Geothermal FAQs

Geothermal is “earth heat” – the energy contained in the subsurface. Wells can be drilled into the earth to tap this energy in the form of naturally occurring steam and hot water. This steam or hot water can be drawn to the surface to generate electricity or provide direct heat to buildings. Subsurface resources can also be used to heat and cool buildings.

Learn more with our fact sheet: What is Geothermal Energy?

Several attributes make geothermal a beneficial source of energy, including:

• Geothermal resources can be used in multiple ways, including to produce electricity, heat and cool homes and businesses, and provide energy storage.
• Geothermal resources are “homegrown” and located in the subsurface, offering a domestic source of secure, reliable energy.
• Geothermal energy is available 24 hours a day, 365 days a year, regardless of weather.
• Geothermal power plants have a high-capacity factor—typically 90% or higher—meaning that they can operate at maximum capacity nearly all the time. These factors mean that geothermal can balance intermittent sources of energy like wind and solar, making it a critical part of the national renewable energy mix.
• Some geothermal plants produce solid materials, or sludges, that require disposal in approved sites. Some of these solids are now being extracted for sale (zinc, silica, and sulfur, for example), making the resource even more valuable. In addition, lithium—a critical material—is present in high concentrations in some geothermal brines. Learning to cost effectively extract that lithium could provide the United States with a domestic source of this important material.

Learn more on our Geothermal Basics page. 

• Geothermal energy is heat that flows continuously from the Earth’s interior to the surface—and has been doing so for about 4.5 billion years. The temperature at the center of the Earth is about the same as the surface of the sun (nearly 6,000°C, or about 10,800°F). 
• This heat is continually replenished by the decay of naturally occurring radioactive elements beneath the subsurface and will remain available for billions of years, ensuring an essentially inexhaustible supply of energy. 

Learn more on our Geothermal Basics page.

In the United States, conventional hydrothermal resources—natural reservoirs of steam or hot water—are available primarily in the western states, Alaska, and Hawai'i. Enhanced geothermal systems (EGS) can expand the availability of geothermal resources for electricity generation or thermal power by using humanmade reservoirs to tap into subsurface heat. Geothermal energy can also be tapped almost anywhere using geothermal heat pumps and certain direct-use applications. Enhanced geothermal systems (EGS), which can produce power wherever there is hot rock, will be increasingly deployed as the technology is further developed. EGS will also help expand geothermal heating and cooling nationwide.

Learn more about GTO's projects to advance geothermal technologies through the Geothermal Everywhere campaign.

District heating systems and geothermal heat pumps can usually be integrated easily into communities, with almost no visual impact. Geothermal power plants tend to have a lower profile and smaller land footprint compared to many other energy-generation technologies, and they do not require fuel storage, transportation, or combustion.

Learn more in the GeoVision analysis.

Geothermal energy is heat that flows continuously from the Earth’s core to the surface—and has been doing so for about 4.5 billion years. This heat is continually replenished by the decay of naturally occurring radioactive elements in the Earth’s interior and will remain available for billions of years, ensuring an essentially inexhaustible supply of energy. Geothermal power plants operate by drawing fluid or steam from underground reservoirs, and these reservoirs have been demonstrated long term at geothermal plants such as Lardarello in Italy (1913), Wairakei in New Zealand (1958), and The Geysers in California (1960). 

Some geothermal power plants have experienced pressure and production declines, but operators are finding solutions to maintain reservoir pressure. For instance, the city of Santa Rosa, California, pipes its treated wastewater to The Geysers geothermal field to be used as reinjection fluid, thereby prolonging the life of the reservoir while recycling the treated wastewater. 

Geothermal heat pumps (GHPs) are cost-effective technologies in the long run, but the costs of ground heat-exchanger loops make them more expensive up front. For geothermal power, exploration activities—from pre-drilling geotechnical studies through exploration, confirmation, and development drilling—can increase overall project costs and success. Overall, the costs of building a geothermal power plant are heavily weighted toward early expenses rather than fuel to keep them running. However, geothermal energy’s high-capacity factor—its ability to produce electricity 90% of the time or more—means that costs can be recouped more quickly because there is very little downtime once a plant is operational.

