There’s a Gap Between EV Range Estimates and Real-World Results

Source: By Kyle Stock, Bloomberg • Posted: Sunday, March 5, 2023

Government-certified ranges for electric cars are based on tests that never go above 60 miles per hour, putting them at odds with highway and road-trip travel.

EV range estimates provided by the government put more weight on how a car performs in a city setting than on a highway

EV range estimates provided by the government put more weight on how a car performs in a city setting than on a highway Photographer: David Paul Morris/Bloomberg

When Bryan Nakagawa purchased an Audi e-tron in 2018, he fell in love with the car’s interior and handling, the space for his kids and surfing gear and, of course, its small carbon footprint. But the Salem, Oregon-based dentist soon discovered that his affection was fleeting — it flew away right around 70 miles per hour.

“I wouldn’t even drive a mile and I’d lose like three miles off the estimated range,” Nakagawa says of cruising the interstate in his electric Audi. “It always made me nervous.”

All over the world, EV fever is running high, but battery-powered vehicles are still underperforming against expectations in one critical place: highways, the most fraught part of electric driving and one of the biggest hurdles to mass EV adoption. As a crowd of buyers like Nakagawa are finding out the hard way, speed is a particularly relentless range-killer. Blame the laws of physics, the federal government or both.

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Bryan Nakagawa, at his home in Oregon, traded in his electric Audi because it didn’t travel as far as he expected at high speeds. Source: Bryan Nakagawa

When deciding which electric car to buy, consumers typically refer to a range estimate provided by the Environmental Protection Agency — treating it as something of an efficiency North Star, just as gas-guzzlers can be loosely categorized by miles per gallon. The EPA arrives at its figure after a vehicle is tested in two ways: one on a prescribed schedule intended to replicate a highway trip, and another as a proxy for the type of city miles one might log running errands or picking up the kids at school.

In determining its final range estimate, however, the government puts slightly more weight (55%) on how a vehicle performed in the “city” portion of the test. Nor do any EPA tests push cars faster than 60 miles per hour, a figure out of step with vast stretches of American interstate and with crowds of time-starved commuters. Some 19 states have speed limits of 75 miles per hour or more (looking at you, Montana). The result is a disconnect between EV performance and expectations.

“The EPA range is for the most part pretty good if you just drove a steady 65 miles per hour,” says Jake Fisher, senior director of auto testing at Consumer Reports. “But not everybody drives like that.”

The disconnect is exacerbated because electric vehicles — unlike gas-burning machines — get more efficient in cities. Thanks to regenerative braking systems that recharge the battery while slowing down the car, automakers tend to ace the urban part of the range test. In the right neighborhood or even when plodding through a halting commute, an electric car will actually travel much farther than its EPA seal states.

At the other end of the speed spectrum, however, engineers can’t do much to change the laws of physics. Because the amount of air resistance an EV needs to overcome compounds as the car speeds up, the amount of battery required to go a certain distance does not increase linearly with speed. Traveling at 65 mph, versus 55, for example, will cut range by 28%, according to Lennon Rodgers, a University of Wisconsin engineering professor. Bumping up to 75 miles an hour chews up 38% of range, all else being equal. The speed tax is particularly pronounced with blocky trucks and SUVs.

“I like to say you can go far or you can go fast; you can’t do both,” says Tom Moloughney, an auto journalist who runs a YouTube channel on EV efficiency called State of Charge.

Many of Moloughney’s days are spent on the New Jersey Turnpike, holding a steady 70 miles an hour until the particular vehicle he is testing is wrung out. Invariably, when he finally limps up to a charging port with his EV on empty, the machine has traveled far fewer miles than its EPA-certified estimated range. “Honestly, if it gets its range rating,” Moloughney says, “it’s a major win for the car.”

One exception: the Porsche Taycan. Moloughney says it consistently achieves more miles than its range estimate, even on the interstate, in part because it’s so aerodynamic. Teslas, meanwhile, are on Moloughney’s naughty list: He says they consistently underperform range estimates on the interstate by 10% to 12%.

The EPA admits that its oversight is imperfect. In a response to e-mailed questions, a spokesman wrote that the certifications are “a useful tool for comparing the fuel economies of different vehicles, but are not going to be an exact measurement.” The agency’s tests also fail to capture a slew of other range-killers, including aggressive driving, off-road tires, cold weather and heating and air conditioning use, to name a few. The EPA has an admittedly imprecise way to account for these handicaps: a blanket reduction of its final estimate, usually by around 30%.

Regenerative braking is another wild card. If a car has a default setting for regenerative braking, that’s what the EPA will use on its tests. Consequently, a driver who shuts the system off will see worse real-world results, while someone who dials it up may outperform estimates.

Rodgers at the University of Wisconsin, who has studied battery-powered range for more than a decade, offers straightforward advice for EV rookies: Trust the car. Range estimates displayed by the vehicle itself are likely to be more accurate than the EPA’s, and they also improve over time as the car’s algorithms build a data library of individual driving style and climate-control settings. “Eventually, people usually just … make their own calculations,” Rodgers says.

Granted, none of this matters for the average commute. All but two EVs on the US market have range ratings over 200 miles, meaning daily EV drivers don’t need to factor in a speed tax. Gas vehicles aren’t exempt from the laws of physics, either; they clock similar efficiency losses at speed and lose mileage in city driving as well.

But as EV adoption climbs, a parade of EV rookies are likely in for a road-trip surprise in coming months. Moloughney, for one, thinks it’s time for the EPA to overhaul its process and build a faster, more idiosyncratic regimen. “I try to tell people not to stress too much, but I like them to understand how it all works,” he says, “because a few days a year, they’ll really need to.”