The EV Brand With The Slowest Battery Degradation Isn’t Tesla

A new study into battery longevity ranks the Kia EV6 at the top, and also reveals that degradation may not be such a big deal.

Kia EV6

Photo by: Kevin Williams/InsideEVs

Rob Stumpf

By: Rob Stumpf

Oct 26, 2025 at 9:14am ET

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A new study has crowned the Kia EV6 the king of battery health. Tesla's Model Y also ranked highly.
80% of used EVs and PHEVs, according to the study, retained 10% or more of the battery's usable capacity.
The study also found that hard use is tougher on the battery than calendar age and miles.

It feels like it was just yesterday when you could hop on Reddit or Facebook and see electric-vehicle naysayers spreading battery longevity panic, as if EVs would end up deader than your three-year-old iPhone. It turns out that concern may have been a bit overhyped. Partly thanks to evolving battery tech, EV battery longevity is surprising researchers.

Swedish used car broker Kvdbil analyzed data from 1,300 used EVs and plug-in hybrids to determine how the cars' batteries have aged. Not only did it provide some interesting insight into how used battery-powered cars fare years later, but it also helped crown one particular EV king of battery health: the Kia EV6. And right behind it is the electric Kia Niro, too.

Kia EV6 Battery

Photo by: Kia

Kvdbil's study looks at the State of Health (SoH), which is a way to measure how much usable capacity an EV's battery has lost over time. The results are almost anti-climactic, but that's a good thing because it means that EV batteries are performing significantly better in the real world than most engineers could have hoped.

Across the entire 1,366-vehicle sample—723 EVs and 643 PHEVs—eight out of ten cars studied retained 90% or more of the original battery capacity. In the Kia EV6's case, it showed the least degradation of all models tested. So after years of road use and gobs of miles on the odometer, the model consistently held a better charge than other EVs studied

"We were a bit surprised that there were so many that were this good," said Martin Reinholdsson, the test manager at Kvdbil, according to the Sweden Herald. He continued to say that even though Kia topped the study, the firm concluded that battery SoH was more related to overall use and environmental factors rather than the manufacturer.

"It is not really tied to a typical car or typical car manufacturer. It is more to the wear, that is our analysis of it," said Reinholdsson. "Age, climate, driving style and charging habits: They play in as fairly large factors on the wear."

Here are the top-10 ranking EVs and PHEVs in the study:

Brands With Highest SoH Models With Highest SoH PHEVs With Highest SoH 1. Kia Kia EV6 Kia Sportage 2. Audi Kia e-Niro Kia Optima 3. Opel Tesla Model Y Volvo XC60 4. Tesla Opel Mokka-e Kia Creed 5. Mercedes Mazda MX-30 Volvo V60 6. Peugeot Audi Q4 e-tron Peugeot 3008 7. Volvo Fiat 500e BMW 530e 8. BMW Volvo XC40 Recharge Volkswagen Passat GTE 9. Volkswagen Citroen e-C4 BMW X1 10. Skoda Volkswagen ID.4 BMW 330e

Reinholdsson's advice outlines points that we've all heard before: don't charge your vehicle past 80% regularly (something applicable more so to non-LFP packs), avoid fast-charging when possible, steer clear of operating in extreme weather and avoid leaving your car fully charged for long periods of time.

Interestingly, Kvdbil's finding of an average 10% SoH loss is identical to another study by British EV dealer RSEV. We covered RSEV's findings back in January, but here's the most relevant snippet:

On average, cars retained 90% of their battery capacity for 90,000 miles. That's already impressive. But consider, too, that battery degradation is the strongest within the first couple of years.

That means that a car with 130,000 miles on it retained 85% of its initial battery capacity. That means we've seen plenty of examples of cars getting past 200,000 and even 300,000 miles with 80% capacity or more.

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As EVs age, it's becoming clear that the old fear of batteries being tossed aside due to usable capacity is a thing of the past. And when they finally do go kaput, replacements are becoming cheaper, and avenues for recycling are becoming abundant.

Maybe the real problem here is one of marketing and education: Automakers aren't doing a good enough job of convincing consumers that EVs can have the same longevity as an old 1992 Honda Accord. If automakers worked on getting the word (and these kinds of studies) in front of people a bit more, perhaps they'd be a bit more willing to purchase one as their next car.

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