Interesting to note that there is ~30kWh of energy in a gallon of gasoline, so the reason EV would only take 20% of US electricity consumption is that they are 5x more efficient (than the 20mpg gas figure used).
I did not verify his figures, but his methodology was BEV efficiency, not the amount of energy in a gallon of gasoline. Electric drivetrains and cars are designed ground-up for efficiency to a degree that ICE cars are not, as well as the fact that something like 80-90% of energy in a gallon of gasoline is wasted (60-70% due to Carnot efficiency alone).