Solar Panel Sizing Calculator
Estimate how many solar panels you may need to offset your home’s electricity use. This is a planning estimate, not a quote or engineering design.
Formula: annual electricity use × target offset ÷ (peak sun hours × 365 × system efficiency). Actual production depends on location, roof orientation, shading, weather, equipment, utility rules, and other factors.
How the estimate works
The calculator converts your monthly electricity use into annual demand, estimates annual solar production from your available sun hours and a system efficiency factor, and then converts the resulting system size into an approximate panel count.
What to do with the result
- Compare the estimated system size with your available roof space.
- Check your local utility’s interconnection and net-billing rules.
- Use your actual electricity bills when evaluating a solar proposal.
- Compare production estimates and financing terms from multiple installers.
Important limitations
This tool intentionally uses a simplified model. A professional solar design should use location-specific solar resource data, roof geometry, shading, panel and inverter specifications, utility requirements, and other site-specific inputs.