Berlin Eyes 250 MW of Geothermal Heat by 2045 – And a 120 MW Power-to-Heat Plant Is Just the Beginning

Berlin Is Drilling for a 250 MW Miracle – And It Might Just Work

The German capital is betting on two radical technologies to kill fossil heat by 2045. One is already under construction. The other lies 2.5 kilometers beneath the Alexanderplatz.

By Robert Buluma 

June 2, 2026

BERLIN – On a gray morning in May, a few blocks from the Berlin-Mitte combined heat and power plant, Kerstin Busch did something that would have been unthinkable a decade ago. She signed off on a 120-megawatt electric boiler that will turn surplus wind and solar power directly into hot water.

“Electricity from wind and solar plants will be directly usable for around 30,000 district heating customers,” said Busch, Technical Managing Director of BEW Berliner Energie und Wärme. The €75 million project, backed by transmission operator 50Hertz, will be online by the end of 2028.

That is the headline. But the real story is what Berlin is planning next.

Deep beneath the city’s sandy soil, in hot water reservoirs that have been sitting untouched for millennia, the Senate sees a second, even bigger prize: up to 250 megawatts of geothermal heat by 2045.

That is enough to replace a fifth of Berlin’s current fossil fuel burn for district heating. And if they pull it off, the capital will do what no other European metropolis of its size has done outside of Iceland – decarbonize its radiators without relying on Russian gas or speculative green hydrogen.

Why Heat Is Harder Than Electricity

Here is the dirty secret of Germany’s Energiewende. Everyone talks about solar panels and wind turbines. But heat accounts for more than half of the country’s final energy consumption. And most of it still comes from burning things – natural gas, hard coal, lignite, even imported wood pellets.

Berlin’s district heating network – a 2,000-kilometer web of insulated pipes – is one of Europe’s largest. It serves 1.4 million households. Right now, roughly 80% of that heat is fossil-based. Natural gas alone provides half. Coal provides another 30%.

The Berlin Senate has mandated that district heating must be climate-neutral by 2045. That gives the city just 19 years to reinvent how it warms itself.

Heat pumps in every basement? Not feasible in a dense, historic city where many buildings are protected landmarks. Ripping up every street to run new pipes for low-temperature heating? Also not feasible.

The only realistic path is to keep the district heating network but change what goes into it. That means two things: Power-to-Heat to absorb surplus renewable electricity, and deep geothermal to provide a steady, weatherproof baseload.

The Power-to-Heat Plant: 120 Megawatts of Flexibility

Let’s start with the project that is already moving. The Berlin-Mitte Power-to-Heat facility is not a heat pump. It is much simpler. Think of three giant immersion heaters, each with 40 megawatts of thermal output, submerged in pressurized water. When the grid has too much wind or solar power – a common problem on windy nights in northeastern Germany – 50Hertz flips a switch. The electrodes turn that surplus electricity into heat. The heat flows directly into the district network.

“For an electricity system with ever more wind and solar energy, we need flexible consumers that can absorb power at short notice,” said Dirk Biermann, COO of 50Hertz.

Without plants like this, grid operators have to pay wind farms to shut down – a practice called curtailment. Last year alone, Germany curtailed enough renewable electricity to power a city the size of Hamburg for six months. That is not just wasted energy. It is wasted money.

The Berlin PtH plant solves that locally. Over its first five years, it will save roughly 76,000 tons of CO2. In winter, it will supply heat to 30,000 households. In summer – when the same plant can run on cheap midday solar – it will provide hot water for 360,000 households.

But here is the catch. Power-to-Heat only works when renewable electricity is abundant. On a cold, calm, dark January week – when solar panels are buried in snow and wind turbines are frozen still – there are no surpluses. The PtH plant sits idle.

That is why Berlin needs geothermal.

The 250 MW Geothermal Target: Heat That Never Sleeps

Two hundred fifty megawatts. That number appears in internal Senate working papers and public statements from the Senatsverwaltung für Wirtschaft, Energie und Betriebe. By 2045, Berlin wants to extract that much thermal power from deep aquifers.

To visualize 250 MW thermal: imagine 250,000 to 300,000 households getting all their winter warmth from water that never sees a flame. No natural gas. No coal. No hydrogen. Just hot brine pumped from two kilometers down, stripped of its heat, and reinjected back into the same rock layer.

