Path-Q Solar

How should I proceed if an installer refuses to provide the assumptions behind its production estimate?

Answer

Treat the estimate as difficult to evaluate and do not rely on it as a basis for commitment until the installer provides enough assumptions to reproduce or reasonably assess the result. Request the design, shading, weather, degradation, equipment, loss, and consumption assumptions in writing, and compare with another transparent proposal.

Key points

  • The installer need not disclose proprietary software, but should disclose material inputs and methodology.
  • Ask for system size, roof sections, orientation, shading, estimated losses, production period, and equipment specifications.
  • A precise number without assumptions is not necessarily more reliable than a range.
  • Document unanswered questions and any contract language tied to the estimate.

What it depends on

  • What information the installer has already provided
  • Whether the estimate is a guarantee or only a forecast
  • Design complexity and shading uncertainty
  • Availability of comparable proposals

Risks and trade-offs

  • Walking away may forfeit a convenient provider or schedule.
  • Proceeding without transparency makes underperformance disputes harder to resolve.
  • Different modeling tools can produce different results even with similar inputs.

Information you may need

  • Full proposal and production report
  • System layout and equipment list
  • Modeling assumptions and exclusions
  • Guarantee, remedy, and measurement terms

Your next step

What to do next

Send a written list of required assumptions with a response deadline; if the provider remains unwilling, exclude the estimate from final comparison and seek a transparent alternative.

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