Makes more sense to do it after if you’re going to do this. Usually after a disaster you have to do something with the roof, electric service equipment, and even the electric utility equipment. These are also things that need to be touched when you’re just simply adding solar. So if there’s going to be aid following a disaster, it makes logistical sense to tack on solar since the overall cost of doing it with everything else should, in theory, cost less.
Obviously the costs may not be kept lower if there’s a way for contractors to game the system.