When adding traditional PV panels to my house a few years ago, I talked to the designer about PV shingles. He said the problem is that PVs are black and get hot in the sun. Traditional panels are raised a few inches above the roof with a gap that allows air flow (stack effect) to cool the panel. Also, the panel shades the roof, keeping the attic cooler (less A/C). With shingles, when they get hot, the attic gets hot (more A/C).