From what I read, the payback is 15 years. Here in NJ you can get them installed for free and they will cut your energy costs by 40-50%. I just ordered a 330 panel system for our clubhouse and we project savings of $8000.00 to $10,000.00 a year for the next 20 years. Our costs was ZERO! On my house, my average bill is about $140.00 a month and with solar they would charge me $93.00 a month. Not sure if they offer this in all states?