Path-Q Solar

How can I tell whether lower solar production is caused by weather or a system fault?

Answer

Compare the observed output with weather-adjusted expectations and with unaffected parts of the array. A broad, gradual reduction during cloudy, hot, snowy, or shaded conditions is more consistent with weather or site conditions; a sudden, persistent, localized drop, alarm, or communication failure is more consistent with a system issue.

Key points

  • Use irradiance, cloud cover, temperature, snow, shading, and soiling information when interpreting output.
  • Compare the same periods with prior years or a nearby reference system only with care.
  • Check inverter status, monitoring communications, breakers, and section-level data without opening equipment.

What it depends on

  • Quality of the production baseline
  • Available weather and monitoring data
  • System layout and level of panel or string monitoring
  • Recent maintenance, construction, shading, or storms

Risks and trade-offs

  • Weather can mask a partial fault, while a monitoring outage can mimic low production.
  • Short-term comparisons can produce false alarms.
  • Roof or electrical troubleshooting by an unqualified person can cause injury or damage.

Information you may need

  • Production data for the affected period
  • Weather and shading conditions
  • Alarm and communication status
  • Section-level comparison and recent site changes

Your next step

What to do next

Create a weather-adjusted comparison for the affected dates and send the evidence to the installer if the reduction is sudden, localized, persistent, or accompanied by an alarm.

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