Solar Panel Calculator
Estimate the number of solar panels needed and annual energy production based on your electricity usage and local sun hours.
kWh
hours
watts
%
Panels Needed
19 panels
System Size7.60 kW
Annual Production11,096 kWh
CO2 Avoided per Year4.63 metric tons
Panels Needed vs Monthly Electricity Usage
How to Calculate Solar Panel Needs
Sizing a solar system depends on your energy consumption, local sunlight, and panel efficiency.
Formula
System Size (kW) = Daily kWh / (Sun Hours * System Efficiency)
Panels Needed = System Size * 1,000 / Panel Wattage
Peak sun hours vary by location: 4-5 hours in the northern US, 5-7 in the south and west. System efficiency accounts for inverter losses, shading, and panel degradation.
Example Calculation
A home using 900 kWh/month in a location with 5 peak sun hours, using 400W panels at 80% efficiency.
- 01Daily usage: 900 / 30 = 30 kWh/day
- 02System size: 30 / (5 * 0.80) = 7.5 kW
- 03Panels needed: ceil(7,500 / 400) = 19 panels
- 04Annual production: 19 * 400 / 1000 * 5 * 365 * 0.80 = 11,096 kWh