I've written on this site many times that solar is not for everyone. Many climates, roof architectures, and other factors often make solar uneconomical. (Let's ignore government and power company subsidies, because there are subsidies for almost all forms of power).
Flexible solar panels, micro inverters, improved manufacturing technique, and scale have helped little by little, but there are still relatively few cases where a homeowner can be 100% guaranteed that solar will save them money. There is still this pesky maximum theoretical efficiency limit in today's cells - 37% of the suns energy is the maximum that could ever be retained.
In the last few weeks new data was published by Princeton that shows they can significantly improve upon this 37% limit. New "nanomesh" technology limits the amount of energy that is reflected away from panels. And there is some promise that this can be manufactured at reasonable rates.
Read more about this solar breakthrough here on extremetech.com.