Making use of windmill power for your house or your farm is a good idea, for it pays for the investments in the long run and it is friendly to the environment. However, efficiency of windmill power heavily depends on the location.
Landscapes and seasonal changes play an important role in the speed and patterns of the wind. In Tehachapi, California, for instance, the wind blows stronger in the period between April and October in comparison to the wind speed of the same region in winter. Air, which is heated in Mojave Desert rises and cooler air from the Pacific Ocean at great speeds surpasses the Tehachapi Mountain.
The rule of thumb is the area should be flat and over one acre and there should be a consistent wind at a certain speed throughout the year with a minimum likelihood of sudden powerful bursts.
The wind blows faster at higher altitudes because of the reduced influence of drag. Therefore you can chose a place such as a flat surface where the wind can rise from lower gaps, or you can build a longer turbine. Doubling the altitude of a turbine, then, increases the expected wind speeds by 10% and the expected power by 34%.
If you have lucky to have these conditions in your farm or yard, you can generate windmill power for yourself.