Enter the actual ready of the plant output and the calculated nominal plant output into the calculator to determine the PV performance ratio.

PV Performance Ratio Formula

The following equation is used to calculate the PV Performance Ratio.

PR = AO / NO
  • Where PR is the performance ratio
  • AO is the actual reading of the plant output (kWh)
  • NO is the nominal calculated plant output (kWh)

To calculate the PV performance ratio, simply divide the actual output by the nominal calculated output.

What is a PV Performance Ratio?


A PV performance ratio measures the difference between the amount of power generated by a solar energy system and the amount of power expected from the system. This number is expressed as a percentage.

For example, if a solar energy system generates 10 percent more power than expected, then it has a performance ratio of 110 percent. A solar energy system with a performance ratio below 100 percent means that it isn’t performing as well as expected.

A PV performance ratio is independent of location. That means it only measured the performance relative to the expected performance in that area, not relative to areas with more sunlight.