Rooftop Solar Feasibility Calculator
Is your roof suitable for solar panels? Enter its size, type, direction, and shade to see how many panels fit, how much power they could make, and a clear rating. Use it before you ask for quotes, so you know what to expect.
Your roof result
Good for solar
This roof looks well suited. It could hold about 13 panels (5.6 kW) and make about 9,970 kWh a year in Los Angeles.
This tool cannot judge roof strength or condition. A qualified professional must confirm both.
Assumptions used
- Direction and tilt
- 100% of the best output here
- Shade loss
- 2.2% a year
- Edge clearance
- 0.4 m
- Layout
- 8 × 2 before obstacles
Your roof from above
Drag an object to move it. Click it to change its type and size. Shadows on your panels change the result.
These objects cost about 2.2% of yearly output, across every month and hour.
What if?
Save this result, change any setting, and compare.
How this is calculated
Usable area
We keep a clear edge around the roof, then remove the share you enter for vents, skylights, and chimneys. Edge rules vary by country, so we use planning values of 0.4 m on pitched roofs and 1 m on flat roofs.
Panel fit
Panels are fitted in whole rows and columns, trying both portrait and landscape. Flat roofs use tilted rows with gaps, so one row does not shade the next.
Rating
We compare your roof's yearly output per kW with the best tilt and direction at your location, after shade. Any extra daily hour of shade you enter counts as about 9% of yearly output.
Score = your output per kW ÷ best possible output per kW
Shade from objects
Place chimneys, trees, buildings, and tanks on the roof plan. For each month and hour, we trace the sun's rays from your panels to see which are blocked, weighted by when they would produce. Shade removes direct sun only, which we count as 70% of the light, and panels under an object are taken off the layout.
Shade loss = shaded share of panels × 70%, weighted by output through the year
Worked example: a 10 × 6 m roof in Los Angeles
This 60 m² roof has about 43 m² of usable space, which fits 13 panels of 430 W, or 5.6 kW.
With one chimney on the roof it could make about 9,970 kWh a year and scores 97 out of 100.
How accurate is this?
This is a screening tool. Yearly output comes from our generation model, which stays within 10% of PVGIS at 20 test cities. Panel fit and shade are simple estimates, so a site visit will refine both.
Common mistakes
- Measuring the whole house footprint instead of one roof face
- Ignoring shade that only appears in winter, when the sun is low
- Forgetting edge clearance required by local fire rules
- Assuming an old roof will last as long as the panels
Limits of this tool
- This tool cannot judge roof strength or condition. A qualified professional must check both
- The shade study treats the roof as flat and uses simple object shapes, so it is not a site survey
- Local rules on edges, heritage, and permits are not included
What to do next
- Compare what fits with what you need in the system size calculator
- Ask an installer to confirm shade and structure on site
Frequently asked questions
How do I know if my roof is suitable for solar?
Look for a sunny roof face with little shade, enough clear space, and several years of life left in the roof. An installer should confirm the structure.
Can you put solar panels on an east or west roof?
Yes. East and west roofs usually make less than an equator-facing roof, but they often stay worthwhile. This tool shows the difference for your location.
How many solar panels fit on my roof?
It depends on usable space. A 10 × 6 m pitched roof with 10% obstacles fits about 13 panels of 430 W.
How much does shade affect solar panels?
Shade on part of a panel can reduce the output of much more than that part. Even an hour or two at midday can matter, so check it through the year.