I understand your point and think its really relevant. But maybe we should ponder that, when you buy an eletric car, you will start thinking for how much you pay on electricity as your costs will really rise.
I think Musk is concerned that an increase in eletricity prices will ultimatily kill the Tesla eletric car model.
But in other way you are spot on the rent, generation problem.
Also, i would like to add another variable to the equation. Maybe a solution for tesla, as already happened on Germany, will be a state police that will oblige people to or adopt eletric cars, ou adopt solar systems. That could be an exterior savior.