Geothermal energy is a clean and renewable source of heat generated from radioactive decay deep within the Earth. It has been used by humans for bathing and heating spaces for thousands of years. Today, large geothermal power plants in locations like California and Iceland generate electricity and provide heat to homes from underground steam reservoirs. Geothermal energy has benefits like being a low-cost, baseload renewable source that reduces greenhouse gas emissions and dependence on fossil fuels. However, the high initial installation costs and limited suitable locations are drawbacks to wider adoption of geothermal technology.