Average Wind Hours & Flow per Year     Assumptions
 

Wind Flow required for most wind turbines to deliver name plate rated power
is a speed of 30 mph, average annual wind speeds are often less.

 

At slower wind speeds, the production falls off dramatically. If the wind speed decreases by half, power production decreases by a factor of eight.

 

On average, therefore, wind turbines do not generate near their capacity.
Industry estimates project an annual output of 30-40%,

but real-world experience shows that annual outputs of 15-30% of capacity are more typical.
 

For this estimation we will use the industry high
       of 40% of the time = 3,500 hours per year
                                  
                            Source:     https://www.wind-watch.org/faq-output.php

 

Also note, in support of the above estimation:

Erich Hau in Wind Turbines: Fundamentals, Technologies, Application, Economics

Springer, 2005,

reports that for economic comparison purposes:
wind turbines operate at full load for between 3,000 and 4,000 hours per year.