Geothermal Power Stations of the World: A Guided History and List

Geothermal power stations turn heat from inside the Earth into electricity. They are among the oldest forms of renewable generation still in commercial use, older than modern wind turbines and solar panels by most of a century, and they are also among the least visible. A geothermal field rarely makes headlines, but in several countries it supplies a large share of the electricity people use every day.

The Wikipedia "List of geothermal power stations" collects operational stations with at least 10 megawatts (MW) of installed capacity. A bare list of names and numbers is useful for looking things up, but it does not explain why the stations are where they are, why some are huge and some are small, why the same "capacity" number can mean very different amounts of actual electricity, or how the biggest fields got that way. This guide uses the list as a backbone and fills in that context: the history of the technology, how the three main plant types work, a tour of the major stations by region, worked examples of how to read the numbers, the limits and environmental issues, and a set of common misconceptions.

All capacity figures below are in megawatts of electrical output (MWe) unless stated otherwise. Where sources disagree, this article says so rather than picking one number silently.

What counts as a "geothermal power station"

A geothermal power station is a facility that generates electricity using heat drawn from underground. In the conventional form, wells are drilled into a reservoir of hot water or steam, the fluid is brought to the surface, its energy spins a turbine connected to a generator, and the cooled fluid is usually injected back underground.

The US Energy Information Administration (EIA) describes the resource these plants use as hydrothermal: underground reservoirs containing hot water or steam. According to the EIA, power plants need water or steam at roughly 300°F to 700°F (about 150°C to 370°C), and some production wells are as deep as two miles. The US Department of Energy (DOE) frames the requirements as three things that must occur together: heat, enough fluid to carry that heat to the surface, and permeability, meaning pathways in the rock that let the fluid move. When nature supplies all three, the result is a conventional hydrothermal system. When one is missing, engineers may try to create it, which is the idea behind enhanced geothermal systems (discussed later).

The word "station" in the list can mean slightly different things. Some entries are a single power plant with one turbine. Others, such as The Geysers in California or Larderello in Italy, are entire geothermal fields containing many separate plants and dozens of generating units. Comparing a single-unit plant with a multi-plant field is a bit like comparing one building with a neighborhood, which is worth remembering when scanning the ranking.

Why the list uses a 10 MW threshold

The Wikipedia list includes only operational stations of 10 MW or more. That cut-off keeps the list manageable and focused on grid-scale generation. It also means small but historically or technically important plants are excluded. For example, the Wikipedia article on geothermal power notes that Chena Hot Springs in Alaska ran a binary plant on fluid at just 57°C in 2006, a remarkable demonstration of how low a usable temperature can be, but a plant of that kind is far below the threshold. The list therefore shows where most geothermal electricity comes from, not where all the interesting engineering happens.

A short history of geothermal electricity

Larderello: the first light bulbs and the first commercial station

People used hot springs for bathing and heating for thousands of years, but geothermal electricity began in Tuscany. The Larderello area had been an industrial site long before it was a power site. According to Wikipedia's article on Larderello, in 1827 François Jacques de Larderel developed a way of extracting boric acid from the volcanic mud using steam-heated cauldrons, with the backing of Grand Duke Leopold II, and a town was founded to house the workers.

On 4 July 1904, Prince Piero Ginori Conti tested the first geothermal electric generator at Larderello, using natural steam to light a handful of bulbs. (Wikipedia's articles give the count as four bulbs, and in one place five.) The EIA confirms that the first geothermal power plant, built in Italy in 1904, used natural steam from the ground. Wikipedia dates the world's first commercial geothermal power station to Larderello in 1911.

Larderello remains a major producer more than a century later. Wikipedia's article says the area produces about 4,800 gigawatt-hours (GWh) a year, enough for roughly a million Italian households, and about 10% of the world's geothermal electricity. The station list gives Larderello 769 MW across 34 units, and lists two further Italian entries, Valle Secolo (120 MW) and Serrazzano (60 MW).

Wairakei: the first big wet-steam plant

The second great milestone came in New Zealand. Larderello is a dry-steam field, where the reservoir produces mostly steam. Most high-temperature fields in the world are not like that: they produce a mixture of very hot pressurized water and steam. Using that kind of resource at scale required a different approach.

