A quiet revolution is taking place beneath our feet. The United Kingdom, a nation long dependent on fossil fuels for warmth, is now at the forefront of a geothermal energy surge that promises to decarbonise heating for millions. This shift, driven by technological advances and policy support, marks a critical step in the energy transition that climate scientists have long urged.
Geothermal energy harnesses the Earth's internal heat, accessible via deep boreholes or shallow ground-source loops. Unlike solar or wind, it provides constant baseload power and heat, independent of weather. In the UK, where heating accounts for roughly 37% of carbon emissions, this reliability is transformative.
The recent boom is anchored in two major projects. The first, the United Downs Deep Geothermal Power project in Cornwall, has completed drilling to a depth of over 5 kilometres, tapping into granite rock at temperatures exceeding 190°C. This will generate electricity and heat for local homes and businesses. The second, the Newcastle University-led ‘GeoEnergy’ initiative, involves retrofitting abandoned coal mines with heat pumps, using geothermal water at around 20-40°C to provide district heating. These two approaches illustrate the spectrum: high-temperature deep geothermal for power, and low-temperature shallow geothermal for heating networks.
Data from the British Geological Survey indicates that the UK has enough geothermal heat potential to supply a significant fraction of its residential heating needs. In Cornwall alone, calculations suggest that deep geothermal could provide up to 10% of the county's electricity. On a national scale, shallow geothermal heat pumps, which extract heat from the ground at depths of 100-200 metres, could reduce heating costs by 30-50% compared to gas boilers.
The government's recent ‘Heat and Buildings Strategy’ has allocated £60 million for heat network projects, including geothermal. This is a fraction of what is needed, but it signals a direction. The Climate Change Committee has recommended a tenfold increase in heat pump installations by 2028, and geothermal heat pumps are among the most efficient, with a coefficient of performance (CoP) of 3-4: for every unit of electricity used, you get 3-4 units of heat.
Critics point to high upfront costs, lack of public awareness, and regulatory hurdles. Drilling a deep geothermal well costs £10-20 million, with risk of dry holes. However, innovations like ‘closed-loop’ systems that circulate fluid through buried pipes rather than extracting water reduce geological risk. Insurance schemes and public-private partnerships are emerging to spread financial risk.
Furthermore, the integration of geothermal with heat networks offers a path to decarbonising dense urban areas. In London, the ‘Geothermal London’ project is assessing the potential under the city, where the London Basin aquifer provides warm water at 40-60°C. A heat network using this source could supply 20% of the capital's heating demand by 2050.
The National Grid’s Future Energy Scenarios project that geothermal could supply up to 5% of UK heat by 2050. That may seem modest, but in absolute terms, it is equivalent to displacing around 10 million tonnes of CO2 annually. For context, the UK's total emissions in 2020 were 414 million tonnes.
This is not a silver bullet. We need a portfolio of solutions: electrification, hydrogen, solar thermal, and energy efficiency. But geothermal offers something unique: a domestic, baseload heat source that works 24/7. In a world where weather-dependent renewables dominate, geothermal provides stability.
As a climate correspondent, I find this development both promising and overdue. The Earth’s internal heat is a vast, underutilised resource. The UK’s leadership in this field is a reminder that solutions exist if we have the will to invest. The urgency is real: every tonne of carbon we avoid today is a tonne that does not accumulate in the atmosphere. If geothermal can help heat our homes while cooling the planet, then we must seize this opportunity with both hands.
Data sources: British Geological Survey (BGS), UK Committee on Climate Change (CCC), The Royal Society report ‘Geothermal Energy in the UK’ (2021).
