How much height is best for tower choose?

In general, the higher the tower, the higher the average wind speed that the turbine will experience, and it is normally the case that a taller tower will generate sufficient extra energy to justify it's additional cost, especially if there are local obstacles to be avoided. For sites where there are obstructions near the turbine, a tall tower may be needed to get the turbine above the turbulence created by nearby trees or buildings, as illustrated by the diagram to the left.