Wairakei Power Station, north of Taupō in New Zealand's Taupō Volcanic Zone, was commissioned in November 1958. Wikipedia's general geothermal article describes it as the first station to use flash steam, the technique of letting high-pressure hot water "flash" partly into steam at the surface. Wairakei is now owned and operated by Contact Energy. Its unit list includes six 11.2 MW units, three 30 MW units, a 4 MW unit and a 14 MW binary unit added in 2005 to use lower-temperature steam that had already passed through the main plant. Sources give its nameplate as 175 MW (infobox) or 181 MW (text), with an infobox capacity factor of 89% and 1,365 GWh of annual net output. The station list gives a larger figure, 352 MW across four units, which appears to count the wider Wairakei development rather than only the original station; this is one of several places where the list and individual station articles do not line up perfectly. Wairakei is scheduled to be phased out in 2027 and replaced by the newer Te Mihi station nearby (166 MW in the list).

The Geysers: America's steam field

In California, the area now called The Geysers had been known since 1847, when William Bell Elliott named it during a survey. The name is misleading: its features were fumaroles (steam vents), not true geysers. According to Wikipedia, a small private plant in 1921 produced 250 kilowatts to light a resort, and in 1960 Pacific Gas and Electric began operating an 11 MW plant, which Wikipedia's geothermal article calls the first successful US geothermal electric station.

The Geysers grew into the largest developed geothermal field in the world. It now tops the list at 1,590 MW of nameplate capacity across 22 units, and generated 6,516 GWh in 2018. The field's story after its expansion is a cautionary one, covered in the section on reservoir management below.

Binary plants open up cooler resources

Dry steam and flash plants need very hot fluid. The third technology, the binary cycle, uses geothermal water to heat a second "working" fluid with a lower boiling point, and it is this working fluid that drives the turbine. Wikipedia's geothermal article states that an organic-fluid binary plant was first demonstrated in the Soviet Union in 1967. Binary technology later made it possible to use resources as cool as 81°C, and, in the Chena Hot Springs case, 57°C.

The modern era

Geothermal growth has been steady rather than explosive. Wikipedia cites IRENA figures of 14,438 MW online at the end of 2020, generating 94,949 GWh. ThinkGeoEnergy, an industry news and data service that publishes an annual ranking, reported global installed capacity of 16,873 MW across 35 countries at the end of 2024, with 389 MW added during that year from 14 new plants and expansions. REN21's Global Status Report puts the global total lower, at about 15.1 GW. The difference is mostly about counting methods (for instance, whether to count gross or net capacity and how to treat plants that are installed but not running), so it is wise to compare numbers only within the same source.

How geothermal power stations work

The basic chain

Every conventional geothermal plant follows the same chain:

1. Production wells tap a reservoir of hot fluid.
2. Surface equipment separates, conditions or exchanges heat from that fluid.
3. A turbine converts the energy of expanding steam or vapor into rotation.
4. A generator converts rotation into electricity.
5. A condenser and cooling system turns exhaust vapor back into liquid so the cycle keeps a pressure difference across the turbine.
6. Injection wells return spent fluid to the reservoir, maintaining pressure and disposing of the water.

The differences between plant types are mainly in step 2.

Dry steam plants

In a dry steam plant, the reservoir produces steam that is piped directly to the turbine. The EIA describes this as the oldest type, first used in Italy in 1904. The DOE notes that dry steam plants use fluid that is already mostly steam, and identifies The Geysers as the world's largest single geothermal source. Dry steam fields are rare, which is why only a handful of entries in the list use this technology. The list tags The Geysers, Cerro Prieto (Mexico, 570 MW; volunteer-maintained technology tags are worth checking against operator data), Darajat (Indonesia, 270 MW), Imperial Valley (US, 403.4 MW) and part of Kamojang (Indonesia) as dry steam.

Flash steam plants

Flash plants are the most common type, according to the EIA. Hot water under high pressure is brought up the well; when the pressure is reduced, part of it "flashes" into steam, which is separated and sent to the turbine. The DOE gives the threshold as fluid hotter than about 182°C (360°F). The remaining hot liquid can be flashed again at a lower pressure in a "double flash" arrangement to extract more energy. Afterward, the steam is condensed and the fluid is injected back underground.

