Path-Q Solar

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

Answer

Normalize the quotes before comparing them: use the same system boundary, weather period, shading assumptions, degradation treatment, losses, panel orientation, and annual energy units. Then compare expected production per installed capacity, the uncertainty range, and the savings model rather than accepting the highest annual-production figure.

Key points

  • Confirm whether production is reported before or after inverter, wiring, shading, snow, temperature, and other losses.
  • Check whether the estimates use the same panel count, capacity, roof planes, and battery operating assumptions.
  • Ask for monthly or hourly production and a clearly identified baseline year.
  • Compare modeled production with the system's intended load and export assumptions.

What it depends on

  • System design and equipment ratings
  • Solar resource and weather dataset
  • Shading and loss assumptions
  • Degradation, availability, and curtailment assumptions

Risks and trade-offs

  • A higher production estimate may reflect optimistic assumptions rather than a better design.
  • Annual totals can hide seasonal mismatch with consumption.
  • Production estimates are forecasts, not guarantees, and should be tested with sensitivity cases.

Information you may need

  • Full production report from each provider
  • Monthly or hourly output and loss assumptions
  • System layout, shading analysis, and degradation assumption
  • Warranty or performance-guarantee terms, if offered

Your next step

What to do next

Put every quote into a common comparison table and request revised projections using identical assumptions.

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