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» Learn about Photovoltaics » Grid-tied » System Sizing » Determining Initial System Size

Determining Initial System Size

So in order to get a rough idea of the size system we need to offset 100% of your electricity needs, you simply divide your average daily kWh usage by the number of Peak Sun Hours. Continuing on with our Flagstaff example:

Average daily usage: 26.3 kWh
Average Peak Sun Hours: 5.6 Hours

26.3 kWh รท 5.6 Hours = 4.7 kW or 4,700 Watts

Remember that this calculation does not factor in equipment efficiency, so our final system size will need to be a little larger (10-20%). So if our equipment were 100% efficient, then a 4,700 watt array would require approximately 27 modules of 175 watts each: 27 x 175 watts = 4,725 watts


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