Industry expert Generational launched the UK’s largest battery health study today, revealing used EVs retain more than 95% of their original battery capacity on average.
The Battery Performance Index analyzed over 8,000 passenger cars and light commercial vehicles across 36 manufacturers. The vehicles ranged from 2013 to 2025 models with mileage spanning zero to more than 160,000 miles.
State of Health (SoH) measures a battery’s current capacity compared to when it was new – shown as a percentage from 0% to 100%. It’s the key metric for determining how long an EV battery will last.
High-Mileage EVs Perform Better Than Expected
The data showed an overall average SoH of 95.15% across all vehicles tested.
EVs with over 100,000 miles frequently scored between 88-95% battery health. Four to five-year-old vehicles averaged 93.53% SoH.
Even eight to nine-year-old EVs maintained a median of 85% battery capacity – well above the 70% threshold where most manufacturer warranties kick in.
The study breaks down performance by age groups using percentile rankings. In the four-five-year category, bottom performers averaged 91.64% SoH while top performers hit 96.49%.
Older models between eight-12 years showed more variation. Bottom performers retained 82% capacity, mid-range vehicles kept 85.04%, and the best performers maintained 90% SoH.
Mileage Doesn’t Tell the Whole Story
The findings challenge assumptions borrowed from petrol and diesel cars about high-mileage vehicles.
A three-year-old fleet vehicle with 90,000 miles might have better battery health than a six-year-old car with just 30,000 miles. Usage patterns and charging behavior matter more than total distance traveled.
Younger high-mileage EVs often outperformed older, low-mileage cars in terms of battery condition.
Battery degradation is no longer the major risk it was once thought to be. The biggest concerns when buying used EVs relate to overall vehicle condition and how it’s been maintained.
“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,” said Generational CEO Oliver Philpott.
Transparency Key to Used EV Market Growth
Battery health transparency remains the main challenge facing the used EV market today. Worst-case assumptions can negatively impact pricing and consumer decisions.
As vehicles age, the performance gap between the best and worst batteries widens. This creates uncertainty that affects residual values.
“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,” Philpott added.
The study provides essential infrastructure for a healthy second-hand EV sector by giving buyers and sellers concrete data about what to expect from battery performance across different ages and usage patterns.
