Elon Musk told the National Governors Association meeting that the solar roof for the Model 3 (or any car) was not practical and was an idea that would be “scrapped.” As of now, a car’s roof is not big enough to make this efficient with current technologies.
In November 2016, Elon Musk said that the upcoming Tesla Model 3 would incorporate the technology of the new solar roof. However, on July 15 at the National Governors Association meeting, Musk squelched the idea in his remarks. When asked about the solar roof, he indicated that he would “scrap that idea” which requires some very complicated engineering. He explained:
I really thought about this. I pushed my team. Is there some way we can do it on the car? Technically, if you have some sort of transformer-like thing that will pop out of the trunk like a hardtop convertible that ratchets solar panels over the car. . .and provided you are in the sun, that would be enough to generate 20 to 30 miles a day of electricity. It’s a difficult way to do it.
As Electrek reports, the issue with the concept of solar panels that cover the top of cars is that they are rarely efficient enough to be worthwhile. Furthermore, their functionality varies based on your location. Even the Prius “solar roof” is really mostly a ventilation system, not a significant source of backup power for the car. In the end, the idea of a retractable array in the trunk is a complicated solution that would, at most, add 20 to 30 miles per day.So, unfortunately, it looks like we won’t be seeing the solar roof option on the Model 3, at least not now.