Many of the large plants in Iceland, Indonesia, New Zealand and the Philippines are flash plants. In the list, Hellisheiði (Iceland, 303 MW), Gunung Salak (Indonesia, 377 MW), Sarulla (Indonesia, 330 MW), Coso (US, 270 MW), Tiwi (Philippines, 234 MW) and Nga Awa Purua (New Zealand, 132 MW) are all tagged as flash.

Binary cycle plants

Binary plants use geothermal fluid below about 182°C, according to the DOE. The geothermal water passes through a heat exchanger and heats a secondary fluid with a lower boiling point; that fluid vaporizes and drives the turbine, then is condensed and reused. The geothermal water never touches the turbine and is returned underground. The EIA notes that this closed system produces no air emissions from the plant itself.

Binary units tend to be smaller and modular, which is why so many entries in the list from Nevada, Utah and California are binary plants in the tens of megawatts: McGinness Hills (138 MW), Heber (81 MW), Ormesa (73.2 MW), Mammoth (60 MW), Blue Mountain (50 MW) and others. New Zealand's Ngatamariki (82 MW) and Te Huka (23 MW), and Croatia's Velika Ciglena (17 MW), are also binary.

Hybrids

Several entries combine technologies. The list records Desert Peak (US) as 71.7% flash and 28.3% binary, Blundell (US) as 70% flash and 30% binary, and Svartsengi (Iceland) as flash and binary. A binary "bottoming" unit added to a flash plant can squeeze extra electricity from fluid that would otherwise be reinjected while still hot. Some sites go further and add solar panels: the list notes that Patua (US) combines a 60 MW geothermal plant with a 10 MW solar farm, and Stillwater (US) combines a 49 MW geothermal plant with a 26 MW solar farm.

Comparison of plant types

The biggest stations in the list

The table below shows the twenty largest entries in the Wikipedia list by installed capacity. It is a snapshot of the list at the time of writing, which, like any list maintained by volunteers, mixes data from different years.

Two things stand out. First, a single entry, The Geysers, is more than twice the size of the next one. Second, the list is dominated by a small number of volcanic regions: the western United States, Italy's Tuscany, the East African Rift, Mexico, the Philippines, Indonesia, New Zealand and Iceland. That is no accident; it follows the geology.

Why stations cluster where they do

High-temperature geothermal resources occur where hot rock or magma sits relatively close to the surface and where water can circulate through it. In practice that means volcanic arcs above subduction zones (Indonesia, the Philippines, Japan, Central America, New Zealand), rifts where continents are pulling apart (Kenya's part of the East African Rift, Iceland on the Mid-Atlantic Ridge), and regions of thinned, stretched crust (the Basin and Range of Nevada and Utah).

This geology explains the distribution in the country totals below. The following table sums the capacities of the entries in the Wikipedia list by country. These sums are this article's own arithmetic from the list, not official national statistics, and they will be lower than national totals because the list only includes stations of 10 MW or more and some entries lack data.

For comparison, ThinkGeoEnergy's national rankings for the end of 2024 are shown below. Note how much larger some figures are than the list sums, especially for Turkey, which has many plants and has grown rapidly.

ThinkGeoEnergy says these ten countries hold about 93% of the world's installed geothermal capacity. Turkey is a good example of the gap between "stations over 10 MW listed on Wikipedia" and real national capacity: the list has only three Turkish entries (Efeler 162.3 MW, Kızıldere 80 MW, Pamukören 68 MW), but ThinkGeoEnergy counts 1,734 MW nationwide, including new plants such as GreenEco 7, Open Mountain T-01 and Hez Morali in 2024.

A regional tour

United States

The United States has more geothermal capacity than any other country, at 3,937 MW according to ThinkGeoEnergy's end-2024 figure; the DOE describes it as "just over 4 GW." It also has more entries in the list (31) than any other country. Most US geothermal capacity is in California and Nevada.

The Geysers dominates. It lies in the Mayacamas Mountains about 72 miles (116 km) north of San Francisco and spans Sonoma, Lake and Mendocino counties. Wikipedia reports that Constellation Energy owns 86.5% of the field and Calpine operates it, and the infobox lists 18 power stations with 22 operating units.

