The British Geological Survey (BGS) has released a new assessment revealing that the UK sits atop a geothermal resource capable of generating up to 50GW of electricity. That is roughly half the nation's peak demand. But there is a catch. The rock is deep, hot, and expensive to tap.
This is not a story of renewable energy triumph. It is a story of physics, economics, and the unforgiving nature of the Earth's crust. Geothermal energy relies on extracting heat from the ground. The heat increases with depth. In the UK, the hottest rocks lie several kilometres down, where temperatures exceed 150°C. To access them, you must drill. Drilling is costly. A single deep well can cost upward of £10 million. Multiply that for a full plant, and you approach billions.
The BGS map, published in collaboration with the UK Geothermal Observatory, identifies regions such as Cornwall, the Weald, and the Cheshire Basin as prime targets. Cornwall, already home to the United Downs deep geothermal project, offers granite that is naturally fractured and hot. The Weald, beneath southern England, contains hot sedimentary aquifers. But the price tag remains the barrier.
Let me be clear: this is not a technological impossibility. Enhanced Geothermal Systems (EGS) exist. They work. The United States, Iceland, and Kenya already harvest geothermal power at scale. The difference is geology. Iceland sits on a mid-Atlantic ridge where magma is shallow. Kenya’s Rift Valley provides similar shallow heat. The UK has none of that. Our heat is deeper, harder to reach, and the drilling is more expensive per watt.
Why does this matter now? Because the UK government has committed to net-zero emissions by 2050. Wind and solar are cheap but intermittent. Nuclear is reliable but politically fraught. Geothermal offers a constant, baseload power source with a small land footprint. It is the workhorse that could complement variable renewables. But without a price signal or subsidy, private investment will remain cautious.
The BGS estimates that if deep geothermal were deployed at scale, the levelised cost of electricity (LCOE) could fall to £80-120 per MWh. That is comparable to offshore wind today. But offshore wind had years of subsidy and learning. Geothermal needs a similar kickstart.
We must also consider the heat pump revolution. Shallow geothermal, using heat pumps, is already economical for heating buildings. But that is a different conversation. Deep geothermal for electricity is a heavier lift.
Some argue that we should focus on the quick wins: solar, wind, storage. They are right in the short term. But if we are serious about a fully decarbonised grid, we need diversity. Geothermal is the insurance policy against a windless winter.
The BGS report is a reminder that the energy transition is not a single solution. It is a portfolio. Geothermal is a promising asset in that portfolio, but it will require patient capital and political will. The Earth is generous with its heat. But it does not come cheap.
