Super-cheap (maybe impossible) system

If you can find solar panels for $3/watt, e.g., from an overstock, you could put together a small system for perhaps as little as $6300 after the CEC buydown.  Here is the effect.

             SOLAR PV SYSTEM WORKSHEET    
             (SoCalEdision variant)       

You must input the following:   
  your summer and winter baseline quantities        
  your summer and winter usage  
  your summer and winter `peak sun hours' (insolation)        

The baseline quantities can be found on your bills, and go by 
`territory' and whether you have electric heat.  Summer is defined      
as June through September, give or take a bit.  The baseline is         
given in kWh/day.  For instance baseline for SCE region 17 is 
13.1/10.5 (summer/winter) or 16.9/24.1 (all-electric).  By contrast,    
region 10 is 9.1/9.2 (summer/winter) or 10.0/16.2 (all-electric).       
(Interestingly, this means `summer' is 122 days and `winter' is         
243.25 days.)

Peak sun hours depend on location and local weather conditions.  I      
do not have much data on these but have sample cities.  Unfortunately   
the average listed in this data is not the computed average,  
which may throw some of these calculations off.     

  city             summer winter   average   average
                  (table)(table)   (table)   (s+w)/2
  Davis              6.09   3.31      5.10      4.70
  Fresno             6.19   3.42      5.38      4.80
  Inyokern           8.70   6.97      7.66      7.83
  La Jolla           5.24   4.29      4.77      4.77
  Los Angeles        6.14   5.03      5.62      5.58
  Riverside          6.35   5.35      5.87      5.85

You will also need a target system size (in watts or kW).  This is      
determined by the number of solar PV modules and their rated (peak)     
output.  Your inverter will have to be hefty enough for this as         
well.  The system size will affect the price, which you must also       
enter.  Finally you have to enter a system efficiency factor, to        
account for losses in the modules and inverter.  Efficiencies of        
82, 71, and 75 percent are typical for batteryless or battery-
backed-up systems.  The 75% efficient battery systems are slightly      
more expensive.          

Finally, you need to enter your utility's rates and tiers, any
local city taxes you pay on electricity, and -- for financial 
comparison purposes -- the rate you would expect to pay on a 30         
year mortgage, and your marginal tax rate for tax deductability.        

              CONSTANTS  

                    30.50 summer days/mo           4 smmr mos 
                    30.41 winter days/mo           8 wntr mos 

             UTILITY RATES      

         tier        rate  limit  smmr kWh  wntr kWh
          I        $.1301   100%    399.55    319.27
          II       $.1516   130%    119.87     95.78
          III      $.2300   200%    279.68    223.49
          IV       $.2800   300%    399.55    319.27
          V        $.4000   none      rest      rest

                INPUTS   

     baseline       13.10< summer (kWh/day)         
  (region 17)       10.50< winter (kWh/day)         

        usage       33.00< summer (kWh/day)         
                    26.00< winter (kWh/day)         

   insolation        6.35< summer (PSH/day)         
  (sun hours)        5.35< winter (PSH/day)         

  system size        1.50< kW   
  system cost   $6,300.00<      
   efficiency         82%<      

     city tax        5.0%<      

    mtge rate       6.75%<           36.0%< your tax bracket  
         term          30< years

             RESULTS - SUMMARY  

       w/o PV     $202.18/smmrmo   $172.41 avg.     
                  $157.53/wntrmo

         w/PV     $133.76/smmrmo   $112.07 avg.     
                  $101.23/wntrmo

        saves      $68.42/smmrmo    $60.34 avg.     
                   $56.30/wntrmo

     mortgage      $40.86/mo        $26.15 (after tax equivalent)       
  net savings      $34.19

             RESULTS - DETAIL   

             without PV system  
       summer     1006.50 kWh:  
          I        399.55 kWh       $51.98
          II       119.87 kWh       $18.17
          III      279.68 kWh       $64.33
          IV       207.40 kWh       $58.07
          V          0.00 kWh        $0.00
                                  --------
                         subtot:   $192.55
                            tax:     $9.63
                                  --------
                                   $202.18

       winter      790.56 kWh   
          I        319.27 kWh       $41.54
          II        95.78 kWh       $14.52
          III      223.49 kWh       $51.40
          IV       152.03 kWh       $42.57
          V          0.00 kWh        $0.00
                                  --------
                         subtot:   $150.03
                            tax:     $7.50
                                  --------
                                   $157.53

             with PV system     
   summer gen      238.22 kWh/mo
   winter gen      200.09 kWh/mo             2553.59 kWh/yr   

       summer      768.28 kWh:  
          I        399.55 kWh       $51.98
          II       119.87 kWh       $18.17
          III      248.86 kWh       $57.24
          IV         0.00 kWh        $0.00
          V          0.00 kWh        $0.00
                                  --------
                         subtot:   $127.39
                            tax:     $6.37
                                  --------
                                   $133.76

       winter      590.47 kWh   
          I        319.27 kWh       $41.54
          II        95.78 kWh       $14.52
          III      175.43 kWh       $40.35
          IV         0.00 kWh        $0.00
          V          0.00 kWh        $0.00
                                  --------
                         subtot:    $96.41
                            tax:     $4.82
                                  --------
                                   $101.23