Measured, not argued
2.3 percent
a year
Across 22,700 vehicles the average is 2.3 percent a year, which leaves about 81.6 percent after eight years.
At a glance
- The number went up. The same researchers reported 1.8 percent in 2024 on a smaller sample, so anything still quoting 1.8 is quoting the old study
- Tesla's own figure is 15 percent lost at 200,000 miles on Model 3 and Y, and 12 percent on Model S and X
- Replacement is rare. Under 4 percent across a 30,000 vehicle fleet, and 0.3 percent for cars from 2022 onwards
- The curve is not a straight line. A steeper first year, a long flat middle, then a knee near the end
Why the headline moved
The 2024 study covered roughly 5,000 vehicles and reported 1.8 percent a year, with a cheerful conclusion that batteries would last twenty years or more. The 2026 study covers 22,700 vehicles across 21 models and reports 2.3 percent, and attributes the rise to growing use of high power fast charging.
Both figures are honest. The second one is better evidenced. A site still telling you 1.8 percent is not lying, it is just out of date.
The finding that should change how you shop
Idaho National Laboratory ran two Nissan Leaf packs through about 780 cycles, roughly 50,000 miles, one charged at 3.3 kW and one at 50 kW. The slow charged pack faded 23.1 percent. The fast charged pack faded 28.1 percent.
Then the important part. The maximum difference between individual cells was under 1 percent. The packs diverged by five points while the cells inside them barely differed. The gap is thermal non uniformity across modules, and the authors state plainly that pack level aging cannot be extrapolated from cell testing.
For a buyer that means two things. A pack is not a big cell, and a car without active cooling is a different product from one with it, not a cheaper version of the same thing.
How often a pack actually gets replaced
Across more than 30,000 vehicles with recalls excluded, under 4 percent have had a battery replaced. Split by generation the picture is much sharper.
- Cars from 2016 and earlier, about 8.5 percent
- Early second generation, meaning the Bolt and the Model 3, about 2 percent
- Cars from 2022 onwards, 0.3 percent
Sudden failure is rare and concentrated in first generation cars. Gradual fade is the normal case.
Questions people actually ask
Will the battery outlast the car
Does fast charging wreck the battery
Buying a Used EV or Hybrid?
Get the battery measured before you pay for it. A PPI Auto inspector tests the pack on the car you are looking at and sends you the numbers. Starting at $225.