Path-Q Solar
What should I ask an installer about production assumptions in a quote?
Answer
Ask the installer to show exactly how expected production was calculated, including site measurements, shading, equipment, losses, weather data, degradation, availability, and uncertainty. Ask for monthly results and a clear distinction between production, bill savings, and financial return.
Key points
- Request the modeled layout, roof orientation and tilt, shading analysis, and usable-area assumptions.
- Ask for exact panel, inverter, optimizer, and battery models and their operating assumptions.
- Review loss assumptions for temperature, wiring, mismatch, soiling, snow, downtime, clipping, and curtailment.
- Ask what solar-resource data and time period were used and whether the estimate includes an uncertainty or sensitivity case.
- Request monthly production, first-year production, degradation treatment, and the inputs used to calculate bill savings.
What it depends on
- Quality of the site survey and shading analysis
- Equipment and system layout
- Solar-resource data and modeling method
- Utility tariff and export assumptions
- Maintenance, downtime, and degradation assumptions
Risks and trade-offs
- Comparing quotes with different assumptions can make one proposal appear better unfairly.
- Production guarantees may exclude weather, grid outages, shading changes, or equipment downtime.
- Savings estimates can be overstated if export credits, fixed charges, or rate changes are treated incorrectly.
Information you may need
- Complete production model and assumptions
- Equipment models and layout
- Monthly production and loss breakdown
- Tariff, export, and savings assumptions
- Any production guarantee and exclusions
Your next step
What to do next
Ask each installer to complete the same production-assumption checklist and compare the proposals using a common, conservative modeling basis.
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SQ00159