Even when completed the 330 MW Sarulla project in Indonesia doesn’t come close to the Geysers project in California, which is the largest geothermal project ever completed. When the Geysers first went online in the 70’s, the capacity of the geothermal field started out at 1.5 GW, then increased to its peak level at 2 GW in 1987. Its production decreased further to its current level of about 700 MW due to the depletion of the aquifer from which the plants draw their steam. This decrease was deemed as poor maintenance by Calpine, its operator, by the EEC. Newer plant designs re-inject the water back into the aquifer order to eliminate this problem.
Despite the EEC’s criticism, The Geysers is still the most productive geothermal field in the world, providing nearly 60 percent of the electricity used in California's North Coast region, which stretches from the Golden Gate Bridge to the Oregon border.
Technically, the Sarulla project can claim to be the largest single contract geothermal plant due to The Geysers’ development as a series of multiple projects which were later consolidated under the maintenance of Calpine. Currently, The Geysers is comprised of 19 facilities spread over the geothermal field.
Indonesia is aggressively pursuing more geothermal power with a stated objective of a very ambitious 4 GW by 2014. This is the equivalent of four nuclear generators. Cost presents the main challenge in this pursuit due to the cheap dirty coal which serves as the country’s main power source. Despite its higher cost, geothermal power remains attractive because it provides constant baseline power at a lower cost than wind and solar.
The Sarulla project, barring financial or regulatory difficulties is planned for completion in five years, with the first phase representing about one-third of the capacity beginning production within three years.
It doesn’t appear that geothermal production in the U.S. is going to increase or play a larger role than it is at present, as evidenced by smaller project sizes due to the diminishing output of the best fields. Geothermal holds much more promise in places like Indonesia and New Zealand with better resources and the potential for much bigger fields in the future.