The best state to invest in solar? The one with the highest irradiance! Florida is the sunshine state, but anything along the southwest such as California and Texas have some of the highest irradiance levels. For more information : https://www.nrel.gov/gis/solar.html has a whole map of the states devoted to it.

I am located in Toronto, Ontario, Canada! Since us Canadians are so high up, Toronto's latitude being 45, which means we have to tilt our solar panels at a 45 degree angle to the south for maximum efficiency, which means the States and everyone south of us (until you're south of the equator) just have to point up!

If you don't have a roof for solar, but want to get into the solar game, try looking into solar shares, where you can invest into solar systems, and get a modest return.