Actually this makes sense. Black and darker colors absorb heat from the sun, which is why you are more likely to see a black dog panting on a cool sunny day than you are a white dog. If a white roof is absorbing less heat, then an AC unit is not working as hard to cool the contents within.
It’s also the obvious difference in temperature when you are in a city compared to a suburb or country. All that black asphalt and concreted holds the heat in- when you go where there is less, there is a significant drop in temperature. The idea is worth a shot and can’t hurt to try.
