Tesla battery degradation: how packs lose capacity
Every battery loses capacity as it ages. What matters is how fast, how it flattens, and how much one reading can tell you about the years ahead.
The shape: fast early, then flatter
A battery does not lose capacity in a straight line. Many packs lose more in the first stretch of their life and then settle into a slower, steadier decline. The exact figures depend on the car, so we quote none here.
| Age in years | Usable energy |
|---|---|
| 0.4 | 91.8 kWh |
| 1.0 | 90.0 kWh |
| 1.8 | 88.3 kWh |
| 2.8 | 86.6 kWh |
| 4.0 | 85.0 kWh |
| 5.5 | 83.6 kWh |
- Dots
- Each is one reading, placed by the car’s age.
- Dotted line
- Falls quickest in the first years and flattens later.
- Dashed guess
- A straight-line guess runs on from the dots. Real wear is rarely straight, so it is a prompt, not a forecast.
That shape is why a young car with a good reading tells you less about the long run than an older car with a good reading. The older car has already been through the quick part.
What tends to speed it up
- Time. A pack ages even when the car stands still.
- Use. More charge and discharge cycles, which usually means more kilometres.
- Heat. Long periods in hot conditions are hard on cells.
- Sitting full. Keeping a battery at a very high charge for long periods.
- Fast charging. Frequent high-power charging, compared with slower charging at home.
These are commonly reported factors. How much each one matters varies with the model and the type of cell, which is another reason one car’s history cannot be read from another’s.
Why readings wobble
Tesla’s figure is an estimate, so two readings a few weeks apart can differ in either direction without anything having happened to the cells. Do not read much into a change of a few tenths of a percent. A trend across several readings, months apart, is far more telling than any one of them.
Why one reading is not a forecast
Our report draws a dashed rough-guess line from the readings to show where the same pace would lead. It assumes a steady loss, and, as above, real packs rarely follow one. Use the dashed line as a prompt for questions, not as a prediction.
Every lookup stores Tesla’s latest estimate, so the life line of a car fills in as readings accumulate. That history is something Tesla’s own service does not give you.
What to do with this when buying
Compare cars of a similar age and distance driven, ask how they were charged, and look at the date of the measurement. The full list is in buying a used Tesla; the meaning of each figure is in Tesla battery health.