I contacted the guys, they are not installing panels themselves, contractors install it instead. here's something I learned:
1) To get tax rebates and other incentives, you must have licensed contractor install 'em
2) for the same reason you must have city/county approve the stuff, and then power company
3) all of that pretty much doubles the cost of the installation before rebates. After rebates, it is still not bad, but significantly (several times) more pricey than I counted before. Although w/o rebates it would even more pricey.
4.8 KW system (worth ~15K) would be ~30K. Also, I don't know how good of a luck the whole rebate thing is, especially from government. Vendors say they would eat the utility company incentive and take check directly from them, but tax rebates are on you.