I hear Toyota is designing an all solar car.
How practical is this?
A typical sedan covered with solar cells on the top, hood, and trunk cover would give at best 180 watts. If you cover every possible area including the sides and pillars, you'd probably get at best a little over 200 watts.

So, lets take the best possible outcome and say we get 200 watts.
We'll take an average commute of about 30 miles.
It would have to be a very light car of less than 2000LBs.