Motorists are being warned that tests for new electric cars significantly overstate how far they can travel on a single charge with real-world driving.
An investigation by What Car? magazine found a shortfall of up to 38% in the range of electric vehicles (EVs) in low temperatures compared with official figures.
Editor Steve Huntingford warned that the testing regime which manufacturers are required to put their vehicles through is “completely unrepresentative of real-world conditions”.
The magazine stated that official analysis under the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) is conducted in laboratories with an ambient temperature of 23C, with each model undergoing an “unrealistically gentle acceleration” to record what distance they can cover before a battery with 100% charge goes flat.
What Car? did its own range tests on 12 electric cars which were taken to a site in Bedfordshire, left in the open overnight in temperatures of between 6C and 10C, and driven in a way that simulated stop-start urban conditions and on motorways.
The largest discrepancy was found with the Lexus UX 300e Takumi, which costs around £57,100 and has an official stated range of 273 miles.
It was found to only be able to cover 170 miles, a 38% reduction.
This was followed by the Lexus RZ 450e Takumi, which is advertised as having a range of 251 miles but was found to be able to cover just 159 miles, some 37% less.
It costs around £74,000.
The third biggest shortfall was for the Volkswagen ID 7 Pro Match (without heat pump), which costs around £51,600 and could only travel for 254 miles in the What Car? test, some 34% below the stated distance of 383 miles.
Mr Huntingford said: “Official testing of electric car ranges is completely unrepresentative of real-world conditions, potentially leaving drivers disappointed and with insufficient mileage.
“It is clear that the results obtained using WLTP methods are unsuitable.
“We need a new system that provides achievable summer and winter figures so that prospective EV buyers can be confident the car they’re looking at will suit their needs.
“Providing a single, overly optimistic figure doesn’t help anyone.”
Mike Hawes, chief executive of industry body the Society of Motor Manufacturers and Traders, said: “Car makers are investing billions in developing zero emission vehicles, with improved battery performance, range and charging times, to make them a compelling choice for all drivers.
“As What Car? rightly acknowledges, car manufacturers are required by law to test all vehicles of all technologies to the same, repeatable official standard – the WLTP test – and publish these results within any advertising to help car buyers make comparisons between vehicles.
“What Car? also acknowledges that there will always be a difference between lab tests and real-world use due to variations in conditions, terrain, load and driving style.
“Cold weather in particular will have an impact on range, but this has not deterred consumers in countries such as Norway and Iceland, which have the world’s highest rates of EV ownership.”