Learn more about how GTO’s research, development, and demonstration is tackling this issue.  

There are three geothermal power plant technologies being used to convert hydrothermal fluids to electricity: dry steam, flash steam, and binary cycle. The type of conversion is selected during project development and depends on the state of the subsurface fluid (steam or water) and its temperature. 

Learn more about power plant types and see illustrations of each on the Electricity Generation page.

Costs of a geothermal plant are heavily weighted toward early expenses, rather than fuel to keep them running. Exploration activities—pre-drilling geotechnical studies, exploration, confirmation, and development drilling—have a collective impact on overall project costs and success. Most geothermal power plants can run at greater than 90% availability (i.e., producing more than 90% of the time), which means that costs can be recouped more quickly. However, operators need to balance operations with costs and electricity prices. Running at 97% or 98% can increase maintenance costs, but higher-priced electricity justifies running the plant 98% of the time because the resulting higher maintenance costs will be recovered.

Learn more about power plant types on the Electricity Generation page.

Elements that indicate a site may be good for geothermal electricity development include hot subsurface geothermal fluid with low mineral and gas content, shallow aquifers for producing and reinjecting the fluid, a location eligible for permitting, proximity to existing transmission lines or load, and other characteristics. Geothermal fluid temperature should be at least 300°F/149°C, although plants can operate on fluid temperatures as low as 210°F/99°C.

Learn more about power plant types and see illustrations of each on the Electricity Generation page.

Geothermal heat pumps, or GHPs, use the constant temperature of the shallow Earth (40–70°F/4.5–21°C) to provide heating and cooling solutions for buildings wherever the ground can be cost-effectively accessed to depths below seasonal temperature variations. The thermal energy storage properties of the rocks and soils allow GHPs to act as a heat sink—absorbing excess heat during summer, when surface temperatures are relatively higher—and as a heat source during the winter, when surface temperatures are lower. This increases efficiency and reduces the energy consumption of heating and cooling for residential and commercial buildings. 

Learn more on our geothermal heat pumps page and in our fact sheet, What are Geothermal Heat Pumps?

The presence of hot rocks, permeability, and fluid underground creates natural geothermal systems. Small underground pathways conduct fluids through the hot rocks, carrying energy in the form of heat through wells to the Earth’s surface when the conditions are just right. At the surface, that energy drives turbines and generates electricity.  

Sometimes conditions are not perfect for natural geothermal systems; the rocks are hot, but they are not very permeable and contain little water. The injection of fluid into the hot rocks enhances the size and connectivity of fluid pathways by reopening fractures. Once created, an enhanced geothermal system (EGS) functions just as a natural geothermal system does. The fluids carry energy to the surface, driving turbines and generating electricity.

Learn about EGS, how it works, and its future in the United States.

District and community-scale geothermal heating and cooling systems use one or more underground loops to create a heating and cooling network that can use a series of heat pumps. New and different configurations of these systems are emerging in universities and communities all over the United States. GTO’s Community Geothermal Heating and Cooling Design and Deployment initiative is focused on supporting communities in implementing such systems and will grow the body of replicable case studies to increase deployment nationwide. 

GTO is committed to directly engaging with communities by providing educational services on geothermal energy, empowering them to make informed decisions based on local energy needs.

Learn more about community geothermal systems and geothermal heating and cooling.

Barriers to deploying geothermal resources are mainly a result of geothermal energy’s unique characteristics as a subsurface resource. Exploring, discovering, developing, and managing geothermal resources is inherently complex and can have greater risks and upfront costs than other renewable energy technologies. Geothermal can also face barriers in land access, permitting, and project financing. In addition, all geothermal resources share a key non-technical barrier: lack of awareness and acceptance. Resources like solar and wind are easy to see and feel, but—by its nature—geothermal energy is relatively unknown because it’s in the subsurface.

