•However, electric car charging still remains cheaper than petrol and diesel, the motoring organisation said.
•Electric cars also usually cost thousands of pounds more than their petrol or diesel counterparts.
The cost of rapidly charging an electric car has risen sharply as energy costs soar, the RAC has said.
However, electric car charging still remains cheaper than petrol and diesel, the motoring organisation said.
Rises in electricity and gas prices, in part since Russia's invasion of Ukraine, are behind the increased charging costs.
But fuel prices have gone up more quickly as crude oil suppliers struggle to meet demand.
The price of charging an electric car on a pay-as-you-go, non-subscription basis at a publicly accessible rapid charger has increased by 21% over the last nine months, the RAC said.
Even charging at home has been getting more expensive as energy bills spiral upwards.
The cost of the electricity used to power electric vehicles varies according to the household tariff the customer is on.
But both rapid charging and home charging are still less expensive than petrol or diesel per mile.
Electric vehicle (EV) charging is nearly half the cost per mile compared to filling a family car with petrol, the motoring organisation said.
The average cost of a litre of petrol has increased by 25% since last September, and diesel by 30%, according to the RAC.
This month diesel prices rose to a record of more than £1.80 a litre.
"While electric car drivers may not be immune from the rocketing price of wholesale energy - most notably gas, which in turn dictates the cost of electricity - there's no doubt that charging an electric vehicle still represents excellent value for money compared to filling up a petrol or diesel car," RAC fuel spokesman Simon Williams told the BBC.
The three main rapid charging companies are BP Pulse, Instavolt and Osprey according to Zap Map, which records charge point distribution and costs.
Mr Williams said that "unsurprisingly" the quickest places to charge are also the most expensive with ultra-rapid chargers costing on average 14% more to use than rapid chargers.
While the RAC analysis charted on-the-road pricing, private EV owners may not use this as their primary way of charging.
The RAC said the most affordable way of charging an electric car is from home, where overnight electricity rates can be much lower than their public charger counterparts.
According to the AA motoring group, some EV car owners use tariffs as low as 4.5p per kilowatt hour during off-peak times when charging at home.
In addition, it said charging from lampposts is 46% cheaper than on-the-road rapid charging.
But it said this option is only available in some parts of the country at the moment.
"Sadly just 87 councils out of almost 400 across the UK have applied for the on-street residential chargepoint grant since 2017," said Jack Cousins, head of road policy at the AA.
"This needs to dramatically improve so that EV drivers across the country have access to good, local chargepoints," he said.
Another reason home charging can be so much cheaper than rapid charging is because of "the bizarre way that electricity is taxed", Simon Williams from the RAC added.
"Right now, VAT on electricity from a public charger is levied at a rate four-times that which applies to domestic electricity, which makes it far more expensive to charge on-the-go than it should be," he said.
Electric cars also usually cost thousands of pounds more than their petrol or diesel counterparts.
This is because EV batteries are expensive to make and a high level of investment is needed to transform existing factory production lines to manufacture the new technology.
However, costs are expected to come down in the near future: industry group the Society of Motor Manufacturers and Traders forecasts electric and internal combustion engine cars should cost roughly the same "by the end of this decade."
Melanie Shufflebotham, co-founder of Zap Map, said: "More electric cars need to be produced at a mid-price range, with the cost of living crisis it's going to be really hard for many people to buy a new car but there are subscription models."
"There should be price parity for EV cars by 2025 as the price of batteries comes down".
"Though costs are up, EV drivers are feeling happy they're saving even when charging on the most expensive public charging spots when compared to fossil fuels," she added.