figure, and in that case, a lower number represents better fuel efficiency—ideally, you want to burn as few gallons as possible when driving 100 miles. Ditto, on an EV’s sticker you’ll find the kilowatt-hours-per-100-miles metric, with lower being more efficient. And a PHEV vehicle’s sticker contains both of those lower-is-better metrics.
But with the proliferation of EVs, the main metric to keep in mind is MPGe. “The EPA said, ‘Okay, well we’re going to need some way of describing these electric vehicles to the average person,” Gohlke says. “The EPA has come up with a conversion factor that translates from a kilowatt-hour of energy into the equivalent amount of energy in terms of a gallon of gasoline.”The kilowatt hours equivalent from gas comes from “the total heat content that exists in a gallon of gasoline,” Gohlke says.
The answer to that question is 33.7 kWh. An EPA spokesperson notes via email that this figure is “a standard number for the energy content in gasoline.”So now the question becomes: How far can an EV travel on 33.7 kWh, which is equal to the energy in 1 gallon of gas? And that’s where the MPGe figure comes from.
For context when it comes to understanding kWh, the average American home used about 886 kWh of electricity each month in 2021,. Considering a 30-day month, that means daily electric use is about 30 kWh. If you have a 1,000-watt microwave and use it for an hour, you’ve used 1 kWh of electricity. So MPGe is saying: Here’s how many miles this EV can travel on an amount of electricity that is just a bit more than the average US household consumes each day.