A Study on Real-Life Tesla Battery Deterioration

It's no wonder that people worry about electric car battery deterioration. Not only does a degraded battery mean a shorter range on a full charge, but buying a replacement battery, if necessary, would set you back thousands. The real question on everyone's minds is—how well does an electric car battery last?

To help answer this question for the renowned electric car maker, Tesla, NimbleFins experts analysed owner-submitted data submitted between 2013 and 2022 from Plug In America for Model S cars made between 2013 and 2019. We now have nine years of data from which to draw some longer-term conclusions about the longevity of Tesla batteries. This study follows our previous study of the Nissan Leaf battery performance.

• How do Tesla batteries degrade over time?
• How do Tesla batteries degrade according to mileage?
• Tesla battery life
• Tesla battery replacement cost

Tesla Battery Degradation by Age of Car

What happens to a Tesla battery after a few years of driving and charging? As you can see in the chart below, a new car starts off giving over 100% of the EPA range, but from there the battery does indeed deteriorate over time. The study data showed that by seven years old the average Tesla battery still provides around 93% of its original capacity and range.

In the chart below, you'll see a significant drop off in year 8. This is because the cars that are part of the study in the 8, 9 and 10-year-old buckets have pretty high mileage readings on their odometers. For example, the average mileage for the 8-year-old bucket was 176,000 miles, whilst the 7-year bucket was a noticeably lower 100,000 miles (the higher mileage for the 8-year-old cars is why they have more battery deterioration). From this data, we can draw the conclusion that mileage is also a considerable factor in how quickly a battery deteriorates—this makes sense, as more miles driven means more charge cycles, and it's mostly the charge cycles that reduce a battery's usable capacity.

Below, we've illustrated the same data in a column chart so you can see the average battery capacity at each year of a car's life. While there is some variation from year to year, it seems that a car loses around 1% of range a year for the first 7 years or so, but then the rates increases. By ten years of age, cars were down to 82.5% of the original capacity. As we discuss in the limitations section below, few data points for the oldest age buckets make this data less reliable, however.

Tesla Battery Degradation by Mileage

Will you still get decent range after your car has covered 50,000 miles, 100,000 miles or even more? The data from the study shows that the average Tesla battery still regularly provides over 90% of the original range up through 100,000 miles or more on the odometer. Past 125,000 miles or so, the range starts to drop off, but cars in the survey still delivered over 80% of their original range even at the highest mileage levels.

For example, the handful of cars with 200,000+ miles were still getting 81 - 87% of their original range, equivalent to over 200 miles.

The chart below shows the type of range you could expect to achieve depending on how much you drive and the mileage you'd expect to put on your car while you own it.

Tesla Battery Life

How long does a Tesla battery last? The data shows that a typical Tesla battery will last in excess of 10 years. We say this with some degree of confidence because even the 10-year-old batteries were still delivering around 80% of the original range.

Tesla Battery Replacement Cost UK

The experts at NimbleFins have contacted local and national service centers to learn about the cost of a Tesla battery replacement. Our research indicates that a Tesla battery replacement starts from a range of £8,000 plus labour (Tesla repair centre) to £10,000 including labour (independent repair shop). We've heard some readers think the figure could be even higher.

The service department specialists reported that they don't really have a fixed cost for a battery replacement, as this can vary and would be determined by their systems when the part fails. We should point out that larger batteries would typically cost more to replace than smaller batteries, so a long range battery will probably cost even more.

One point to note is that it's possible to buy an extended warranty to cover battery failure after the standard 8-year battery warranty expires. The independent Tesla repair shop we spoke to charges £899 for a 3-year extended warranty that includes breakdown.

Insurance for a Tesla

Given the high cost of a battery, it is important to have good, comprehensive car insurance to protect your financial investment in a Tesla. To learn more about car insurance for EVs, including Teslas, please see our article on the average cost of EV insurance and also our article on the best cheap car insurance. And you can find deals for your Tesla car insurance by comparing prices—if you're ready to get started, click the link below.

Methodology

We downloaded owner-submitted information on the Tesla Model S from Plug In America which provided data for over 500 cars including the purchase date, battery size, EPA range and, for the date of submission, the odometer reading and estimated range (for a full charge and/or a partial charge—and what percentage charge achieved at that point).

Then we had to scrub the data, looking for human error data entry mistakes. For instance, there were instances of battery charge percent that didn't make sense (e.g., 900 for the percent charged) or where it was clear that the range and percentage charge had been swapped (e.g., values 80 for range and 267 for percent charge were probably meant to be entered as 267 for range and 80 for the percent charged). We either made corrections where the error seemed obvious or deleted a data point where we were unsure. We also removed some data points that seemed 'to good to be true'—if in fact these points were correct then the Tesla S battery performs even better than we show in this study. (An example of a 'to good to be true' was a data point for a car that was over 6 years old and reportedly getting 125% of the original estimated range.)

We also removed cars that had had a battery replacement, as these would muddy the results.

To determine the level of deterioration in a battery, we calculated a ratio by dividing the full range at the time of survey by the EPA range for that car. This allowed us to include cars with batteries of different sizes.

For the full range estimates, we included both full charge ranges and also converted partial charge ranges, since many people do not charge their battery to 100% capacity. For these, we divided the partial charge range by the percentage charged to estimate a full charge range. For example, if an owner entered a range of 200 miles for an 80% charge, we estimated that a full charge would achieve a range of 250 miles (200 divided by 80%).

Next, we organised the data and cut it according to a car's age or mileage and graphed it. For the column charts we then grouped the data into buckets to further observe trends in the data.

Study Limitations

This study is meant to give a general idea of how a Tesla battery performs in terms of available range over years of use and mileage. There are some limitations to this study, including: