Geothermal energy remains one of the most tantalising contradictions in the renewable sector. The heat beneath our feet is effectively limitless, but the price of extracting it has historically kept it on the periphery of the energy transition. However, a wave of British innovation is now challenging this paradigm, and early results suggest a path to parity with fossil fuels.
At its core, geothermal energy is simple: drill deep enough, and the Earth’s internal heat provides a constant, carbon-free power source. Unlike solar or wind, it is not intermittent. A geothermal plant can run 24 hours a day, 365 days a year. The problem lies in the capital cost. Conventional geothermal requires drilling several kilometres down, often through hard rock, at a cost that can reach tens of millions of pounds per well. For years, this made geothermal viable only in areas with natural hotspots, such as Iceland or parts of the United States.
But the United Kingdom, not known for its volcanic activity, is now leading a quiet revolution. The key is not in finding hotter rocks, but in reducing drilling costs. A consortium led by the University of Glasgow and the British Geological Survey has developed a novel plasma drilling technique. This technology uses high-voltage electrical pulses to fracture rock, rather than mechanical grinding, significantly reducing wear on drill bits and energy consumption. Early field trials in Cornwall have demonstrated a 40% reduction in drilling time and a 30% reduction in cost per metre. If scaled, this could open up vast swathes of the country to deep geothermal.
Meanwhile, a separate initiative from the UK firm Geothermal Engineering Ltd has focused on repurposing abandoned oil and gas wells. By sealing existing wells and injecting water into the deep rock formations, they have achieved power generation at a cost of approximately £80 per megawatt-hour, competitive with offshore wind. This is a striking figure when one considers that the levelised cost of energy from new geothermal projects has historically hovered around £120 to £150 per megawatt-hour. The company has already connected two such retrofitted sites to the National Grid.
These innovations come at a crucial time. The International Energy Agency has repeatedly warned that the global energy transition requires not just expansion of solar and wind, but a baseload renewable source that can compensate for their variability. Geothermal is uniquely suited to fill this role. A recent report from the Grantham Institute estimates that if the UK’s deep geothermal potential were fully exploited, the country could meet over 20% of its electricity demand from geothermal alone, a figure that rises to 50% when including heating. The heat sector is often overlooked in climate discussions, yet it accounts for roughly half of global energy consumption.
Of course, challenges remain. The initial investment for a new geothermal plant is still higher than for a gas-fired plant. There is also the risk of induced seismicity, although modern monitoring techniques have mitigated this substantially. The British innovations are not a magic bullet. They are however a clear sign that the cost curve for geothermal is bending, and faster than many analysts predicted.
The real world implications are significant. For developing nations that lack infrastructure for large-scale solar or wind, geothermal could offer a direct path to decarbonisation. In East Africa, the Kenyan government has already partnered with British firms to explore deep geothermal in the Rift Valley. If the cost reductions seen in Cornwall can be replicated there, it could transform the energy landscape of the region.
The narrative that renewables are cheap but unreliable is itself becoming outdated. Solar and wind have seen dramatic cost reductions over the past decade. Now geothermal is joining them. The technology is not yet ready to replace fossil fuels on its own, but as part of a diversified clean energy portfolio, it offers something unique: reliability. The Earth will not stop radiating heat when the wind dies down or the sun sets. That simple physical reality may eventually make geothermal indispensable. And for the first time in decades, the economics are beginning to align.
