Terra Firma Energy – 4 March 2026

The United Downs facility marks a landmark moment for British baseload renewable energy — and opens a new front in domestic critical mineral supply.

The UK’s first deep geothermal power plant has officially switched on, with the Geothermal Engineering Ltd (GEL) plant near Redruth now feeding electricity generated from hot granite rocks directly to the National Grid.

The £50 million United Downs site draws water at temperatures exceeding 190°C from the deepest well ever drilled on UK soil — more than 5km down — to drive turbines generating power for around 10,000 homes. Octopus Energy has secured a long-term offtake agreement for the output.

For an industry long accustomed to variable generation, the significance is hard to overstate. Unlike wind and solar, geothermal delivers constant 24/7 electricity with no price fluctuations tied to fuel costs, making it a genuine baseload complement to the UK’s renewables mix.

TWO DECADES IN THE MAKING

GEL was founded in 2008, but the geological groundwork stretches back further. Cornwall’s Cornubian granite batholith — which runs from Dartmoor to the Isles of Scilly — contains high concentrations of heat-producing isotopes, giving United Downs a heat flow roughly double the UK average. That geology, combined with natural fault zones that allow geothermal fluid to circulate, made southwest Cornwall the only viable location for a first-of-its-kind project.

GEL chief executive Ryan Law said reaching this point was both exciting and a relief after nearly two decades of development work.

LITHIUM: THE UNEXPECTED BONUS

The plant’s commercial case extends beyond electricity. The water drawn from depth contains high concentrations of lithium, which will be extracted to produce zero-carbon lithium carbonate — a critical material for EV batteries and grid storage. GEL says the site will produce 100 tonnes of lithium carbonate per year, enough for around 2,500 car batteries.

The company plans to scale lithium carbonate production to more than 18,000 tonnes per annum over the next decade — a volume that would represent a significant share of UK EV demand and reduce reliance on imports, primarily from China.

THE ROAD TO SCALE

United Downs produces 3MW at launch. GEL has two further deep geothermal sites under development in Cornwall, targeting an additional 10MW of baseload capacity by 2030. The longer-term potential is substantial: the British Geological Survey estimates the UK’s onshore geothermal resource could theoretically yield more than 200GW of thermal heat at temperatures suitable for electricity generation.

The economics, however, remain the central challenge. Drilling costs are high, productive heat wells are not guaranteed, and Cornwall’s geology is not easily replicated elsewhere in the UK. Whether United Downs becomes the first node in a national geothermal network — or remains a regional showcase — will depend on policy support, investor appetite, and the willingness to absorb early-stage capital risk.

For now, the sector has what it has long needed: a working plant, grid-connected and generating. The proof of concept is in the ground.