The UK’s largest study of used electric vehicles suggests battery degradation is far less severe than many fear.
Battery diagnostics specialist Generational analysed more than 8,000 electric cars and light commercial vehicles, covering 36 manufacturers, with vehicles aged 0 to 12 years and mileages from zero to more than 160,000 miles.
Key findings from the 2025 Battery Performance Index include:
Average battery state of health across all vehicles: 95.15%
4 to 5 year old EVs: median 93.53% SoH
8 to 9 year old EVs: median 85% capacity retained
100,000 plus mile vehicles frequently returning 88 to 95% SoH
Most manufacturers warranty batteries to 70% SoH for eight years or 100,000 miles, and Generational found the vast majority comfortably exceed that threshold.
Data also shows growing variation as vehicles age. Among 8 to 12 year old EVs, the 25th percentile sits at 82%, the median at 85.04%, and the 75th percentile at 90%.
Oliver Phillpott, CEO of Generational, said: “The Generational Battery Performance Index definitively shows that EV batteries are performing far better than many consumers and industry stakeholders have been led to believe.”
The study also challenges the assumption that mileage equals wear. In some cases, a three year old fleet vehicle with 90,000 miles can outperform a six year old car with 30,000 miles, depending on charging behaviour and usage.
A range of EV brands have established battery-health policies:
BYD extends battery warranty
Used Polestars get battery health reports