Geothermal energy provides clean, steady and renewable electricity and heat, but the use of geothermal energy has conventionally been constrained to locations with adequate subsurface heat and fluid flow. Enhanced geothermal systems (EGS) enable geothermal energy usage in unconventional areas by enhancing the subsurface permeability and increasing fluid flow, which is then extracted as a carrier of the thermal energy. In this Review, we discuss the development of EGS and its role in providing energy. Some EGS are operating commercially in Europe and provide heat and/or electricity, but technical issues and concerns over induced seismicity have historically hindered the broader expansion of EGS. Adaptation of advanced drilling techniques (including the use of polycrystalline diamond compact bits, multiwell drilling pads, horizontal drilling and multistage stimulation) is enabling an increase in scale and decrease in cost of EGS projects. As a result, in the USA, enhanced geothermal is expected to achieve plant capital costs (US$4,500 kW⁻¹) and a levelized cost of electricity (US$80 MWh⁻¹) that are competitive with market electricity prices by 2027. With further development of EGS to manage induced seismicity risk and increase system flexibility, EGS could provide stable baseload and potentially dispatchable electricity in clean energy systems.

• Enhanced geothermal systems (EGS) have the potential to supply clean and firm energy in the form of electricity and/or direct heat.
• EGS projects have been developed since around 1975, with many in Europe. There are larger scale projects currently in development in the USA.
• Several EGS projects operate commercially in Europe. Around 20 well-to-well circulation EGS projects have been developed, but most operate for research purposes or produce modest amounts of energy (a few megawatts electrical or a few tens of megawatts thermal).
• There have been reductions in drilling time and therefore cost in EGS projects developed in the 2020s. Adaptation of oilfield drilling strategies has shortened EGS drilling times by 50–70%.
• Owing to innovation, EGS is expected to be scaled to much larger projects (for example, hundreds of megawatts electrical) at a cost that is competitive with other sources of electricity.
• Induced seismicity is an important issue for EGS, as earthquakes associated with EGS development can impact social acceptance and risk loss of a project’s social license to operate.