Wake up, we don't talk about computers. We talk about cars. Big heavy maschines that can't be shrinked and where the technic is not evolving as fast as the first years in computers. You will need the same amount of energy to bring a car today or in 20 years from a to b. And this amount of energy needs to be transfered to the place where you want to charge your battery. And there is the problem that will not change in 20 years. You can supercharge 5 cars an a parking lot now, but for 50 cars you need a complete other infrastructur thats bind on the same physics that cars have today.

And no, you never ned 1GB of hard drive for anything that was done with computers at this time. Now we use computers for completly other things. I suppose on cars the usage will not change as far as with computers.