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Choosing LED or HPS Lights for Commercial Growers

By Dan Vaillancourt
Published: June 8, 2022
Key Takeaways

Many commercial growers still cling to the notion that HPS lights are the best for growing cannabis. However, Dan Vaillancourt (a commercial grower) argues good commercial LED lights should be the choice for medium to large greenhouse production.

The haters will say its fake, and old-school growers will swear by high pressure sodium (HPS) lighting because it has worked fine for decades, but the truth is LED grow lighting is undeniably making big waves in the cannabis industry — with good reason.

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High pressure sodium lighting has earned its heavyweight title because of its high micromole value over time, but there are many good commercial LED lights entering the ring lately that are exceeding what HPS lighting has been offering with spectrums that can be closer tuned, produce far less heat, and offer a lower power draw.

When choosing the right grow light of any variety there are some basic principles we need to focus on to select the right light.

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par chartSelecting The Right Light

A grow light needs to offer the right spectrum for our cannabis plants throughout the various stages of the plant’s life, intense light penetration, low heat generation, and good power consumption. That’s not too much to ask, is it?

Clone & Seed Lights

Very early on in the plant’s life (for seedlings or clones) it is best to use either fluorescent lighting or low-powered LED lighting. The intensity is not important in this stage but lighting with a full spectrum leaning towards more blue light to promote shorter internode spacing is ideal. The ideal intensity range would be between 350-550 μmol/s.

Vegetative Lighting

Plants that are further established and in the vegetative phase will require more intense light than clones and seedlings but not as much as flowering plants. Ideally you keep a full spectrum in this room and use half as much as a flowering room. The ideal intensity for veg growth is between 1,000-1,300 μmol/s.

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Lighting For Flowering Stage

The flowering rooms are where light intensity and spectrum will become very crucial to your success. Many people will choose a cheap LED light to test them out and not have great success at this stage. This is because we want very intense light (1,700–2,300 μmol/s) at this stage to properly penetrate our canopies which are generally three feet or more and full of buds and leaves.

Generally, most LED lights that can outperform an HPS light in this department cost more than $800 each, making “test lights” harder for many growers and leaving many people stuck in the HPS days.

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Good flowering lighting in either LED or HPS has far more red spectrum to promote larger flower growth. The red-light spectrum will promote larger leaf growth and further internode spacing as well, so it is still carefully mixed with a full spectrum to provide the right mixture. Blue light will help keep our plant’s structure tight so that flowers form together better, and during the flowering phase it is still required to help tighten the buds. The ideal light intensity range for flowering is 1,700-2,300 μmol/s.

These ideal intensity ranges are subject to the light’s distance from the plants and plant variables such as stress or insects. This is in ideal conditions for healthy plants and assuming lights are placed at the right distance from the canopy. Light intensity should be lowered by half for plants undergoing stress of any kind.

Dehumidifiers for these rooms added 18,000 BTU of heat per room.


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Comparing LED Vs. HPS In A Commercial Grow

For this comparison we will be comparing 1,000W double-ended HPS grow lights and 850W commercial LED grow lights. The commercial LED grow light is exactly similar in μmol value as an average 1,000W double-ended grow light (2,100 μmol/s).

This is the minimum light intensity we would want to achieve to be able to penetrate the average canopy thickness properly so all your flowers can get dense. The light distance from the canopy will vary with each type of light, though double-ended lights need to be kept much further away from the canopy then LED lights, but LEDs have no light spread like HPS does.

heat generation illustrationAverage heat from a 850W LED: 2,600 BTU. | Average heat from a 1,000W HPS: 4,000 BTU.

Heat Generated

High pressure sodium lights produce a lot of heat. Nearly double what an average high-powered commercial LED light will produce. This is something to think about when building your growroom as you will immediately need to calculate the heat load and apply the right amount of HVAC needs. High pressure sodium lights may be cheaper, but air conditioning is costly and purchasing bigger cooling units can add up immediately as well as in future energy costs.

energy draw illustrationAverage energy draw of an 850W LED at 120 volts: 5 AMPS. | Average energy draw of a 1000W HPS at 120 volts: 9 AMPS.

Energy Consumption

LED grow lights are considerably more energy efficient and eco-friendly than HPS lighting, which is why many places are offering rebates for switching your growroom to LEDs. The 100,000-hour run time on the LED lights means much less disposing of old lights that is necessary with HPS lights every second harvest. The energy savings are equivalent to the HVAC reduction as well, with nearly half the power draw of its counterpart. When grow lighting energy costs is one of the biggest ongoing expenses with growing, this is something to consider.


light spread of HPS lightsHPS light spread
LED light spread

Spread

The light spread of HPS lights is excellent. They can cover a large area and be spaced further apart, however, this is not always ideal. You get hot spots and cool spots where light is intense and then drops off dramatically. It is much harder to achieve even coverage this way opposed to the light bars that LED lights offer. LED lights offer little to no spread and because of this, growers are forced to place them very close together. Lining the ceiling in LED lights like this with evenly placed LED light bars allows you to have extremely even light coverage with little hot and cool spots.

New Heavyweight Champion?

If you are a small-scale grower, or on a budget and living in a cool area, then HPS is a fine choice. However, with the spectrum options from HPS lights coming from a mixture of gases, versus LED lights being added to change the spectrum, the argument of which one can offer a better spectrum is put to an end. We know they are cooler, offer better light distribution, and cost less to operate. With the only major downside being their price, LED is the clear heavyweight champion.

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Written by Dan Vaillancourt | Owner of 4Trees Cannabis Building Ltd.

Profile Picture of Dan Vaillancourt

Dan has designed and built hundreds of growing facilities as well as grown thousands of plants himself and spent countless hours in both the grow room and consulting. He owns 4Trees Cannabis Building Ltd., a company that designs and constructs growing facilities for both ACMPR as well as recreational (Micro-cultivation, LP). He is proud to be shaping Canada's cannabis industry.

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