Gearhead News

March 29, 2021
Tesla's EPA Driving Ranges Didn't Hold Up to Testing. It Tried Again and Still Fell Short

Back in February, Edmunds published data that it gathered from testing the driving range of 17 EVs currently for sale and compared its findings to their official U.S. Environmental Protection Agency figures. The Porsche Taycan did incredibly well, surpassing its predicted range by over 100 miles, but as it’s to be expected, not every car fared as well. Specifically, every single Tesla—six models were tested—actually fell short of their EPA estimates. 

According to the publication, that aggrieved some engineers at Tesla, of course, who reached out to Edmunds staff to say that its test procedure was all wrong: In a Tesla, the claimed driving range apparently doesn’t end at zero miles remaining, but when the car actually drains its “safety buffer” and comes to a complete stop.

Edmunds

In a nutshell, even when using the safety buffer, in controlled conditions, four of the six Tesla cars Edmunds
tested for range did not hit their EPA mileage. Two did—but in the real world, you’re not actually meant to use that safety buffer, both because it’s bad for your battery and because it’s, well, out of range. You don’t have any idea how much further you can drive once the remaining range drops below zero, so while that buffer might be a life-saver in an emergency, it’s really not something that folks should count on using or abusing on a daily basis. Plus, as I said, it actually harms the battery—so why would Tesla insist on counting this buffer as part of the EPA-estimated driving range?

There are some factors that affect battery capacity and range, like cold weather or uphill driving, for example. Edmunds claims to have controlled these variables by performing these tests at a temperate, flat track. On the other hand, you can argue that running at a consistent 65 mph, as it did—not the world’s most thrilling track day—robs the cars of potential regeneration under braking and lift-and-coast, plus it doesn’t actually reflect real-world driving. So, Tesla, there’s your get-out-of-jail card.

The original test where the Teslas fell short wasn’t that dramatic; the 2021 Model 3 Long Range and the 2020 Model S Performance only came in eight miles below their EPA estimates. That difference may have felt amplified because pretty much every other EV was delivering figures in excess of the EPA numbers, but it’s not a giant gap that can probably be explained through environmental conditions and driving styles. Both those cars eventually went on to meet their EPA estimates when using the sub-zero mileage format recommended by Tesla, although as noted above – this isn’t actually meant to be drivable range.

For the other Teslas tested, however, things didn’t go as “well.” The 2018 Model 3 Performance was off by 54 miles—this might not look that notable on a couple-year-old model—but when the testing is performed in such friendly conditions that the 2020 Mini Cooper SE, with an EPA range of 110 miles, is exceeding that by 40 miles, then it just doesn’t paint a pretty picture for the Tesla cars.

Edmunds then decided to retest the cars under the conditions Tesla told them to, charging the cars to 100 percent and then running until they came to a complete stop. The staff used a 2021 Mustang Mach-E and a 2020 Volkswagen ID.4 as sort of controls or “lead cars” along with three recent Tesla: the 2020 Model Y Performance, the 2020 Model 3 Standard Range Plus, and the 2021 Model 3 Long Range. Of those, the 2021 Model 3 Long Range went a massive 25.9 miles after it had hit zero remaining mileage, the 2020 Model 3 went 17.6, and the 2020 Model Y 12.9 miles. That’s further than either the Mach-E, which traveled 7.3 miles after zero, or the ID.4, which squeezed another 12.6 miles after zero. This wasn’t a huge deal for the Ford or the VW, as both had previously exceeded their EPA mileage under the test conditions by 34 and 37 miles respectively.

The 2021 Model 3 Long Range only met its EPA estimate using the extra mileage below zero, but more damningly, the other two didn’t. The 2020 Model 3 Standard Range Plus had originally fallen 18 miles short of its EPA estimate, but then stopped at 0.4 miles off its target by driving past the zero mark. The 2020 Model Y Performance had fallen 28 miles short in the first test, and it was still 15.1 miles off target after fully draining the battery.

Will this push away prospective Tesla customers? Probably not. Tesla still offers some of the best driving ranges on any EV, after all. It’s also still the leader in overall EV performance. It’s just an odd situation, especially because you really shouldn’t be cycling your battery to empty unless you have to. EV batteries, like all lithium-ion cells, stay healthiest if you keep them somewhere between 20 and 80 percent charged. 

Tesla told Edmunds that the disparity was caused by its software being ultra-conservative about mileage estimates, with the safety buffer overestimated to get people home. But when every other car is, under the same conditions, exceeding their EPA estimate, it’s at least a weird quirk that’s landed Tesla on the wrong side of the numbers.

Got a story with mileage? Mail me at hazel@thedrive.com