New Study Shows EV Batteries Last Longer Than Most Drivers Expect

Battery degradation has long been one of the biggest question marks hanging over electric vehicles (EVs), particularly in the used market. But a new large-scale study suggests those concerns may be largely overblown, with real-world data showing EV batteries are holding up far better than many buyers expect.

The Generational 2025 Battery Performance Index looked at more than 8,000 electric cars and vans across 36 manufacturers, offering one of the most comprehensive looks yet at how EV batteries age in real-world conditions. The results paint a clear picture—battery degradation is happening far more slowly than many consumers assume.

Key to the study is the concept of State of Health (SoH), which measures a battery’s remaining capacity compared to when it was new. Across all vehicles analyzed, the average SoH came in at an impressive 95.15%, meaning most EVs retain nearly all of their original range and performance even after years on the road.

Even as vehicles age, the numbers remain strong. EVs between four and five years old showed a median battery health of around 93.5%, while those approaching a decade old still averaged roughly 85% capacity. High-mileage vehicles—those with over 100,000 miles (160,000 km)—frequently retained between 88% and 95% battery health, further reinforcing the durability of modern battery technology.

For context, most automakers warranty EV batteries to maintain at least 70% capacity over eight years or 100,000 miles. The study’s findings suggest the majority of vehicles comfortably outperform those thresholds, often by a wide margin.

Perhaps more surprising is what doesn’t matter as much as people think. Mileage alone, long considered a key indicator of vehicle condition, appears to be a poor predictor of battery health. In many cases, newer high-mileage vehicles—such as fleet cars—can outperform older vehicles with significantly lower mileage.

Instead, factors like charging habits, battery chemistry, and thermal management play a much larger role in long-term performance.

This shift has major implications for how used EVs are valued. Traditional metrics like age and mileage are being replaced by battery condition as the most important factor in determining a vehicle’s long-term usability and resale value. Tesla has addressed this introducing a battery health testing option in their mobile app, allowing owners, and potential buyers, to know exactly how healthy the high-voltage battery is.

That transparency is becoming increasingly important as more EVs enter the used market. Without clear battery data, buyers may assume worst-case scenarios, which can suppress resale values and slow adoption.

You can read the full study below.