Solar Panel Wattage Calculator

Your details

The rated watt-peak (Wp) of a single panel, found on the panel datasheet or packaging.
W
Total panels in the array.
The number of hours per day when sunlight intensity averages 1,000 W/m². Ranges from about 3 h in the UK and northern Europe to 7 h in the US Southwest and Middle East. Check NREL's PVWatts for your exact location.
h/day
Accounts for inverter losses (typically 4-6%), wiring losses (1-3%), temperature derating (3-8%), soiling and shading (2-5%). A clean, well-sited system averages 80-87%.
%
Daily outputResidential system
15.3kWh/day

Average energy produced per day

System capacity4kWp
Monthly output465.7kWh/month
Annual output5,585kWh/year
Daily (kWh)15.3
Monthly (kWh)465.7
15.3 kWh/day
Low output<5Typical residential5-20Large system20+

Your system produces about 15.30 kWh per day.

  • Your 10-panel, 400 W array has a total capacity of 4.00 kWp.
  • At 4.5 peak sun hours and 85% system efficiency, it produces about 15.30 kWh on an average day.
  • Annual output of 5585 kWh is roughly 53% of the US average household consumption (10,500 kWh/year).
  • Output varies month to month with season and weather. Sizing for your winter minimum avoids shortfalls; sizing for the annual average is most cost-effective.

Next stepCompare the annual output figure to your electricity bill kWh total to see what percentage of your demand this system covers.

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