Charging an electric car at motorway services can cost 8p a mile more than filling up with petrol or diesel, research reveals.
Testers plugged two EVs into rapid and ultra-rapid public chargers to establish how much it costs per mile.
The figures, based on costly pay-as-you-go tariffs, will raise eyebrows among users who believe EVs are economical as well as ecofriendly.
Which? looked at running costs of a family Hyundai Kona and a more powerful Mercedes-Benz EQC.
With a 55p per kwh ultra rapid charger, the EQC cost 24p per mile. It was 16.2p for the petrol equivalent and 19.5p for diesel.
The Kona cost 14.8p per mile using an ultra-rapid charger, compared to 13.6p for the petrol.
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EVs are expensive to buy compared to traditional models. Home chargers are typically £700 to £1,500 – but are then cheaper to run, if slower.
Which? found the EQC cost as low as 3.3p per mile and the Hyundai Kona just 2p when charged off-peak overnight at home.
The Government wants to stop sales of new fossil fuel powered cars by 2030.
But Steve Gooding, director of the RAC Foundation, said: “People who opted for electric cars on the promise of cheap per-mile motoring might well be shocked by these findings.
"Drivers who charge cars where they live are still likely to be well in-pocket, but not everyone has that option. Only two-thirds of homes have off-street parking, meaning drivers reliant on public charge points need to shop around.
“Throw in the rising cost of energy – and the Government’s desire to recoup the money lost from declining fuel duty revenue – and drivers considering battery-powered might need to look at their sums.”
Many EVs do fewer than 200 miles, so M-way journeys can require a re-charge on machines, taking 15 to 40 minutes.
Researchers looked at those charging 50p per kilowatt-hour or more, which is not uncommon.
There are more than 32,000 charge points in the UK, of which 6,000 are rapid or ultra-rapid.
The average cost of rapid charging has risen from 35p per kwh in December to 44p, while slower charging rates are up from 24p to 35p. That is due to the soaring cost of generating electricity.
Natalie Hitchins, Which? head of home products and services, said: “EVs are fantastic, but some chargers are so expensive that they cost more to use than filling the equivalent-sized car with petrol or diesel.”
There are 400,000 EVs in the UK – exempt from road tax and congestion charges.
The AA’s Jack Cousens said: “EV drivers want to see cheaper charging and the right mix of reliable chargers across the board.”
