In what’s being claimed to be the UK’s largest used battery electric vehicle study, the impact of age and mileage on the charging capacity of batteries has been revealed.
Generational, a specialist in battery electric vehicle (BEV) battery condition diagnostics, tested more than 8,000 electric cars and light commercial vehicles (LCVs).
It found that 8-9-year-old vehicles retain a median 85% battery capacity, compared to new, while the median battery state of health (SoH) for 4-5-year-old EVs was 93.53%.
The average battery SoH across the whole test fleet was 95.15% of capacity compared to new.
The results, published in Generational’s 2025 Battery Performance Index, draws on battery assessments conducted across 36 manufacturers, with vehicle ages from 0-12 years and mileages from 0 to more than 160,000 miles.
Manufacturers typically warrant batteries to a minimum of 70% SoH for eight years or 100,000 miles, whichever criterion is met first.
Generational’s data indicates that the vast majority of vehicles will comfortably outperform this, although a very small proportion does fall outside of warranty parameters and will likely result in claims.
For example, it found high-mileage EVs (100,000-plus miles) frequently return 88-95% SoH.
The Index also breaks down into percentile benchmarking by vehicle age. For example, among 4-5-year-old vehicles, the 25th (bottom-performing) percentile sits at 91.64% SoH, the median at 93.53%, and the 75th (top-performing) percentile at 96.49%.
In the 8-12-year-old cohort, the 25th percentile is 82%, median 85.04%, and 75th percentile 90%.
Source: Generational
This widening spread with age shines a sharp spotlight on how while averages remain strong, variance increases materially over time, creating a growing performance gap between well-maintained vehicles and underperformers.
The new Index also demonstrates that mileage alone is an increasingly unreliable indicator of battery condition.
In many cases, younger high-mileage vehicles outperform older low-mileage equivalents, challenging traditional appraisal models inherited from the internal combustion era.
A three-year-old fleet vehicle with 90,000 miles may represent a stronger battery proposition than a six-year-old vehicle with 30,000 miles, depending on usage and charging behaviour.
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.
“With an average state of health of over 95%, and even older vehicles comfortably exceeding warranty thresholds, the underlying fundamentals are extremely strong.”
He added, “Transparency in battery condition is the main challenge facing the market today, 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.
“By establishing clear benchmarks for what is typical, above and below average as we look to drive further growth in 2026, we are giving the market the reference points it needs to price risk accurately, strengthen residual values and accelerate adoption.”
