Journal · August 10, 2026 · updated July 13, 2026
Tesla Battery Degradation: How to Measure It on Your Own Car
A Model Y never shows a battery-health percentage — Tesla doesn't display one on the car or in the app. So the question "how much capacity has mine lost?" has no direct answer, only a proxy. This page explains the proxy, what the published studies found across real fleets, and how to build a trend for your own car that's worth more than any average.
The number Tesla doesn't show you
There's no "battery health: 94%" screen on a Model Y the way there sometimes is on other EVs. The closest proxy an owner has is the rated range shown at a 100% charge: compare it to what the car displayed when new, under similar temperature and on the same wheel and tire size, and the drop is a reasonable stand-in for capacity loss. It isn't a lab measurement. A single reading can be skewed by cold weather, a software update recalibrating the range estimate, or a change of tire — so a trend built from several 100% charges over time is worth far more than one screenshot.
What the published data actually says
Tesla's own vehicle warranty guarantees a minimum of 70% battery capacity retention over 8 years / 100,000–120,000 miles depending on trim — that's the contractual floor, not an expectation. Geotab's fleet study of more than 22,700 EVs found an average annual degradation rate of 2.3%, projecting 81.6% retained capacity at the 8-year mark, with most loss front-loading in the first 20,000–30,000 miles and then flattening rather than tracking a straight line. Recharged's aggregated Model Y data puts typical real-world loss at 5–8% by 100,000 miles, with Tesla's own fleet figures showing roughly 15% by 200,000 miles on Long Range packs.
Those are the three sources we could verify. Each is linked at the foot of this page — check the dates on them, because fleet studies get revised.
The one habit the data singles out
Geotab's study isolates charging power more clearly than any other variable: vehicles leaning heavily on high-power DC fast charging (above 100 kW for more than 12% of sessions) degraded at roughly 3.0% a year, against about 1.5% a year for those charging mostly at lower power. That's close to double, and it's the one finding worth changing behaviour over. The rest of the standard advice — avoid sustained high states of charge, avoid leaving the car hot and full — appears in Tesla's own support content and in every serious study, but without the same size of effect attached.
How to build a trend for your own car
This is the part that produces a number you can trust, because it's measured on the car you own:
- Take a baseline this week. Charge to 100% and note the rated range, the odometer, the ambient temperature and your current tire size. Without those four together, a future comparison isn't like-for-like.
- Repeat in about six months, in comparable weather. Two readings a season apart beat six readings in one month, because temperature moves the estimate more than a year of degradation does.
- Compare the trend, not the pair. Three or four readings over a couple of years show a shape — front-loaded then flattening, per the Geotab data — and a shape is diagnosable where a single delta isn't.
- If you're buying used, ask for the same series. A seller's one screenshot of a range figure tells you almost nothing; a history tells you what the pack has been doing. Recharged makes the same point: a reading with no history behind it "only tells part of the story."
The honest summary: published fleet data gives you the expected range of outcomes, your warranty gives you the floor, and only your own tracked series tells you where your specific car sits between them. No third party — including this page — can supply that middle number for you.
Sources:
- Tesla Support — Vehicle Warranty
- Geotab — EV Battery Health study (22,700+ vehicles)
- Recharged — Tesla Model Y Battery Degradation Guide