You’re doing the wrong sum, the argument is about the cost of heating using electric
electricity is broadly 4x the price per kwh, but you get to remove a standing charge of £100 – so based on using £600 of gas for heating, you’d be using £2,300 of electricity. That’s expensive, but not so expensive it would write a house off. Rent for a 3-bedder around here is £2000 a month, so you’d have to drop rent by 10% (which would probably drop the value of a house by 10%) compared to a passivehaus.
it will drive efficiency, but I can’t see it being cost effective to knock anything down