Path-Q Solar
How can I tell whether an installer is using realistic production assumptions?
Answer
Ask the installer to show how the estimate accounts for site geometry, shading, weather, equipment losses, degradation, downtime, and consumption or export assumptions. Compare the model with an independent estimate and inspect whether the quote reports uncertainty rather than presenting one optimistic number as guaranteed.
Key points
- Verify roof planes, orientation, tilt, obstructions, shading, and system layout.
- Ask what loss factors, weather data, inverter limits, downtime, and degradation are included.
- Separate energy production from bill savings; the latter also depends on usage and billing rules.
- Request monthly or hourly production estimates where they materially affect the decision.
What it depends on
- Accurate site survey and shading analysis
- Equipment specifications and system layout
- Weather and degradation assumptions
- Consumption, rate, and export assumptions
Risks and trade-offs
- A modest production overstatement can materially extend payback.
- A production guarantee may have exclusions, measurement rules, or limited remedies.
- Historical utility use may not represent future consumption.
Information you may need
- Detailed production report and modeling assumptions
- Site imagery or shade analysis
- Equipment data sheets
- Utility bills and proposed billing assumptions
Your next step
What to do next
Have another qualified installer or independent analyst review the site and compare production estimates using the same system design.
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