For a vertical system, holes (approximately four inches in diameter) are drilled about 20 feet apart and 100 to 400 feet deep. Two pipes, connected at the bottom with a U-bend to form a loop, are inserted into the hole and grouted to improve performance.

It's clean, offering energy that can be extracted without burning fossil fuels such as coal, gas, or oil. Using geothermal for electricity produces only about one-sixth of the carbon dioxide of a natural gas power plant, and little—if any—nitrous oxide or sulfur dioxide.

Geothermal energy is heat energy from the earth—Geo (earth) + thermal (heat). Deep underground, the presence of hot rocks, fluid, and permeability (the ability for that fluid to move among the rocks) offer conditions from which electricity can be generated.