If drivers of electric cars plug in their vehicles when they get home from work and add to the evening electric peak, even the modest amounts of new generation will force us to build more energy capacity, which could lead to be more fossil fuel-fired plants. But if people wait until bedtime to charge their cars, we won’t have to add more generating power because that’s when demand for electricity is lowest. Waiting till bedtime can also lower electricity bills and put less strain on our energy grids, which benefits the environment.