Cost per mile makes no sense as that isn't how people see cars. It's more like "membership fee plus marginal per mile". 20K miles is quite high, I probably do about half that, so I guess that swings more in favour of petrol.
That said, it wouldn't surprise me to see car leases priced per mile (probably with an exponential reduction for higher mileages) being offered in the market at some point, including charging.
So about 8 months ago I ordered a Kia Niro EV to replace an ageing Renault Scenic. I then had to persuade the wife...
Based on the 10,000 miles a year the Renault was doing, I showed that over 6 years, the new car will break even compared to the Renault:
Avoidance of £2k repairs required for next MOT
Avoidance of £1k cam belt change due January
"Fuel cost" of 1.8p per mile (when charged at home, but we only do a few long journeys per year so public charging costs will be negligible) versus 30p per mile (and even more now).
Avoidance of whatever else was going to go wrong with it next for a 7 year warranty.
I mean, just the fuel savings alone almost pay for the monthly PCP payments! In reality we're saving even more because I use my Peugeot 208 less in preference for the EV.
In the real world it has 200 mile range at motorway speeds. In practical terms this means stopping around every 2.5 to 3 hours on a long journey. It's not the fastest charging car in the world, but 30 minutes will put in enough for another 2 hours of driving at motorway speeds. Norfolk to Cardiff with one stop is easy. Coming back we set off with 40% charge, stopped at Chippenham for 20 minutes and then for another 20 minutes somewhere on the M25. (And I never even got charged for the second charge because it just never came through on the account linked to the RFID card I used). It was at Shell, and given they make about £45k profit every minute of the day at the moment I don't think they'll miss it.
My wife was concerned about range, charging etc but is fully converted.
Much more relaxing drive, quiet and so effortless. I can do 5 or 6 hour journeys and not feel fatigued when I arrive. Overtaking on country roads is a doddle.
I will never, ever buy another ICE car again. BEV is just better in every way and if it's got a WLTP range of 250+ miles that's enough for all practical purposes.
Public charging costs will come down again (in fact one network has already reduced their prices from the peak) and over the next 5 years electricity is going to get super cheap so I'm not sure why anyone would want to continue paying £2/litre for fuel.
Until about 12 month ago I was an EV sceptic, thought they were useless and impractical etc. Then I drove one...