Solar Panel Count Calculator

About this calculator

This calculator works backward from your daily energy consumption in kWh to the number of solar panels needed, dividing that demand by the output a single panel realistically produces in a day — panel wattage × peak sun hours (the local average of full-intensity sunlight equivalent hours) × system efficiency, which discounts for inverter losses, wiring, temperature derating and panel soiling, typically bringing real-world output to 75-85% of the panel's rated capacity.

Solar installers use this sizing method during initial consultations to give homeowners a rough panel count and system size (in kW) before a formal site survey, and homeowners planning an off-grid cabin or RV system use it to make sure their proposed array can actually cover daily usage through cloudier, lower-sun-hour seasons.