1. Find your monthly average electrical usage from your electricity bill. This will be listed in kWh
2. Find your daily average electric use. This will be your monthly average kWh divided by 30
3. Find your locations average peak sun hours per day
4. Calculate the system size (AC kW) to cover 100% of your electric bill.Divide your daily average electric use in #2 by the figure in #3
5. Divide your result in #4 by .7 to get a derate factor for the components in the system. This takes into consideration temperature, wire loss, component inefficiencies, etc.
6. Multiply your result in #5 by 1000 to get watts of system. Divide the wattage of the module that you would like to use into this number to determine the number of modules you would need.