Solar Panel Calculator
Size your solar PV system based on monthly energy usage and location. Get panel count, system kW, payback period, and projected 25-year savings.
How to Size Your Solar System
Follow these three steps to design your residential solar PV system.
Enter Your Usage
Type in your average monthly kWh usage or your monthly electric bill. Select your location to set the peak sun hours for your area.
Set Panel & System Parameters
Adjust the panel wattage, system cost per watt, and utility rate to match your situation. The defaults work for most residential systems.
Review Your Solar Plan
See the number of panels needed, system size in kW, annual production, payback period, and projected 25-year savings with a monthly bar chart.
Solar Savings by Location
Estimated annual production for a typical 6 kW system in different regions.
| Location | Peak Sun Hours | Annual Production (6 kW) | Est. Annual Savings ($0.14/kWh) |
|---|---|---|---|
| US Southwest | 6.0 hrs | 8,760 kWh | $1,226 |
| US Northeast | 4.25 hrs | 6,205 kWh | $869 |
| Australia | 5.5 hrs | 8,030 kWh | $1,124 |
| UK | 3.0 hrs | 4,380 kWh | $613 |
| Germany | 2.75 hrs | 4,015 kWh | $562 |
Frequently Asked Questions
Common questions about solar panel system sizing and savings.
Divide your daily energy consumption (monthly kWh / 30.44) by the daily production of one panel (panel wattage × peak sun hours × 0.80). The calculator handles this automatically based on your location and panel choice.
Payback period is the total system cost divided by annual savings. Typically 6-12 years depending on location, electricity rates, and system cost. This calculator estimates payback based on your inputs.
Total 25-year savings = (annual savings × 25) minus the upfront system cost. With rising utility rates, solar panels often save $20,000-$50,000 over their lifetime depending on location and usage.