Enter Values
Formula
Array kW = daily kWh ÷ (peak sun hours × efficiency)
Panel count = array watts ÷ panel watts, rounded up
Example
For 30 kWh/day, 5 peak sun hours, 80% efficiency, and 400 W panels, the estimate is 7.5 kW or 19 panels.
Peak Sun Hours
Peak sun hours convert variable daily irradiance into equivalent hours at 1,000 W/m². Use location-specific monthly or annual data that matches the design goal.
Annual-average sun hours may be suitable for a grid-connected energy estimate, while an off-grid system often needs a conservative low-sun-period value.
System Losses and Design Limits
Efficiency should account for inverter loss, temperature, wiring, mismatch, soiling, shading, and other derating. The estimate does not determine string voltage, inverter compatibility, roof area, structural loading, battery storage, or electrical protection.
Use a site-specific solar resource and qualified system design before purchasing equipment.