Output from wind farms in the western US during the first quarter 2015 was off by as much as 50% from forecasts, possibly due to a warmer-than-average winter, according to a report in North American Windpower. Over- or underperformance can last years. However, wind speeds were 5% to 10%, and in some cases as high as 20%, above normal in Montana, the Dakotas, Minnesota and Nebraska.

by Keith Martin in Washington