Gov. Peter Shumlin is questioning why a wind farm in the Northeast Kingdom was told to power down right in the middle of a heat wave.
Green Mountain Power says it was asked to turn off its 21 turbines on Lowell Mountain and replace that output by firing up fossil fuel generators.
Shumlin says that decision runs counter to Vermont's goal of producing, clean renewable energy.
But ISO New England, which manages the New England power grid, says it makes decisions based on reliability, not environmental concerns. ISO says power lines in northern Vermont cannot carry enough voltage to be a reliable source of energy during periods of high demand.