What an electric vehicle’s MPGe rating really means

For a long time, motorists across the United States have been able to assess the effectiveness of their gasoline-powered vehicles using the simplest of criteria: miles-per-gallon. The Environmental Protection Agency started publishing the mpg rating for cars during the 70s, and it is a fact that is logical. Theoretically, how far could your vehicle go on just one gallon of gas? The figure of mpg will give you the answers.

However, the situation becomes more complicated with electric vehicles and plug-in hybrids. A pure EV does not consume gasoline. It receives the energy from its batteries via the grid and is more environmentally beneficial.

Enter the MPGe measurement for miles per gallon gasoline equivalent, which “allows [for] a reasonable comparison between vehicles using different fuels,” the EPA declares.

What is MPGe?

The new EPA labeling for vehicles was introduced at the end of 2012. for electric cars, the label includes the electric vehicle’s “fuel economy” listed in MPGe and other indicators, such as its range. You can find the EPA’s”EV” label on their website. For plug-in hybrid electric automobiles, that PHEV label will show the car’s efficiency while running only on the battery (in MPGe) and its efficiency when it is burning gasoline in mpg. The traditional car running solely on gasoline can also display a label that uses the standard MPG measure.

The most commonality between the MPGe and mpg metrics is that a higher value implies greater efficiency. “Miles per gallon is designed such that bigger numbers are better,” says David Gohlke, an energy and environmental analyst at Argonne National Laboratory in Illinois. “Higher miles per gallon means you go farther–you get more goodness out of the gallon of gasoline that you’re burning.”

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The more powerful metric could seem obvious, but other measures of the efficiency of vehicles are different. For example, the gasoline vehicle sticker also features a gallons-per-100-miles figure. 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. The sticker of a PHEV car has both of these lower-is-better measures.

However, with the increasing number of EVs, the most essential measure to be aware of is MPGe. “The EPA said, ‘Okay, well, we’re going to need some way of describing these electric vehicles to the average person,” Gohlke states. “The EPA has come up with a conversion factor that translates from a kilowatt-hour of energy into the equivalent amount of energy in a gallon of gasoline.”

How do you calculate MPGe determined?

The kilowatt hour (kWh) equivalent to gas is derived directly from “the total heat content that exists in a gallon of gasoline,” Gohlke declares. “They say, ‘Okay, if we took this gallon of gasoline, and set it on fire, effectively, how much heat energy can we get out of that?'”

The answer to this question will be 33.7 kWh. An EPA spokesperson explains in an email that this number corresponds to “a standard number for the energy content in gasoline.”

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The question is how far electric vehicles travel using 33.7 kWh, equivalent to the amount of energy contained in a gallon of gasoline. That’s where the MPGe figure comes from.

To give context for understanding kWh, the typical American house consumed around 886 kWh in monthly electricity through 2021, per the US Energy Information Administration. When you consider a 30-day period which is a specific month, daily electrical consumption is around 30 kWh. If you have a 1000-watt (1 Kilowatt) microwave and use it for one hour, you’ve consumed 1 kWh of power. This means that MPGe’s saying: Here’s how far this vehicle can travel with the electricity it consumes, which is a little more than what the average US household consumes daily.

How do you determine the MPG of an electric vehicle?

To determine what the EPA rate an EV using the MPGe metric, it is possible to search for the car on fueleconomy.gov. One example is that one model from 2023, Hyundai Ioniq 6, is rated at 140 MPGe by combining it with its highway (153) and road (127) scores. That’s superb. It’s 2023. Tesla Model 3 gets an impressive 132 MPGe. What’s with the huge GMC Hummer EV? It’s estimated to get 47 mpg. It’s not. The Hyundai and the Tesla are much superior to the Hummer.

Although the MPGe measurement is challenging to get used to, Paul Waatti, manager of analysis for the industry at AutoPacific, claims that it plays a vital part. This is because the range of an electric vehicle, as stated on the label, is only part of the story. “That doesn’t necessarily tell you how efficient the vehicle is,” He declares. “You might have a really high range number, like [with the electric] Hummer for example, but if you look at the MPGe figure for that, it shows that it’s very inefficient.”

The final verdict is that the MPGe measure isn’t ideal; however, it’s good to have. “From a consumer perspective, I think there’s still quite a bit of confusion on what it means,” Waatti declares. However, he believes that it’s a crucial metric for giving people a better understanding of the efficiency of the vehicle.

The bottom line is that a higher MPGe is a sign that the efficiency of the EV currently, a number at or near 140, is the ideal number.


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