Performance Ratio (PR) of a plant for a period of time is energy measured(kWh)/(Irradiance(kWh/m2) on the panel x Active area of PV module(m2) x PV module efficiency). PR is a measure for the performance of a PV system taking into account environmental factors (temperature, irradiation, climate changes etc.).PR will take into account the availability of the grid, minimum level of irradiation needed to generate electrical energy, irradiation levels at a given period of time.