Solar One, the 10 MWe Solar Thermal Central Receiver Pilot Plant near Barstow, Calif., completed a three-year period of power production testing in July 1987. During this period the plant’s capacity factor, system efficiency, and availability were studied to assess the operational capability of Solar One to reliably supply electrical power. The long-term performance of key plant components, such as the heliostats and the receiver, was also studied. During the three years of power production operation, Solar One achieved increases in capacity factor, system efficiency, and availability. Heliostat operation was reliable, and only small amounts of mirror corrosion were observed. Receiver tube leaks did occur, however, and were the main cause of the plant’s unscheduled outages. Solar One provided valuable lessons which will aid in the design of future solar central receiver plants.