A wind turbine does not produce electricity either continually or constantly. The wind must blow at a specific speed for the turbine to start up; this threshold is usually 4 m/s (14.4 km/h). Once the turbine is in motion, the stronger the wind, the more electricity the generator produces, although production levels out when the turbine reaches its rated speed. Production is not allowed to exceed this upper threshold, generally 12 m/s or 90 km/h to preserve the structural integrity of the wind turbine.
Like on a sailboat where the sails are trimmed when a storm approaches to avoid shearing the mast, wind turbines are stopped when wind speed exceeds 90 km/h to prevent accidents.
Wind turbines operate most of the time, but they do not always reach their rated speed. In Québec, a standard wind farm produces about 35% of its rated capacity; this means a 100-MW wind farm produces 35 MW/h on average.