That’s 100 free miles a week. Sure, most people will need to charge it anyway, but that’s still 100 free miles a week.
But I don’t think it’s a good idea. It would be more efficient to just put the same solar panels in your roof, where they don’t contribute to the car’s weight, don’t force your to park in sunlight instead of indoor parking or garage, and whose output can be used for charging the car OR for anything else as needed.
It’s not any more free than any other EV. it still uses energy. That energy can only be used for the car though. Put some solar on your house and it can charge your car (not free, the price of the panels same as the car). It will also be more efficient because it can be placed ideally, unlike the car. It’ll also be cheaper for a larger area because it can take advantage of cheap standard panels instead of expensive custom ones.