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LED Vs HPS Lights: Which Are Best For Growing Cannabis?

For decades, high-pressure sodium (HPS) lamps have been a standard feature of pretty much all indoor grow rooms, allowing for fast growth and consistently high yields. However, a recent improvement in the quality of light-emitting diode (LED) lighting modules has ignited a debate over whether it’s time for a sea change in the cannabis lighting world.

The fact that LEDs are way more energy efficient than HPS lights has historically been overshadowed by the fact that they are also considerably more expensive to install. Yet as the technology improves, prices are a-tumbling, and with recent research highlighting the ability of LEDs to increase the cannabinoid content of marijuana plants, many growers are beginning to think about making the switch.

What Kind of Light Does Cannabis Need?

Before grow rooms existed, cannabis grew wild in the great outdoors, typically germinating in spring and flowering in autumn. You don’t need to be a cannabis grower to know that different seasons are characterised by different colours, with the autumn sunlight taking on a golden hue as it caresses the reds and browns that dominate the landscape. This change in lighting is caused by the angle of the sun, which is lower in the fall than it is in the summer, resulting in longer wavelengths of light that fall closer to the red portion of the light spectrum.

When growing cannabis indoors, you’ll generally want to replicate the optimum natural conditions that your plants need in order to grow to a good size and produce lots of cannabinoid-rich bud. This usually means providing them with plenty of red or infrared light during the flowering stage, typically with a wavelength of 600 to 780 nanometres.

So, Which Are The Best Lamps To Use?

Without getting too technical, it’s worth knowing that HPS lights use vaporised sodium in order to generate a strong orange glow, which has a long wavelength and is great for flowering cannabis. This is usually augmented by certain other gases that add in a wider range of wavelengths, resulting in a whiter light.

The lights themselves are very affordable and have been doing the trick for years, which is why they are still by far the most common lighting system in grow rooms worldwide. After all, they’re easy to use and always give great results – so if it ain’t broke, why fix it?

Well, in the endless struggle for perfection, some pioneering growers have discovered that LED lights can actually provide greater yields and a higher quality of bud. This is because LEDs can be configured to emit certain colours of light, which allows growers to provide their plants with the specific wavelengths they need in order to generate the maximum concentration of cannabinoids.

As previously mentioned, the high price of installing an LED array has been a major stumbling block for many years, although these systems are getting cheaper all the time. On top of that, LED modules typically use about a quarter to half as much energy as HPS lights, which can lead to massive savings in the long run.

Cannabis Growing Canada

Given that lighting accounts for up to 85 percent of the energy usage of a typical commercial grow room, making the switch to LED clearly brings major financial and environmental benefits.

That said, some degree of technological know-how is required in order to get to grips with LED lights, and novice growers may find these much more complicated to use than HPS lights.

What Does The Latest Research Say?

A few notable studies have highlighted the potential benefits of LED lights over HPS. One paper that came out in July of this year found that certain LED lights can generate more flowers and higher cannabinoid content than HPS lights[i]. In particular, an LED array that was configured to emit pink-looking light resulted in extremely high concentrations of CBD.

This particular light consisted of 77.71 percent red light and 16.75 percent blue light.

A separate study compared the effect of HPS lamps with several different LED arrays, and found that the HPS set-up regularly resulted in greater flower yields, but that the concentration of cannabinoids was much higher under LEDs. For instance, an LED array that was configured to emit a light consisting of 68 percent red light and 21 percent infrared light was found to increase THC content by 38 percent when compared to HPS lamps[ii].

As the evidence continues to mount, some are predicting that LEDs will soon overtake HPS as the optimal lighting system for growing cannabis. Many growers, however, remain reluctant to ditch their tried and tested HPS lamps for a technology that is still very much under development. Only time will tell if LED has the potential to become the new champ in the cannabis lighting world.

[i] Amrein P, Rinner S, Pittorino T, Espel J, Schmidmayr D. Influence of Light Spectra on the Production of Cannabinoids. Medical Cannabis and Cannabinoids.:1-8. –

[ii] Magagnini G, Grassi G, Kotiranta S. The Effect of Light Spectrum on the Morphology and Cannabinoid Content of Cannabis sativa L. Medical Cannabis and Cannabinoids. 2018;1(1):19-27. –

Cultivation information, and media is given for those of our clients who live in countries where cannabis cultivation is decriminalised or legal, or to those that operate within a licensed model. We encourage all readers to be aware of their local laws and to ensure they do not break them.

Ben Taub