The United Kingdom sits atop a vast, largely untapped reservoir of geothermal energy. Beneath our feet, the Earth's internal heat offers a continuous, carbon-free power source that could provide baseload electricity and heating for centuries. Yet despite this abundance, the UK has drilled only a handful of deep geothermal wells. A new report from the British Geological Survey and the Royal Academy of Engineering urges the government to accelerate investment in deep drilling, warning that without immediate action, the nation will miss a critical opportunity to decarbonise its energy system.
The physics is straightforward. For every kilometre you descend, the rock temperature rises by roughly 25 to 30 degrees Celsius. At depths of 4 to 5 kilometres, temperatures reach 150 to 200 degrees Celsius, sufficient to generate electricity via binary cycle or flash steam plants. The UK's geology, particularly in Cornwall, the South West, and parts of Scotland, contains hot granitic rocks that are ideal for enhanced geothermal systems. The potential capacity is estimated at over 100 gigawatts, equivalent to several nuclear power stations. Yet the current total installed capacity is less than 10 megawatts.
The problem is cost. Deep drilling is expensive. A single 5 kilometre well can cost £10 million to £20 million, and a viable power plant requires at least two wells: one to inject water and one to extract steam. The upfront capital expenditure is high, and the financial risk of dry holes deters private investment. The report estimates that the levelised cost of electricity from deep geothermal could be £90 to £120 per megawatt-hour, higher than offshore wind or solar. But these costs are falling as drilling technology improves, and geothermal offers advantages that wind and solar cannot: 24/7 availability, no intermittency, and a small surface footprint.
The government's current support schemes, such as the Contracts for Difference auction, have not prioritised geothermal. The report recommends creating a dedicated deep geothermal drilling fund, modelled on Norway's successful programme, to cover a portion of the upfront risk. It also calls for streamlined planning permissions and a clear regulatory framework for heat networks that could be supplied by geothermal sources. Without such measures, the UK risks falling behind countries like Iceland, New Zealand, and Kenya, which already generate significant shares of their electricity from geothermal sources.
There is a sense of calm urgency here. The climate crisis demands that we deploy every available low-carbon technology. Geothermal is not a silver bullet; it requires careful site selection and significant capital. But it is a proven technology with a high capacity factor and a long operational life. The heat is there, waiting to be tapped. The question is whether the government has the will to drill.
Dr. Helena Vance, Science & Climate Correspondent
