If I know what my components are rated for, how do I properly predict the realistic capacity of my solar system in watt-hours or amp-hours? I am basically going to start with a single trolling motor battery paired with a 15 watt-hour panel. Obviously, output will be load times time (55 watt light ran three hours would be 165 watt hours, or about 14 amp-hours at 12 volts, but I need guidance on the input.) In Alabama, how many watt-hours per rated watt-hour can I expect?