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How to choose LEDs for cannabis cultivation

October 5, 2022  By Jonathan Fernandes

Photo: 2H Media

Cannabis grow lights have a myriad of specifications. Traditionally, wattage and lumen values have determined how strong and effective they are, although in recent years, newer equipment such as Light Emitting Diodes (“LEDs”) have emerged onto the market boasting new lighting technology.

We have now identified essential parameters exhibiting how effective good lighting can be for improving a cannabis grow operation. The specifications of the light’s output are probably the most significant information when deciding what light is best for your cultivation environment.

When examining output, know these important terms:

Photosynthetically Active Radiation (or “PAR”) and Photosynthetic Photon Efficacy (or “PPE”).


These are the two most crucial details when choosing the right fit for your grow. Let’s discuss what each term means and why they are vital to cannabis plants.

Photosynthetically Active Radiation

The most significant of these terms to understand is PAR, or the energy available from the light source that drives photosynthesis. Lighting companies traditionally listed wattage and lumens/lux as a reference to measure the strength of a light, however measuring lumens only indicates how bright the light source is, which is not a driver for plant growth.

Humans can distinguish brightness with our eyes, but plants don’t “see” it that way.

Photoreceptors in plant leaves collect available energy to make photosynthesis happen. Therefore, it is more beneficial to understand how much of that energy is available for a plant to use, especially cannabis.

PAR is measured by examining the Photosynthetic Photon Flux (“PPF”), which is the available number of photons in µmol per second from the light source. When measuring how much photon energy hits the top of the canopy, and subsequently the leaves to drive photosynthesis, it is measured in PPFD — the “D” being the Density of the photons in µmol, per meter squared, per second.

The PPF tells you how much energy is available, while the PPFD tells you the actual amount of energy hitting the canopy.

To think of it in simpler terms, think of a rain cloud during a storm: the PPF would be equivalent to the amount of available rain coming from the cloud per second, and PPFD would be the actual measured amount of rain that hits the surface in a given density area.

Knowing how much energy is available and how much is used by the plants should be the most critical factor when selecting fixtures and designing a lighting layout.

Start setting cultivation goals and establish the physical environment based on requirements for nutrition, temperature, humidity, and supplemental compounds such as CO2. Next, determine how much PAR would keep the metabolic rate of your plants at an optimal pace, and use that assessment to seek specific requirements for each piece of equipment, including the PAR from a light.

Photosynthetic Photon Efficacy

PPE is the PPF divided by the number of watts consumed, usually expressed in µmols/Joules of energy. The result shows how efficient the light and its components are in converting the electrical input wattage to achieve the stated PAR value. Here, the components refer to the individual LED diodes used to produce light and the electrical drivers that deliver the power to the diodes.

Even if the light has a high PPF value, if the PPE is low, then the fixture is not efficient in converting power into useable light radiation. A light like this might be wasting a lot of electricity. Hence why wattage alone should not be the sole deciding factor in any lighting decision.

Energy efficiency and savings are significant selling advantages of LEDs and any certifications which prove the efficacy are valuable, especially for commercial operations. Lights with a higher PPE rating produce the same amount of light with less energy costs.

Higher efficiency in LEDs assists in energy conservation and additional savings for cooling because traditional ballasts and lamps convert a significant amount of energy into heat. Highly efficient LED lights can hit up to 3.0 μmol·J, which is a massive shift in efficacy from conventional grow lights.

Multifunction grow lights

A great grow light has the capabilities of precisely dialling in PAR and spectrum to conserve energy and produce higher-quality flowers. Spectral variability can also unlock the genetic potential in plants.

Third party certification can help establish product specifications. Designated Light Consortium (DLC) — the largest non-profit energy-saving agency in the world — is one of the most established entities in the world that help verify energy consumption and photon output. Having electrical certifications such as UL and ETL allow consumers to buy products that are safe for electrical use.

LEDs in the cannabis space are continually evolving with new technology, standards, and certifications. Many believed the power of the wattage found in traditional HPS and HID lights would never be supplanted by other technology. However, through discoveries in research and science of cultivation, it is becoming increasingly clear that LED lighting is the future of indoor and even greenhouse growing.

Stay tuned! We will examine the various aspects of growing and understanding the technology behind LEDs in future articles.


Founder and President of Green Amber Canada, Jonathan Fernandes is a cannabis creator experienced in farming, extraction, education and equipment design. With over 20 years in the Canadian legacy market, he aims to educate and support consumer needs. Prior to working in cannabis, Jonathan worked with the Ontario government. His experience in enforcement, policy and legislation development makes him a driving force for the evolving cannabis regulations. Currently he spends his time researching and developing cannabis lighting technology.

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