1 kW of solar panel produce 3 kW energy / day in a yearly average. This calcul is accepted here in Europe, it's calculled 3 hours/day with maximum capacity (the maximum capacity production for 1kW solar panel is 1kW energy / hour =>3 kW in 3 hours). This mean 1095 kW energy production / year. Here, the price of electricity is around $0.14 => 1095 kW = $153.3 => the ROI (return of investment) is around 6.52 year. I think it is not bad! BUT... it depends on various countries legal systems, the electricity costs, etc...so it's possible to be less profitable in USA.. And finally...this was only my opinion, and math. We installed 6kW of solar system 3 years ago, and I'm totally satisfied with that :)