Path-Q Solar
How can I verify that a claimed solar production guarantee uses a fair weather adjustment?
Answer
Ask for the complete guarantee calculation, including the baseline production model, weather data source, adjustment formula, allowed exclusions, degradation treatment, and measurement period. A fair adjustment should compare actual system conditions with a clearly defined long-term or contract baseline rather than selectively excusing poor performance.
Key points
- Confirm whether the adjustment uses irradiance, temperature, snow, shading, outages, or other defined variables.
- Check whether weather data is measured at the site or taken from a nearby station and how gaps are handled.
- Require the method for separating weather effects from equipment downtime, curtailment, shading, and maintenance.
- Compare the guarantee's adjusted result with independent production records where possible.
What it depends on
- Contract wording and guarantee formula
- Weather dataset and site representativeness
- Metering and monitoring accuracy
- Exclusions, degradation assumptions, and claim deadlines
Risks and trade-offs
- A broad weather adjustment can make a guarantee difficult to enforce.
- A strict adjustment may not account for site-specific shading or unusual conditions.
- A production guarantee is not necessarily a promise of bill savings or a fixed financial return.
Information you may need
- Full guarantee and warranty documents
- Production model and assumptions
- Weather data source and adjustment calculation
- Metering records and outage history
Your next step
What to do next
Request a worked example using one past production period and compare the result with the contract's stated threshold before accepting the guarantee.
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