I'm not doubting you at all but I wonder how accurate this really is? In my example, I will do 95%+ of my charging at home. If MidAmerican gave me a discounted rate for charging at night, I could easily change my settings in the Tesla to only charge at certain times. My understanding is that the power grid is most taxed between 2-6pm, during the weekdays, and only during the summer. Would it really be to taxing on the system?
Or encourage more people to go residential solar, that would add a lot of capacity to the grid.