Path-Q Solar

How can I tell whether a quote's production estimate is unrealistic for my roof's usable area, orientation, and shading?

Answer

Check whether the modeled array fits the roof after setbacks, access paths, obstructions, and structural exclusions, then compare the production estimate with orientation, tilt, shading, weather assumptions, and system losses. A high annual output is not credible if the layout or loss assumptions do not match the site.

Key points

  • Verify panel count, dimensions, roof planes, setbacks, vents, skylights, chimneys, and access areas.
  • Review orientation, tilt, horizon shading, and seasonal shading from trees or nearby structures.
  • Check the modeled system capacity against the usable roof area.
  • Compare the estimate with an independent production model or another quote using the same site constraints.
  • Require the installer to explain unusually high specific production per unit of system capacity.

What it depends on

  • Measured roof geometry and usable area
  • Panel dimensions and layout
  • Orientation, tilt, and shading
  • Weather and production-model assumptions
  • System losses and equipment configuration

Risks and trade-offs

  • A larger modeled system may be impossible or may require sacrificing maintenance access.
  • Shading can affect output unevenly across the array and may not be captured by a simple annual percentage.
  • Different software or weather datasets can produce different estimates even with the same roof.

Information you may need

  • Scaled roof layout
  • Panel count, dimensions, and location
  • Shading assessment or imagery
  • Annual and monthly production forecast
  • Loss assumptions and modeling software or method

Your next step

What to do next

Have an independent reviewer or a second installer validate the layout and production using the same roof measurements and shading conditions.

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