The Earth’s crust beneath the British Isles holds enough heat to power the nation for centuries. That is not hyperbole. It is physics. Yet as the UK government pushes for energy security and net zero emissions by 2050, geothermal energy remains a tantalising but stubbornly expensive prospect.
Geothermal energy exploits the natural thermal gradient of the planet. For every kilometre you drill, the temperature rises by roughly 25 to 30 degrees Celsius. At depths of five kilometres, you can reach water hot enough to drive turbines. Unlike wind and solar, geothermal is baseload power. It runs 24/7, unaffected by weather or season. It is, in essence, a nuclear reactor without the radioactive waste.
Britain has a distinct geological advantage. The granitic batholiths of Cornwall and the hot sedimentary aquifers of the Wessex Basin and the East Midlands hold significant heat. The UK’s deep geothermal resource could technically supply the country’s entire heat demand, according to the British Geological Survey. But technical potential is not economic reality.
The barrier is cost. Drilling a single deep geothermal well costs between 5 million and 10 million pounds. For a commercial power plant you need at least two wells, and exploration risk means you may drill a dud. The levelised cost of electricity from geothermal in the UK is currently around 150 to 200 pounds per megawatt hour, roughly three to four times the cost of offshore wind. For heat, where geothermal excels, the economics are better but still require upfront capital that the private sector is reluctant to risk.
Recent developments are trying to change that. In Cornwall, Geoscience Energy is developing the United Downs Deep Geothermal Power project. It aims to drill to 4.5 kilometres and generate about 3 megawatts of electricity, enough for about 3,000 homes. The project received 18 million pounds from the European Regional Development Fund. Without that subsidy, it would not exist.
The Eden Project, also in Cornwall, is tapping deep geothermal for heat. Its well reached 5 kilometres and found water at 195 degrees Celsius. The project cost 24 million pounds. It will provide renewable heat for the biomes and a district heating network for local homes. Again, public funding was critical.
At a national scale, the UK’s approach to geothermal has been cautious. The government’s recent Energy Security Bill included measures to support heat networks and geothermal exploration, but no specific funding stream. Meanwhile, countries like Iceland and Kenya generate over 25 percent of their electricity from geothermal. Even France and Germany have operating geothermal plants.
Why the difference? Geology and policy. Iceland sits on a mid-Atlantic ridge, with shallow, high-temperature reservoirs. The UK’s heat is deeper and less accessible. But the physics does not change. With enough drilling depth, heat is there. The issue is cost reduction through learning curves and technology.
Innovation is underway. Enhanced geothermal systems (EGS) use hydraulic fracturing to create artificial reservoirs in hot dry rock, a technique derived from fracking for oil and gas. The US Department of Energy’s FORGE project in Utah has shown EGS can increase permeability and economic viability. The UK has similar potential, notably in the Weardale granite in County Durham where a prototype EGS plant operated briefly in the 1980s.
There is also the potential for closed-loop systems, which circulate a working fluid through a sealed loop of pipes in deep boreholes, avoiding the need for natural water and reducing environmental risk. Companies like Eavor in Canada are commercialising this approach. If it works at scale, it could unlock geothermal even in areas with less favourable geology.
Climate urgency demands we pursue every zero-carbon option. Geothermal offers firm, flexible, low-land-use power. It can provide heat for industry, district heating, and even generate electricity. But it will not happen without policy support. The UK needs a floor price for carbon, subsidies for deep drilling, or a contract-for-difference scheme similar to that for offshore wind. Without it, the heat beneath our feet will stay there.
The clock is ticking. The atmosphere does not read economic reports. We have the technology. We have the resource. The only question is whether we have the will to pay for it. The answer, so far, has been no. But that can change. It must change. The Earth is hot. And it is waiting.
