Path-Q Solar
How can I distinguish normal panel degradation from a sudden performance fault?
Answer
Normal degradation is generally gradual, broadly distributed, and consistent with the equipment's documented expectations. A sudden fault is more likely when output drops abruptly, affects one panel, string, or inverter, coincides with alarms or physical damage, or fails to recover after comparable weather and operating conditions.
Key points
- Review multi-year, weather-adjusted production rather than relying on annual totals alone.
- Compare affected and unaffected sections under similar irradiance and temperature.
- Look for step changes, recurring outages, clipping changes, hot spots, cracks, or connector issues.
- Account for new shading, soiling, snow, curtailment, and monitoring changes before attributing the loss to degradation.
What it depends on
- System age and equipment specifications
- Data quality and weather normalization
- Changes in shading, soiling, configuration, or operating conditions
- Whether the decline is system-wide or localized
Risks and trade-offs
- Normal year-to-year weather variation can resemble degradation.
- A system-wide decline can result from inverter, grid, or monitoring issues rather than panels.
- Waiting too long to document a sudden fault may make warranty diagnosis harder.
Information you may need
- Installation date and module documentation
- Multi-year interval production
- Weather, shading, cleaning, and maintenance history
- Alarms and section-level performance data
Your next step
What to do next
Plot weather-adjusted production by month and compare the timing and location of any step change; escalate a localized or persistent decline for testing.
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SQ02135