Great idea - I agree!
So, what would that look like?
- 1.6 million cars: Ontario has about 8 million registered cars. 20% = 1.6 million
- 6600W electricity to charge: Electric cars charge with a 6600W electricity supply (220V * 30A) at the fastest-available home charging rate. Nissan Leaf uses a 6600W charger
- 1,600,000 * 6600 watts = 10,560,000,000 watts
Unfortunately, Ontario only produced about 17,000,000,000 watts at its peak for the overnight period 8:00pm last night to match consumption.
So, to maintain current consumption and add the load of 20% of Ontario vehicles charging overnight, we'll need to bump overnight generation by 62% to support our goal. Ontario has that capacity, but would likely not generate it at current overnight rates as more expensive generation would need to be activated to get there, so it potentially turns the overnight period into "peak consumption" period.
Unless you think the world will never run out of affordable oil or gasoline (I don't know what you'd reference to support this), shouldn't this be enough to convince most people that we need to deal with this problem, and that it might be better to look at our living/working arrangements to remove the car from the equation as much as possible?