Path-Q Solar

How can I check whether a solar production estimate is realistic?

Answer

Review the model's inputs and method: usable roof area, orientation, tilt, shading, weather data, equipment losses, system degradation, and consumption or export assumptions, then compare the result with an independent estimate.

Key points

  • Confirm that the proposed layout matches the actual roof and includes obstructions, shading, setbacks, and orientation.
  • Check whether the estimate identifies annual and monthly production, loss assumptions, degradation, and expected system availability.
  • Ask whether the model uses measured or documented site conditions rather than generic assumptions.
  • Compare the estimate with an independent modeling tool or qualified reviewer using the same site information.
  • Distinguish energy production from bill savings; savings also depend on rates, usage, and export treatment.

What it depends on

  • Roof orientation, tilt, shading, and obstruction changes
  • Equipment configuration and operating losses
  • Local solar resource and weather assumptions
  • System availability, degradation, and utility billing treatment

Risks and trade-offs

  • No forecast can guarantee exact future production because weather and equipment conditions vary.
  • An optimistic model can overstate savings and distort system sizing or financing decisions.
  • A conservative estimate may appear less attractive while better reflecting uncertainty.

Information you may need

  • Layout and shading report
  • Equipment specifications and loss assumptions
  • Monthly production forecast and degradation assumption
  • Independent estimate based on the same site conditions

Your next step

What to do next

Ask for the complete production model and have an independent qualified reviewer compare its inputs and output with the proposed design.

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