Musk has only just started selling the tiles and you might need to do some more research on their "capability". You charge at night when its cheap and low demand, you don't need a supercharger at home except in very rare circumstances. All chargers can be inter-connected via microgrids and managed by software so the power is given out evenly and/or stopped if necessary. And those EV batteries can also be part of the grid supplying power back to it in emergencies. Powerwalls etc are a one off cost which will pay for itself whereas buying and burning coal, diesel, petrol is a continual cost. Plus its still early days in the move the renewables so any challenges will be mitigated.