Wind turbines convert the kinetic energy in moving air into rotational energy, which in turn is converted to electricity. Since wind speeds vary from month to month and second to second, the amount of electricity wind can make varies constantly. Sometimes a wind turbine will make no power at all. This variability does affect the value of the wind power……Editor’s Note: This ‘fact sheet’ is, on the whole, a comparatively fair report. The definitions provided for capacity factor, efficiency, reliability, dispatchability, and availability are useful. Its discussion of back-up generation, marginal emissions and Germany & Denmark, however, is disingenuous as is, to a lesser degree, its discussion of capacity factor and availability. IWA's comments (updated October '06) on these issues follow selected extracts from the 'fact sheet' below.