Solar Panel Sizing Calculator
Calculate the right solar panel system size for your home. Get recommendations for number of panels, roof space needed, and estimated costs based on your electricity usage.
Your Energy Usage
US average: 900 kWh/month
US average: $0.12/kWh
4-6 hours typical in US
Higher wattage = fewer panels needed
South-facing, unshaded area
100% covers your current usage
75-85% typical (accounts for inverter losses, wiring, temp, shading)
Solar Sizing Basics
The right solar system size depends on your electricity usage, roof space, and local sun exposure. Most residential systems range from 5-10 kW.
- • 1 kW system produces ~1,200-1,600 kWh/year
- • Average US home needs 6-8 kW system
- • Each panel requires ~17.5 sq ft of roof
How to Use
- Find your monthly electricity usage on your utility bill
- Enter your electricity rate (also on your bill)
- Look up peak sun hours for your area (NREL has maps)
- Measure or estimate your available roof space
- Click Calculate to see your recommended system size
FAQ
How do I find my peak sun hours?
Peak sun hours vary by location. The Southwest US gets 6-7 hours, while the Northeast averages 4-5 hours. Search "peak sun hours [your city]" or check NREL's solar resource maps for accurate data.
Should I size for 100% offset?
100% offset is a good target, but consider future needs like EV charging or a growing family. Some utilities have net metering caps, so check if oversizing makes financial sense in your area.
What if I don't have enough roof space?
Consider higher-efficiency panels (400W+) which produce more power per square foot. Ground-mounted systems, carports, or community solar programs are alternatives if roof space is limited.
Further Reading
Is Solar Worth It? 7 Factors That Make or Break Your ROI
Key variables that determine your solar investment return.
Solar Panel Payback Period in 2025
Current costs, incentives, and realistic ROI expectations.
Buy Solar Now or Wait? Tax Credit Analysis
Why timing matters for your solar purchase decision.