Imperial Valley in Southern California (403.4 MW in the list, 11 units) and Coso in the desert east of the Sierra Nevada (270 MW, flash) are the other giants. Then come the Nevada plants, many of them binary: McGinness Hills (138 MW), Desert Peak (92 MW), Steamboat (73 MW, with the list noting a planned expansion to 93 MW), Stillwater (75 MW including solar), Patua (70 MW including solar), Dixie Valley (61 MW), Soda Lake (37 MW), Jersey Valley (10 MW) and others. Utah's entries include Blundell (36 MW) and Cove Fort (27 MW); Idaho has Raft River (11 MW); Oregon has Neal Hot Springs (22 MW). Hawaii's Puna plant (38 MW, binary) is notable as the only entry on a mid-ocean volcanic island in the US; the list notes a planned expansion to 46 MW with completion expected by the end of 2027.

The Philippines

The Philippines ranks third globally by ThinkGeoEnergy's count (1,984 MW at the end of 2024) and has nine entries in the list. Its large fields include Mak–Ban (458 MW), Tiwi (234 MW, flash), Malitbog (233 MW), Bacman (209.8 MW), Palinpinon (192.5 MW), Mahanagdong (180 MW), Upper Mahiao (125 MW), Tongonan 1 (113 MW) and Mindanao (106 MW). The country's volcanic islands give it abundant high-temperature resources. ThinkGeoEnergy credited 2024 growth to projects at Tiwi, Palayan and Biliran.

Indonesia

Wikipedia's geothermal article notes that Indonesia has the largest estimated geothermal resource of any country, about 29 GW, but had only about 1.8 GW installed as of 2017. By the end of 2024, ThinkGeoEnergy put its installed capacity at 2,653 MW, second in the world, partly reflecting a government data correction plus expansions at Sorik Marapi Unit 5, Salak and Lahendong. The list's Indonesian entries are all in Java and Sumatra: Gunung Salak (377 MW, six units), Sarulla (330 MW, three units), Darajat (270 MW, dry steam), Kamojang I–V (235 MW), Wayang Windu (227 MW), Ulubelu (220 MW), Muara Laboh (85 MW) and Karaha (30 MW).

Darajat and part of Kamojang are tagged as dry steam in the list, which puts them alongside The Geysers in the small group of fields where the reservoir produces mostly steam.

New Zealand

New Zealand has nine entries, all in the central North Island's Taupō Volcanic Zone: Wairakei (352 MW in the list), Te Mihi (166 MW), Mokai (132 MW), Nga Awa Purua (132 MW, flash), Ohaaki (104 MW), Kawerau (100 MW), Ngatamariki (82 MW, binary), Poihipi (55 MW) and Te Huka (23 MW, binary). ThinkGeoEnergy reported New Zealand at 1,207 MW at the end of 2024, and noted that Tauhara II, at 174 MW, was the single largest geothermal addition anywhere in the world that year. Tauhara II is new enough that it is not yet in the list snapshot used here, which is a good reminder to check dates.

Wikipedia's geothermal article, citing EIA data for 2021, puts geothermal at 18.0% of New Zealand's electricity.

Iceland

Iceland sits on the Mid-Atlantic Ridge and a hotspot, and it uses geothermal heat both for electricity and, on a very large scale, for district heating. The list includes Hellisheiði (303 MW), Reykjanes (130 MW), Nesjavellir (120 MW), Þeistareykir (90 MW), Svartsengi (77 MW) and Krafla (60 MW), all flash or flash-and-binary.

Hellisheiði, owned and operated by ON Power, a subsidiary of Reykjavík Energy, began generating electricity in 2006. Besides its 303 MW of electrical capacity, it supplies 200 MW of thermal output (MWth) for Reykjavík's district heating, a figure that was raised to 200 MWth in 2020. Since 2014, the plant has reinjected non-condensable gases underground to cut hydrogen sulfide pollution in the capital area. The site also hosts a direct air capture facility run by Climeworks; Wikipedia states it "captures up to 4,000 metric tons of carbon dioxide each year," with the gas injected underground and mineralized, a process linked to the CarbFix project. Steam levels at Hellisheiði began dropping around 2013, which prompted a new drilling program in 2016.

According to the EIA data quoted by Wikipedia, geothermal supplied 29.4% of Iceland's electricity in 2021. (Most of the rest comes from hydropower.)

Kenya

Kenya is the standout in Africa. The list has one consolidated entry, Olkaria I–V, at 727 MW, located in and around Hell's Gate National Park in the Rift Valley. Kenya Electricity Generating Company (KenGen) says the first unit of Olkaria I was commissioned in June 1981, with the second and third units following in November 1982 and March 1985, bringing the original plant to 45 MW. Airbus describes Olkaria I as Africa's first geothermal power station. Later expansions added two 70 MW units at Olkaria I between October 2014 and February 2015 (part of a 280 MW phase described by POWER magazine), and an 83 MW Unit 6 commissioned in July 2022.

ThinkGeoEnergy put Kenya's national capacity at 985 MW at the end of 2024, with progress at Menengai bringing it near the 1 GW mark. Most strikingly, EIA data for 2021, cited in Wikipedia's geothermal article, put geothermal at 43.4% of Kenya's electricity, the highest share of any country in that dataset.

Mexico and Central America

Mexico's Cerro Prieto in Baja California is listed at 570 MW with nine units, and Los Humeros at 25 MW. ThinkGeoEnergy put Mexico's total at 976 MW at the end of 2024.

Central America has a string of volcanic plants: Berlín (115.4 MW) and Ahuachapán (95 MW) in El Salvador, Miravalles (100 MW) in Costa Rica, and San Jacinto Tizate (74 MW) in Nicaragua. These are small by world standards but large relative to national electricity systems. EIA data quoted by Wikipedia show geothermal providing 23.9% of El Salvador's electricity and 16.9% of Nicaragua's in 2021, and Wikipedia's introduction also names Costa Rica among the countries where geothermal produces more than 15% of electricity.

Turkey

Turkey's geothermal fields lie mostly in the Aegean region of western Anatolia. The list includes Efeler (162.3 MW, with a note that it was expanding toward 259.9 MW by 2022 as of August 2019), Kızıldere (80 MW) and Pamukören (68 MW). Turkey's national capacity, 1,734 MW at the end of 2024 according to ThinkGeoEnergy, is much larger than the list suggests because it is spread over many plants, some of which are not yet captured in the list.

Japan, Russia and others

Japan has a large volcanic resource but relatively modest development. The list includes only Hatchōbaru (112 MW, 98.2% flash and 1.8% binary), while ThinkGeoEnergy reports 601 MW nationwide, with 2024 growth at Appi, Suginoi and Minami-Kayabe. Russia's entries are both on the Kamchatka Peninsula: Mutnovskaya (50 MW, flash) and Pauzhetskaya (14.5 MW). Papua New Guinea's Lihir (55 MW) is the list's only entry from Melanesia. Croatia's Velika Ciglena (17 MW, binary) is a reminder that geothermal power is not limited to obviously volcanic countries: binary plants can run on the moderate temperatures found in some sedimentary basins.

Reading the numbers: capacity versus generation

The most common mistake when reading a list like this is to treat capacity as if it were output. Capacity (in MW) is the maximum power a plant can deliver at a given moment. Generation (in GWh or MWh) is how much energy it actually delivers over a period. The link between them is the capacity factor: actual generation divided by what the plant would have produced if it ran at full capacity all the time.

Geothermal is often described as "baseload" because, unlike solar or wind, it does not depend on the weather. Wikipedia's geothermal article reports that capacity factors up to 96% have been demonstrated, that the IPCC put the global average at 74.5% in 2008, and that the EIA's 2021 global average was 71%. But individual plants vary a lot.

Worked example 1: The Geysers

The list gives The Geysers 1,590 MW of nameplate capacity and 6,516 GWh of generation in 2018.

• A year has 8,760 hours.
• If 1,590 MW ran all year: 1,590 MW × 8,760 h = 13,928,400 MWh, or about 13,928 GWh.
• Actual generation: 6,516 GWh.
• Capacity factor: 6,516 ÷ 13,928 ≈ 0.468, or about 47%.

That is much lower than geothermal's reputation would suggest. The reason is not the weather; it is the reservoir. Much of The Geysers' nameplate capacity was installed when steam was more plentiful, and the field can no longer supply enough steam to run every unit flat out. The nameplate figure tells you how big the equipment is, not how much energy the ground can currently deliver.

