Elon Musk has thrown down the nay-sayers and stated that all supercharger stations will eventually be off-the-grid. Given their recent acquisition of Solar City this was always on the cards.
I have recently been researching the viability of power from the sun and it is looking to be more reality than dream. My goal is to be able to run the air-con and charge my car completely from the sun. The investment required to set up such a system is nowhere near as high as I feared. More on that project later.
All Superchargers are being converted to solar/battery power. Over time, almost all will disconnect from the electricity grid.