1. Find the roof
2. Confirm roof geometry
Source: -
Trace the roof from above
Tilt can't be read from above — set it per facet below.
Roof facets
| # | Area | Tilt (deg) | Facing |
|---|
3. Choose a panel
Pick a tier based on budget.
A free solar estimate for your own roof
SolPan gives homeowners a quick, free answer to "would solar panels make sense on my roof?" Enter your address, outline your roof on a satellite map, and pick a panel tier. You don't need an account, and we don't ask for your name, email, or phone number.
What the estimate shows
- Panel count: how many panels fit on the usable part of each roof plane.
- System size: the total rated power of those panels, in kilowatts (kW).
- Electricity produced: expected output month by month and for the whole year, in kilowatt-hours (kWh).
- Estimated savings: that yearly output multiplied by the average residential electricity rate for your local utility.
How it works
- Find the roof. Your address is placed on a satellite map. Where Google already has roof data for the building, SolPan starts from the roof planes it found. Otherwise you trace each roof plane yourself by clicking its corners.
- Set each plane's tilt. A roof's pitch can't be measured from above, so you confirm it for each plane. The direction each plane faces is worked out from the outline, and you can flip it if it's wrong.
- Fit panels and model the output. SolPan assumes about 75% of each plane can hold panels, which leaves room for edges, vents, and fire-access setbacks. It then sends each plane to PVWatts, the solar production model from the National Renewable Energy Laboratory (NREL), which uses years of local weather data.
The full method, including the assumptions behind each number, is on How SolPan estimates your solar output.
Where the numbers come from
Google supplies the address lookup, the satellite imagery, and, where available, the detected roof planes. NREL, a U.S. Department of Energy laboratory, supplies the PVWatts production model and average local electricity rates. SolPan is built for homes in the United States.
How accurate is it?
Treat it as a first look, not a quote. The estimate allows for typical losses from wiring, the inverter, dirt, and general shading, but it can't see a specific tree or the house next door. It also leaves out equipment and installation costs, tax credits, your roof's condition, and your utility's net-metering rules. If the numbers look promising, an installer's site visit is the next step.
Common questions
How many solar panels will fit on my roof?
It depends on the size of each roof plane you outline. SolPan counts how many standard-sized panels fit on roughly three quarters of each plane, so a roof with more large, unbroken planes fits more panels.
Does it matter which way my roof faces?
Yes. In the U.S., south-facing planes generally produce the most, and east- and west-facing planes produce somewhat less. Steeper or flatter pitches change the output too. See how roof tilt and direction affect solar output.
Which panel tier should I pick?
The Budget (300 W), Standard (400 W), and Premium (440 W) tiers use the same panel size, so a higher tier makes more power from the same roof. Trying all three shows how much panel choice matters on your roof. See how the panel tiers compare.
Is this a quote?
No. SolPan doesn't sell or install solar, and the estimate doesn't include prices. It's meant to help you decide whether solar is worth looking into.
What happens to my address?
It's used only to produce your estimate and isn't stored after your session. Our privacy policy has the details.