There are several factors that come in to play when it comes to the electricity being generated by a wind turbine. How fast the rotor can turn, how big the turbine is, and how strong the wind in the area is will effect how much energy is produced.

The best way to answer this is through an example. From an article by Gary Ashby, "A 10-kW wind turbine can generate about 10,000 kWh a year at a location with wind speeds averaging 12 miles per hour, or about enough to power a typical household (Source)." If a home or office produces more energy than they consume, the electricty goes back to the main electric company and the home or office gets paid for the excess electricity they generate!