led vs hps cannabis


An Essential Grow Light Comparison Guide

It’s inevitable: once you begin growing Cannabis, you’ll eventually wade into the controversial debate of which grow light is best.

Factions on each end claim their preferred lighting method produces more cannabis buds than all other options.

Join us as we compare and contrast metal halide, high-pressure sodium, CFL, plasma and LED grow lights to determine which system works best for you.

The Difficulty in Choosing the Right Grow Light

Your Grow Room. Your Choice

Types of Plants

Grow Room Temperature

Types of Grow Lights

The Stages of Growth

Ease of Use and Doing it Yourself

The Difficulty in Choosing the Right Grow Light

When I first started growing, I made the mistake of looking into articles that boldly declared a winner between MH vs. HPS, LED vs. MH, CFL vs. HPS, and HPS vs. LED.

It’s not that these weren’t helpful, it’s that some lights work well in one scenario and not so well at another.

The various growth stages of plants require different intensities of light, and each of the lights that we’re going to cover in this article all has different power outputs and wavelengths.

It’s for these reasons that we’re discussing the pros and cons of each light so that you’re equipped with a well-rounded education so you can make the best choice on your own.

Your Grow Room. Your Choice

It’s essential for us to note that each and every grow room will be different.

This is why we can say that there is no “ultimate” setup, but only appropriate lighting.

It’s your job to adequately determine a few factors before you begin searching for the best grow light, whether it be Metal Halide, HPS, LED or CFL bulbs.

Room to Grow: HPS vs LED

Are you growing in a grow tent or in a warehouse? Although these two examples are polar opposites, they still ask the same question. The space of your grow room will significantly impact your decision on which lights to purchase.

When growing in an 8’x8’ grow tent, your initial thought shouldn’t be to go for the power-saving CFL bulbs. Although CFLs are incredibly economical and emit little heat, they’re inadequate to cover the footprint required in an 8’x8’ grow tent.

Instead, a decision between metal halide and high-pressure sodium should be considered, and especially the wattage of the bulb.

The higher the wattage, the higher the hood can be placed, therefore increasing the available light footprint. Of course, with each inch raised, the lumens emitted will have a diminishing effect

Types of Plants

The types of plants that you decide to grow are also going to impact your lighting choice.

Growing a 6’ Cannabis sativa strain?

Well then, depending on the available height in your grow room, you may be better off with a flat lighting system such as LEDs

If you decide to super-crop an already-bushy Cannabis indica strain, then you’ll need the most extensive lumen footprint available. This may be in the form of a high-intensity discharge (HID) light, such as metal halide or high-pressure sodium.

Maybe you’ve decided to keep your cannabis plants small, but pack as many into your grow room with the Sea of Green (SOG) technique.

Since canopy height should be uniform and the apical portion of the plant is where you’re focusing all the light on, then a LED system or even CFL lights could do the trick.

Grow Room Temperature

I’ve grown in just about every temperature imaginable.

I’ve grown in humid summer conditions in unventilated attics and sub-zero winters in un-insulated out-houses.

Although other vital aspects come into play when it comes to grow room temperature, lighting choice can make or break your operation.

When growing in an already hot environment, a 1,000-watt HPS just isn’t feasible. Nor is a set of 600-watt MH. What is reasonable is a low heat-emitting light such as CFLs and LEDs.

These efficient systems will still pump out lumens while simultaneously having little effect on the overall temperature of the grow room.

When growing in a frigid environment, low-heat emitting lights are not the best option because your plants will become affected by the cold temperature.

This is the case where a 1,000-watt HPS will come in handy, and effectively raise the overall temperature while shining vital lumens directly at your plants.

Now that we’ve got the basic considerations under our belt. Let’s take an in-depth look at each available light

Types of Grow Lights

When it comes to growing indoors, there are a few tried and tested grow light systems you can’t go wrong with.

They go by many different names, So let’s take a closer look…

Metal Halide (MH)

Metal halide is a HID style grow light. It comes in a wide range of wattages, from 250 to 1,000. MHs have been used in growing cannabis because they emit a strong blue wavelength, which helps the vegetative phase of growth.

Studies have shown that the blue wavelength in light increases the overall growth of plants.

Since MHs generate so much power, they require a separate ballast to safely send the required lumens to it. These ballasts are either magnetic or digital, and they can weigh upwards to 30 pounds each.

High-Pressure Sodium (HPS)

HPS is also a HID style grow light. These lights also range from 250-1,000-watts. HPS lights are known for their red and orange wavelength that is meant to increase the overall size of buds and speed up the transition from the vegetative phase to the flowering stage.

HPS is used to mimic the natural response in cannabis plants to react to the suns’ position when it’s on the horizon. This red wavelength triggers an internal response to begin flowering due to shorter days ahead.

LEDS (Light Emitting Diode)

LED grow lights have gained in popularity due to their low heat emission and custom wavelength configuration. This means that it’s possible to place red, white, and blue diodes to give a full spectrum of light to your plants.

