- Recurrent estimates 91% battery health after one year and 25,000 miles.
- The Model Y still covered nearly 300 miles in a highway range test.
- Battery degradation is usually steepest early in an EV’s life, then slows.
It seems the brunt of an EV’s battery degradation happens early on and then tapers off, as large-scale battery tests suggest. After one year and around 25,000 miles, YouTuber Andy Slye checked the battery health of his 2026 Tesla Model Y Premium Rear-Wheel Drive after one year of ownership, and it showed an estimated 91% of its original battery health remaining—but he sees little reason for concern.
Slye did not perform Tesla’s full overnight battery-health test, which requires the car to stay plugged into an AC charger for over 16 hours while it discharges the battery to near empty and then charges it fully. Instead, he used Tesla’s in-app diagnostic, which returned only a general “healthy” verdict.
The 91% figure comes from Recurrent, a third-party service that estimates battery health by analyzing data collected from the vehicle. It works by recording information such as the battery’s state of charge, estimated range, mileage, charging activity, and temperatures, then comparing it with data from similar vehicles to produce an estimate.
But Slye says he isn’t worried about the apparently high early degradation of his Model Y’s battery. He previously ran a range test from full all the way down to 0%, driving mostly at interstate speeds, and managed to cover almost exactly 300 miles. He estimates that an 80% daily charge should provide around 240 miles of real-world range, which he says is more time than he’d like to drive without stopping anyway.
The apparently high degradation shouldn’t be attributed to much fast charging. Slye mostly charges his Model Y at home and only occasionally plugs it in to a Supercharger. It has also spent its first year in Kentucky rather than a consistently hot climate like Arizona, which is another factor known to accelerate battery aging.
The result is consistent with what Voltest considers normal degradation for a nickel-based long-range Tesla like Slye’s. These cars seem to experience their largest decline during the first two to three years or 50,000 miles. Voltest considers roughly 90% state of health a useful reference point for the initial drop before the degradation curve flattens.
This early decline doesn’t really tell us how the battery will fare over the next 100,000 miles, since many factors influence it. But we’ve seen a three-year-old high-mileage Model 3 taxi retain 88.5% capacity, while the 2015 Model S P85D I recently drove had an estimated 86% remaining after nearly 160,000 miles.
