In the global race towards decarbonisation, solar panels and wind turbines often capture the spotlight.
Yet, beneath the surface of the Earth lies a powerful, persistent and often-overlooked hero of the energy transition: geothermal power.
Unlike its intermittent counterparts, geothermal energy provides firm, 24/7 baseload electricity, tapping into the Earth’s natural heat.
With a global installed capacity now exceeding 16,873 MW, this quiet renewable is a cornerstone of the energy strategy for nations blessed with the right geology.
The geothermal landscape, however, is not evenly distributed. It is dominated by a select group of colossal projects, true giants that account for a disproportionate share of global output.
This concentration is a direct consequence of geology; the world’s most potent geothermal resources are clustered in tectonically active regions like the Pacific Ring of Fire and the East African Rift Valley.
This reality means that the investment climate, energy policy and technological prowess in a handful of countries have an outsized impact on the growth of the entire sector.
Energy Digital has ranked 10 of the top geothermal energy projects.
10. Darajat Power Station, Indonesia
Operator: Star Energy Geothermal
Headquarters: Jakarta, Indonesia
CEO: Hendra Soetjipto Tan
Harnessing a rare dry steam field in West Java, the Darajat Power Station achieves its 271 MW capacity through three separate units of 55 MW, 95 MW and 121 MW respectively and has been online since 1994.
Its defining feature is its use of dry steam, the original and most direct form of geothermal generation where steam is piped directly from underground reservoirs to turn turbines. This technology is highly efficient but requires rare geological conditions, making Darajat one of only a few such fields worldwide.
9. Tiwi Geothermal Complex, Philippines
Operator: AboitizPower, through its subsidiary AP Renewables, Inc.
Headquarters: Philippines
CEO: Danel C. Aboitiz
As the Philippines’ first and oldest geothermal power plant, the Tiwi Geothermal Complex is a landmark of Southeast Asian renewable energy. Commissioned in 1979 and located in Albay province, this 289 MW facility has been a stalwart of the Luzon grid for more than four decades.
Binary cycle units use the hot brine leftover from the primary flash process to heat a secondary fluid with a lower boiling point, driving another turbine and generating additional electricity from the same heat source. This boosts overall efficiency without the cost and risk of drilling new primary wells.
8. Hellisheidi Power Station, Iceland
Operator: Reykjavik Energy (Orkuveita Reykjavíkur), through its subsidiary ON Power
Headquarters: Reykjavík, Iceland
CEO: Sævar Freyr Þráinsson
Nestled atop the Hengill volcano, Iceland’s Hellisheidi Power Station is a marvel of geothermal engineering. With an electrical output of 303 MW and 400 MW of thermal energy for district heating, it is the largest plant of its kind in Iceland – but its true global significance lies in its pioneering integration of carbon capture.
The co-located Climeworks facility injects captured CO₂ into the volcanic basalt, mineralising it into stone. This makes Hellisheidi a blueprint for not just clean energy, but negative-emissions power generation.
Dr Ingunn Gunnarsdóttir, Leader of Innovation at ON Power will be moderating The Future of Energy Transition panel at Sustainability LIVE London 2025. Get your tickets here.
7. Sarulla Geothermal Power Plant, Indonesia
Operator: Sarulla Operations Ltd.
Headquarters: Jakarta, Indonesia
CEO: Taku Kimura
The 330 MW Sarulla Geothermal Power Plant in North Sumatra is one of the world's largest and a testament to modern project financing. Brought online in three phases between 2017 and 2018, it powers more than two million homes.
The project’s development, which took decades, was revived by a complex international consortium including Medco Power, Ormat, Itochu and Kyushu Electric. Utilising an advanced integrated combined-cycle technology, Sarulla efficiently extracts energy from both steam and brine.
6. CalEnergy Generation’s Salton Sea Geothermal Area, US
Operator: Berkshire Hathaway Energy, through its subsidiary CalEnergy Operating Corporation
Headquarters: Des Moines, Iowa, US
CEO: Scott W. Thon
In Southern California’s Imperial Valley, the Salton Sea geothermal area is a 345 MW powerhouse and a hotbed of future-facing innovation.
