: always-on, baseload power that balances the grid when the wind isn't blowing or the sun isn't shining. Geothermal plants also cover far less land than the equivalent solar farm or wind park. There's another edge too — it can deliver heat as well as electricity, making it a powerful tool for replacing natural gas, a fact that hasn't gone unnoticed among Europe's politicians.

“Russia's invasion of Ukraine has changed everything,” says Kumar. “Europe is now piling into geothermal as it looks for sovereign, clean sources of energy.”

According to the International Energy Agency, geothermal energy could meet humanity's electricity needs 150 times over. But for now, it remains expensive and geographically limited. Traditional systems can only tap into pockets of land where hot water naturally rises close to the surface. And concerns over earthquake risks from underground drilling still hang over the sector.

Eavor wants to disrupt the status quo and unlock this potential — and it's not alone. There are currently over 100 geothermal startups working to make geothermal cheaper and safer. For many, the sole focus is to invent faster, more powerful drills — and turn the economics in geothermal's favour.  

Drilling deep

One company striving to reinvent the geothermal drill is Slovakia's GA Drilling. The startup has built a rig that combines a traditional diamond-tipped drill with an electrical device that blasts hard rock with ultra-hot “plasma pulses.” These discharges weaken underground formations, making it easier for the drill to break through hard bedrock. 

“The key to scaling geothermal is getting drill costs down,” says Matus Gajdos, the company's head of product. He claims the plasma pulse drill could bore at twice the speed of standard equipment, depending on the underlying geology. That could make tapping Earth's heat more viable.  

The company's ultimate goal is to reach depths of 10km or more — almost as far as the deepest hole ever dug. At these depths, water gets so hot it becomes “supercritical,” meaning it's both a liquid and a gas at the same time. This superheated water could potentially enable geothermal systems to extract 10 times more energy from deep, hot rock formations.

However, GA Drilling is starting at more moderate depths. The company is currently in talks to drill a 6km well in the Netherlands in 2026. It is also eyeing a second project to power a data centre in the country. 

Once proven in the field, the company plans to license its tech to fellow startups like Eavor as well as oil and gas companies. “It's difficult to make it in geothermal without oil and gas,” Gajdos admits.

The founding teams of most geothermal startups, including Eavor, began their careers in the fossil fuel industry. The technical expertise in drilling, reservoir management, and subsurface engineering is directly transferable. Now, many of them are using their expertise to pursue cleaner avenues. 

Canopus Drilling, a Dutch startup founded by ex-Shell executive Jan Jette Blangé, is resurrecting a shelved oil-and-gas technology. Its diamond drill fires tiny steel balls — or “shots” — to fracture rock, while a steerable bit helps navigate horizontal wells. Early tests suggest the tech could triple heat extraction per borehole.

But not all geothermal has to go deep.  

Shallower ground

While geothermal energy often conjures up images of boiling pools or steam erupting from a surface power plant, tapping Earth's heat is often less, well, hot.

Geothermal or ground-source heat pumps, which use stable temperatures underground to heat homes in winter and cool them in summer, don't need extreme depths or temperatures to work.

“In many European countries, at a depth of 250 metres, you have an average temperature of 14°C,” Moritz Pill, co-founder at Swiss startup Borobotics, previously told TNW. “This is ideal for efficient heating in winter, while still being cold enough to cool the building in summer.”

Borobotics has developed an autonomous drilling machine — dubbed the “world's most powerful worm” — that promises to cut the costs of drilling holes for geothermal heat pump installations.  

Ground-source pumps don't generate electricity, but they're highly efficient and relatively easy to install, especially in Europe's radiator-equipped homes. 

As part of its €300bn REPowerEU plan, the EU aims to install 43 million new heat pumps by 2030. Borobotics' tech could make that target easier — and cheaper — to hit.

Torsten Kolind, founder of investment firm Underground Energy Ventures, sees a role for both deep and shallow geothermal in Europe's future energy mix. “Europe's well-positioned to deploy geothermal, and with energy security a top priority, they really ought to,” he says.

A geothermal revival? 

Across Europe, politicians are slowly warming up to the potential of geothermal.

France plans to double geothermal production by 2028. The Netherlands wants to nearly triple output by 2030, mainly to warm its greenhouses. Germany aims to boost geothermal heating tenfold by 2030, to 10 terawatt-hours a year.

Most of this new heat will go into homes, not power plants. That's because district heating systems and radiator-based infrastructure already exist in much of Europe. Heat also requires lower temperatures than electricity, making it cheaper to produce. Heating makes up half of the EU's total energy consumption and about 30% of its CO2 emissions.

While channelling heat from Earth's core to warm our homes may seem like low-hanging fruit, challenges remain. Building geothermal plants is still expensive, despite the innovations in the pipeline. And without sufficient government backing, geothermal remains a risky bet for investors. 

To lower the stakes, Kolind says governments should offer geothermal developers feed-in tariffs, which would guarantee a set price for heat or electricity produced. The German government has provided a positive example, granting Eavor a generous price of €252 per megawatt of electricity produced at the Gereitsreid site until 2042. Such incentives have proved remarkably effective at boosting solar and wind deployment.   

Public perception also remains a hurdle. In Switzerland, a 2006 project triggered earthquakes and was shut down. That project used fracking — a technique borrowed from the oil and gas industry, which injects water to crack rock and release heat.

Fervo Energy, backed by Bill Gates, is pursuing similar techniques in the US. But Eavor avoids fracking entirely. “The chance our technology causes earthquakes is zero to none,” says executive vice president Winsloe.

If the risks can be managed, the upside is massive. The IEA estimates geothermal could provide 15% of global energy by 2050, up from just 1% today.

If the new generation of geothermal startups can prove their tech works at scale, they could spark a new era of clean energy — one where the Earth powers itself.