The average battery State of Health stands at 95.15%
Generational, the UK-based innovator in EV battery condition diagnostics, has launched its 2025 Battery Performance Index, the largest analysis of EV battery condition undertaken in the UK, revealing that the average battery State of Health (SoH) across over 8,000 tested passenger cars and light commercial vehicles stands at 95.15% cappacity compared to new
The index establishes clear benchmarks for what constitutes typical, above-average, and below-average battery degradation in UK vehicles throughout 2026, providing a new reference point for customers and the industry.
Drawing on battery assessments conducted across 36 manufacturers, vehicle ages from 0-12 years, and mileages from 0-160,000+ miles, Generational’s data found:
- Overall average State of Health: 95.15%.
- 8-9-year-old vehicles retain a median capacity of 85%.
- High-mileage EVs (100,000+ miles) frequently return 88-95% SoH.
- Even within the 4-5-year cohort, median SoH remains strong at 93.53%.
- OEM warranty thresholds (typically 70% SoH over 8 years/100,000 miles) are rarely approached.
The Index also provides percentile benchmarking by vehicle age. For example:
- Among 4-5-year-old vehicles, the 25th percentile (bottom-performing) is 91.64%, the median is 93.53%, and the 75th percentile (top-performing) is 96.49%.
- In the 8-12-year-old cohort, the 25th percentile is 82%, the median 85.04%, and the 75th percentile 90%.
This widening spread with age highlights how, while averages remain strong, variance increases materially over time, creating a growing performance gap between well-maintained vehicles and underperformers.
The data confirms that battery degradation is not the systemic risk as it was assumed to be, with uncertainty around condition now the main determinant of used EV confidence, residual values, performance, and risk.
The new index also reveals that mileage alone is an increasingly unreliable indicator of battery condition. In several 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 offer a stronger battery proposition than a six-year-old vehicle with 30,000 miles, depending on usage and charging practices.
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. 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.”
What this means for consumers
In most cases, EV batteries are likely to outlast the vehicle itself. Even vehicles approaching the end of typical OEM battery warranty periods are performing comfortably above minimum thresholds.
However, the rising dispersion of performance over time underlines why verified battery testing is becoming critical. Without transparent condition data, worst-case assumptions can dominate pricing and decision-making.
As the Index highlights, battery transparency is becoming as fundamental as service history or mileage verification.
Philip Nothard, chair of the Vehicle Remarketing Association, said, “Potential buyers of used electric cars and vans understandably place a huge emphasis on battery health. They need to trust that this fundamental and expensive vehicle component will meet their needs without any unpleasant surprises. Transparency will prove crucial in building future consumer confidence and dispelling the many misconceptions that have gained currency around EV batteries.”
What this means for the industry
The index identifies strategically significant implications for players in the automotive ecosystem:
- For vehicle manufacturers: The data shows a positive durability story. With real-world degradation materially slower than many assume, OEMs can communicate battery longevity with greater confidence and strengthen residual value.
- For insurers and warranty providers: Real-world data enables more precise actuarial modelling. Pricing and coverage can be aligned with verified battery condition rather than conservative age-and-mileage assumptions.
- For fleets: Battery transparency supports enhanced duty-cycle optimisation, holding-period decisions and stronger remarketing outcomes, improving total cost of ownership calculations.
- For policymakers: Standardised battery condition disclosure can reduce the perceived financial risk of battery replacement, one of the most influential barriers to EV adoption.
The findings of the 2025 Battery Performance Index establish battery testing as essential market infrastructure for a maturing EV parc. Without condition visibility, the market risks penalising the majority of well-performing vehicles, as a minority cannot be confidently identified.
Verified battery condition can reduce uncertainty, strengthen residual values, lower finance costs, and accelerate transaction speed, providing a robust basis for reinforcing confidence across the industry and buyer spectrum moving forward.
