Solar Panel Calculator
Calculate how many solar panels you need based on daily electricity usage, panel wattage, peak sun hours, and system efficiency.
kWh
W
hrs
%
Results
Panels Needed
18
Total System Size
7.2 kW
Estimated Daily Output
30.6 kWh
Output per Panel
1.70 kWh/day
How is Solar Panel Output Calculated?
The number of panels needed is determined by dividing your daily electricity usage by the daily output of a single panel. Panel output depends on its wattage, the average peak sun hours in your area, and system efficiency losses.
Example
If you use 30 kWh per day, have 400W panels, 5 peak sun hours, and 85% efficiency, each panel produces about 1.7 kWh daily. You'd need roughly 18 panels (7.2 kW system) to cover your usage.
Common Use Cases
- Estimating how many solar panels your home needs.
- Planning a solar installation budget and roof space requirements.
- Comparing panel wattages and system configurations.
FAQs
What are peak sun hours?
Peak sun hours represent the number of hours per day when solar irradiance averages 1,000 W/m². This varies by location and season — check solar maps for your area.
Why is efficiency less than 100%?
Real-world losses come from inverter inefficiency, wiring, temperature effects, soiling, and shading. 80–90% is a typical system efficiency range.