February 20, 2026: Mileage alone is an increasingly unreliable indicator of battery condition in EVs — with uncertainty around condition now the principal determinant of used EV confidence, residual values, performance and risk, according to new analysis.
Generational, the UK-based EV battery condition diagnostics firm, released details on February 18 in its 2025 Battery Performance Index.
According to the BPI, which Generational said is the largest analysis of EV battery condition undertaken in the UK, the average battery state of health across more than 8,000 tested passenger cars and light commercial vehicles stands at more than 95% of capacity compared to new.
Drawing on battery assessments conducted across 36 manufacturers, vehicle ages from 0-12 years and mileages from 0 to over 160,000 miles, Generational’s data showed eight to nine year-old vehicles retain a median 85% capacity.
High-mileage EVs (100,000+ miles) frequently return 88U%-95% SoH while, even with the four to five-year cohort, median SoH remains strong at nearly 94%.
Warranty thresholds of original equipment manufacturers (OEMs) — typically 70% SoH over eight years/100,000 miles — are rarely approached, according to the data.
In terms of age, among four to five-year-old vehicles the 25th (lowest-performing) percentile sits at nearly 92% SoH and the 75th (top-performing) percentile at over 96%.
In the eight to 12-year-old cohort, the 25th percentile is 82%, median and 75th percentile 90%.
In the vast majority of cases, EV batteries are likely to exceed the lifespan of the vehicle itself, Generational said. “Even vehicles approaching the end of typical OEM battery warranty periods are performing comfortably above minimum thresholds.”
However, the increasing dispersion of performance over time underlines why verified battery testing has always been essential.
Oliver Phillpott, CEO of Generational, said the BPI definitively shows that 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,” he said. “And essential infrastructure for a healthy used EV sector. As vehicles age, the variance between the best and worst performers widens, and that dispersion defines risk.”
