Wind power is vital

The Sustainable Development Commission's attitude to wind power (Letters, May 2) is based on thorough analysis of all data over several years. Our report concluded that while wind, of course, blows at variable speed, this variability "is not a problem for the electricity grid. Wind is accurately forecast over the timeframes relevant to network operators . . . Increasingly, the proportion of wind power in the electricity system does not require back up' capacity as is often believed, but it does slightly increase the cost."