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How to Choose the Best Cannabis Grow Lights

By Aimee O'Driscoll

Published: Jan 10, 2022   
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Every cannabis grower wants to produce the highest quality product possible. With light being a crucial factor in plant cultivation, part of optimizing the process involves using the ideal grow lights. Choosing the right lights can be tricky as there are multiple types to choose from, each with their pros and cons. What’s more, rapid advancements in research and technology means it can be tough to stay on top of the most up-to-date information.

Armed with the right knowledge, however, any grower can be well-equipped to make a solid decision based on your unique situation. Factors to consider include cost, power consumption, heat output, and light spectrum. And the choice will be different depending on the types of plants you’re growing and the space you’re working with. 

In this article, we’ll help ensure you choose the right lighting setup that fits your needs and budget. We explain the different types of lights available, reveal key factors to consider, and discuss recent advancements in the field, so you can make the right decisions.

Types of grow lights available

There are really two main types of light on the market today: LED (light emitting diode) and HID (high-intensity discharge). LEDs are newer and popular due to their efficiency and other factors. 

“HID lamps are incredibly inefficient, which is why they generate so much waste heat,” Taylor Kirk, horticulture services specialist at Fluence by OSRAM, tells Analytical Cannabis. “In comparison, LEDs are nearly twice as efficient. They also last two to four times longer than metal halide or fluorescent fixtures and do not require bulb changes, which reduces operating costs in the long term.”

Kirk also notes that LEDs offer more control over light spectrum and intensity without color filters. This enables growers to better manipulate plant morphology and the metabolic processes that determine flower yield and quality.

But while LEDs are increasingly common, HID bulbs are still broadly used. There are two main types of HID: MH (metal halide) and HPS (high-pressure sodium). These are often used in combination, because MH bulbs – which produce a bluish light – are good for vegetative growth, while HPS lamps – which produce a yellow-orange glow – are better suited to flowering plants.

Factors to consider when choosing the best grow lights

As Brendan Delaney, director of cultivation at Solar Cannabis Co., explains, there’s a lot that goes into the decision-making process when choosing which type of light a grower should use, including the cost, quality, intensity, and desired spectrum.

Here we’ll go over the main factors to consider when choosing grow lights:

  1. Cost and efficiency
  2. Facility layout
  3. Light spectrum

Let’s look at each of these in detail:

1. Cost and efficiency

In general, the cost to purchase HIDs is lower than for LEDs, but prices on LEDs are decreasing. Plus, many companies offer rebates, helping to offset the upfront costs. But when calculating capital expenditure, you also must consider the net running costs of lights, including how much power they consume and how much heat they give off.

“Plain and simple, LEDs are extremely energy efficient,” says Delaney. “When talking about efficiencies, it’s not just about the light itself but more in terms of environmental variables. LEDs throw off considerably less heat than other lights, such as HPS. This has a dramatic impact on cutting cooling costs, making it more efficient all the way around.”

That said, as Kirk notes, some growers rely on the heat from HID lamps to provide warmth to their facility. “If a grower is replacing HPS lamps – which often provide heat for the grow room due to their low efficacy – with LEDs, which run cooler, they’ll need to properly compensate by adjusting the HVACD [heating, ventilation, air conditioning, and dehumidification] system to add heat to the room.”

 Image credit: Solar Cannabis Co.

2. Facility layout

Another key consideration is the space that cannabis cultivators are working with. With vertical farming increasing in popularity, growers are now able to produce high yields within a limited footprint. Plants are grown in tiers, which means a multi-level lighting system is required to supply all plants with the right amount of light.

HPS lamps are usually unsuitable in this scenario, as they tend to be large and give off a lot of heat. On the other hand, LEDs have a slim profile, fit easily into racking systems, and don’t emit much heat. As such, they can be strategically placed to ensure that all plants have the right amount of light, no matter their position on the racks.

3. Light spectrum

Plants require different levels of light intensity and spectrum composition depending on their cultivar as well as their stage in the growing cycle. Recent advancements in research mean that lighting manufacturers and growers are now equipped with more in-depth knowledge in this area and are tailoring lighting systems accordingly.

As mentioned, LED lights offer more control here, but not all LEDs are made equal. This is definitely an area where you need to do some research and find out what the different lighting manufacturers are able to offer.

As Delaney reveals, “When you’re looking deeper into the light spectrum, we’re really starting to see companies experiment more in-depth with diodes, adding deeper reds and more UV at various stages. With these initiatives, we’re seeing better results with higher yields. It’s still early on, but this is a big trend within the market.”

Indeed, Kirk tells Analytical Cannabis that research by Fluence – conducted in partnership with Wageningen University and Research in the Netherlands and Texas Original Compassionate Cultivation – found that, in some chemovars, monoterpene and cannabinoid content were inversely proportional to the fraction of red light introduced to plants. As such, cultivators need to pay particular attention to their spectral composition.

Kirk notes that recent cannabis lighting research has also delivered another critical insight: that most cannabis cultivars perform well under high photosynthetic photon flux density (PPFD), creating potential to maximize yields without jeopardizing quality.

“These insights together show how important it is for growers to adopt a high PPFD lighting strategy with a more balanced ‘white light’ spectral composition,” remarks Kirk. “This will result in significantly higher yields, better crop morphology, and improved cannabinoid profiles.”

Final comments

Overall, when deciding on the right lights, growers need to establish their key objectives. For example, Kirk notes that “for those who want greater environmental control or need to introduce new spectra and light intensities to optimize plant attributes like morphology, cannabinoid content, and overall yield, LEDs should be the first option.”

That said, cost is often top of mind for growers and HIDs can sometimes win out here. Just remember to factor in all long-term expenses including the upfront price, utility fees, and replacement costs when calculating expenditures.

This article originally appeared in Analytical Cannabis' Advances in Cannabis Cultivation eBook in December 2021. 

Aimee O'Driscoll

Freelance Science Writer

Aimee is a freelance science writer with over a decade of experience as a development chemist. She has written for Analytical Cannabis since 2020.


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