Path-Q Solar
How can I verify that a solar production estimate accounts for local weather patterns?
Answer
Ask for the production model's location, weather-data source and period, assumptions, shading analysis, system losses, and uncertainty range. Compare the estimate with an independent modeling tool or long-term regional data, and require the installer to explain how unusual weather, snow, heat, haze, and seasonal variation are represented.
Key points
- The model should use a location close enough to reflect the site's climate and solar conditions.
- Review whether the estimate is based on long-term data rather than a short favorable period.
- Check assumptions for orientation, tilt, shading, temperature, snow, soiling, inverter losses, and degradation.
- Request monthly production estimates and a conservative case, not only an annual total.
What it depends on
- System layout and equipment
- Site shading, orientation, tilt, and local obstructions
- Weather-data source and modeling method
- Expected operating and maintenance conditions
Risks and trade-offs
- A precise-looking estimate can conceal substantial weather and modeling uncertainty.
- A nearby weather station may not represent the site's elevation, exposure, or microclimate.
- Comparing models with different loss assumptions can produce misleading conclusions.
Information you may need
- Full production report and assumptions
- Weather-data source and data period
- Shading study and site layout
- Installer's low, expected, and high production cases
Your next step
What to do next
Request the complete modeling report and compare its assumptions with an independent estimate using the same system layout.
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