Berlin sits on the North German Basin, a deep sedimentary trough filled with porous sandstone and limestone. At depths of 1,500 to 2,500 meters, water temperatures reach 60°C to 100°C – perfect for district heating, which typically runs at 70-90°C.

The technology is called a geothermal doublet. One well pumps the hot water up. A heat exchanger transfers the thermal energy to the district heating loop. A second well pumps the cooled water back down. The same water cycles underground for centuries, reheated naturally by the Earth’s core.

No fracking. No earthquakes. No combustion. Just a closed loop and a pump.

Berlin has already identified several promising sites. Reinickendorf is the frontrunner, with a feasibility study completed. Tegel is next, with exploratory drilling planned for 2028. Rudow is in permitting. The old Mitte CHP plant – where the PtH facility is being built – could even host a deep well by the mid-2030s.

But 250 MW means roughly 10 to 15 successful doublets. That is one new well pair every 18 months from 2028 to 2045. It is doable. Munich is already on a similar trajectory, targeting 400 MW by 2040. But Munich started drilling in 2005. Berlin is starting now.

The Hybrid Future: How PtH and Geothermal Split the Job

Here is the clever part. Berlin is not choosing between Power-to-Heat and geothermal. It is using both, like a hybrid car that switches between battery and gasoline depending on the load.

Summer months: Solar PV floods the grid. The 120 MW PtH plant runs frequently, turning cheap, abundant electricity into hot water for showers and dishwashers. Geothermal provides overnight residual heat but runs at partial capacity because demand is low.

Winter months: Solar surpluses vanish. The geothermal doublets ramp up to full baseload, running 8,000 hours per year at 95% availability. The PtH plant stands by for the occasional wind surplus. Gas peakers – converted to green hydrogen by 2040 – cover only the worst cold snaps.

The two technologies also complement each other in a third way that few people talk about. The Berlin-Mitte site will eventually add a river water heat pump that extracts low-grade heat from the Spree River. Combine that with the medium-grade heat from geothermal wells and the high-grade heat from PtH electrode boilers, and you have a full-spectrum thermal system that can match any demand curve.

That is the real blueprint. Not one miracle technology. Three working together.

The Money Question: Who Pays for 250 MW of Geothermal?

Drilling a single 2.5 km geothermal well costs €10 million to €20 million. If one in three exploration wells is a dry hole – a realistic risk in urban sedimentary basins – the economics get scary.

Berlin has learned from Munich, which spent nearly a decade and over €100 million before its first commercial plant turned a profit. The key is risk sharing.

The €75 million PtH project is already a model. 50Hertz invested that money not out of charity but because it gains direct control of the plant for five years under a redispatch agreement. When the grid is congested, 50Hertz can switch the PtH plant on at will, avoiding much more expensive measures like curtailing wind farms.

A similar model could work for geothermal. If a geothermal plant includes a modest electrical heat booster (to raise outlet temperatures during peak demand), the local TSO could pay a premium for that flexibility. The German federal government already offers grants covering up to 40% of capital costs for deep geothermal district heating through the Bundesförderung für effiziente Wärmenetze (BEW).

State Secretary Severin Fischer of the Berlin Senate put it plainly: “By efficiently using renewable electricity instead of curtailing it, we not only strengthen our supply security and independence but also drive climate protection and the decarbonization of district heating supply.”

That statement was about PtH. But it applies even more to geothermal – which is domestic, weather-proof, and creates long-term jobs for geologists and drilling engineers.

The Risks Nobody Wants to Talk About

Let’s be honest. There are four ways Berlin’s 250 MW geothermal target could fail.

First, dry holes. The North German Basin is promising but not uniform. A few kilometers north of Berlin, in Potsdam, exploratory wells have disappointed. The city must accept that some €20 million wells will produce nothing but hot, salty disappointment.

Second, corrosion. Berlin’s deep groundwater is rich in chlorides and silica. It eats standard steel pipes. It clogs heat exchangers with mineral scale. Advanced materials – titanium alloys, lined carbon steel – solve the problem but add 20-30% to capital costs.

Third, urban drilling. You cannot drill a 2.5 km well in a dense city without annoying people. Noise complaints, traffic disruptions from heavy trucks, and the sheer footprint of a drilling rig (the size of a football field) will test local patience. And while hydrothermal systems rarely induce felt earthquakes, any micro-seismicity will trigger headlines.

