The nominal power of a PV module is based on Standard Test Conditions (STC) conditions:

  • Irradiance: 1,000 W/m²,
  • Module temperature: 25°C,
  • Air Mass: 1.5

or Normal Operating Cell Temperatures (NOCT):

  • Irradiance: 800 W/m²,
  • Ambient temperature 20°C,
  • Wind speed: 1m/sec.
PV empSpecs
PV Temperature Specifications

The electrical resistance of a conductor increases with its temperature. Photovoltaic cells as semi-conductors follow that rule.  The power temperature coefficient is approximately -0.4% / °C. The efficiency decreases when the ambient temperature increases. PV modules operating in a cold climate, such as in Canada, will have better overall efficiency than if they were installed in a warmer location, such as for example California.

According to a simulation of annual energy yield taking into account the hourly ambient temperature, a typical overall efficiency loss in the north due to temperature is 1.1%.   This loss factor would be much lower in warmer climate.


Other performance factors

  1. GHI to POA ratio
  2. Far shading
  3. Inter-shading
  4. IAM
  5. Soiling
  6. Snow
  7. Low irradiance
  8. Temperature
  9. Module quality
  10. Mismatch
  11. Inverter efficiency
  12. Power clipping
  13. Wiring
  14. Transformer
  15. Dispatch
  16. PID
  17. Light soaking
  18. Aging