Robert Bryce points out that during the recent heat wave in Texas, the state’s $25 billion investment in windmills and wind transmission lines produced almost no useful electricity. At a time when the electrical grid was close to breaking down from overload, the state’s 10,000 megawatts in wind capacity produced an output of only around 1,500 MW – less than 2 percent of the state’s overall consumption. Ironically, output did rise to the range of 5,000 MW – 50 percent of capacity – precisely when it wasn’t needed, during the 25 percent decline in demand at night. The reason is a well-known principle among meteorologists. Air currents are the most torpid on hot summer afternoons and don’t begin to stir until the earth cools at night. Windmills also generate more power in the spring and fall, when changing temperatures stir the earth’s wind patterns but the lack of temperature extremes reduces the demand for electricity. Critics have long argued that windmills were being rated only by their capacity and that their biggest output would be at periods of low demand. The experience in Texas last week has confirmed this.