Would painting the roof of my car white make any discernible difference to how hot it gets on a sunny day?

I don’t know but you might get mistaken for a police car then people would always be slowing down in front of you.

Slightly. It would be better to put solar panels on the roof that power the airconditioning

White definitely makes a difference. Silver or gold plating would be even better.

In the NT of Australia which gets extremely hot, white is definitely the color of choice for most vehicles. And yes, they always seem cooler than dark colors. It’s interesting that @ETpro says silver or gold. I can understand silver but I would have thought that a golden color would absorb more than reflect???

Cars get hot in the heat, period. Doesn’t matter what color they are. (We have learned not to leave transparent lighters in the car when parked during the summer—they explode.) Just have to open them up and cool them off before you get in.

@rooeytoo Gold paint probably would not beat white. The binders used to carry the metal flakes are absorptive, and some of the metal flake surfaces are not aligned parallel t the painted surface, thus reflecting solar heat into other areas of the binder instead of back out into the ambient air. Gold, silver or chrome plating would be a great reflector.