Path-Q Solar

How can I compare solar quotes that use different assumptions about annual production?

Answer

Normalize the quotes before comparing them: use the same usable roof layout, system boundary, weather assumptions, shading assumptions, degradation treatment, and energy units. Then compare estimated production by month or hour, not just the annual total, and ask each provider to explain every material difference.

Key points

  • Confirm whether production is AC energy delivered, DC panel output, or another measure.
  • Check panel count, orientation, tilt, shading, equipment losses, availability, and degradation assumptions.
  • Review first-year production, lifetime production, and production by month.
  • Use the same consumption and bill assumptions when comparing financial results.

What it depends on

  • System layout and equipment specifications
  • Weather, shade, temperature, and loss assumptions
  • Modeling software or method
  • Consumption, export, price, and degradation assumptions

Risks and trade-offs

  • A higher production estimate is not necessarily more accurate.
  • Small modeling differences can materially affect payback and lifetime savings.
  • Quoted guarantees may cover equipment performance rather than actual site production.

Information you may need

  • Full production model or assumptions from each quote
  • Monthly or hourly production estimates
  • Panel, inverter, shading, loss, and degradation details

Your next step

What to do next

Create a comparison table with identical assumptions and ask each provider to reissue its production estimate on that common basis.

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