Calpine's ownership in power generation began with the purchase of a five percent interest in a 20 MW facility at The Geysers in 1989. Since then, Calpine has consolidated ownership of 19 of the 21 facilities within the geothermal resource area. As a result, Calpine said they are now the world's largest private producer of electricity derived from geothermal resources. Calpine also operates a Geothermal Visitor Center in Middletown, California. The center offers free admission and tours of one of Calpine's Geysers facilities.