Worked example 2: Wairakei

Wikipedia's Wairakei article gives 175 MW and 1,365 GWh of annual net output.

• Full-time output: 175 MW × 8,760 h = 1,533,000 MWh, or 1,533 GWh.
• Capacity factor: 1,365 ÷ 1,533 ≈ 0.89, or 89%.

This matches the 89.0% capacity factor in the article's infobox, and it is a good example of a mature field run close to its sustainable limit.

Worked example 3: a hypothetical 100 MW plant

Suppose a new (hypothetical) 100 MW flash plant runs at a 90% capacity factor.

• Annual generation: 100 MW × 8,760 h × 0.90 = 788,400 MWh, or about 788 GWh.

If the same plant ran at 70%, close to the EIA's 2021 global average, it would produce 100 × 8,760 × 0.70 = 613,200 MWh, about 613 GWh. That 20-point difference in capacity factor changes annual output by about 175 GWh, which shows why operators care so much about reservoir management and plant availability.

Worked example 4: emissions

Wikipedia's geothermal article states that geothermal plants average about 45 grams of CO₂ per kilowatt-hour, compared with about 1,001 kg of CO₂-equivalent per megawatt-hour (1,001 g/kWh) for coal without carbon capture.

For the hypothetical 788 GWh plant above:

• Geothermal: 788,400,000 kWh × 45 g = about 35,500 tonnes of CO₂ a year.
• The same electricity from coal at 1,001 g/kWh: about 789,200 tonnes a year.

The geothermal figure is under 5% of the coal figure, which matches the article's statement. Real plants vary widely: some fields release more CO₂ from the reservoir fluid, while closed-loop binary plants that reinject everything emit very little from the plant itself.

Reservoir management: what The Geysers taught the industry

A geothermal reservoir is renewable in the sense that the Earth keeps supplying heat, but the fluid in a given reservoir can be extracted faster than it is replaced. The Geysers is the clearest case.

Wikipedia reports that by 1999, steam extraction had depleted the field and production began to fall. The fix was to put water back. Injection of treated wastewater began on 16 October 1997 to recharge the steam field. The Southeast Geysers Effluent Pipeline, finished in 1997, carries about 9 million gallons a day over 40 miles from Lake County. The Santa Rosa Geysers Recharge Project, finished in 2003, adds about 11 million gallons a day through a 42-mile pipeline. Together they supply roughly 20 million gallons of reclaimed water daily, and the injection supported about 77 MW of capacity in 2004.

This approach turned a sewage disposal problem for nearby communities into a fuel supply for the power plants. But it has a side effect: injection is linked to small earthquakes. According to Wikipedia, about 99% of seismic events at the field are around magnitude 3.0 or smaller, and magnitude 3+ events have trended downward since 1990, but there have been larger events, including a magnitude 4.5 in 2014, a magnitude 5.0 in 2016 and a magnitude 3.8 in 2022.

Wairakei taught a similar lesson. Wikipedia's article notes that early operation discharged spent fluid rather than reinjecting it, and that steam extraction increased visible surface activity at places like Craters of the Moon, caused land subsidence and reduced steam volumes. Reinjection of used water is now common practice. Wairakei is also the main source of arsenic in the Waikato River, with concentrations reaching 0.035 g/m³ in places, a reminder that geothermal fluids carry dissolved minerals and gases that must be managed.

Hellisheiði's falling steam levels from around 2013 and the 2016 drilling program are a more recent example of the same challenge: a field's output is not fixed when the plant is built, and keeping it up requires continued investment.

Costs and economics

Geothermal is capital-intensive. Wikipedia's geothermal article states that drilling accounts for over half of capital costs, and gives plant-plus-well costs of about €2 million to €5 million per MW, with levelized energy costs of about €0.04 to €0.10 per kWh. The DOE's GeoVision work, as summarized on DOE pages, puts well construction at up to 50% of total capital cost.

Once built, a plant has no fuel bill, so it is protected from fuel price swings. The main operating risks are geological: a reservoir that turns out smaller or cooler than expected, wells that produce less than planned, scaling and corrosion from mineral-rich fluids, or gradual pressure decline. These risks are concentrated at the beginning of a project, before the first wells prove the resource, which is why geothermal development often relies on public funding or risk-sharing schemes for exploration drilling.

