The Advertising Standards Authority has criticised EV charging company Ecotricity for misleading customers in an email advising them of changes to its Electric Highway service.

In the email, which announced the company would charge users £6 per 30-minute recharge earlier this year, the company claimed the fee could work out to be cheaper than refuelling “equivalent” petrol or diesel cars.

“A rapid charge of up to 30 minutes will cost £6, significantly less than the cost of an equivalent petrol or diesel car,” Ecotricity said in its email to customers.

However, the ASA said the green energy provider failed to clarify the definition of an equal fossil-fuelled vehicle and said the comparison was “vague”.

The ASA intervened after seven Ecotricity customers complained about the misleading text.

The wording must not be used in adverts again, the ASA ruled.

“In the absence of sufficient qualification, consumers would understand that they were comparing the cost of running an electric vehicle against that of all petrol and diesel vehicles in the UK market. As we did not consider that the implied claim had been adequately substantiated, we concluded the ad was misleading,” the advertising body said.

In the same email, Ecotricity claimed its network of chargers would remain free to use for home energy customers, but three people complained the 52 free charges a year granted to users under its fair use policy didn’t accurately define free use.

“We considered that the limitation on the number of charges that consumers could obtain without paying contradicted the claim that the charging was free for Ecotricity energy customers. We therefore concluded that the ads were misleading,” the ASA said as part of its explanation for upholding the second complaint.