Use this calculator as a guide to see if solar is viable for you    
Step 1 - Select the system size      
   
Step 2 - Calculate your aggregated electricity tariff  
From your electricity bill;  
Enter total amount paid & the total amount of electricity consumed (TAB = Enter)  
    $ (Exc GST) kW.hrs    
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Total      
         
 
         
Step 3: Define your financing parameters (For no financing set term to 0 years)  
Enter your interest rate   %    
Enter the term of the loan/lease   years    
Enter balloon percentage if any   %    
           
Step 4: If the chart below shows you're saving more than your losing, then it's viable.