Solar System Size Calculator

Calculate KW system size from electricity usage and sun hours.

Monthly Usage

kWh

Peak Sun Hours

hrs/day

System Losses

Panel Wattage

Tab to move between fields

System Size

6.98 kW

≈ 7 microwaves

Number of Panels

Annual Production10,950 kWh

Daily Production30 kWh

How to Use This Calculator

Enter your average monthly electricity consumption in kWh.
Set your local peak sun hours per day (use NREL PVWatts for your location).
Input the system efficiency or derate factor (typically 80–85%).
Review the recommended system size in kW DC.
Adjust the system size based on available roof space and local net metering policy.

How the result changes with Peak Sun Hours

Monthly Usage: Average monthly electricity consumption from your utility bill.
Peak Sun Hours: Average peak sun hours per day for your location.
System Losses: Total system losses including wiring, inverter, and shading.
Panel Wattage: Rated wattage per solar panel.

Identify Input Parameters
4 parameters
Monthly Usage = 900, Peak Sun Hours = 5, System Losses = 14, Panel Wattage = 400 = 4 input(s) provided
Calculate System Size
System Size
6.98 = 6.98
Calculate Number of Panels
Number of Panels
18 = 18
Calculate Annual Production
Annual Production
10950 = 10950
Calculate Daily Production
30 = 30