Some don't have an ideal roof layout (which can easily double costs). Even more so, trees can sometimes be in the way, which can be even more inhibiting. 2-3x

Some don't have an ideal roof layout (which can easily double costs). Even more so, trees can sometimes be in the way, which can be even more inhibiting. 2-3x cost can still see an ROI, but when you get into 5-10x cost things tend to break down. Check out Google's "Project Sunroof" to see.