For years, battery degradation has been one of the biggest fears holding people back from buying an electric vehicle. Will the battery die in five years? Will range drop off a cliff? A major new study suggests these fears are largely unfounded — and the data is particularly encouraging for Tesla owners.
What the Study Found
UK-based company Generational analysed 8,000 electric cars from 36 different manufacturers, covering vehicles ranging from brand new to 12 years old with mileages from zero to over 160,000 miles. The results, published in the Generational 2025 Battery Performance Index, paint a far more optimistic picture than most consumers expect.
95%
Average battery health across all 8,000 vehicles
85%
Median health in vehicles aged 8–12 years
88–95%
Health range in vehicles over 100,000 miles
70%
Typical warranty replacement threshold
The headline figure is striking: the average battery health across the entire sample sits at 95% — substantially above the 70% threshold that typically triggers a warranty replacement. Even the oldest vehicles in the study (aged 8–12 years) showed a median health of 85%, with the best-maintained examples retaining around 90% of their original capacity.
High-Mileage Vehicles Hold Up Surprisingly Well
Perhaps the most reassuring finding is what happens at high mileage. Vehicles that had covered more than 100,000 miles showed battery health ranging between 88% and 95% — with significant variation that suggests how a battery is charged and used matters far more than the miles alone. This challenges the assumption that high mileage automatically means a degraded battery.
| Vehicle Category | Battery Health |
|---|---|
| Full sample average | 95% |
| Aged 8–12 years (median) | 85% |
| Aged 8–12 years (best maintained) | ~90% |
| Over 100,000 miles | 88–95% |
| Warranty replacement threshold | 70% |
The Expert View
"EV batteries are performing far better than many consumers and industry stakeholders have been led to believe. Transparency in battery condition is the main challenge facing the market today."
— Oliver Phillpott, CEO of Generational
Phillpott emphasised that establishing clear benchmarks for battery health is essential for supporting the used EV market in 2026. Buyers and sellers currently have little standardised information to work with, which creates uncertainty — and often unfair pricing.
What This Means for Tesla Owners
Tesla's battery management system is widely regarded as one of the best in the industry, and this study's findings are consistent with the data we see through this site. Teslas across all model years regularly show battery health well above the 80% mark, even with significant mileage. The Model 3 Long Range, Model Y, and older Model S/X vehicles all tend to retain capacity impressively over time.
That said, individual results vary based on charging habits, climate, and how frequently fast charging is used. The study reinforces a key point: looking up a used Tesla's battery health before buying is far more meaningful than judging by age or mileage alone.
Check your own Tesla's battery health in under a minute — all you need is your energy consumption data from the Tesla app.
Check Battery HealthThe Bottom Line
Battery degradation in EVs is real, but the scale of it has been dramatically overstated. A study of 8,000 real-world vehicles shows that even a 12-year-old EV is likely to have around 85% of its original battery capacity — more than enough for most daily driving needs. If you've been putting off buying an EV or worrying about your current battery, the evidence suggests there's much less to fear than the headlines imply.