Before the depression, I did a lot of boat work. Solar is a favorite among sailors. As soon as an owner asked me about it, I would sit them down with my laptop running a spreadsheet and my DC ammeter.
One page was power demand and the next was money. Both of these have to be based on real data and only a few assumptions can be included before there are problems. Sometimes I got a job and sometimes I only made another friend. But, I never quoted a job without that analysis. When we would get done, I would offer them the completed analysis for the price of the thumb drive I would put it on.
Moral: You have to do the WHOLE and REAL analysis to know if it is worthwhile. There is no telling without that analysis. Some place the usable sun just does not work.
Matt