Today's bigger turbines are taller, with blades that spin more slowly, so that birds can more easily see the blades and avoid them, says Chuck McGowin, of the Electric Power Research Institute in Palo Alto, California.

ECONOMIST: Wind power

And, notes Mr McGowin, in many places it tends to blow when demand is low, such as in the middle of the day, and dies down in the evening, when Americans watch television (400 kilowatt hours per year) and run dishwashers (1, 570).

ECONOMIST: Wind power