The U.S. Department of Transportation is expected to propose new fuel economy standards in April that would require automakers to build more fuel-efficient cars, trucks, and SUVs. But first, the government wants to change a rule that, some say, has done the opposite.
Current Corporate Average Fuel Economy (CAFE) standards require that each automaker’s lineup of cars average 49 mpg by model year 2026. Acting National Highway Traffic Safety Administration head Ann Carlson in January told reporters the agency would propose new fuel economy rules in April. Observers expect an increase to that 49 mpg goal.
However, the most significant change in regulations may concern cars that don’t burn fuel at all. It comes from a different federal agency.
MPG and “MPG equivalent”
The Department of Energy determines each electric car’s “mpg equivalent,” or MPGe. The figure is intended to show how the electricity an electric vehicle or plug-in hybrid (PHEV) uses equates to the fuel an internal combustion engine car would use.
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To calculate it, the DOE uses a mathematical formula involving average driving patterns and “national average electricity generation and transmission efficiency.”
That system, Reuters says, “has not been updated in more than two decades.” Most of the factors that go into it have changed in that time.
DOE has proposed a new formula reflecting how the electric power industry has changed and how Americans’ driving habits have evolved in the years since.
MPGe numbers could fall dramatically
The change could radically reduce the MPGe figures for most EVs.
Reuters explains, “A Volkswagen ID.4 EV with a current 380.6 MPGe under CAFE would get 107.4 MPGe under the DOE proposal, while a Ford F-150 EV drops from 237.1 to 67.1 MPGe and a Chrysler Pacifica plug-in hybrid falls from 88.2 to 59.5 MPGe.”
Also see: Your complete guide to MPGe, the electric equivalent of miles per gallon
Different numbers on window stickers
To make matters more confusing, the MPGe figure used in CAFE standards differs from the numbers on window stickers. For instance, the Ford F, +1.28% F-150 Lightning electric truck gets a 237.1 MPGe rating for CAFE calculations. But the window sticker on the truck reads between 66 and 70 MPGe depending on the model.
This change affects only the CAFE calculation. The number on the window won’t change.
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Environmental groups say current rules are counterproductive
When manufacturers calculate their fleetwide average MPG, they include MPGe figures for their EVs and PHEVs. That, the Energy Department says, “allows manufacturers to maintain less efficient ICE vehicles in their fleet by utilizing a few EV models to comply with the CAFE standards.”
Environmental groups have long complained that high MPGe figures let automakers build less-efficient gasoline engines.
In a 2021 letter to regulators, the Natural Resources Defense Council and Sierra Club explained that high MPGe figures mean that “a relatively small number of EVs will mathematically guarantee compliance without meaningful improvements in the real-world average fuel economy of automakers’ overall fleets.”
The Nissan NSANY, +0.81% Leaf EV, for instance, has an MPGe figure so high that it may be part of the reason Nissan has stuck with an inefficient standard V-8 engine in its Titan pickup long after most rivals started offering more fuel-efficient turbocharged engine options in full-size trucks.
The Energy Department says the current system “can lead to increased petroleum consumption” by weighting EVs too heavily.
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Ars Technica reports that the new system “means automakers would have to sell nearly four times as many EVs as they currently sell to receive the same reduction in their CAFE number.”
This story originally ran on KBB.com.
