Ah, I see the issue. I keep forgetting that yachts are horribly inefficient when it comes to heat load as compared to the buildings that I build. I just installed a 6kW solar system on a 6,000s.f. home and it supplies all the electricity needed, including a/c in the Utah desert. A 70' yacht has much less load in terms of lighting and electronics, but it doesn't have r-50 insulation on the roof and r-23 in the walls. I would guess that even the best insulated yachts are about r-15 and they have excessive amounts of glass. So yeah, I guess you would be looking at a 6kW system for a 70' yacht. That would be almost 400s.f. of solar panel. Pretty much the entire main deck.