There's one other minor factor that helps even if the solar panel did nothing: By making the sun hit at a layer above the ceiling (and assuming you have proper

There's one other minor factor that helps even if the solar panel did nothing: By making the sun hit at a layer above the ceiling (and assuming you have proper air circulation below), your attic area will heat less, hence your house will get less hot. (This is similar to the effect you get by staying under a tree shadow) As per the article, yes, if everybody had air conditioners city wide that would increase the city temperature. But that would require everyone to blast it at the same time