Solar Panel Calculator

SolversPro Solar Panel Calculator is a free renewable energy estimation tool that computes total photovoltaic system kilowatt capacity (kW) and required module panel quantities based on daily kWh consumption and local peak sun hours.

Regional Peak Sun Hours & System Output Reference

Average solar insolation ratings across North American climate zones and expected daily generation for an 8 kW array:

US Climate Zone / Region	Daily Peak Sun Hours	8 kW Daily Yield (@ 80% Eff.)	Estimated Annual Output
Southwest (AZ, NV, Southern CA)	6.0 to 7.0 hours	38.4 - 44.8 kWh	14,000 - 16,300 kWh
Southeast & Central Plains (TX, FL, CO)	5.0 to 5.8 hours	32.0 - 37.1 kWh	11,600 - 13,500 kWh
Mid-Atlantic & Midwest (NY, OH, IL)	4.0 to 4.8 hours	25.6 - 30.7 kWh	9,300 - 11,200 kWh
Pacific Northwest & Alaska (WA, OR)	3.2 to 3.8 hours	20.5 - 24.3 kWh	7,400 - 8,800 kWh

Frequently Asked Questions

/What are Peak Sun Hours?

Peak sun hours refer to the number of hours per day when solar irradiance averages 1,000 watts per square meter. It is not just the hours of daylight, but the hours of usable solar energy.

/Why is System Efficiency defaulted to 80%?

Solar systems never operate at 100% efficiency. Energy is lost due to inverter inefficiency, wiring resistance, shading, dust on the panels, and temperature fluctuations. 80% is a standard conservative estimate for a well-designed grid-tied system.

/How is the number of panels calculated?

We first determine the required total system size (in kW) by dividing your daily usage by your peak sun hours and efficiency factor. Then, we divide that total size (in Watts) by your individual panel wattage and round up to the nearest whole panel.

/How much roof area is needed for a residential solar array?

Each standard residential 400W solar panel occupies approximately 17.5 to 21 square feet (1.6 to 2.0 m²). A typical 20-panel (8 kW) installation requires roughly 350 to 420 square feet of unshaded south or west-facing roof space.