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Thanks to a petition penned in 2021 by the Natural Resources Defense Council (NRDC) and Sierra Club, the way in which we rate EVs fuel consumption might have to change due to its outdated ways. In fact, the system for calculating eMPG might be so outdated that they are just plain wrong. This could have major implications for automakers and gas engine production

Are EVs as fuel efficient as we think? 

The US Department of Energy (DOE) is thinking about throwing out the National Highway Traffic Safety Administration‘s (NHTSA) current fuel consumption figures for electric vehicles. This is significant for multiple reasons: 1) The NHTSA is a well-respected institution from which we get many of our cars’ safety stats. 2) This could very well affect car production. 

As of 2027, new automotive efficiency rules are to take effect. These new rules will “dramatically reshape new cars on America’s roads,” according to CarBuzz. The original plan was to get the manufacturers’ annual production fleets to reach 52 mpg by 2026. This is doable for many car makers, but for supercar and sports car builders, this simply wasn’t going to happen without the help of EVs.

Automakers were relying on EVs to offset the overall fuel efficiency of their fleets, but now the DOE is saying that EV numbers aren’t legit. 

For instance, According to CarScoops, the killer fuel consumption figures of the Ford F-150 Lightning and Mustang Mach-E offset the Corporate Average Fuel Economy (CAFE) figures, even with the old Dinosaurs like the Shelby GT500 and the Super Duty trucks. If the EV numbers aren’t right, then that would have major ramifications for Ford and likely all other major automakers. 

What is the petroleum equivalence factor (PEF)?

2022 Ford F-150 Lightning might not be as efficient as we think.
2022 Ford F-150 Lightning | Allison Barfield, MotorBiscuit

According to the DOE, the PEF is “Gasoline-equivalent energy content of electricity factor 1/0.15.” At the risk of getting too mathy, we’ll leave that where it is and just discuss the rubber hitting the road. The PEF is meant to put electric vehicle consumption into terms the average person can understand by comparing it to a gallon of fuel.

The DOE hasn’t updated the PEF in 23 years. If you recall, EVs were quite a different thing in 2000. Using any EV calculations from then to now seems silly even to the layest of laymen. According to CarScoops, this only became public knowledge in 2010 when the EPA called for new fuel economy stickers for new cars. 

This isn’t a new problem. In fact, it dates back 42 years to April 1981, when the government first decided to study EV consumption. It’s hard to think of EVs in the ’80s, but the first electric car is much older than you think. According to Automotive News, it took the government seven years to come up with a metric and a value, which is how the USA finally got the PEF. 

How will this affect eMPG ratings? 

We currently use the 82,049 watt-hours per gallon model. The proposal for the new PEF is 23,160 watt-hours (23.16 kWh) per gallon. This would change the Ford Lightning‘s current rating of 238 mpg to 67 mpg. 

The real question is, what happens when the figures get updated? Will EVs still have the same appeal if they end up not being as efficient as we thought? This could turn the EV haters into even bigger gasoline and diesel supporters. EVs are still helpful in mitigating harmful automotive emissions, but with their promised efficiency in question, what will that do to public reception? 

The long and the short of it is, by using this outdated PEF model, we have overvalued EVs. While this information could be seen as detrimental, it’s always helpful to get closer to the truth and report figures as they are, not what we want them to be. 

“This runs counter to the need of the nation to conserve energy, particularly petroleum,” said the DOE. “Encouraging adoption of EVs can reduce petroleum consumption but giving too much credit for that adoption can lead to increased net petroleum use because it enables lower fuel economy among conventional vehicles, which represent by far the majority of vehicles sold.”


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