Home off-peak to public rapid is roughly a tenfold difference in price per kWh. No two mainstream EVs differ in efficiency by even twofold — so the socket sets your running cost, not the car.
At UK off-peak rates an efficient EV runs at about 2p a mile; the same car on public rapids costs about 22p, against roughly 15p for a 45 mpg petrol car. Charging exclusively on rapids can cost more per mile than petrol, which is the opposite of what people expect when they buy one. You also pay for the energy that never arrives: the meter counts what the charger draws, and about 12% of it is lost on home AC charging.
It stops holding where the price gap closes. Somewhere with cheap public charging and expensive domestic electricity narrows the tenfold spread to something modest, and a driver who cannot charge at home has no choice to optimise in the first place.
Estimate with the rule, then check it against the calculator that models it properly.
Open EV Charging & Running Cost →Home off-peak to public rapid is roughly a tenfold difference in price per kWh. No two mainstream EVs differ in efficiency by even twofold — so the socket sets your running cost, not the car. At UK off-peak rates an efficient EV runs at about 2p a mile; the same car on public rapids costs about 22p, against roughly 15p for a 45 mpg petrol car.