Comment by didgetmaster

People often do this calculation without considering the time value of money. If you took that same $8K you spent on your system and put it in a bank CD; you would earn about $420 each year in interest. That means your real savings for the solar system is only $580 a year, not $1000. That makes the payoff time expand from 8 years to nearly 14. Still might be worth it to you, but also might not.