I think if we can figure out how to get 40% efficiency solar panels (which have been made in labs, but not mass produced) embedded in electric cars' paint, we're looking at about 1 mph of range added per square foot of solar panel (400 wh per mile / 400 watts per sq foot), and that may work out to 30-40 miles per day of added range just by parking in direct sunlight, which may cover many people's commute, especially for apartment dwellers who probably live closer to work than people who have space for conventionally inefficient solar panels.