The United Kingdom has officially classified geothermal energy as a national security asset, a move that repositions the ancient heat of the Earth’s crust within the modern calculus of energy independence. The announcement, made jointly by the Department for Energy Security and Net Zero and the Treasury, unlocks £74 million in direct funding and introduces a new licensing framework designed to accelerate deep geothermal projects. For a nation that built its industrial revolution on coal and its post-war economy on North Sea oil and gas, this pivot is neither sentimental nor symbolic. It is a pragmatic response to a material reality: the energy beneath our feet is abundant, but extracting it remains stubbornly expensive.
Geothermal energy operates on a simple thermodynamic principle. The Earth’s core radiates heat outward at a rate of about 47 terawatts. At depths of four to six kilometres, rock temperatures can exceed 200 degrees Celsius. Drill a well, circulate water through the hot rock, and bring the steam back to the surface to spin a turbine. No combustion. No carbon dioxide. No intermittency. The resource is continuous, baseload, and immune to the geopolitical whims that buffet natural gas markets. The UK’s geothermal resource, concentrated in Cornwall, the Weald Basin, and parts of Northern Ireland, could theoretically supply the nation’s heat and electricity for centuries.
Yet theory and practice remain separated by the physics of drilling. Deep geothermal wells can cost upwards of £20 million each, with no guarantee of sufficient permeability. The rock may be hot, but if the fractures do not allow water to circulate, the well is a dry hole. This is not a resource that can be turned on like a switch. It requires geological surveys, seismic imaging, and a tolerance for risk that private capital has historically been unwilling to absorb. The government’s new licensing regime attempts to de-risk the early stages by covering 50% of exploration costs through a newly created Geothermal Development Fund. In return, developers will pay a royalty only after electricity generation begins.
The security imperative is straightforward. The UK currently imports around 50% of its natural gas, much of it from Norway and Qatar, but vulnerable to disruption in the Strait of Hormuz or the North Sea pipeline network. A single gigawatt-scale geothermal plant, akin to a modern nuclear reactor, could displace approximately 1.5 billion cubic metres of gas per year. Multiply that by a dozen plants and the arithmetic becomes strategic. The Treasury’s internal modelling suggests that a 3 GW geothermal build-out by 2035 would reduce the UK’s gas import bill by £2.5 billion annually at current prices.
Critics point to the levelised cost of electricity from geothermal, currently estimated at £120 per megawatt-hour, versus £75 for offshore wind. This is true. It is also a flawed comparison. Wind and solar require backup storage or gas peaker plants. Geothermal delivers constant power. When the cost of firming capacity is included, the gap narrows to within 15%. Moreover, geothermal heat can be used directly for district heating networks, displacing individual gas boilers, which is an application where wind power cannot compete. The first such network, in Stoke-on-Trent, is already under construction using shallow geothermal technology.
There is also the matter of timing. A deep geothermal project takes five to eight years from exploration to commissioning. Offshore wind farms take four to six. Nuclear takes fifteen. In the race to meet net zero by 2050, geothermal occupies a middle ground: slower than wind, faster than fission, and far less politically contentious than either. The government’s announcement includes a fast-tracked planning process for projects deemed of national significance, cutting the pre-construction phase by up to two years.
The environmental footprint deserves scrutiny. Geothermal operations can induce microseismicity, though the magnitudes typically remain below 2.0 on the Richter scale. More serious is the risk of groundwater contamination from dissolved minerals brought up with the brine. The new regulations mandate closed-loop systems where the brine is reinjected into the same aquifer after heat extraction. In Iceland and New Zealand, where geothermal already supplies 30% and 18% of electricity respectively, such measures have proven effective.
The Earth’s heat is not a renewable resource in the strict sense. Over human timescales, it is essentially inexhaustible. The UK’s decision to treat it as a security asset rather than merely a climate solution reflects a growing recognition that energy policy is no longer just about emissions. It is about resilience. The cost of geothermal is high now. But the cost of not diversifying our baseload generation is higher. The rock is waiting. The question is whether we have the patience and the capital to drill deep enough.
