Solar Panel De-rate Factor

Please use the attached spreadsheet to calculate the de-rate factor for photovoltaics.

In most cases, only the values for Shading, Snow, and Inverter should be changed from their default values on the Derate Factor Calculator spreadsheet.  If you have advanced knowledge of the losses of the other system components, you may override them as well.

The attached spreadsheet provides default values resulting in a 0.825 default derate factor. These values match the current PVWatts default values, including a default inverter efficiency of 0.96.

NOTE: If you have received a detailed solar production analysis from a solar system designer, you can optionally choose to use Ekotrope's "Other Onsite Generation?" section and enter the annual kWh production directly instead. Please verify that this approach is acceptable to your quality assurance provider.