Learn more about barriers to geothermal deployment in section 2.4 of the GeoVision analysis and this report on non-technical barriers.

The 2021 Bipartisan Infrastructure Law includes $74 million for the Geothermal Technologies Office (GTO) to fund several projects to demonstrate enhanced geothermal system (EGS) demonstrations in different geologic and geographic settings—including one in the eastern portion of the United States—using a variety of techniques and well completions.

Learn more about GTO's EGS pilot demonstration sites.

The Inflation Reduction Act (IRA) has numerous provisions that include geothermal. The IRA will lower costs for families, combat the climate crisis, reduce the deficit, and ask the largest corporations to pay a fair share. This includes lowering energy costs—saving families $500 per year on energy bills—and tackling the climate crisis as the most significant legislation in U.S. history to cut pollution, advance environmental justice, and improve American energy security.

The IRA extends the investment tax credit (ITC) and the production tax credit (PTC) for renewables, including geothermal, through 2024. It also provides a 30% tax credit, up to $2,000, for the purchase of a heat pump (geothermal or air source), as well as funding for states to offer rebates on household efficiency improvements.

Learn more about the Inflation Reduction Act by the Numbers and its impact in your state.

GTO works to reduce costs and risks associated with geothermal development by supporting innovative technologies that address key exploration and operational challenges. In partnership with industry, academia, and the Department of Energy’s national laboratories, GTO works on research and development activities in the following areas:

• Enhanced Geothermal Systems
• Hydrothermal Resources
• Low Temperature and Coproduced Resources
• Data, Modeling, and Analysis

GTO’s Geothermal Everywhere page is a great place to find out about some of GTO's latest initiatives. You can also subscribe to all GTO email updates or sign up for the Drill Down monthly newsletter for updates about GTO’s initiatives, funding opportunities, and other news.

Learn more about GTO’s areas of research.

GTO’s budget is set through congressional appropriations. Each year, GTO proposes a body of research to be pursued in the next fiscal year and the accompanying budget through what is called a Congressional Budget Justification, or CBJ. Congress reviews the information and sets a budget within the scope and confines of the overall federal fiscal year budget. CBJs are a matter of public record. 

GTO organizes its portfolio to ensure we are investing in high-value and high-return research with real potential to expand geothermal deployment. Small businesses interested in research and innovation around geothermal are encouraged to review and apply for our current Small Business Research in Geothermal Energy topics.

Learn more about what GTO does and how it funds projects.

GTO offers a range of funding opportunities that help industry, academia, national laboratories, communities, and entrepreneurs research, develop, and demonstrate geothermal innovations. GTO creates Funding Notice webpages for each funding opportunity to help potential applicants understand the objectives, major requirements, and application timeline, as well as navigate the application process. Some opportunities also have shorter versions of that guidance, called Quick Guides, to help potential applicants understand the FOA and application requirements. For example, explore our Geothermal Energy from Oil and gas Demonstrated Engineering (GEODE) Funding Notice page and Quick Guide.

GTO’s website also includes a page dedicated to open funding opportunities, and the Office of Energy Efficiency and Renewable Energy (EERE)—of which GTO is a part—has a dedicated funding opportunities page as well. All funding opportunities and application details are accessible at the EERE Exchange portal. 

GTO also funds projects as part of the Small Business Innovation Research program and through several geothermal-related prizes under the American-Made Challenges program. DOE offers technical assistance, grants, vouchers, and other opportunities for communities interested in pursuing clean energy solutions. 

To stay up to date on our latest funding opportunities and prizes, subscribe to all GTO email updates or sign up for the Drill Down monthly newsletter.

DOE participates in several initiatives designed to give students real-world experience in geothermal.

The Geothermal Collegiate Competition offers students the opportunity to compete for cash prizes, gain resume experience in the renewable energy industry, and engage with established industry professionals as well as their local communities. 

The U.S. National Science Foundation (NSF) and DOE are partnering on an opportunity through NSF’s INTERN program that will support 10 to 20 six-month research internships per year to work in the geothermal industry on projects that advance geothermal technologies.

