Solar in the vast majority of places in the US is a laughable gimmick(currently) without taking advantage of subsidies. You're average payback time is going to land in the 30-40 year range assuming no major issues with the system. Subsidies can alleviate some of that, however that's a whole game in and of itself. If you very seriously want to pursue this option, hire a firm to work everything out for you and give you the numbers, because it can be a bunch more complicated than people make it out to be. My personal suggestion is run a circuit and new panel to your shed. The money you save from meter renting will fairly quickly offset, and your household power bill will increase somewhere between $0.50 and $1.50 depending on your rate. There are easier places to save money than with a solar system.