The average electric vehicle battery retains 95.15% of its original capacity after years of use, according to a new report released today by UK-based battery diagnostics firm Generational. The 2025 Battery Performance Index, based on over 8,000 battery health assessments, challenges common assumptions about rapid degradation and suggests EVs may last longer than previously estimated.
The study, the largest of its kind undertaken in the UK, analyzed batteries from 36 manufacturers in passenger cars and light commercial vehicles ranging in age from zero to twelve years and with mileages exceeding 160,000. Findings indicate that even eight-to-nine-year-old vehicles retain a median battery capacity of 85%, comfortably above the 70% threshold often stipulated in original equipment manufacturer (OEM) warranties.
“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,” said Oliver Phillpott, CEO of Generational. He believes establishing clear benchmarks for battery health will improve pricing accuracy, strengthen residual values, and encourage wider EV adoption.
The report highlights that mileage alone is not a reliable predictor of battery health. Vehicles with over 100,000 miles frequently demonstrated a State of Health (SoH) between 88% and 95%. A Generational analysis suggests a three-year-old fleet vehicle with 90,000 miles may have a stronger battery proposition than a six-year-old vehicle with only 30,000 miles, depending on usage and charging habits.
The findings are expected to boost confidence in the used EV market, which has faced challenges with residual values due to concerns about battery life. The index demonstrates that worst-case scenarios regarding battery degradation are often overstated, and that real-world performance is frequently better than anticipated. Even in the 8-12 year old cohort, the 25th percentile still showed an average State of Health of 82%.
Generational emphasizes that factors beyond mileage, such as driving style, charging behavior, and climate, significantly influence battery health. The company advocates for verified battery tests for all used EVs to provide transparent condition data and avoid pricing decisions based on worst-case assumptions.
