Don
That's a nice deal. Weather it is cost effective depends on your utility rates. You may have to hire the job to qualify for the rebate. Some numbers for your consideration:
$8.00 per watt installed system "typcial costs" - (found it to be closer to $10 in Mass)
$4.50 per watt rebate
$2,000 fed tax credit
$10,250 installed price for 3.5kW system
1,900 kWH per Kw size produced per year in central Texas
6,650 kwH produced per year (multiply by utility rate to calc savings) At MA rates of $0.165 per kWH = $1,100 saved per year - <10 year straight payback
Residual value of system - ~$20K
I'd go for it in a second, there is a study done that depending on mortgage rates, buyers will pay ~$20 for every $1 less in annual utility bills.