A home near us just had panels put on both the south facing and west facing roofs. What amazed me is the shingles are visibly old starting to curl on the corners and the roof isn't flat and straight. Who would put that on top of something that will need replaced soon?
At the local university they did a solar power demonstrator on a three story building and then built massive dorms around it so that it only gets full sun about three hours a day. It demonstrates something OK, but not what they think.