Rapidly rising electricity demand — driven by data centres, manufacturing and electrification — is pushing companies, politicians and investors to look at niche technologies. One of them is next-generation geothermal, which uses high-tech drilling techniques borrowed from the oil and gas industry to harness heat deep in the earth’s crust. While conventional geothermal energy has been around for decades, and harnesses naturally occurring reservoirs underground, next-generation technologies tap hot rock underground in places that lack the naturally occurring water and permeable fractures that would have been needed in the past.

Next-gen geothermal is promoted as a Goldilocks power source: unlike wind and solar, it can run around the clock; unlike fossil fuels, it’s relatively clean; and unlike advanced nuclear, it’s less of a technological moonshot. Its cheerleaders say it could be a low-emitting source of reliable power just as the grid needs more of it — but costs will have to come down. How does it work? Conventional geothermal finds naturally occurring reservoirs, while next-generation technologies create them.

The conventional method is constrained by geology: developers must find places where heat, water and permeable rock naturally coincide. Next-generation geothermal can create or mimic those conditions instead. The two main ways this is achieved are enhanced geothermal systems (EGS) and closed-loop geothermal.

EGS borrows methods from oil and gas by creating fractures in rock, so water can circulate through and pick up the heat. When it returns to the surface, it helps create a vapour which is used to spin a turbine and create electricity. It uses the large rotary drilling rigs and cementing techniques found in the industry.

The closed-loop method drills kilometres-deep wells and adds sealed, fluid-filled pipes that absorb heat from the surrounding rock, which it returns to the surface, where it is used to heat another fluid that generates electricity. EGS projects are best suited to places where developers can safely fracture hot rock, while closed-loop is better in places where water and geological conditions are more uncertain. What are the pros and cons? Next-gen geothermal could make it possible for vast swaths of land to produce electricity.

The US has 40 gigawatts of potential conventional geothermal sources, according to the Department of Energy. Next-gen methods could unlock 5,500GW in the US alone, according to the energy department. Even if only 90GW is developed by 2050, as the US government estimates, that would be enough to power 68mn homes.

Geothermal has a rare advantage in the US of benefiting from bipartisan political support. Democrats support it because of its potential to supply bountiful clean energy while Republicans like how it is a reliable and continuous source of power. Unlike solar and wind, the Trump administration did not cut tax credits supporting geothermal and, in February, it announced $171.5mn to fund full-scale tests and drilling.

But costs are high and will need to come down for the technology to prove economic — conventional geothermal plants can cost between $4,800 and $6,300 per kilowatt while next-generation plants come in at $15,000 per kilowatt. These costs may come down by making drilling faster, cheaper and more resource-efficient, but that is a long way away. And since next-gen geothermal plants lack the decades-long operating record of conventional plants, it is far more uncertain how their wells and reservoirs will perform over time.

Will it save the planet? Next-gen geothermal is not exactly zero-emission, since it requires huge amounts of steel, cement, diesel and electricity to build the plants. Its median lifecycle emissions are 32g of carbon dioxide per kilowatt hour.