Of all the various aspects of renewable power, geothermal seems to have risen to the top of the heap. According to data collected by the Energy Information Administration, only nuclear power has a higher average capacity factor.
The term “capacity factor” compares the power produced with the maximum generating capacity to be expected from a particular energy form. The long-term coverage is around 90% for nuclear, 70% for geothermal and 50-70% for coal-fired and natural gas-fired power sources.