Tesla has no battery degradation warranty on its Model S and X luxury EVs, but guarantees that the Model 3 will retain 70 percent battery capacity after 120,000 miles (long-range battery) and 100,000 miles (shorter-range battery). That's a bit more generous than the one Nissan offers on the Leaf (66 percent over 100,000 miles) for instance. According to the survey data, Tesla will easily be able to meet this mark.

Lost battery capacity over time is one of the biggest concerns for EV buyers, so this new data, based on real-world usage, should be reassuring. There are some outlier EVs that lost capacity more quickly than others, for reasons that aren't clear, though. As such, while the data looks promising, it might be best to reserve judgement pending larger scale surveys with higher-mileage EVs.