A new study from the British Geological Survey has quantified the immense, untapped geothermal resource lying beneath the British Isles. The report, published today in Nature Geoscience, estimates that the heat stored in accessible hot rocks could supply the nation's energy needs for over a century. This is not a distant promise. It is a physical reality we have largely ignored.
The numbers are stark. At depths of 3 to 5 kilometres, temperatures reach 150 to 200 degrees Celsius, sufficient to drive turbines for electricity generation. The East Midlands, Cornwall, and parts of Scotland sit atop granite batholiths that act as natural radiothermal reactors, producing steady heat from decaying uranium and thorium. The United Downs Deep Geothermal Power project in Cornwall has already demonstrated this, achieving flow rates of 60 litres per second at 180 degrees Celsius.
Yet the United Kingdom currently derives a minuscule fraction of its energy from geothermal sources. Compare this to Iceland, where geothermal meets 66 per cent of primary energy use, or France, where the Paris Basin supplies district heating to over 200,000 homes. The difference is not geology; it is inertia.
The levelised cost of electricity from deep geothermal is now competitive with onshore wind and solar, at approximately £70 per megawatt-hour. Unlike renewables, geothermal provides baseload power, operating 24/7 irrespective of weather. For each gigawatt installed, we could displace roughly 1.5 million tonnes of carbon dioxide annually. The required investment is substantial, around £4 million per megawatt, but the returns span decades. Oil and gas infrastructure, pipelines and skilled drillers, can be repurposed. The skills transfer is direct.
There are challenges. Drilling to such depths requires precision and carries risk of induced seismicity, though modern techniques have minimised this. The upfront capital is high, but the fuel is free and infinite on human timescales. The government must reform the licensing regime and offer contract-for-difference support equivalent to that provided to offshore wind.
The climate crisis does not allow for half measures. We need every tool available. Geothermal is not a silver bullet; it is a powerful addition to the mix. The science is settled. The rocks are hot. The question is whether we have the will to drill.
