In Cornwall, the UK’s first-ever geothermal power plant has just put pen to paper on a 10-year deal to sell its supply of electricity to 10,000 local homes.

The plant creates power by mixing water down two wells, one of which is three miles deep, that pass through the Porthtowan fault zone and the red hot water and granite rocks within.

The United Downs Deep Geothermal Power Project was funded throughout the 2010s by a mixture of private and public support.

Now set to be fully operational in 12 months’ time, Ecotricity, the world’s first renewable energy company, has signed a deal to buy three megawatts of geothermal power for the area.

“Geothermal is a really exciting form of energy that is currently untapped in the UK. We’re pleased to be part of this project and to add the power to our customer’s energy mix,” said Dale Vince, founder of Ecotricity.

“It has a big role to play in our plans to decarbonize the country.”

Another buyer came in the form of a local rum distillery, which is preparing a £10 million ($14 million) contract to mature nearly half a million liters of their rum using a geo-heated/powered biome.

But why would someone go through all the trouble of digging a three-mile deep hole when solar panel and wind turbine technologies are advancing as fast as they are?

It’s because geothermal is always running and doesn’t rely on the weather, and while there may be plenty of wind in Cornwall, the sun is not, by any means, a constant.

Geothermal Engineering Limited, owners of the United Downs plant, responded to a Sunday Times feature on the construction, saying that while exciting it’s still very much early days for the plant and any future geothermal developments.

“There’s a huge amount of energy below the surface of the Earth,” Ryan Law, the firm’s managing director, told the Times of London.

“The limiting factors are the drilling costs and the connections to National Grid on the surface.”

Even still, Ecotricity predicts a growth in the geothermal capacity of the island nation, suggesting in a statement that perhaps as much as 10% geothermal energy in the national power supply could, and maybe should be looked at as possible.

Yet sites must be looked at beyond just Cornwall, such as the northeast of England, or the South Downs in Hampshire.