tuna writes: A real-world test by the Dutch province of Zeeland (a very windy place) demonstrates that small windmills are a fundamentally flawed technology (pdf of tests results in Dutch, English summary). Twelve much hyped micro wind turbines were placed in a row on an open plain. Their energy yield was measured over a period of one year (April 1, 2008 — March 31, 2009), the average wind velocity during these 12 months was 3.8 meters per second, slightly higher than average. Three windmills broke. The others recorded ridiculously low yields, in spite of the optimal conditions. It would take up to 141 small windmills to power an average American household entirely using wind energy, for a total cost of 780,000 dollar. The test results show clearly that energy return is closely tied to rotor diameter, and that the design of the windmill hardly matters.