We were driving purely at city speeds (which is below 50 mph on roads with stoplights) by the time each vehicle reached zero indicated miles of range. And, to our surprise, both Teslas ended up with shorter buffer ranges than at our proving ground's closed facility test.
We contacted Tesla to discuss these findings. The automaker told us that there was no fixed range buffer and that it would be impacted by the following:
- "Near-past conditions — ambient temperature and driving style leading up to the final few miles."
- "Instantaneous conditions — there's a strong interaction between speed/acceleration and the battery's ability to provide its last little bit of energy."
Tesla engineers concluded that "for these reasons, the buffer cannot be defined exactly to a number every time — it will change based on external conditions, driving profile, etc."
Our key takeaways
- Some Teslas (2021 Tesla Model 3 Long Range, 2020 Tesla Model S Performance) do meet their EPA range estimates on the Edmunds EV range loop but with the caveats that they:
- are charged to 100% battery capacity, which Tesla does not recommend for daily use;
- are driven conservatively and without too many ancillary power draws, such as strong climate settings;
- are driven in a temperate climate; and
- are driven beyond the point where indicated range drops to zero.
- Other Edmunds-tested Teslas (2020 Model 3 Standard Range Plus, 2020 Model Y Performance, 2018 Tesla Model 3 Performance) won't hit their EPA range estimates even following all of the above conditions.
- There's no consistent way to determine exactly how much an EV's buffer range will be. While some Teslas appear to have long range buffers beyond zero, the range of others is comparable to the range of alternative EVs we've tested.
Edmunds says: What does this mean for you?
Our answer to Tesla's dismay with our initial results is that, yes, two of the automaker's vehicles can match the EPA's range estimates in the Edmunds EV range test. But that's only under specific circumstances and by driving each vehicle past zero indicated miles of range.
The majority of Teslas we tested, four of the six, do not meet their EPA estimates, even allowing for a safety buffer.
We'd also argue that the point is academic. For you as an EV driver or future EV driver, it's unlikely you'd expect an EV's buffer range to be included in the EPA's range estimate. A buffer is meant to provide an extra cushion or protection to avoid an unwanted outcome. Moreover, it's difficult to know, or plan for, how much extra range there is beyond an indicated zero or whether you'll be able to maintain your current speed.
Here is also what you need to keep in mind:
- Many factors are at play that can affect an electric vehicle's range including driving style, terrain and weather.
- Regularly dipping into a vehicle's buffer range increases charging time, decreases charging efficiency and could decrease battery longevity.
We admit our standardized Edmunds EV range test isn't perfect — no test is. But it is a good approximation of what you might expect to achieve in real-world driving and, we believe, a complement to the EPA's current laboratory-based range figures. And we'll continue to test to an indicated zero because we'd never advise EV consumers to drive their vehicle beyond this point.
As the technology evolves and more people choose electric cars, it's critical that consumers have real-world measures that are relevant, trustworthy and believable.