If the number of plug-in hybrid electric cars and trucks grows significantly, the power grid might need to be re-vamped, depending on when people decide to re-charge their rides. Researchers at the Oak Ridge National Laboratory have projected the impact of these vehicles in 2020 and 2030 in several regions in the U.S., and found that if everyone pulls into the driveway and plugs in right away–thus taxing the grid all at once–the country could require as many as 160 new large power plants.

The upswing, however, is that if electric drivers would wait a few hours, and plug in later in the evening once levels of electricity demand drop significantly, we might not need any new plants. Then it’s just a matter of getting them to wait.