I've noticed that many of you are long time devotees of EVs, and that several of you are engineers. So I figured you might have an answer for my question: Why currently available EVs don't include solar panels to charge the traction battery? I have a Prius with a fairly large solar panel on the roof, so price isn't that big of an huge issue, but as you all probably know the Prius solar panel runs a fan to keep the car cool when it's sitting in the sun on hot days (as an aside I've tested the temp inside the car on sunny 100+ days and the solar fan cools the interior temp of the car by up to 20 degrees F). Main point, the Prius solar panel does not charge the traction battery. I'd noticed that some models of the Leaf have a solar panel, but then read that it charges the auxiliary battery, not the traction battery. You can imagine cars sitting in the sun all day taking in all those free photons to charge the traction battery.... seems ideal. So what gives? Too costly to put enough panels on the car to get enough charge? Would a solar panel not provide enough juice to make it worth the extra cost? Are there technical issues that prevent this from happening, or is it just a matter of dollars and cents?