A high-mileage electric car might have a better chance of passing its MOT than a petrol car with similar mileage, according to new analysis of 47.4 million UK MOT tests.
The research, commissioned by the British Vehicle Rental and Leasing Association (BVRLA) and carried out by independent transport research organisation New AutoMotive, examined official DVSA MOT records to see how electric, petrol, diesel and hybrid cars perform as they get older and cover more miles.
The findings challenge the assumption that a used EV with a big number on the odometer is automatically a risky buy.
The important caveat is that an MOT only tells you so much about an electric car. Battery condition, remaining capacity and charging performance are outside the test, so anyone buying a high-mileage EV still needs to do some proper homework.
EV MOT failure rates improve at higher mileages
At lower mileages, there is relatively little separating electric and petrol cars once age and mileage are taken into account.
Between 20,000 and 40,000 miles, 12 per cent of battery-electric vehicles in the study failed their MOT, compared with 11.7 per cent of petrol cars.
The picture changes at around 60,000 miles. From that point, the EV failure rate levels off at roughly 16 per cent, while petrol and diesel failure rates continue to rise.
For cars between three and eight years old with 90,000 to 120,000 miles on the clock, 16.5 per cent of EVs failed their MOT. The equivalent figure was 22.1 per cent for petrol cars and 21.2 per cent for diesels.
At more than 120,000 miles, the gap becomes wider. Electric cars recorded an MOT failure rate of around 16 per cent, compared with 23.5 per cent for petrol cars.
That is a sizeable difference, although the research does not claim that every EV will be more reliable than every petrol car.
Do high-mileage EVs last longer?
The study also looked at whether vehicles continued appearing in the MOT system as they aged.
Researchers tracked vehicles through consecutive MOT years and found that electric cars remained in the dataset at higher rates than combustion-engined cars.
At age 15, 94.6 per cent of the electric cars studied returned for another MOT within 30 months, compared with 88.1 per cent of petrol cars.
That equates to an implied road-exit rate of 5.4 per cent for EVs and 11.9 per cent for petrol cars.
There is an important qualification here. A car disappearing from the MOT dataset does not necessarily mean it has been scrapped. It could have been exported or placed on a Statutory Off-Road Notification.
The research also found that older EVs were not simply surviving because owners were keeping them as occasional second cars.
Electric vehicles recorded higher median annual mileages than petrol cars at every age examined between four and 16 years. At age 12, for example, the median annual mileage was around 4,920 miles for electric cars compared with approximately 4,410 miles for petrol models.
EV tyres can be a weak point
The MOT data also shows that electric cars have some areas where they perform worse.
Tyres are the clearest example.
Across the dataset, EVs recorded around 1.8 times as many tyre defects as petrol cars. The researchers found that this was particularly noticeable among some earlier electric cars that had been adapted from combustion-engine platforms.
There are several reasons why tyres deserve close attention when you're buying a used EV. Electric cars can be heavy, while instant torque can put additional demands on the driven tyres.
That means checking tread depth, wear patterns and tyre condition should be part of any used EV inspection, especially on a car that has covered serious mileage.
Regenerative braking changes the MOT picture
Brakes produce a more complicated result.
High-mileage electric cars recorded substantially fewer brake defects in the research. That makes sense to some extent because regenerative braking allows the electric motor to handle much of the work normally done by the friction brakes.
There is a downside for some older, low-mileage EVs, though.
If the conventional brakes are used less frequently, corrosion can become an issue. The study found increased friction-brake defects among older EVs with low mileages, with the researchers linking this to the brakes being used less often.
So a car with a surprisingly low mileage is not automatically the better used EV. Its age, condition and maintenance history still matter.
EV battery health is missing from the MOT
This is the biggest limitation to keep in mind when interpreting the research.
An MOT checks whether a vehicle meets the required roadworthiness standards. It covers components including lights, brakes, steering, suspension, tyres and electrical wiring.
It does not assess the health of an EV's high-voltage battery.
The test does not measure battery state of health, electrochemical degradation, remaining usable capacity or how well the car performs when charging.
That matters because two otherwise similar used EVs with the same mileage can have very different battery conditions.
The research therefore points to battery-health information as something buyers should consider alongside the mechanical condition revealed by an MOT.
For a used EV, I'd want to know the car's service history, previous use, charging history where available and the condition of its battery before handing over any money.
Hybrids also perform strongly
Fully electric cars weren't the only powertrain to produce encouraging results.
Hybrids also recorded low MOT failure rates in the analysis. Across the total 12-month dataset, hybrids had a failure rate of 11.8 per cent, compared with 13.5 per cent for fully electric cars and 21.4 per cent for petrol cars.
The researchers are careful about what these numbers can prove. The study was designed to investigate whether concerns about electric cars becoming less roadworthy as they age and accumulate mileage are supported by MOT data.
It does not establish that one type of powertrain is universally more reliable.
That's an important distinction because an MOT failure is only one measure of a vehicle's condition.
What does this mean if you're buying a used EV?
The big takeaway is simple. A high mileage figure should not automatically put you off an electric car.
If you're looking at a used EV with 80,000, 100,000 or even more than 120,000 miles, the MOT data suggests the mileage itself may tell you less about its roadworthiness than you might expect.
Condition still matters enormously, though.
Check the MOT history for recurring advisories and failures, inspect the tyres carefully and look at the brakes, suspension and bodywork. Then go beyond the MOT and find out as much as possible about the battery.
A battery-health report can give you information that the annual MOT simply cannot provide.
Toby Poston, chief executive of the BVRLA, said the research suggests buyers should reconsider how much weight they put on mileage when assessing used electric cars. He also stressed the importance of checking a vehicle's history, condition, tyres and battery health.
That is particularly relevant as more former company and leasing vehicles enter the used market. Many of these cars have covered substantial mileage during their first few years, potentially giving buyers access to relatively affordable EVs with plenty of life left in them.
Verdict on high-mileage EV durability
The MOT evidence makes a convincing case that high mileage alone is a poor reason to reject a used electric car.
The most interesting finding is the way EV failure rates level off at around 60,000 miles while petrol and diesel failure rates continue rising. The longer-term MOT data also points towards electric cars remaining on the road at higher rates as they age.
But don't mistake a clean MOT history for a battery health certificate. It isn't one.
For me, the sensible way to judge a high-mileage used EV is to treat the mileage as one piece of the puzzle. A well-maintained car with a documented history and a healthy battery can make much more sense than a lower-mileage example with an unknown past.
The research gives high-mileage EVs a useful boost in credibility. The next step for buyers is making sure the battery gets the same level of scrutiny as the rest of the car.