Geothermal Energy
Geothermal energy provides ~16 GW of installed electricity capacity and ~110 GW of direct-use heat capacity worldwide. The US, Indonesia, Philippines, Turkey and New Zealand are the largest electricity producers; Iceland leads on share of national supply. Conventional geothermal depends on hydrothermal resources (hot rock + water + permeability) found in specific tectonic settings. Enhanced Geothermal Systems (EGS) could expand the geography significantly.
Key insights
Geography determines the resource
Hydrothermal geothermal requires three things at the same depth: hot rock, water, and permeability. This combination occurs naturally at plate boundaries (Pacific Ring of Fire, East African Rift, Iceland) and at hot spots. The US (mostly California and Nevada), Indonesia, Philippines, New Zealand, Mexico, Italy, Turkey, Kenya are the dominant producers. Most major economies lack significant conventional geothermal resources.
EGS could change the geography
Enhanced Geothermal Systems use hydraulic stimulation to create artificial reservoirs in hot dry rock — extending geothermal beyond natural hydrothermal sites. Fervo Energy's Cape Station (Utah, commissioning 2024-25) is the first commercial-scale EGS project in the US. Project Innerspace and similar startups aim to take EGS to scale. If technical and economic challenges are overcome, EGS could provide 60+ GW of US generation potential.
Geothermal heat pumps are a separate, larger technology
Ground-source heat pumps (GSHPs) use shallow ground temperature (10-15°C year-round) as heat source/sink for buildings. Installed capacity worldwide is ~120 GW thermal. Much more widely deployable than deep geothermal — works in any climate where the ground is at moderate temperature. China, US, Sweden, Germany are leaders. Higher upfront cost than air-source heat pumps but lower operating costs.
Top geothermal electricity producers (2024)
Installed capacity, MW
Key Finding: USA leads in absolute terms; Iceland leads in per-capita and share of national supply.
Direct-use geothermal heat capacity 2010-2024
GW thermal, including district heating, agriculture, aquaculture, ground-source heat pumps
Key Finding: Direct use has grown ~7× since 2000, dominated by ground-source heat pumps in China, US and Europe.
Methodology & caveats
Capacity vs energy
Geothermal capacity factors are exceptionally high (85-95%) — among the best of any electricity source. A 1 GW geothermal plant produces ~7.5 TWh/year; a 1 GW solar plant produces ~1.7 TWh/year. Capacity figures understate geothermal's share of generation, the inverse of solar/wind.
Resource estimation
Geothermal resources are categorized as: identified (drilled and measured), inferred (similar geology to identified), undiscovered (model-based estimates). Identified geothermal resources support ~30 GW of additional electricity capacity globally; inferred + undiscovered estimates run into hundreds of GW. EGS could add far more if technical challenges are solved.
EGS challenges
EGS faces three main challenges: (1) creating sufficient permeability in hot dry rock without inducing earthquakes (Basel, Pohang projects had seismicity issues); (2) drilling costs at the high temperatures and pressures required; (3) parasitic energy consumption to circulate working fluid. Recent technical progress has been encouraging but commercial-scale EGS remains pre-validated.