High-Mileage Electric Cars Fail Fewer UK Tests, but Batteries Go Unchecked

High-mileage electric cars failed Britain’s annual roadworthiness inspection less often than comparable combustion cars in a 47.4-million-test analysis. Yet the result leaves their most consequential powertrain component unexamined: the inspection does not measure an electric vehicle battery’s remaining capacity or charging health.

That boundary is central to interpreting research conducted by transport consultancy New AutoMotive for the British Vehicle Rental and Leasing Association. Among cars above 120,000 miles, approximately 16% of electric vehicles failed the inspection, known in Britain as the MOT, compared with 23.5% of combustion vehicles. The analysis covered cars aged three to eight years and compared vehicles by both age and accumulated mileage.

What the lower failure rate measures

The MOT is a legally required annual inspection for most UK-registered cars more than three years old. It checks minimum safety, roadworthiness and emissions requirements, including tires, steering, suspension, brakes, lights and vehicle structure. Official guidance also stresses that an MOT certificate is not a guarantee that a car will remain roadworthy after the test; a defect can develop later. Britain’s testing authority separately defines how major, dangerous and minor defects are recorded.

Within that scope, the high-mileage comparison is substantial. Electric cars with 90,000 to 120,000 miles had a 16.5% failure rate, against 22.1% for combustion cars. At 20,000 to 40,000 miles, however, there was almost no difference: 12% of electric cars failed, compared with 11.7% of combustion cars.

Ben Nelmes, chief executive of New AutoMotive, said separating vehicle age from mileage was important. According to Nelmes, failure rates for electric cars flattened beyond roughly 60,000 miles while the rate for petrol cars continued to rise. The data therefore supports a focused conclusion: in this sample, greater mileage did not translate into worse inspected roadworthiness for electric cars relative to combustion vehicles.

Why it is not a complete reliability verdict

An MOT does not assess an electric car’s usable battery capacity, charging performance or broader high-voltage system health. Nor does it test the performance and internal condition of a combustion engine or transmission. A vehicle can consequently pass its MOT while still having an expensive or operationally significant powertrain problem outside the inspection’s remit.

This distinction matters because roadworthiness and reliability describe different system outcomes. Roadworthiness concerns whether inspected components meet minimum legal standards at a particular time. Reliability concerns whether the complete vehicle and its subsystems continue performing as intended over an operating period. The MOT dataset is exceptionally large, but its size cannot compensate for variables the inspection never measures.

Battery condition also varies with design and use. A separate 2025 Geotab analysis of more than 22,700 electric vehicles found an average capacity loss of 2.3% per year across 21 models, with variation associated with charging power, climate, usage and vehicle design. Those findings cannot be applied directly to the cars in the MOT study, but they illustrate why mileage and an inspection pass are insufficient to establish the condition of an individual battery.

Electric cars showed different wear patterns

The roadworthiness advantage was not uniform across every inspected component. Electric vehicles recorded nearly twice as many tire defects as combustion cars. The analysis does not by itself establish a cause, but the result shows that removing an engine and transmission does not eliminate conventional chassis wear or the need to manage tires as safety-critical components.

Brake defects were also flagged among lower-mileage electric vehicles. Regenerative braking can reduce how frequently the friction brakes are used, and infrequent use has been suggested as a likely contributor to corrosion-related wear. The study did not demonstrate that mechanism as the cause of the recorded defects, however, so it remains an engineering explanation rather than a confirmed diagnosis.

The 47.4 million inspections provide strong evidence that high mileage alone is not a reliable proxy for poor MOT performance in electric cars. What they cannot reveal is whether a 120,000-mile battery retains adequate capacity, charges normally or is approaching a costly fault. Until roadworthiness records are paired with standardized powertrain-health information, the apparent EV advantage will remain both meaningful and incomplete.

By Thomas Caldwell — AMI’s senior editor for mechanical and mobility engineering, covering vehicle electronics, systems integration, electrification, chassis systems, propulsion, and safety policy.