The US has 60GW of unused geothermal energy capacity.

That’s the verdict from the US Department of Energy (DoE), which says the underground power source is “America’s untapped energy giant”.

A new report published by the government department says geothermal energy is renewable, flexible and reliable, as well as being well-suited to contributing to grid stability and resiliency.

It says only a fraction of the “always-on” energy source’s potential has been capitalised upon, due to “technical and non-technical barriers that constrain industry growth”.

The study suggests technology improvements could reduce costs and increase geothermal electric power deployment nearly 26-fold by 2050.

Around 60GW of capacity would make up around 3.7% of total US installed capacity by 2050, potentially producing 8.5% of the nation’s electricity generation.

The DoE says it would also benefit the non-electric sector, predicting technology improvements could enable more than 17,500 geothermal district-heating networks to be installed and help 28 million US households get affordable heat and cooling by using geothermal heat pumps.

US Secretary of Energy Rick Perry said: “Making geothermal more affordable can increase our energy options for a more diverse electricity generation mix and for innovative heating and cooling solutions for all Americans.”