Analysis of 2,000 used plug-in hybrids and EVs from car retailers shows both hold up well on average, but PHEVs have much more variation in battery health.
Key Takeaways:
- PHEVs averaged 94.3% SoH vs 94.9% for BEVs
- PHEV standard deviation: 5.5% vs 4.1% for BEVs
- 7% of PHEVs below 85% SoH vs just 1.5% BEVs
Why the difference?
BEV owners tend to charge consistently since it’s their only power source. PHEV drivers vary wildly, some treat them like EVs, others barely plug in or do shallow charges. Same age/mileage, totally different battery stories.
This alarms for better battery transparency in the used market.
According to Generational’s new data, it proves that mileage alone doesn’t tell you battery condition, individual usage patterns matter way more as cars age.
2025 Battery Performance Index
Their 2025 Battery Performance Index (8,000+ tests) found even 8-9 year old EVs averaging 85% capacity, high-mileage beaters hitting 88-95%. Battery degradation isn’t the apocalypse just the uncertainty around individual cars killing confidence and values.
What Generational Found Out?
The analysis, covering 1,000 PHEVs and 1,000 BEVs of comparable age and mileage, found that both vehicle sets retained strong average battery State of Health (SoH).
However, Generational observed materially greater variation among PHEVs, suggesting that PHEV battery performance may be more heavily shaped by differing usage profiles, charging behaviour and driving patterns than those seen in BEVs.
Key Comments
Oliver Phillpott, CEO of Generational, said: “Average state of health evidently remains strong across both PHEVs and BEVs. What stands out is the wider spread of results among PHEVs, which underscores how both buyer and seller need to double down on checking the usage profile of the vehicle in question.
“Even while the averages are reassuring, for both parties the data reinforces how battery condition is something that needs to be assessed on a case-by-case basis. Transparent testing allows strong vehicles to be priced confidently and problematic vehicles to be identified early. So, across both segments, retailers and consumers can go into the market confident of finding a robust vehicle to meet their needs.”
Phillpott added: “The used EV and PHEV market is entering a rapid growth phase. Buyers increasingly understand that the battery is the most valuable component in the vehicle, but they still need clear, trusted information before they can buy with confidence.
“Our latest analysis shows why a single mileage or age figure cannot tell the whole story. Battery condition is becoming the defining factor in used plug-in vehicle value, and the industry now has the data and tools to make that condition visible.”
Generational’s battery health checks and State of Health certification are designed to help retailers, leasing companies and remarketers assess used EV batteries quickly and consistently.
The company says its tools enable retailers to certify battery health and real-world range, support stronger buyer confidence and reduce risk when acquiring, valuing and selling used plug-in vehicles.
To Know More About The Recent Battery Performance Index: CLICK HERE
