When we published our real-world Edmunds EV range test, Tesla challenged our finding that its vehicles fell short of their EPA range estimates. Was the challenge valid? Here's the test we conducted to find out.
www.edmunds.com
In February 2021, we published our independent and continually updated
Electric Car Range test. Our results were surprising, to say the least.
Some electric vehicles dramatically exceeded the EPA's range estimates, while others fell short. Most notably, all five Tesla vehicles we tested missed those estimates.
Needless to say, Tesla was not happy with our test results, and we received a phone call. Tesla's engineers disputed our figures. They argued that we'd underestimated their cars' true range because our test ran to an indicated zero miles rather than to a stop.
Tesla argued that even when the indicated range hits zero, there's still a safety buffer. The engineers reckoned that if you add this buffer, the distance measured to when the battery is spent, their cars would match the EPA results.
We needed to test Tesla's theory. Would their vehicles' buffer make a difference and see them hit their EPA range target? And does Tesla's buffer approach differ from that of other manufacturers? We headed to a vehicle proving ground to find out. The results may or may not surprise you.
Five EVs, one test: mapping out our plan ... safely
Our plan was to literally drive these EVs until they ran out of juice. This approach would allow us to measure the buffer — the difference between an indicated zero miles (displayed on each car's dashboard) and the true zero (when the battery runs out).
Given that driving a group of EVs to a stop on a public road is far from advisable, Edmunds' vehicle testing team rented a 7.5-mile-long closed-course oval at an unaffiliated automaker's proving ground in California's Mojave Desert. This allowed us to put Tesla's claim to the test in a more controlled environment, but one still subject to real-world conditions.
We brought three Teslas — a 2020 Model 3 Standard Range Plus, a 2021 Model 3 Long Range and a 2020 Model Y Performance — and two control vehicles: a 2021 Ford Mustang Mach-E and a 2021 Volkswagen ID.4, both of which comfortably exceeded their EPA estimates in our tests. Tesla loaned us the Model 3 Long Range, and Ford and Volkswagen loaned us their vehicles. The
Model Y and Model 3 Standard Range Plus test cars are vehicles we own and were used for the original range test.
Driving to zero and beyond
Many range meters, for both gas and electric cars, take your recent driving habits into account when forecasting remaining range. So we needed to drive the cars exactly the same way in order to normalize all of our vehicles' range meters before they reached their indicated zero range. This would provide a level playing field.
Testing Tesla's Range Anxiety - Lineup.
2021 Ford Mach-E - Charging.
2021 Ford Mustang Mach-E - Interior.
2021 Volkswagen ID.4 - Testing.
This was our approach:
- We drove all the EVs at a 65 mph constant speed around the oval because that's the average speed limit for urban interstate highways in the U.S.
- We charged the EVs at the same outdoor ambient temperature overnight to 100% battery capacity and disconnected the charging cords at the same time.
- We correctly set each vehicle's tire pressures to manufacturer specifications.
- To further equalize our test measurements, we fitted Racelogic GPS-based data loggers to each car and used the vehicle's cruise control to maintain a true, GPS-verified 65 mph.
- We maintained these speeds in hour-long driver stints, with large 30-second gaps between vehicles to equalize the aerodynamic conditions, until all batteries were spent and the cars limped to a stop.
- Each driver set the automatic climate control to 72 degrees.
- All audio systems remained off.
- We did not plug in any cellphones or personal accessories.
- We even rotated the drivers through the cars at every stop.
It sounds like purgatory by boredom, but it was a small sacrifice for science.
2019 Tesla Model Y - Interior.
Our graphic above highlights the distance each test EV traveled after reaching an indicated zero miles while still maintaining 65 mph. We consider this to be the more realistic endpoint because if a vehicle isn't able to maintain a safe highway speed (65 mph) on a flat road like at our test facility, then it's probably unsafe to be on public roads.
We also measured the distance each vehicle kept going even after it could no longer maintain 65 mph — the total distance traveled after the vehicle hit zero indicated range. This is what's measured by the EPA in its laboratory-based tests and was the basis of Tesla's challenge.
Mach-E
The Ford Mach-E had the shortest range reserve buffer in our test: It went 5.8 miles past its indicated zero range at a steady 65 mph. After it could no longer maintain 65 mph, there was a pretty consistent drop in speed over a relatively short 1.5 miles before the Mach-E came to a total stop at 7.3 miles. So Ford's indicated range of 0 is closer to zero.
We discussed the results with Jim Antal, Ford's Vehicle Energy Management manager. "We give [our customers] plenty of warning so we don't strand them," said Antal. "We don't want to tell them they only have 5 miles left when they have 40 miles left. So we have to walk that fine line between making sure we're as honest as possible with the customer about what they truly have and giving them plenty of opportunities to stay safe and finish [their trip]."
ID.4
The ID.4 had more energy in reserve than the Mach-E, going 9.4 miles past an indicated zero at 65 mph. Once it was unable to maintain 65 mph, it continued to lose a couple of mph about every minute. We kept driving and made it a total of 12.9 miles beyond zero, just feet ahead of where the Model Y stopped.
Commenting on the buffer, Matthew Renna, vice president of e-mobility, Volkswagen Group of America, said, "It is standard practice from most [auto]makers to build a small buffer into the batteries, for obvious reasons, so we weren't surprised by the result. It is analogous to ICE [internal combustion engine] vehicles, where automakers usually have some fuel in reserve when the car shows zero."