The United Kingdom is turning its attention to a resource that has long been overlooked: geothermal energy. The Earth's internal heat, a constant and virtually inexhaustible source, could provide a significant portion of the nation's baseload power. However, the technical and financial hurdles remain formidable.
Geothermal energy harnesses heat from the planet's core, typically accessed by drilling wells into hot rock formations. At depths of several kilometres, temperatures can exceed 200 degrees Celsius, sufficient to generate steam for electricity production. The UK government recently announced a new funding round for exploratory drilling, signalling a strategic shift towards diversifying the energy mix beyond wind and solar.
The advantages are clear. Unlike intermittent renewables, geothermal plants can operate 24/7, providing consistent power. The land footprint is minimal, and emissions are near zero once the plant is running. The British Geological Survey estimates that the UK has enough geothermal potential to meet its electricity needs for centuries. Yet only a handful of pilot projects exist.
Why is geothermal not already widespread? The answer lies in upfront costs. Drilling a single well can cost millions of pounds, and the risk of hitting insufficient heat or fluid flow is high. The technology is borrowed from oil and gas extraction, but the geology is different: rock formations must be permeable and water-bearing. In regions like Cornwall, where granite is hot but dry, enhanced geothermal systems are needed. These involve fracturing the rock and injecting water, a process that requires careful management to avoid seismic activity.
Moreover, the levelised cost of geothermal electricity is currently around £150 per megawatt-hour, roughly double that of onshore wind. This gap has deterred private investment without government subsidies. The new funding is intended to lower these costs through innovation and shared risk.
The UK is not starting from zero. In 2022, the United Downs Deep Geothermal Power project in Cornwall began producing small amounts of electricity. It is one of the deepest geothermal wells in the world, drilled to 5.2 kilometres. The project demonstrated that the technology is viable, but scaling it up will require a fleet of similar installations.
There is also potential for direct heat use. Geothermal heat pumps, which tap shallow ground temperatures, are already used in many homes. But deep geothermal can supply district heating networks, as seen in Iceland and parts of Europe. The UK's ageing gas grid could be partially replaced by geothermal heat, reducing carbon emissions from the residential sector.
Critics argue that the focus should remain on wind and solar, which are now the cheapest energy sources. However, the intermittency problem remains unsolved without vast storage. Geothermal offers a stable complement, reducing the need for gas-fired backup plants. In this sense, it is a hedge against the volatility of renewable output.
The challenges are not insurmountable. Improved drilling techniques, such as laser or plasma drilling, could reduce costs. And the oil and gas industry has a skilled workforce that could transition to geothermal projects. The government's role is to de-risk early investments and create a regulatory framework that encourages exploration.
The Earth's heat is a constant, reliable resource. The question is whether we can tap it economically. The UK's latest moves suggest a growing recognition that the answer must be yes. With the right policies, geothermal could become a cornerstone of a low-carbon, secure energy system.
