About This Tool
Sun-Calc is a free solar panel calculator for U.S. homeowners. Enter your home address and it analyzes your actual roof — its size, pitch, and orientation — to estimate how much electricity a solar system would produce, what it would cost, and how long it would take to pay for itself.
Most online solar calculators ask you to manually enter your roof size or just use your zip code. Sun-Calc uses real aerial imagery and roof geometry data from Google's Solar API, combined with the National Renewable Energy Laboratory's PVWatts model, to give you estimates grounded in the physics of your specific home and location — not a national average.
I was considering solar for my own home and frustrated by how hard it was to get a straight answer on whether it made financial sense. Most tools either required a sales call or gave vague estimates that didn't account for my actual roof. I wanted something that gave real numbers quickly, without giving my contact information to a solar installer first.
Sun-Calc is the tool I wished existed. It's free, requires no sign-up, and doesn't sell your information. The goal is to help homeowners make a more informed decision before talking to any installer.
Sun-Calc combines three data sources to generate its estimates:
All estimates are approximations. Actual production will vary based on shading, local weather, equipment quality, and installation. Always get quotes from licensed installers before making purchasing decisions.
Sun-Calc is designed to give you a reliable starting point, not a final quote. The Google Solar API data is highly accurate for most suburban and urban properties in the U.S., but may be less precise for rural properties, homes with complex rooflines, or areas with lower imagery resolution. The NREL PVWatts model is widely considered the gold standard for solar estimation, but it uses historical weather averages and cannot predict future conditions.
The financial estimates (cost, payback period, ROI) depend heavily on the electricity rate and install cost you enter. These vary significantly by region and installer. Use your actual utility bill rate for the most relevant estimate.
Sun-Calc does not store your address or any personal information. When you enter an address, it is sent directly to Google's servers to retrieve map and solar data. We do not operate any backend servers that receive or log your data. See our Privacy Policy for full details.