Inaccuracy of official EV range figures exposed

Official testing of electric car ranges is completely unrepresentative of real-world conditions, potentially leaving drivers disappointed and with insufficient mileage, What Car? testing has revealed.

The official Worldwide Harmonised Light Vehicle Test Procedure (WLTP), which is used to measure range, was found to be particularly unrealistic in cold conditions, where the shortfall reached almost 40% for some cars.

Comparing a selection of 12 new fully electric vehicles (EVs), the latest What Car? winter range test found that none of the cars could get within 20% of the official figures, which manufacturers are legally required to publish.

This is because the official tests subject EVs to unrealistically gentle acceleration and are conducted in a laboratory at an ambient temperature of 23deg C, instead of at colder temperatures where batteries are less efficient. Indeed, What Car?’s real-world testing shows an average drop in range of 18% in winter versus summer conditions.

What Car? is calling for a new testing regime which provides drivers with realistic range estimates for both summer and winter conditions, to ensure buyers aren’t left disappointed and put off electric cars. However, in the absence of this, the What Car? Real Range testing provides drivers with figures that are in line with what they can expect to achieve on the road. 

To find out how far the 12 EVs could really go on a full charge in winter, we took them to a private test centre and drove them until their batteries were flat.

The 12 cars were charged to 100%, before being left out in the open overnight, for roughly 14 hours in 6-10deg C ambient conditions. Then the following morning they were plugged in again to check they were still fully charged, plus their tyre pressures were checked to ensure these were at the recommended levels, the climate control systems were set to 21deg C and the headlights were switched to dipped beam.

Eco (or the closest equivalent) driving mode was selected, and the cars were left in their default regenerative braking setting – or if an ‘automatic’ or ‘adaptive’ mode was available, this was selected.

For the tests themselves, the cars followed a route of roughly 15 miles, which included 2.6 miles of simulated stop-start urban driving, four miles at a steady 50mph and eight miles at a constant 70mph. At the end of each loop, there was a driver swap and a change in running order so that no car was at a disadvantage.

Two of the EVs tested got very close to, or reached, 300 miles on a full charge: the Mercedes EQE 300 Sport Edition managed exactly 300 miles, while the Tesla Model 3 Long Range achieved 293 miles. In addition, the EQE got closest to its official range (it fell 21% short).

By contrast, the driving conditions (10-11deg C) proved most challenging for the Lexus UX 300e Takumi, which fell 37.9% short of its official range.

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Read the full winter range test story >>