The Energy Innovator Fellowship program, sponsored by GTO and seven other offices, funds recent graduates and energy professionals to work with energy organizations for up to two years to advance clean energy solutions and increase access to clean energy career opportunities across the country.

Other student programs GTO participates in include GEM fellowships, the Oak Ridge Institute for Science and Education (ORISE) fellow program, and fellowships under the American Association for the Advancement of Science and the Presidential Management Fellows program.

Additionally, all GTO-funded projects are required to upload their data to the Geothermal Data Repository (GDR) for public use. Those data are complemented by Final Technical Reports that GTO researchers upload to OSTI.gov. Students are encouraged to access and use the GDR for research and educational purposes. 

Learn more about student opportunities by signing up for all GTO email updates, the Geothermal Collegiate Competition newsletter, and/or the Drill Down monthly newsletter.

It’s great that you are interested in using geothermal in your home or business! There are a few ways you can research possible installers. A good place to start to gain better understanding of your needs and options is on the Energy Saver Geothermal Heat Pump page, which describes the various types of systems. To find designers, installers, and other professionals who can assist you, you can contact your state energy office, use the searchable directories provided by the International Ground Source Heat Pump Association and Geothermal Exchange Organization, or do an Internet search on “geothermal installers in my area” or similar terms; most installers have websites that explain their services and provide contact information. To assess whether your home or business meets the characteristics for installing a geothermal heat pump, it is recommended that you contact a geothermal designer (instead of an installer) or a local professional engineer. 

To learn more about the tax credits and incentives that may apply to your installation, explore our Tax Credits, Incentives, and Technical Assistance for Geothermal Heat Pumps page and the Database of State Incentives for Renewables and Efficiency. A qualified installer may also be able to help you understand any incentives that might be available for the system(s) you are considering.

Lithium (abbreviated “Li”) is a light, silvery metal that is used to make batteries, ceramics, and medications. It is found in certain types of rock (known as "spodumene”), in claystones, and in mineral rich water called brine. Lithium is a critical mineral, with particular importance for electric vehicles (EVs), energy storage, and global demand is expected to grow more than 40 times by 2040. 

Lithium batteries also power devices (e.g., computers and smartphones) and are increasingly being used to store energy on the electricity grid. As a result, demand for lithium is growing significantly.

The deposits are concentrated around the southeast shore of the Salton Sea, in a zone called the Salton Sea Known Geothermal Resource Area (SSKGRA). The lithium is not in surface water of the Salton Sea, but rather dissolved in the geothermal reservoir distributed throughout the bedrock about a mile below Earth’s surface.

Learn more about the Geothermal Technologies Office research in lithium extraction from geothermal brines.

Direct lithium extraction (DLE), which extracts lithium from underground brines, could be a game-changing extraction method—potentially delivering 10 times the current U.S. lithium demand from California’s Salton Sea Known Geothermal Resource Area alone.

The process of DLE first involves removing other minerals from the brine to make it easier to recover lithium. To do this, plant operators add inputs like limestone that react with interfering minerals (mainly silica and iron) to turn them into solids, which then sink. This is called “precipitation” and the solids are called “precipitate.” The clarified brine—now free of what are called “precipitate” solids—then moves on to a lithium recovery circuit. 

Following the removal of precipitates, the brine undergoes a multi-step process that involves an absorbent, electrochemical (using electricity to change the brine chemistry)   electrodialysis (using electricity to remove salt), and a membrane or filter to extract the lithium from the brine.adsorption, which basically means “making one thing stick to another thing.” Operators run the brine through columns filled with small aluminum or titanium oxide beads, which selectively stick to dissolved lithium and remove it from the brine. The aluminum or titanium oxide beads are then washed and prepared to be used again. The remaining brine is reinjected back into the geothermal reservoir.  

The Geothermal Technologies Office awarded a total of $2 million to three teams in the American-Made Geothermal Lithium Extraction Prize for research to advance DLE technologies.

