Geothermal energy makes up .41% of the United States energy production as of 2012, according to era.gov. This highly scalable renewable energy technology uses that heat under the Earth's surface to produce energy at an industrial level, and maintain heating levels for residential and commercial use. The process requires special equipment to drill into or dig up the ground. Then lay tubing or other kinds of technology into the Earth and use the transfer of heat to produce energy or capture that heat.
Industrial energy production occurs by drilling much further into the Earth's surface, where temperatures rise to over 250 degrees Celsius (482 degrees fahrenheit). Residential and commercial operations dig roughly 25 feet (can be more or less) down to reach temperatures that maintain nearly 55 degrees fahrenheit year round in many locales.
(CC Image (left) showing estimated industrially available geothermal energy resources in the continental United States at a depth of 6KM or 3.7 miles. Source: Energy Information Administration, Geothermal Energy in the Western United States and Hawaii: Resources and Projected Electricity Generation Supplies, DOE/EIA-0544 via Wikimedia Commons) (Click to enlarge)
The technology is relatively simple, easy to maintain, and reliable over a long period. The costs can be prohibitive, costing roughly $1,000 per kilowatt(KW) of energy. This technology is highly scalable, meaning it can be used at a home, community, city, or larger scale. Furthermore, this technology helps individuals and communities become fossil fuel free and live a more resilient energy lifestyle.
Geothermal energy and heat production (like all energy production) has definitive downsides. The building and drilling into the Earth has an immediate and clear impact on the surrounding area by disturbing/destroying the immediate area's habitat and soil structure. Furthermore, industrial scale geothermal energy production can release greenhouse gases such as carbon dioxide (CO2), methane, and other minor damaging effects on the local ecosystem.
(CC Image of residential geothermal drilling courtesy of Kecko via Flickr)