I put in my solar system DIY in the fall of 2011. It is a ground mount, 40 panels, 9.2 KW, using a single 10KW grid tie inverter. My costs were a bit 0ver $ 30,000. In received state and federal credits/incentives equaling $ 20,000, so $ 10,000 out of pocket. My break-even was at 6.5 years...