The world's largest geothermal well, called Vonderahe-1, sits in Imperial County and is owned and operated by Cal Energy.The well goes a mile-and-a-half down into the Earth and pulls up pressurized water that has been heated by the Earth's core. It can reach temperatures up to 500 degrees.The steam from that water is used to propel a turbine, which turns a generator, which then produces electricity. The Vonderahe-1 can generate up to 50 megawatts -- enough power for 50,000 homes.10News was given a tour of Cal Energy's geothermal plants in Imperial County Friday. Operators said geothermal energy is the most reliable green energy because the Earth's core is always on and always producing heat day and night."It is not dictated by when the wind is blowing, it is not dictated when the sun is shining," said Cal Energy Director of Geothermal Resources Alex Schriener Jr.The only way to tap geothermal energy is through cracks in the Earth's crust. One of the best places in the world is the Salton Sea area, where the San Andreas Fault is always opening new cracks."We have tremendous power from the earthquakes in the area, the faulting in the area," said Schriener.Cal Energy said there's enough geothermal energy generated by plants in Imperial County to power 600,000 homes. If all of the potential geothermal energy in Imperial County was harvested, there'd be enough for 2.3 million homes."It has tremendous potential, probably more than all the other fields in the U.S. combined," said Schriener."We're barely scratching the surface," said Geothermal Energy Association Executive Director Karl Gawell.Gawell added once the Sunrise Powerlink is up and running, San Diego could benefit from geothermal power. He said it if was already operating, San Diego may not have suffered from the recent blackout. The Imperial County plants never stopped running but currently only supply Southern California Edison customers with power, not San Diego Gas & Electric."We could provide over 90 percent of the state's electricity from its geothermal resources and most of that is going to come from Southern California," said Gawell.Right now, San Diego County does not have any geothermal plants of its own.Gawell said geothermal energy currently only makes up only 5 percent of the state's power but almost half of the state's renewable energy.