Calculate number of solar panels needed and potential savings based on your electricity bill and sunlight hours. Free online solar energy calculator.
The solar panel calculator estimates how many solar panels you need to offset your electricity bill, along with system cost, yearly savings, and payback period. This helps homeowners evaluate whether solar is a good investment and plan their renewable energy system.
Monthly kWh = Bill / $0.12/kWh
Daily kWh = Monthly kWh / 30
Panel Daily kWh = (Wattage/1000) × Sun Hours × 0.85
Panels = Daily kWh Needed ÷ Panel Daily kWh
Cost = System kW × $3,000/kWThe average electricity rate of $0.12/kWh is used to estimate consumption. Panel output accounts for 85% system efficiency (inverter losses, shading, temperature). Installation cost estimates $3,000/kW (varies by region). Payback period = total cost ÷ annual savings. Actual results vary by location, roof orientation, and local incentives.
| Input | Output |
|---|---|
| $150/month bill, 5 sun hours, 400W panels | ~11 panels, 4.4 kW, ~$13,200, payback ~7.3 years |
| $200/month bill, 6 sun hours, 400W panels | ~13 panels, 5.2 kW, ~$15,600, payback ~6.5 years |
| $80/month bill, 4 sun hours, 350W panels | ~9 panels, 3.15 kW, ~$9,450, payback ~9.8 years |