How much power do you get?

Wind turbines are often classified by their power rating.

Wind turbines are often classified by their power rating (225 kW, 1 MW etc). Big turbines sweep a wider area than small ones, which is why they generate more electricity (but see http://www.selsam.com/ - things may be changing): the power rating of a wind turbine has more to do with the volume of air passing through the rotor than the speed at which it turns.

The sitting of a wind turbine can dramatically affect how much energy it converts, even though the power rating of the turbine stays the same. What changes from site to site is the amount of energy in the wind.

So, the answer to the question ‘How much power do you get?’ is: it depends. However, as a general rule, bigger turbines and windier sites will generate a lot more energy.

The Warwick Microwind Trial project is currently underway with the aim of providing independent and objective data on the on-site performance of rooftop wind turbines - see www.warwickwindtrials.org.uk. The initial project data suggests wind will deliver tens to hundreds of kWh per year on typical urban sites rather than the hundreds to thousands of kWh optimistically forecast by some.

[pictures: this 750W turbine meets the electricity demand of a couple on a houseboat: a 1.5 MW turbine can power a small town]