Beyond the list: enhanced and next-generation geothermal

The stations in the list are almost all conventional hydrothermal plants. The next frontier is to make geothermal work where nature does not supply all three ingredients.

Enhanced geothermal systems (EGS) inject fluid into hot, low-permeability rock to open or create fractures, forming an engineered reservoir, then circulate water between wells. Wikipedia lists demonstration projects at Landau-Pfalz in Germany and Soultz-sous-Forêts in France, and notes that a project in Basel, Switzerland, was shut down after triggering earthquakes. A 2006 MIT study estimated that $1 billion in research and development over 15 years could enable 100 GW of US EGS capacity by 2050.

The DOE also describes closed-loop systems (sealed underground pipes that circulate fluid without relying on a fracture network), superhot systems that tap rock above 375°C, and the use of sedimentary resources, including idle oil and gas wells. DOE's 2019 GeoVision analysis projected at least 60 GW of US geothermal by 2050 with EGS advances, and a later DOE analysis raised that to at least 90 GW. ThinkGeoEnergy describes enhanced and advanced systems as having large potential but remaining at an early stage.

Wikipedia's geothermal article gives an estimated global potential ranging from 35 GW to 2 TW, and states that only about 6.9% of global potential has been tapped. The wide range reflects deep uncertainty about how much of the hot rock beneath the continents can be economically accessed.

Limits and challenges

• Geography. Conventional high-temperature resources are concentrated in a few volcanic and tectonic regions. Many countries have little or none.
• Exploration risk. A resource can only be confirmed by drilling, and drilling is the most expensive part of a project.
• Reservoir decline. As The Geysers and Hellisheiði show, fields can lose pressure and steam over time without careful reinjection and make-up drilling.
• Induced seismicity. Injection and stimulation can cause earthquakes. Most are tiny, but the Basel EGS project was halted over seismic events, and The Geysers has recorded events up to magnitude 5.0.
• Gases and minerals. Geothermal fluids can contain hydrogen sulfide, CO₂, arsenic and other substances. Hellisheiði's gas reinjection system and Wairakei's arsenic issue show both the problem and the mitigation.
• Land and cultural values. Geothermal fields often coincide with geysers, hot springs and protected landscapes, such as Kenya's Hell's Gate National Park, creating trade-offs between development and conservation.
• Data quality. National and global totals differ between sources such as ThinkGeoEnergy, REN21 and IRENA, and station lists mix data from different years.

Common misconceptions

"Geothermal plants always run at nearly full output." Some do, like Wairakei at 89%. But The Geysers, the largest field, produced only about 47% of its nameplate potential in 2018 because the reservoir cannot feed all the installed equipment.

"The biggest number in the list is the biggest power plant." The Geysers is a field of 18 plants with 22 units. A single-unit plant such as Hellisheiði (303 MW listed as one unit) is a different kind of entity.

"Geothermal is only possible near volcanoes." High-temperature flash and dry steam plants mostly are. Binary plants can use far cooler water, as low as 57°C in the Chena Hot Springs demonstration, and are used in non-volcanic places such as Croatia and Nevada's Basin and Range.

"Geothermal produces no emissions." Plants emit far less CO₂ than fossil plants (about 45 g/kWh on average versus about 1,001 g/kWh for coal), but not zero. Binary plants that reinject all fluid emit very little from the plant itself.

"Geothermal is inexhaustible at any one site." Heat is replenished over geological time, but reservoir fluid and pressure can be drawn down within decades if extraction is not balanced by reinjection.

"Countries with the most capacity get the most benefit." The United States has the most capacity, but geothermal is a small share of its huge grid. Kenya, Iceland, El Salvador, New Zealand and Nicaragua get a much bigger share of their electricity from it.

How to use and check a geothermal station list

If you are using the list for research or writing, a few habits help:

1. Check the year. Capacity changes as units are added or retired. Tauhara II (174 MW, 2024) and Olkaria I Unit 6 (2022) are recent examples.
2. Check what the entry covers. A single plant, a complex of plants, or a whole field.
3. Check gross versus net. Some figures are gross generator ratings; others subtract the plant's own electricity use.
4. Look for generation, not just capacity. Where available, GWh per year tells you far more about real contribution.
5. Cross-check national totals. Compare a sum from the list with ThinkGeoEnergy, REN21 or IRENA figures, and expect differences.
6. Watch for inconsistencies. For example, Wairakei appears as 352 MW in the list but 175 to 181 MW in its own article, and Olkaria I's capacity varies between sources depending on whether recent units are counted.

Frequently asked questions

Which is the largest geothermal power station in the world? The Geysers in California, with 1,590 MW of nameplate capacity across 22 units, according to the Wikipedia list. It is a complex of many plants within one field.

Where was the first geothermal power plant? Larderello in Tuscany, Italy. Prince Piero Ginori Conti lit bulbs with geothermal steam on 4 July 1904, and the first commercial station there dates to 1911.

Which country has the most geothermal capacity? The United States, with 3,937 MW at the end of 2024 by ThinkGeoEnergy's count, followed by Indonesia (2,653 MW) and the Philippines (1,984 MW).

Which country relies most on geothermal electricity? In the 2021 EIA data cited by Wikipedia, Kenya had the highest share at 43.4%, followed by Iceland (29.4%), El Salvador (23.9%), New Zealand (18.0%) and Nicaragua (16.9%).

How much geothermal capacity is there worldwide? About 16,873 MW across 35 countries at the end of 2024 according to ThinkGeoEnergy; REN21 gives a lower figure of about 15.1 GW. IRENA reported 14,438 MW at the end of 2020.

What is the difference between flash and binary plants? A flash plant lets very hot pressurized water turn partly into steam and sends that steam to the turbine. A binary plant uses cooler geothermal water to boil a separate working fluid, and only that fluid passes through the turbine.

Why do some geothermal plants produce less than their capacity? Usually because the reservoir cannot supply enough steam or hot water, as at The Geysers. Maintenance, grid limits and declining well output also matter.

Is geothermal power renewable? The heat source is effectively renewable on human timescales, but individual reservoirs must be managed, mainly by reinjecting fluid, to avoid depletion.

Can geothermal cause earthquakes? Yes. Injection and reservoir stimulation can induce seismic events. Most are very small, but some have been large enough to stop projects, as in Basel, or to be felt, as at The Geysers.

Why are there so few geothermal plants compared with wind or solar? Conventional plants need a specific combination of heat, water and permeable rock that occurs in limited places, and drilling to prove a resource is expensive and risky. Enhanced and closed-loop systems aim to remove that geographical limit, but they remain at an early stage.

Summary

The list of geothermal power stations is short compared with lists of wind farms or solar parks, but it tells a clear story. Geothermal electricity began with a few light bulbs at Larderello in 1904, scaled up with flash steam at Wairakei in 1958 and dry steam at The Geysers from 1960, and spread to cooler resources with binary plants. Today about 17 GW is installed worldwide, concentrated in the volcanic and rift regions of the United States, Indonesia, the Philippines, Turkey, New Zealand, Kenya, Mexico, Italy, Iceland and Japan. For a handful of countries, especially Kenya and Iceland, it is a pillar of the electricity system.

Reading the list well means looking past nameplate capacity to generation and capacity factor, noting what each entry actually includes, and remembering that a geothermal field is a living reservoir that must be managed. The next chapter, if enhanced and closed-loop systems succeed, may be geothermal plants far from any volcano.

Sources

• List of geothermal power stations (Wikipedia)
• Geothermal power (Wikipedia)
• Geothermal power plants, U.S. Energy Information Administration
• Geothermal Electricity Generation, U.S. Department of Energy
• ThinkGeoEnergy's Top 10 Geothermal Countries 2024 (Power)
• REN21 Global Status Report 2025: Geothermal
• The Geysers (Wikipedia)
• Larderello (Wikipedia)
• Wairakei Power Station (Wikipedia)
• Hellisheiði Power Station (Wikipedia)
• KenGen: Geothermal Power Generation
• Olkaria I Geothermal Power Station (Wikipedia)
• POWER magazine: Olkaria Geothermal Expansion Project
• U.S. DOE: Subsurface Accessibility / drilling costs