I think it is simple - electricity from solar panels is cheaper than electricity from the utility companies, which have been too slow to build out solar farms o

I think it is simple - electricity from solar panels is cheaper than electricity from the utility companies, which have been too slow to build out solar farms of their own, and it is fashionable to boot. ("Fashionable" is not exactly the word I want; I mean that it would be less popular with your friends and neighbors to operate a coal-fired generator on your balcony.)