If every residential and business building had a sufficient amount of solar panels to power itself during the day, then even if a disaster or attack destroyed a part of the grid, or the entire grid, it would not significantly affect people outside that one small area where the event occurred. As it is now, if the grid goes out in Pennsylvania several States could be without power for weeks. This is foolish and unnecessary with the technology we now possess.
Current guess at specifics of powering your house with soar cells. Calculates number of cells needed, area they would occupy, and cost of cells at street prices.