The big heat

Geothermal energy is a universal resource; regardless of where you are on Earth, heat lies beneath your feet. It is accessible, consistent, sustainable, low in carbon emissions, and more equitably distributed than coal, oil, gas, wind, waves, tides or sunlight. 

The Earth is hot, very hot. It became hot as it formed around 4.5 billion years ago and will still be hot in around five billion years when the Sun expands and obliterates the Earth. Heat is arguably the Earth’s greatest resource which by any human measure is sustainable and inexhaustible. This huge heat engine drives plate tectonics and the movement of continents across the globe; it creates and maintains the magnetic field and thus protects our atmosphere. The plate tectonics coupled with the heat preserved past biological remains, turning them into coal, oil and natural gas, and yet this massive heat resource is largely untapped. Indeed, geothermal energy accounts for less than 1% of global energy supply. 

Geothermal energy has been exploited by humans since pre-history, and humans are not alone in making the most of hot water expelled naturally at the Earth’s surface. Geothermal energy has been used to generate electricity at Lardarello in Italy since 1904. Geothermal energy development transformed Iceland’s energy landscape. Once shrouded in coal-induced smog, Reykjavik is now a model of clean energy. Today, the entire country is powered and heated almost entirely by geothermal, creating energy security and environmental sustainability whilst facilitating local food production through greenhouse farming, enhancing Iceland’s self-sufficiency. 

Italy and Iceland are tectonically active regions, and it is tempting to think that volcanoes are needed for geothermal energy, but this is not so. The USA is the largest generator of geothermal derived electricity, with 3.8GW in 2022, accounting for almost 25% of the world total. Even more geothermal energy is used directly as heat, at around 23GW in 2023, with China leading the list of 88 countries with geothermal heat schemes. 

Several countries in mainland Europe, including Germany, France, the Netherlands and Sweden, have similar geology to the UK and yet much better developed geothermal resources. Several reasons explain this disparity, including specific policies that limit the choice of energy options available, such as Germany’s move from nuclear energy, or policies that explicitly promote geothermal development. In addition, availability of and access to subsurface data, state-backed support measures including payments for every unit of geothermal heat or electricity produced, and drilling risk insurance schemes. These things are lacking in the UK, therefore providing a barrier to investment in and growth of UK geothermal. 

Our calculations show a huge potential for geothermal energy in the UK. Until recently the UK had but one geothermal development, of about 1.7MW, supplying a heat network in central Southampton. The Southampton District Energy Scheme was something of an anachronism. Heat is extracted from a deep well drilled in 1981 in response to the 1973 oil crisis. It was one of seven in the UK: one more in Hampshire, together with Cornwall (three), Lincolnshire and Northern Ireland. All seven wells found heat, but by the time they were drilled, North Sea oil had been discovered, and the UK had become a petro-economy. The Southampton well was the only one of these developed into a working scheme, by Southampton Council accountant Mike Smith. 

“Times are a changin’” and the UK needs secure, sustainable, low carbon heat and power as part of a just energy transition. Geothermal energy can and is beginning to deliver. As we write in May 2025, the UK has 1GW heat on stream. 

North-east England is leading the way in delivering low-grade space heating, by extracting tepid mine water from the region’s abandoned and flooded mines. Gateshead Council is delivering around 6MW heat, and nearby Lanchester Wines uses about the same to keep its wine warehouses at a constant temperature. At the opposite end of the country, Cornish projects are drilling deep. Two wells, one each at United Downs near Redruth and Eden, were drilled to more than 5km. Eden is already producing heat into its biodomes, and United Downs is set for electricity generation in 2025. 

The appetite of local councils and a portion of our industry to develop geothermal energy is growing fast. The Durham coast made famous by the Billy Elliot film will soon have a garden village heated from the mines it overlies. Deep drilling has already occurred and is being evaluated at Stormont in Northern Ireland. There are projects for deep and shallow geothermal energy developments in Scotland, north-west England, Yorkshire, Wales, the Midlands and south-west England in various stages of execution. 

Policy and regulation are not keeping pace with the desires of communities to develop shared and equitable geothermal resources. To facilitate the uptake of geothermal energy in the UK, the National Geothermal Energy Centre was constituted in 2024. It covers policy and regulation; technology and innovation; infrastructure and research; and has targeted delivery of 10GW heat, 1.5GW electricity, 50,000 skilled jobs and displacement of ten million tonnes of CO2 by 2050. Help us make this happen.