All LEDs are Not Created Equal: Check LED Efficacy
By: Heidi Lindberg and Erik Runkle
There has been a flood of light-emitting diodes (LEDs) to hit the horticultural market in recent years. The types of fixtures, light quantity and spectrum, optics, and light fixture efficacy (i.e., efficiency) vary widely from one LED product to the next. All of these factors make it very difficult for greenhouse growers to compare the lighting options. As we enter late March, the need for supplemental lighting of ornamentals and many vegetables is limited to the most cloudy, northern latitudes in the United States. However, you might already be considering your options for LED fixtures for your greenhouse for next season.
One resource that all growers and owners should know about is the Design Lighting Consortium (DLC) (www.designlights.org). The DLC is a non-profit organization improving energy efficiency and lighting quality and has data specifically on horticultural fixtures. As of March 2022, there are 659 lamps that are DLC compliant. What does that mean?
To be DLC-compliant, the lamp must have a fixture efficacy (number of photons emitted per amount of energy consumed) of 10% or greater than the best-performing high-pressure sodium (HPS) fixture. The best-performing HPS lamp has an efficacy of around 1.7 μmol×J–1.
With one exception, the efficacy of LED products ranges from 1.81 to 4.06 μmol×J–1. The greater the number, the more efficient the lamp. There is one LED product that with an efficacy of 4.06 μmol×J–1, but it only emits red light and thus is not suitable for most crops.
As of March 2022, there currently are:
· 351 lamps with efficacy of ≥ 2.5 μmol×J–1
· 31 lamps with efficacy of ≥ 3.0 μmol×J–1
· 8 lamps with efficacy of ≥ 3.5 μmol×J–1
Moral of the story? If you are looking at purchasing LED lamps (either for low-intensity, photoperiodic lighting or for high-intensity, supplemental lighting), check the lamp efficacy of the product you are considering on the Design Lighting Consortium (www.designlights.org) website. It will help you compare the efficacy of competing products and might help you make your decision.
While fixture efficacy is an important selection criterion, there are many others too. For more information, check out "A Closer Look at LED Efficacy” by Dr. Erik Runkle in the January 2022 issue of Greenhouse Product News (GPN)Magazine. For more information on light intensity of popular light fixtures, check out "Light Fixtures and Their Photon Fluxes” in the May 2021 issue of GPN Magazine.
Heidi LinbergGreenhouse Extension Educator, Michigan State University
Heidi Lindberg is a greenhouse and nursery extension educator based in West Olive, Michigan. She serves growers in western Michigan, especially the dense number of growers in Ottawa, Kent, and Muskegon counties. She provides research-based educational programming and diagnostic support for greenhouse growers in southwest Michigan.