Operated by BHE Renewables, this cluster of ten plants has been a reliable energy source since 1982.
What makes this project globally significant is its pioneering work in direct lithium extraction. The super-saline geothermal brine is rich in minerals, and BHE is developing technology to co-produce battery-grade lithium alongside clean electricity. This positions the Salton Sea at the nexus of the energy transition and the electric vehicle supply chain.
5. Gunung Salak Geothermal Power Plant, Indonesia
Operator: Star Energy Geothermal
Headquarters: Jakarta, Indonesia
CEO: Hendra Soetjipto Tan
With a capacity of 377 MW, the Gunung Salak geothermal plant is Indonesia's largest geothermal facility and a critical component of the national grid.
Located in the volcanic region of West Java, the plant has been operational since 1994, with its six units developed in stages.
Like its sister plant Darajat, Gunung Salak was acquired by Star Energy from Chevron in a landmark deal, consolidating major Indonesian geothermal assets under a single, powerful domestic operator. Its recent expansion with a new binary unit underscores a strategy of continuous optimisation.
4. Mak-Ban Geothermal Power Complex, Philippines
Operator: AboitizPower, through its subsidiary AP Renewables, Inc.
Headquarters: Bonifacio Global City, Philippines
CEO: Danel C. Aboitiz
The Makiling-Banahaw Geothermal Power Complex, known as Mak-Ban, is a giant of the Philippine energy system, boasting a capacity of 458 MW. Commissioned in 1979, the same year as its sibling plant Tiwi, Mak-Ban was instrumental in establishing the Philippines as a global geothermal leader.
Operated by AboitizPower, the complex spans six power plants across two provinces, and primarily uses single- and double-flash steam technology, complemented by binary cycle units. Its long and productive history, transitioning from state-supported development to private-sector operation, makes it a model for the successful management and sustained output of large-scale geothermal assets.
3. Cerro Prieto Geothermal Power Station, Mexico
Operator: Comisión Federal de Electricidad (CFE)
Headquarters: Mexico City, Mexico
CEO: Emilia Esther Calleja Alor
With a total installed capacity across all its units reaching as high as 820 MW, Cerro Prieto is a true behemoth. The complex consists of five main powerhouses, designated CP1 through CP5, which were constructed in phases between 1973 and the late 2000s using primarily flash steam technology.
The entire operation is owned and run by Mexico's state utility, CFE, making it a prime example of a state-controlled energy mega-project, in contrast to the public-private models seen in the Philippines or the corporate-owned assets in the US.
A remarkable feature is its geology; the plant sits on a terrestrial spreading fault, a rarity that provides an immense and powerful heat source.
2. Larderello Geothermal Complex, Italy
Operator: Enel Group through its subsidiary Enel Green Power
Headquarters: Rome, Italy
CEO: Salvatore Bernabei
The Larderello Geothermal Complex in Tuscany, Italy is the birthplace of geothermal power generation and a living monument to the industry. With a net capacity of 769 MW from 34 plants, it is Europe's largest geothermal source.
Its history dates to 1904, when Prince Piero Ginori Conti first lit five light bulbs with geothermal steam, and the first commercial plant was built in 1913.
Now operated by Enel Green Power, Larderello accounts for an estimated 10% of the world's total geothermal production, supplying power to millions and heat to local communities.
1. The Geysers Geothermal Complex, US
Operator: Calpine Corporation
Headquarters: Houston, Texas, US
CEO: Andrew Novotny
Sprawling across 45 square miles of California’s Mayacamas Mountains, The Geysers is the undisputed heavyweight champion of geothermal energy.
As the world's largest geothermal field, its complex of 18 power plants boasts an installed capacity of more than 1,500 MW.
Operated primarily by Calpine, The Geysers generates enough clean, baseload electricity to power a city the size of San Francisco.
A model of resource sustainability, it pioneered the use of treated municipal wastewater, injecting millions of gallons daily to replenish its steam reservoirs, ensuring this geothermal giant continues to power Northern California's green economy.
