Tesla battery packs are justifiably famous for holding up well. Active liquid cooling, sophisticated battery management, and over-the-air updates mean the average Tesla loses significantly less range over time than the average EV from any other brand. That's the good news.
The problem is that "average" is doing a lot of work in that sentence. High-mileage Supercharger-dependent Model 3 Performance examples can degrade at nearly double the rate of a gently-used Long Range. And unlike other EVs, you can't see real SOH percentage in the car — Tesla only shows you a range estimate, which is a calculated figure, not a measurement.
Typical SOH by Model and Age
These are realistic ranges for UK-market Teslas in private use. Add 1–3% deduction for heavy Supercharger use, and another 1–3% for hot-climate cars imported from the US or Europe.
Model 3 (2019–2022): 88–94% — LFP Standard Range Plus degrades slightly slower than NCA Long Range. Generally good.
Model 3 Performance (older): 85–92% — hard-driven examples often at the lower end. Test it.
Model Y (2021–2023): 89–95% — newer packs, less real-world data, generally excellent.
Model S (2016–2019): 80–90% — older NCA packs, watch for BMS calibration issues. Test it.
Model S (pre-2016): 72–85% — high-mileage early cars can be considerably lower. Risky.
Model X (2016–2019): 80–90% — heavy car, heavier demand on the pack. Test it.
Why the Tesla App Won't Tell You the Truth
The Tesla app and in-car display show you estimated range, not State of Health. That range figure is calculated from recent driving data, temperature, and the BMS's own model of the battery — not from a direct measurement. It can be optimistic, it can be pessimistic depending on recent conditions, and it cannot tell you how much of the original factory capacity remains.
Two Teslas with identical range displays can have very different SOH. The car with conservative driving in mild weather will show the same figure as a car with a genuinely healthier pack. You need independent measurement to know which one you're looking at.
The Five Red Flags That Should Stop the Sale
- SOH below 80% on a car under 5 years old. This indicates above-average degradation — likely heavy Supercharger use or a thermal event.
- Significant cell imbalance in the pack. Individual cells degrading faster than others causes the BMS to limit charge and discharge to protect the weakest cell, reducing usable range further than SOH alone suggests.
- Evidence of battery replacement without full documentation. A replaced pack isn't inherently bad, but the paperwork must show a genuine Tesla-sourced or authorised replacement — not a grey-market refurbished unit.
- Cleared fault codes in BMS history. An OBD scan reveals codes that have been cleared but were present — often the sign of a seller managing symptoms rather than addressing causes.
- SOH drop of more than 3% per year. Tesla's expected degradation for a well-maintained car is roughly 1–2% per year after the first year of ownership. Faster than 3% per year suggests something is accelerating the loss.
Supercharging, Cold Weather, and the Welsh Climate
Wales is actually good for Tesla batteries. Cooler temperatures and mostly moderate speeds reduce the thermal stress that accelerates degradation. Cars that have spent their life in South Wales on slow home charging are among the best-preserved used EVs you'll find — significantly better than equivalent cars from warmer regions or with motorway-heavy histories.
The exception is rapid charging frequency. A Welsh Tesla that's been rapid-charged daily — at work, or on regular long-distance runs — will degrade faster than its climate advantage would suggest.
What a PAD Aviloo Test Gives You on a Tesla
The Aviloo Flash Test works on all UK Tesla models from 2016 onwards, including Model 3, Model Y, Model S, and Model X. The test is non-invasive, takes around 3 minutes, and the certificate is issued digitally on site.