In general, solar cells like the ones shown here, sell for about $2.50 each in lot of 100 or so. Each cell measure 3” X 6” inches and generate 1/2 a volt at 3 amps. This equates to 1-1/2 watts of energy For ever cell that is add to this system you gain another 1-1/2 watts. So 10 cells will give 15 watts, 100 cells 150 watts. There is also the cost of wiring up the cell the mounting and cover for the cell array. More to come latter