The world will see a significant increase in the use of geothermal as an energy source between now and 2020. That's according to a report released this week by Pike Research. The research analyst constructed several scenarios based on an estimated 10.7 gigawatts of geothermal capacity in existence throughout the world in 2010. That 10.7 gigawatts equates to about 67 terawatt-hours (TWh) of electricity, with the U.S., which currently possesses 3.1 gigawatts of installed geothermal systems, as the world's leading user. In fact, 88 percent of the world's geothermal energy systems currently in operation are used in only eight countries, according to the report. Peter Asmus, the senior analyst on the report, emphasized that geothermal is currently one of the world's least-tapped opportunities for alternative energy. In the report's high-growth forecast, geothermal capacity increases 134 percent to 25.1 gigawatts. In the report's most conservative forecast, Pike estimated that world geothermal capacity will grow to 14.3 gigawatts by 2020.