How big a system do I need?

The size of the system depends on the amount of southerly roof area one has on their roof. Typically, a 2 kilowatt system employs about 200 square feet of roof space, a 5 kilowatt system 500 square feet of roof space, and a 10 kilowatt system about 1000 square feet of roof space. The California Solar Initiative Program (CSI) allows the owner to generate 100% of their historical demand, providing they have adequate roof space. Normally, systems are sized to meet 25-95% of their total annual electric demand, with the balance of their electricity purchased from the electric utility.