The key element to making a wind turbine cost effective is the amount of electricity generated from the unit and this is dependent upon the wind speed at the site.
Any obstructions such as other buildings and trees will limit the wind speed.
A study conducted by the Energy Saving Trust's (EST) into wind turbines showed that there were many fewer sites than thought were suitable for wind turbine technology.
If you are considering installing a wind turbine you should first install an anemometer (wind speed gauge) for a minimum of three months to see if the average wind speed for your home makes it worthwhile before investing in a wind turbine.
Lots of wind turbine manufacturers and the Energy Saving Trust say that you should only consider installing a wind turbine where the local average wind speed is 5m/s or more. Sadly, for wind generation, the majority of UK homes have an average wind speed of less than this.