Path-Q Solar

What questions should I ask an installer about projected solar production?

Answer

Ask the installer to explain the site-specific production model, its data sources and assumptions, monthly output, shading and loss calculations, degradation, uncertainty, and how the estimate relates to your actual bills. Request the proposal and assumptions in writing so multiple installers can be compared on the same basis.

Key points

  • Ask what roof planes, tilt, azimuth, shading, weather dataset, and system losses were modeled.
  • Ask for monthly and annual kilowatt-hours, not only system size or estimated savings.
  • Ask whether the estimate includes snow, soiling, clipping, downtime, degradation, and equipment availability.
  • Ask how exports, battery operation, rate changes, and household usage affect the financial forecast.

What it depends on

  • Quality of the site survey
  • Completeness of the production model
  • Your historical and expected electricity use
  • Current utility, financing, incentive, and export assumptions

Risks and trade-offs

  • Savings estimates can appear precise even when production, rates, and usage are uncertain.
  • Different installers may use different loss and weather assumptions.
  • A production guarantee may have exclusions or measurement rules that differ from the sales estimate.

Information you may need

  • Full production model and assumptions
  • Equipment specifications and proposed layout
  • Warranty or production-guarantee terms
  • Current bill, tariff, financing, and incentive inputs

Your next step

What to do next

Ask at least two installers the same questions and compare their written production assumptions, monthly estimates, guarantees, and exclusions.

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