Path-Q Solar

What weather data is useful when investigating a single month of unusually low solar production?

Answer

Use monthly and daily irradiance or sunshine data, cloud cover, precipitation, snow, haze or smoke, temperature, and unusual shading conditions, compared with a multi-year baseline for the same location and month. Also check outages and curtailment so weather is not blamed for an equipment or data problem.

Key points

  • Global solar irradiance or a comparable solar-resource measure is more useful than temperature alone.
  • Daily data helps distinguish a few storm-related days from a broad performance decline.
  • Snow, smoke, dust, fog, and persistent clouds can reduce output without creating a hardware fault.
  • Compare weather at or near the site when possible because regional data may miss local conditions.

What it depends on

  • Available site or regional weather data
  • Production interval and outage records
  • Historical baseline and system changes
  • Local shading, snow, smoke, and soiling conditions

Risks and trade-offs

  • A single month has limited diagnostic value and may be normal variation.
  • Weather stations may not represent roof-level conditions.
  • A weather explanation can delay action on an inverter or monitoring failure.

Information you may need

  • Daily and monthly production
  • Irradiance, cloud, precipitation, snow, and smoke data
  • Inverter events and monitoring availability
  • Comparable historical production

Your next step

What to do next

Compare the affected month with a multi-year, weather-adjusted baseline and investigate equipment events if the production loss exceeds what the weather explains.

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SQ02527