How a report is made
Every figure on a report is one of five things: reported by Tesla, calculated by us, compared with other cars, entered by a person, or not available. This page says which is which, what each one is and how far to trust it.
What each field is
| Field | Kind | What it is |
|---|---|---|
| State of health | Reported | Tesla’s estimate for the VIN, with Tesla’s own timestamp: the day the car reported it. We never grade it. |
| Capacity in kWh | Reported | Tesla describes it as the estimated usable (net) energy of the pack. Tesla gives it no timestamp, so the day of the report dates it. |
| Date of the reading | Reported | Tesla’s timestamp, worded “reported by the car on”. Where Tesla gives none, the day of the report, worded “read on”. |
| Car and equipment | Reported | Model, model year, trim, build date, paint and options as Tesla lists them for the VIN. |
| Original price | Calculated | Tesla’s total price for the car, with the currency inferred by us. |
| Factory, serial and check digit | Calculated | Worked out from the characters of the VIN. |
| Age at the reading | Calculated | From Tesla’s production date to the date of the reading. |
| Reference and grade | Calculated | Our reference for the exact pack and our own scale: see the reference and the grade below. |
| Standing among comparable cars | Compared | The car’s rank among comparable cars: see comparable cars below. |
| Mileage | Entered | Typed by the person who looked the car up. Never a figure from Tesla. |
| A value Tesla did not return | Not available | Shown as not reported, never as zero or a guess. A 0% from Tesla counts as not reported. |
In the app, a line under the figures names which is which: “Reported by Tesla”, “Derived by us” and “Not available”.
Not a battery test
We did not examine the car. What you get is Tesla’s estimate as of one date: it can be missing, change after a software update or differ from a workshop measurement. A dealer’s figure comes from the dealer’s method, so the two numbers can differ.
It is not a warranty, not a condition report and not advice about a price. It does not assess the battery’s safety and does not predict its remaining life. What the percentage means is explained in our guide to Tesla battery health.
Two figures, two dates
The percentage carries Tesla’s timestamp. The kWh figure carries none, so the day of the report is its date. The two can be months apart, and we never say that both were measured at the same time.
The online copy of a published report marks which date is whose.
What the percentage is measured against
Tesla does not publish what its percentage is measured against. In the cars we have seen, the figure it implies (the kWh figure divided by the percentage) is nearly the same for every car of some packs and spreads between cars of others. It matches neither the marketed (gross) size nor a usable figure consistently.
So we never turn one car’s kWh and percentage into its original capacity, and we never grade Tesla’s percentage. The grade compares Tesla’s kWh figure with a reference on the same basis as that figure.
The reference and the grade
There is one reference per genuinely different battery. A car is matched to its pack by model, the factory its VIN shows, model year, the words in Tesla’s trim name and the generation.
The pack’s reference is the median of the figure Tesla’s own readings imply across several cars of that pack, each car counted once. Until enough cars have been seen, it is a researched figure on Tesla’s basis. A pack without a reference on that basis gets no grade: the report says “No grade for this model yet” and the car still gets its specification and cell chemistry.
The grade is our scale, not a Tesla rating: Excellent from 97%, Good from 92% to below 97%, Fair from 85% to below 92%, Weak below 85%.
- The reference is what the model holds when new, on the same basis as Tesla’s kWh figure. Individual cars can start above or below it.
- Tesla’s kWh reading is itself an estimate.
Comparable cars
Comparable cars have the same model and generation. LFP packs are never mixed with NCA or NMC packs. Trims count together when their references are within 1 kWh of each other, and are kept apart otherwise.
Cars are sorted into age bands of six months (one year when a group spans more than ten years) and 10 000 km mileage bands. Age runs from Tesla’s production date to the reading; mileage is what users entered. Each car counts once, however many people look it up.
A band shows a median once enough cars share it, the middle half with more, a trend line and a verdict with more still. Smaller groups are left out and no number of cars is shown, so no single car can be picked out.
The verdict is the car’s rank among its peers on capacity and degradation against the typical curve, said in one of five phrases:
- Among the best. The top 15% of comparable cars.
- Better than most. The next 25% of comparable cars.
- About typical. The next 20% of comparable cars.
- Below most. The next 25% of comparable cars.
- Among the weakest. The bottom 15% of comparable cars.
A published report freezes the verdict on the day it is issued.
How old the data is
Every figure carries its date, shown on the report. The older the date, the less it says about the battery today.
A published report is frozen at its issue date. Its online copy also shows later readings and says how many were added after the report was issued.
When there is nothing to show
Tesla does not have a battery estimate for every VIN. Battery data is most common on Model 3 from 2018 and Model Y, S and X from 2020. Older Model S and X often have none, and some VINs are unknown to Tesla.
Then we show the specification Tesla returned and say that the battery figures are missing. Such a lookup is free up to a daily allowance; after that it uses 1 lookup.
Independent of Tesla, and how to question a figure
Battery Figures is independent and not affiliated with, endorsed by or sponsored by Tesla, Inc. The battery figures are Tesla’s own estimate, and Tesla may change or limit what it provides. The service is run by Kingpin Consulting AB in Sweden.
A reading that looks wrong: choose “Looks wrong? Tell us” on the car, or contact us. We cannot change Tesla’s figure, but we can check what Tesla reported and when. To see every field on an example, open the sample report.