Surprisingly the building regulations have not caught up with the installation of solar panels on roofs.
Roof live loads of 150kg/m.sq would not be a issue with the installation of solar panels as panels, I would assume are not trafficable.
Solar orientation in regard to overshadowing of panels by adjacent development is becoming an issue.
I have seen solar water heaters and solar electric panels overshadoed by adjoining construction especially in build up areas and as yet, there is no provision for direct solar access for renewable energy in the building regulations, although there is for north facing habitable room windows.
As a stop gap some control could be provided under the planning scheme at development accessment stage but it is unlikely that would happen.