Electricity Doesn’t Come in Gallons

To help consumers compare the fuel economy of an EV or PHEV, the EPA requires window stickers for gasoline, electric, and plug-in hybrid vehicles. For PHEVs and EVs, you’ll find “miles per gallon equivalent” (mpg-e). A gallon of gasoline has the energy equivalent of 33.7 kWh of electricity—so a car consuming 33.7 kWh per 100 miles will be rated at 100 mpg-e.

MPG-E is only useful when comparing electric vehicles or PHEVs in electric mode. The new EPA PHEV label shows a gasoline-only mpg rating. The actual mpg-e for PHEVs will vary with the miles driven on electricity versus gasoline. You’ll also find a one-to-10 fuel economy and greenhouse gas (GHG) rating and similar smog emissions (tailpipe only) rating on the label.