About the EV Battery Degradation Calculator
This EV battery degradation calculator estimates how much capacity an electric vehicle’s battery will have left after a given number of years and miles. It splits capacity loss into two parts: calendar ageing, which happens with time regardless of use, and cycle ageing, which grows with the miles you drive. The result is the battery’s state of health (SOH), the usable kWh remaining and the range you can expect compared with new.
Use it when buying a used EV, planning how long to keep your car, or checking whether a battery is likely to stay above its warranty threshold — many manufacturers guarantee around 70% capacity for 8 years or 100,000 miles. The default rates (1% per year plus 1% per 10,000 miles) give roughly 2.2% a year at 12,000 miles, close to the 2.3% average annual degradation in Geotab’s 2025 analysis of telematics data from more than 22,700 EVs across 21 models.
Real batteries often lose a little more in the first year or two and then flatten out, and heat, frequent DC fast charging and long periods at 100% charge speed up wear. Adjust the two rates to model a hotter climate or gentler use. The model is linear, so treat results as an estimate, not a diagnosis of a specific car.
With the default inputs, the estimated battery health (soh) is 89%. Change any value above to recalculate instantly.
How to use the ev battery degradation calculator
- 1Enter the car’s original rated range and usable battery size.
- 2Enter the battery’s age and how many miles a year it is driven.
- 3Keep the default loss rates or raise them for hot climates or frequent fast charging.
- 4Set the warranty threshold (often 70%).
- 5Read the estimated health, remaining range and years until the threshold.
Formula and method
Battery state of health is modelled as 100% minus two linear losses: a calendar loss for every year the battery ages, and a cycle loss for every 10,000 miles driven (miles = years × miles per year). Remaining usable capacity and range are the original values multiplied by SOH.
The years until the threshold is reached divide the capacity you can lose (100% − threshold) by the combined yearly loss rate. A linear model is a deliberate simplification — real cells usually fade faster at first and then slow — so it can understate the loss in the first year or two and overstate it later in the battery’s life.
- SOH
- State of health: remaining capacity as % of new
- calendar
- Percent lost per year from time alone
- cycle
- Percent lost per 10,000 miles driven
Worked examples
5-year-old 300-mile EV, 12,000 miles a year
Five years of calendar ageing costs 5% and 60,000 miles costs 6%, leaving 89% health. That is 66.75 kWh of the original 75 kWh and about 267 miles of range. At 2.2% a year it would take about 13.6 years to reach 70%.
High-mileage 8-year-old EV
Eight years (8%) plus 120,000 miles (12%) gives 80% health: 48 kWh and roughly 200 miles of a 250-mile rated range. At 2.5% a year the 70% mark arrives after about 12 years.
Hot-climate car with faster calendar ageing
Doubling calendar loss to 2% a year for heat gives 6% + 3% = 9% loss after three years, so 91% health and about 273 miles of range. At 3% a year it reaches 70% in 10 years.
Frequently asked questions
How fast do EV batteries degrade?+
Large fleet studies put average degradation at roughly 2% a year. Geotab’s analysis of over 22,700 EVs found an average of 2.3% per year, with variation by model, climate and charging habits.
What is a good battery state of health for a used EV?+
For a car around five years old, 85–92% is typical. Much lower than that can indicate heavy fast charging, heat exposure or a weak module. Ask for a battery health report from the dealer or a diagnostic tool.
Does DC fast charging damage the battery?+
Frequent DC fast charging, especially in hot weather or to 100%, generates more heat and can speed up wear somewhat. Occasional fast charging on road trips has a small effect; most daily charging on AC is gentlest.
What does an EV battery warranty cover?+
In the US most EV makers warrant the battery for 8 years or 100,000 miles, and many also promise it will keep at least about 70% of its original capacity during that period. Terms vary, so check your manufacturer’s booklet.
How can I slow battery degradation?+
Keep the daily charge limit around 80% unless you need full range, avoid leaving the car at 100% or near 0% for long, park in shade or a garage in hot weather, and use AC charging for routine top-ups.