Generational’s 2025 Battery Performance Index shows used EV batteries are far healthier than many assume, averaging 95% State of Health across 8,000 vehicles and rarely nearing OEM warranty limits. The real issue is visibility: as variance widens with age, accurate battery testing, not mileage, is critical to pricing risk and protecting values.
Generational, the UK-based innovator in electric vehicle battery condition diagnostics, today launches its 2025 Battery Performance Index, the largest analysis of electric vehicle battery condition undertaken in the UK, revealing that the average battery State of Health (SoH) across more than 8,000 tested passenger cars and light commercial vehicles stands at a robust 95.15% of capacity compared to new.
The Index establishes clear benchmarks for what can be considered typical, above-average, and below-average battery degradation in UK vehicles moving through 2026, providing a new reference point for consumers and the industry across retailers, fleet operators, insurers, and financiers.
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 shows:
- Overall average State of Health: 95.15%.
- 8-9-year-old vehicles retain a median 85% capacity.
- 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 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% State of Health, 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%.
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 data confirms that battery degradation is not the systemic risk once assumed, with uncertainty around condition now the principal determinant of used EV confidence, residual values, performance and risk.
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.
The full Battery Performance Index can be downloaded here.
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 the findings mean for consumers
In the vast majority of cases, EV batteries are likely to exceed the lifespan of the vehicle itself. 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 is becoming essential. Without transparent condition data, worst-case assumptions can dominate pricing and decision-making.
As the Index underlines, battery transparency is fast 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 the findings mean for the industry
The Index identifies strategically significant implications for players across the automotive ecosystem:
For vehicle-manufacturers: The data presents a highly positive durability story. With real-world degradation materially slower than many assume, OEMs have an opportunity to communicate battery longevity with greater confidence and reinforce residual value strength.
For insurers and warranty providers: Extensive real-world data enables more precise actuarial modelling. Pricing and coverage can increasingly be aligned with verified battery condition rather than conservative age-and-mileage assumptions.
For fleets: Battery transparency supports improved duty-cycle optimisation, holding-period decisions and stronger remarketing outcomes, improving total cost of ownership calculations.
For policymakers: Standardised battery condition disclosure can dismantle perceived financial risk around battery replacement, which stands as one of the most influential barriers to EV adoption.
The findings of the 2025 Battery Performance Index establish battery testing as critical market infrastructure for a maturing EV parc. Without condition visibility, the market risks penalising the majority of well-performing vehicles because a minority cannot be confidently identified.
Verified battery condition therefore reduces uncertainty, strengthens residual values, lowers finance costs and accelerates transaction speed, providing a robust basis for reinforcing confidence across the industry and buyer spectrum moving forward.
Further Reading on ATF Professional
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Government backs UK-first AI platform for circular EV batteries
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Connected Energy to develop UK’s most advanced second-life EV battery testing facility
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UK’s first electric vehicle battery circular supply chain completed as pioneering RECOVAS project wraps up
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UK’s Project COMET Secures £8.1M to Pioneer Circular EV Battery Recycling
