To the individual wind generator, doing this balancing act is a life threatening exercise. Yet to the electricity system operator, wind's supply variations are so small in the big scheme of things they are absorbed at no extra cost, just like the variations in demand. Even when wind forms a significant proportion of generation, the measures needed to account for it are neither complex nor costly (Windpower Monthly, July 2001).
In the huge power systems of today, ups and downs of power supply and demand are part of everyday life, with a specified amount of reserve generation always at hand in case a major power plant trips out. In other words, there is always reserve enough to cope with variations from considerablel numbers of wind turbines.
For the same reason there is no need for individual generators to balance supply with demand by building lots of their own spinning reserve -- something that the New Electricity Trading Arrangements in Britain encourage. Reliance on their own reserves was the only option for generators in the last century, when power supply was a fragmented business with big gaps between generating areas. Those days have long been superseded by the efficiencies of highly integrated national and international power systems.