A bigger production forecast can make a solar quote look better than it is. Ask what went into the number and whether those assumptions fit your roof.
By ProjectSide · October 21, 2026
Start here.
A production estimate is a forecast, not automatically a guarantee. Panel capacity, layout, shading and other inputs affect the result. Compare those inputs when similar-size systems predict different output.
Request the inputs, not just the result.
Ask for the proposed panel capacity, layout, orientation and shading assumptions. Have the installer explain how roof obstructions and different roof planes were accounted for. An early remote estimate may need revision after a site assessment.
Compare estimates using the same scope.
One offer may include more panels, different equipment or a different layout. Put those changes beside the predicted annual output. Comparing production alone can hide an important design difference.
Separate production from your consumption.
A forecast of electricity generated is not a forecast of exactly when your household will use it. Ask how the proposal treats daytime use, exports, seasonal variation and any future load. A planned EV or HVAC conversion should be an identified assumption.
Ask about uncertainty and performance obligations.
Which parts of the forecast are modeled, and is anything contractually guaranteed? If there is a guarantee, request its measurement method, exclusions and remedy. A manufacturer’s panel performance warranty is not automatically the same as a guarantee of your home’s total production.
Use a written explanation to resolve a big difference.
If similar-size proposals predict noticeably different output, ask both installers to explain the input differences. Do not choose the larger forecast just because it creates a shorter payback period. Our paid Full Advocacy service can help you question those assumptions and compare the answers.
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