High-mileage EVs pass MOTs better. Check the battery

High-mileage electric cars are about 25% less likely to fail their MOT than petrol cars covering the same distance. That's the headline from new research published on 22 September by the British Vehicle Rental and Leasing Association (BVRLA), which asked the independent transport research group New AutoMotive to crunch 47.4 million MOT tests.

For anyone eyeing a used EV with a big number on the odometer, it's reassuring. It also comes with a large asterisk shaped like a battery.

Beyond around 60,000 miles the failure rate for EVs flattens while the petrol failure rate continues to rise.
— Ben Nelmes, chief executive, New AutoMotive

The numbers behind the headline

At low mileage there's almost nothing in it. Between 20,000 and 40,000 miles, 12.0% of battery electric cars failed their MOT, against 11.7% of petrol cars. The gap opens as the miles pile up. EV failure rates level off at about 16% from around 60,000 miles, while petrol keeps climbing.

Between 90,000 and 120,000 miles, 16.5% of EVs failed compared with 22.1% of petrol cars. That's where the "25% less likely" figure comes from. Above 120,000 miles it was 16.0% against 23.5%.

The research also looked at how many cars disappear from the road. By age 15, 5.4% of electric cars had left the road, against 11.9% of petrol cars. And older EVs aren't being tucked away in garages: at every age from four to 16 years, they had a higher median annual mileage than petrol cars. At 12 years old, that was 4,920 miles a year against 4,410.

Where EVs do worse

It isn't a clean sweep. EVs recorded about 1.8 times as many tyre defects as petrol cars, particularly early electric models adapted from petrol platforms. Brakes were mixed: high-mileage EVs had far fewer brake problems, but older, low-mileage EVs showed more friction-brake defects caused by corrosion from lack of use.

The feared weight penalty on suspension didn't show up. Between 60,000 and 90,000 miles, EVs recorded 4.7 suspension defects per 100 tests against 6.1 for petrol cars.

The battery-shaped asterisk

Here's the catch, and to its credit the report says so plainly. It doesn't measure battery health, degradation or charging performance. An MOT checks tyres, brakes, lights and suspension. It doesn't tell you whether a ten-year-old EV's battery still holds 90% of its charge or 60%.

For a used EV buyer in the UK, that's the most expensive question. So Ada's take is simple: this research makes a good case that an EV's mechanical bits age better than a petrol car's. It doesn't tell you the car is a good buy. BVRLA chief executive Toby Poston seems to agree: "This isn't an argument for buying a used EV without doing your homework."

In practice, that means asking for a battery health report before you buy, checking the tyres closely, and looking through the car's MOT history for signs of corroded brakes on low-mileage cars.

To be fair to the BVRLA

Yes, the BVRLA represents leasing and rental companies that put huge numbers of used EVs back on the market, so it has an interest in buyers feeling confident. But the analysis was done by an independent research group, it's based on tens of millions of real MOT tests rather than a survey, and it's upfront about what it doesn't cover. As Poston puts it, "Mileage has always been one of the first things people look at when buying a used car... This research suggests we need to think differently." On the evidence, that's fair.

Mind the hype. The mileage may be high, but check the battery before you check out.

Sources: Renewable Energy Magazine, Auto Express, EV Powered