It’s currently difficult to estimate water consumption for direct lithium extraction because we don’t have enough data yet about the processes that will be used and how the technology will perform at commercial scale. Transparent and ongoing reporting from demonstration facilities will be necessary so we can understand the implications for water consumption before the technology scales up. 

Geothermal power plants currently in the Salton Sea region use 16 acre-feet of water yearly per MW capacity. That’s roughly equivalent to one Olympic swimming pool per year to power around 100 homes.

None of the geothermal facilities use water from the Salton Sea itself or affect Salton Sea water levels through any of their operations.  

The GEOTHERMICA initiative combines the financial resources and technical expertise of 16 countries to promote research and innovation in geothermal energy and make it more reliable, safe, and cost-competitive. The Geothermal Technologies Office participates in GEOTHERMICA, with goals to collaborate with other countries that are testing and demonstrating geothermal technologies, create international partnerships that leverage the technical excellence of DOE national laboratories for analysis and modeling, and enable data and information sharing that allows the United States to learn from international research and industry partners. 

The GEOTHERMICA portfolio includes projects focused on geothermal heating and cooling systems, underground thermal energy storage, and enhanced geothermal systems (EGS) storage. Some successes from this initiative include: 

• Fostering Collaboration with the Limerick Community – The Geothermal Community Heat Technology and Transfer (GeoCoHorT) project is designing a geothermal district model for part of Limerick, Ireland, where one potential geo-source is the groundwater connected to the River Shannon. The aim is to heat several local buildings using the groundwater geo-source, with heat extraction from the river offering a possible secondary benefit by mitigating estuary warming.  

  Community involvement is crucial in determining how and if to allow drilling or river use for geothermal heating and cooling purposes. Project partners Mälardalen University in Sweden and DOE’s National Energy Technology Laboratory have engaged with the local community multiple times to learn about stakeholders’ concerns, through Irish collaborators Micro Energy Generation Association and the International Energy Research Centre University of Cork. From this work, the team has learned that Irish citizens have questions about environmental impact on the estuary and implementing direct installations in the river; they want to assess various methods for using geothermal, both with and without links to the river. The GeoCoHorT team is fostering collaboration with the Limerick community and implementing the feedback in many ways, including consulting with local ecologists about district heat extraction to help an overheating estuary. 

• Quantified Impact of Thermal Energy Systems – The FLXenabler project aims to quantify the impact of the flexibility in thermal energy systems (TES) in accelerating and reducing costs for energy system decarbonization and has made great strides since launching in 2023. Using the National Renewable Energy Laboratory’s Renewable Energy Deployment System capacity expansion model to simulate impacts, the project group produced initial results quantifying the impact of geothermal heating and cooling to the United States grid in three areas: reduced power system costs, reduced heating fuel, and reduced CO2 emissions. These regional results will be used to inform the location of detailed subsurface TES simulations coupled with techno-economic modelling, with the goal of identifying U.S. locations for installing geothermal networks that would have the greatest impact.  

• De-Risking Superhot and Supercritical Geothermal Plays – The DE-risking Exploration of geothermal Plays in magmatic Environments (DEEPEN) project developed methodologies for de-risking magmatic geothermal systems, including supercritical plays, to enable use of geothermal resources at the highest end of the temperature spectrum. These superhot (>425°C) systems have significantly higher power production potentials than lower-temperature geothermal systems but are difficult to develop due to their extreme temperatures. Methodologies developed by this project will be tested and demonstrated in the field on exploration cases in Iceland and in the superhot EGS site at Newberry Volcano in Oregon. 

Learn more about GTO and DOE’s activities related to geothermal and lithium on GTO’s webpage and interactive storymap, and subscribe to all GTO updates or to the monthly GTO newsletter, The Drill Down, to stay on top of the hottest news in geothermal! You can also visit Lawrence Berkeley National Laboratory's FAQs page to learn more about lithium research in the Salton Sea Known Geothermal Resource Area.