Availability

Availability is the share of time a solar or storage plant, or a piece of its equipment, was able to operate, usually reported as a percentage over a month or a year.

It separates time the equipment was down from time it produced little because the sun was weak. Availability is the usual basis of an operations and maintenance guarantee, so the definition of counted hours, excluded hours such as grid outages, and how a partial outage is weighted all matter and are written into the contract. The data acquisition system supplies the device status history that availability is computed from.