What Is PPE?
The ratio of the produced PPF to the applied electrical power in watts is a common way to represent the efficiency of the light fixture. The efficiency unit is μmol/J. The PPE of the lighting system increases with the value of this parameter, as it indicates the amount of electrical energy transformed into PAR. But keep in mind that this figure excludes the wavelength of light above 700 nm and says nothing about how well the light is working on your crops.
How to Measure it?
You can calculate the PPE of a fixture by simply dividing its PPF and wattage. For instance, the PPE of a 60 watt light with a PPF of 168µmol/j is 2.8µmol/j.
HPS has the greatest efficacy rating in the past, up to 1.9µmol/j. But LEDs have already surpassed HPS and are nearing 3.0 umol/j. While HPS efficiency is fixed, LED efficiency will continue to rise.
