Not as big as you may think, here in the UK all electricity meters run backwards ie if you put more power in you turn the meter backwards. This is really good as most of the summer you will use less power than needed and could on the really good windy days be accruing bonus points ( meter going backwards ) on the cold winter days you then use up all those bonus points with extra heating etc.

As a wind turbine sceptic having just spent a large deal of time looking at green energy I have to say that the cost has fallen such that any house away from other houses and a known windy spot ( top of a hill or windy side of a valley ) should be looking at wind turbines, its nearly worthwhile now and with any more movement of the oil price its starting to look economic. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />