hyundai ioniq mods

With the improved engineering of electric cars today, why don't more of them just have solar panels on their roofs?

Because the ,physics and the finances don’t work,. The top of an electric car has maybe 3–5 square meters of flat space. Solar panels, even at high noon, usually only produce about 200 watt-hours per square meter. The most efficient production electric vehicles today (probably the Hyundai Ioniq and the Tesla Mod 3) would only be able to travel 2–4 miles on that amount of electricity…in an hour. ,Most people could walk faster. Financially, the ,cost of the panels ,and electronics, R&D and assembly ,would never pay for itself, in the life of the vehicle, compared to charging from the wall in your garage. Edit Dec.2019: Tesla is talking about offering solar cells on the Cybertruck, and getting 15 miles of range per day. Let’s talk about some assumptions on that. The truck is much bigger than a car. It looks like the back slope on the Cybertruck is about 4x2 meters, for about 8 square meters. Tesla would probably use pretty high efficiency cells, I think their rooftop cells are 21.7% efficient. If we assume the truck is parked pointing exactly the right direction, in a sunny climate….(8 square meters)*(21.7% conversion efficiency)*(~6 hours/day direct sun)*(~1 kilowatt hour insolation) = ~10.5 Kilowatt hours per day. It could be a bit more or a bit less. 15 miles/10.5 Kilowatt hours= ~700 watt hours/mile (including conversion losses). More importantly, if you’re off in the wilderness for a week, you could build up a substantial amount of usable electricity for tools, utilities, or range on the vehicle. For some usages, that could be practical. I don’t know how expensive that capability will be, but since you can’t just plug in out in the boonies, it will be worth it for some people.