Availability is usually high with modern wind turbines. Most wind plants using newer technology are running at greater than 98.5 percent efficiency, with effective forced outage rates typically less than 1 percent. Turbine maintenance is usually completed twice a year, resulting in about 12 to 18 hours of downtime for each session, although only a few turbines are generally down at any one time due to maintenance. The only time an entire facility comes off-line is for substation maintenance, which lasts for less than 12 hours and occurs twice a year, usually during low production periods.