Fourth, labor. Germany’s drilling industry shrank after the phase-out of conventional gas exploration. There are not enough reservoir geologists or directional drilling specialists to build 10-15 doublets in 17 years. Berlin will need to import expertise from New Zealand, Iceland, or the United States – exactly where Fervo Energy, the company you previously asked about, is proving that geothermal can scale.

What This Means for Berliners

For the average Berliner in a Prenzlauer Berg altbau, these megawatt numbers sound abstract. But they will show up in two tangible ways.

First, heating costs. Geothermal heat is immune to natural gas price spikes. Once the wells are paid off – typically after 15-20 years – the marginal cost is just the electricity to run the pumps. That is €0.03 to €0.05 per kilowatt-hour. Compare that to volatile gas prices that hit €0.30 per kWh during the 2022 energy crisis. Your Nebenkostenabrechnung (utility bill) will stabilize and eventually fall.

Second, building value. By 2045, any building connected to Berlin’s district heating network will have a top-tier energy certificate (A+). That increases resale value and rental income. Real estate investors who ignore this are making a costly mistake.

For contractors, the message is different. Specialized deep drilling rigs, directional drilling services, and corrosion-resistant heat exchangers will be in high demand from 2028 to 2045. The companies that enter this market now will own it a decade from now.

Berlin vs. The World: How the 250 MW Target Stacks Up

Paris already has about 200 MW of geothermal district heating from the Dogger aquifer. Munich has 80 MW online and is drilling toward 400 MW by 2040. Reykjavik, Iceland, is in a league of its own with 1,500 MW – but that is volcanic, cheating, and irrelevant for the rest of the world.

Berlin’s 250 MW by 2045 would put it slightly ahead of where Paris is today. That is respectable. But it requires a drilling pace that Germany has never sustained.

The lesson from Munich is clear: the first well is the hardest. After you prove the reservoir, standardisation drives costs down. Berlin’s advantage is that it can borrow Munich’s templates, license their drilling contracts, and hire their retired geologists.

The question is whether the political will survives the inevitable dry hole.

The Timeline: From 2026 to 2045

The 120 MW PtH plant at Berlin-Mitte is already on track for 2028 commissioning. That is the easy win.

Seismic surveys for the first geothermal pilot in Reinickendorf will happen in 2027. The first exploration well should spud in 2028 or 2029. If it hits a productive aquifer, the first 15-20 MW doublet could be online by 2030.

From there, Berlin would need roughly one new doublet every year and a half. By 2038, cumulative capacity would reach 100 MW. By 2042, 200 MW. By 2045, 250 MW.

That is the optimistic path. The pessimistic path: the first two wells fail, political enthusiasm evaporates, and Berlin ends up with only the PtH plant and a few symbolic geothermal pilots – maybe 50 MW by 2045.

The difference between those two outcomes is not technology. It is courage.

A Final Word on Hydrogen

Every time I write about geothermal, someone asks: “Why not just use green hydrogen for heating?”

Because hydrogen’s round-trip efficiency is terrible. You take renewable electricity, run an electrolyzer at 70% efficiency, compress or liquefy the hydrogen (losing another 10-20%), then burn it in a boiler at 90% efficiency. Net useful heat: roughly 50% of the original electricity.

Geothermal, once the well is drilled, delivers heat at effectively 99% efficiency – because the Earth did the work of heating the water for free.

Hydrogen is for steel mills, ammonia plants, and seasonal power storage. It is not for warming your living room. Berlin’s Senate understands this. That is why they are betting on PtH and geothermal, not hydrogen boilers.

Conclusion: The Heat Beneath Our Feet

On a cold January night in 2045, if everything goes right, a Berlin family in Wedding will turn up their radiator thermostat. The heat that flows through their pipes will have started as a combination of surplus wind power from the North Sea and 95-degree water pumped from two kilometers under the Alexanderplatz.

No gas from Russia. No coal from Colombia. No questionable offsets.

Just engineering, geology, and a political system that decided to act two decades earlier.

The 120 MW PtH plant at Berlin-Mitte is the first step. The 250 MW geothermal target is the second. Neither is guaranteed. But both are possible. And for any other cold-weather city – from Warsaw to Toronto to Beijing – Berlin’s hybrid model is the most replicable blueprint on the table.

The future of heat is not in foreign imports. It is beneath our feet. Berlin just has to be brave enough to dig.

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Source: Why So Germany 🇩🇪¿