[gknoy]

There are more ways to generate solar power than with solar panels. Presumably, they could invest in solar power plants. Heck, the highly illuminated towers of a solar power plant can be seen for miles, and could even be used for publicity: "Free power beacons on the road for Tesla cars..."

[sbierwagen]

Solar concentrating thermal plants only work in direct sunlight, and their mirrors don't like to be dirty. They're not terribly commercially attractive outside the Mojave.