What determines battery longevity: what 10,000 EVs taught Geotab about degradation

The largest real-world dataset on EV battery health says the fear is overblown. Telematics company Geotab’s “Taking Charge” report, based on data from 10,000 EVs operating in North America and Europe, found average battery degradation of 1.8% per year — down from 2.3% per year in its 2019 analysis. At that rate, batteries could last 20 years or more, retaining over 80% state of health after 12 years — generally beyond the usual life of a fleet vehicle.

Degradation is not linear. Batteries typically take an initial drop, plateau through most of their life, then fall more steeply toward end of life. And averages hide differences: some vehicles in Geotab’s sample degraded at less than 1% per year, while liquid-cooled packs — as in Tesla models — consistently outperformed air-cooled designs like the early Nissan Leaf.

What actually moves the needle: heat and fast charging. Geotab found a correlation between greater DC fast-charging use and faster-than-average degradation — especially in hotter climates. Hot climates accelerate degradation on their own. What does not move it: mileage. Higher EV use doesn’t mean higher degradation, provided daily range is respected. The practical takeaways are unglamorous: park in the shade in hot weather, prefer Level 2 charging when time allows, and let the thermal management do its job.