How the verdict works

Last updated 2026-10-17.

EV Deal Check answers one question: is this used electric car's battery good value? It does not check whether the price is fair for the market. Everything is worked out in your browser from published data.

1. Battery health now

• If you type a battery health % from a battery report, we use it. A report measures battery capacity.
• If not, we estimate it: 100% minus the model's wear rate (% a year) times the battery's age in years. The estimate never goes below 50%.
• Wear rates come from fleet studies. Some measure battery capacity (Geotab, AVILOO). Tesla figures (Recurrent) measure range loss, not capacity. Every figure says which.
• Battery age counts from the model year. We have no source for wear per mile, so mileage does not change it.

2. Range

• Range now = the official range when new (EPA in the US, WLTP in the UK) × battery health.
• Range in 3 years uses the same wear rate for 3 more years, never below 50%. A battery already below 50% is shown as staying where it is: it never goes up.
• Winter loss is a % from a published cold-weather test. We only turn it into miles when the test used the same baseline as the official rating. Otherwise we show the % only, because percentages against different baselines are not comparable.

3. Battery life left

• Battery life left = the years until battery health falls to 70%, at the model's wear rate.
• Price per year of battery life = the price ÷ battery life left. The compare tool ranks cars by this.

4. Replacement cost and warranty

• Replacement cost vs price = the battery replacement cost ÷ the car's price.
• A car is under battery warranty when its battery is younger than the warranty years, it has miles left (or the warranty has no mileage limit), and the warranty is not stated as non-transferable.
• Warranty years count from the model year. The real warranty starts on the first registration date, so check it: it can be up to a year different.
• No sourced warranty means "not covered". That can only make a verdict more careful, never better.

5. The verdict

• Good: at least 8 years of battery life left, and either under warranty or a replacement cost of at most 50% of the price.
• Bad: under 3 years of battery life left, or out of warranty with a replacement cost above 100% of the price.
• Fair: everything in between.
• A low-confidence figure alone can never make a car "bad". The verdict is then "fair", with a warning.

6. Confidence

• Each verdict shows a confidence: high, medium or low. It is the lowest confidence of the facts it relies on.
• A sourced or data-set figure is high. An estimate is medium. A projection over years of use is at most medium. A battery report you type is high.
• Replacement costs: a maker's list price or a real invoice is high; a quoted range, garage guide or recall average is medium; a cost converted from another currency or scaled from a similar battery is low. A cost drops one level if labour is not included, and one level if it was priced more than 4 years ago.
• A warranty whose transfer to a second owner is not stated drops one level.

7. Chevy Bolt recall batteries

Many Bolts got a new battery under GM's recall. The tools show two results: one for the original battery and one "if the recall battery was fitted". The second counts the battery's age from the earliest year the recall batteries were fitted, or from the car's model year if the car is newer (a battery cannot be fitted before the car was built). So the new battery is treated as old as it could be. It also counts all of the car's miles against the recall battery's warranty, because we cannot know the miles since fitting.

8. Badges and sources

• sourced: a quote from the linked page states the figure.
• data set: a row from an open data set (EPA fueleconomy.gov or Open EV Data).
• estimate: we worked it out or borrowed it from a similar car. The model pages show how. Our own calculations, such as expected health, are always estimates.
• Every figure links to its source with the date we checked it. See all sources.

What this does not do

• It does not check the market price, the car's history or its condition.
• It does not test any one car. A battery report from a real test of the car beats any estimate.