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Both calculators run independently — change the inputs on either side to compare results.

Solar Panel System Sizing Calculator

Size a rooftop solar PV system from your real electricity usage, local peak sun hours, system losses, and your target offset — and get the number of panels you actually need.

Average monthly electricity use (kWh)

Peak sun hours (daily average) (h/day)

Share of usage to offset (%)

System losses (inverter, wiring, soiling, heat) (%)

Panel power rating (W)

Solar Energy

Solar Load Calculator

Calculate the total daily energy demand of your home's lighting, appliances, and HVAC to correctly size a solar system. Use this before getting solar quotes to know exactly how many kilowatt-hours per day you need to generate.

Lighting Load (watts)

Appliances Load (watts)

HVAC Load (watts)

Average Daily Usage (hours)

System Efficiency Factor

Key differences

	Solar Panel System Sizing Calculator	Solar Load Calculator
Category	Solar Energy	Solar Energy
Inputs required	5	5
Result	Solar panels needed (panels)	Required Solar Capacity (kW)
What it does	Size a rooftop solar PV system from your real electricity usage, local peak sun hours, system losses, and your target offset — and get the number of panels you actually need.	Calculate the total daily energy demand of your home's lighting, appliances, and HVAC to correctly size a solar system. Use this before getting solar quotes to know exactly how many kilowatt-hours per day you need to generate.