There is 30% rebate tax incentive with solar purchase. I don't think it applies to lease unit but I am not sure. On our 3 kW it came out like this:
Retail cost = $15,000
Builder cost = $10,000 (charged to homeowner)
30% tax rebate calculated from RETAIL to be reflected in 2014 IRS tax return= $5,000
Overall, the purchase cost is only $5,000 and for our family the payback is going to be 2-3 years. I expect close to 0 electrical bill after averaging annually (including SCE credit when we produce more than we consume).