What is kWh/kWp Performance?

The peak kilowatt (kWp) rating for a solar PV module represents the instantaneous DC power output rating of an individual module under standard testing conditions. For multiple modules connected as a PV system, module kWp ratings are summed to establish the kWp PV system rating.

The PV system generates AC electrical energy measured in kilowatt-hours (kWh). kWh/kWp is a measurement of the PV system performance in the field for a period of time and varies depending on the local solar resource, module characteristics (i.e. temperature coefficients, degradation rate) and system installation factors (shading, tilt, orientation, inverter efficiency, etc.). For a given location, kWh/kWp provides the best means of comparing installed PV system performance and is independent of system size or module efficiency rating.

All PV systems are not the same.

Many installed PV systems are underperforming their potential production through sub-optimal design, installation or maintenance practices. 

The above graph of a selection of publicly available commercial roof-mounted PV system kWh/kWp performance in the Boston, MA area demonstrates the great variation in solar PV system performance and the opportunity for significant improvement. For 15 systems, kWh/kWp values range from 758 to 1,417 with an average of 1,133 for the year.

621 Energy uses the best project management, up-front engineering, installation, commissioning, monitoring/analysis and maintenance processes to provide a high-performing (kWh/kWp) PV system in a cost-effective manner.