The efficacy of any electrical lighting system was dependent on the perception of lighting in humans until recently.The proper metric to measure plant lighting will be PPE (Photosynthetic Photon Efficacy). It is measured by dividing PAR Photon Output (namely, PPF value) (μmol·s–¹) or micromoles/second unit with Watts (W) required as input power to produce the light.
Compared with HPS lights, LED lights are relatively new in the horticultural and many people are not yet familiar with their benefits and drawbacks. Also, LEDs were typically cost-efficient than the HPS lights.
It is important to understand that there is no universal rule for how far to placeLED lights from plants in each phase of growth. The power and angle of individual LEDs within a fixture and the use of lenses to reflect light downwards should be taken into consideration.
Energy-efficient/power-saving LED grow lights are the lighting of the future of agriculture. They are not only economical in their use but they produce better plant growth as well, in comparison to all traditional lighting options.