Do purchases of electric vehicles necessarily replace driving in gasoline-powered cars?

Electric vehicles offer emissions benefits if (and only if) they reduce driving in dirtier, gasoline-powered cars. Recent research shows that EVs in Northern California charge at home less than half as much as regulators anticipated. This implies that EVs are likely driven substantially less than gasoline cars; however, more direct measurements of EV odometers and away-from-home charging are needed to be sure. Additionally, the purchase of an EV very often leads to a household increasing its number of cars (the EV is an “extra car”), whereas the purchase of a gasoline car replaces another car in one out of four cases. Carbon reduction is not achieved if miles driven in EVs are not largely displacing miles driven in gasoline-powered cars.