How many appliances would run to be the equivalent of a car? So, the capacity may be down to 2 to 3 cars before the switch flips.
The top and bottom of it is, batteries are the Achilles Heal. If they can advance Graphene Supercapacitors technology to have battery capacity, charging will be one to two minutes.
Not likely.
The rate at which a battery can be charged (or a capacitor) is one part of the problem.
A gallon of gasoline contains the equivalent of roughly 33.7 kilowatt-hours of energy that can be released by burning it. My present car has, I think, a fourteen-gallon fuel tank. So, {14 33.7 ×} about 470 kilowatt-hours of energy in my fuel tank, when full of gasoline. Let's say I coast in to a gas station, my car having just run out of gas a dozen feet short of reaching the pump. Having barely coasted to the pump, let us suppose it takes me about five minutes to fill my tank. ( think I am being pessimistic in this estimate. It's probably closer to two or three minutes, depending on the pump, but let us assume five.) So, fourteen gallons of gasoline, 470 kilowatt-hours of energy, in 5⁄60 of an hour. {470 1000 × 5 60 ÷ ÷} about 5,600,000 watts. Not sure what voltage car chargers run at, but let us assume 480 volts, which is the common high industrial voltage. So, 5.6 megawatts, at 480 volts, would be 11,750 amperes.
No!
You are not going to be charging any electric car at a rate of 11,750 amperes. It simply isn't going to happen. Period. Do you have any idea how big a wire it takes to safely carry that much current? I'm an electrician, and I have no clue. None of the references that I have at hand go nearly that high. Wires that I have worked with, big enough to be unwieldy and impractical for a consumer to try to connect to a car only go up to about a thousand amps or so.
And I was assuming five minutes. You're talking about two or three. So, now we're talking about power in the 10 to 14 megawatt range, currents in the 20,000 to 30,000 ampere range.
Is it even possible to get a connection from the grid to the electrical counterpart to a gas station, with that much capacity? I very much doubt it; especially when you consider that such a station would want to have several chargers, just as a gasoline station has several pumps.
And there is certainly no way in Hell that you're ever getting that sort of capacity to a residential building.