Solar economics

This is my solar bill.  Total cost of the installation.  I originally want more esthetic, all-black panels from Sunpower…however the cost is around $8.5/w.  After negotiating with the installer, we knock the price down to $7.3/w which is more reasonable.  However we had to go with less efficient panels (Serengeti panels).  Notice the rebate and tax credit significantly reduced the total bill. Sunpower System Size:          5016 Watts-DC Panel output:                            228 Watts-DC  per Serengeti panels Number of panels:                      22      (x) panels rated output:        202 Watts      (x) inverter rating:                  95.5%  (Sunnyboy 5000m)      (=) system rated output:     4244 Watts-AC Cost of the total system, including installation:     $36655 Roofing cost:                                                     $  3100 Permit cost:                                                       $    300 Total cost, before incentives & credit                 $40055    (-) Edison rebate amount (4244 x 1.55)          $  6578.23    (-) Federal tax credit  (40055 x 30%)             $12016.50  Net cost after incentives                                      21460.27