In their early days, LEDs were seen as low-wattage alternatives to HPS and MH. Now, LEDs pack a serious punch and are seen in various power outputs as high as 1,000-watts.

LEDs also offer dimming options and include a “night mode” that mimics the light wavelengths of the moon. Some even come equipped with green diodes so you can check on your plants during the night cycle without doing any significant harm.

CFL (Compact Fluorescent Lights)

CFLs are perfect alternatives to power-hungry LEDs and HIDs. These are also routinely found in hardware shops at an affordable price.

Not only are they easy to find, but they are also easy to set up without the need of having to deal with an external ballast.

The heat that CFLs emit is negligible, and they are ideal when a grow room space is difficult to cool down.

The Stages of Growth

Cannabis undergoes various stages between its initial germination and future harvest.

Each light has a pro and con for these different stages.

Seedling Stage: HPS vs LED

From the point of germination, seedlings are at there most vulnerable during their initial growth into juvenile cannabis plants. Too intense lighting impacts them negatively, as they don’t have the foundation to support such bright light.

CFLs (T5 grow lights) are ideal for this stage because they can be placed nearly right above the seedling cotyledons without burning them. This keeps the seedlings short, and not leggy by stretching for the light.

LEDs can also be ideal for this stage of growth because of their full-spectrum capabilities and dimming options. Their low heat emission also allows them to be placed above your precious seedlings without harming them.

HIDs, such as HPS and MH are both not as ideal for seedlings as they are during the later stages of growth.

These high-watt lamps would need to placed rather high from the canopy to not do any damage, and even if they have a dimming option, they will still need to be a fair distance away.

HIDs tend to be kept in the closet until the later stages of growth when the plant has enough leaves that can actually benefit from the high light output.

Vegetative Stage: HPS vs LED

This stage includes juveniles that have at least 3 nodes. The vegetative stage is an integral part of the cannabis plants’ lifecycle since it lays the overall foundation.

The leaves grow, and the root system expands, and the photosynthesis required from the lights is as crucial as ever.

HID Lighting System (Vegetative Stage)

HIDs, such as HPS and MH are great for this stage if you’re looking for efficiency. The growth rates increase with the added watts from HIDs, and the dimming option can come into use at this point.

On the other hand, since the vegetative stage requires 18 hours or more of light, the power from HIDs will mean a massive electricity bill.

Some claim that MHs are better than HPS during the vegetative stage because of their blue and white wavelength.

According to studies, the blue wavelength is associated with summer light, when cannabis naturally grows during its vegetative phase. This makes using MH over HPS more appealing.

LED Lighting System (Vegetative Stage)

LEDs might be the most ideally suited for the vegetative stage because of minimal heat and electricity costs. The long periods of light required to make for this efficient system to shine.

CFL Lighting System (Vegetative Stage)

CFLs work well during the juvenile stage of growth, but as the plant grows and demands more light, CFLs underperform in stimulating new and vigorous leaf growth.

Their low-wattage will keep your electricity bill in the green, but their overall lack of intensity will keep your plants craving more.

Flowering Stage: HPS vs LED

This is the stage every grower waits for. Although all previous stages contribute to the overall flowering stage, it’s essential to make the best environment possible for a bountiful harvest.

HID Lighting System (Flowering Stage)

HIDs are potentially the best lighting method for this stage. Studies show that cannabis reacts better to the red and orange wavelength of HPS because it mimics the sun during its transition to the Fall season.

Fall is associated with a lower sun on the horizon due to shorter days, and cannabis naturally flowers at this point to make sure it becomes pollinated.

This rush for pollination forces the female cannabis plant to push out ever more pistils to find pollen. Since we grow cannabis with only female flowers, they increase in size giving us the big buds we seek.

The disadvantage of HIDs in general, whether MH or HPS, is a large amount of heat they produce. The growing buds are vulnerable, and increased heat stress can diminish their yield.

MHs can still be used with excellent results, but there may or may not be a significant difference in bud production. Regardless of HID choice, these wattage-machines won’t fail to yield abundant and resinous buds.

LED Lighting System (Flowering Stage)

LEDs can optimally be used during the flowering stage. Since many LEDs are digitally variable, users can select an all red diode spectrum.

This flexibility from blue to red without having to buy additional bulbs may be a game changer for those on a budget.

LEDs are capable of yielding similar harvests to that of HIDs. This is generally the case when the grower is exceptionally experienced because the lower wattages from LEDs tend to create medium sized harvests.

CFL Lighting System (Flowering Stage)

CFLs have been and can be used during the flowering stage. They are not as ideal as the other lighting methods because of their low-wattage to efficiently cover the plant’s many bud sites.

Since CFLs have a harder time reaching bud sites throughout the plant, the yields are significantly smaller compared to the other options.

HPS vs LED | Comparison of the Most Popular & Optimal Grow Lights to use in your Cannabis Grow Room | The Highest Crop


This article was Authored by Illumenedge in Jan 2018. This is the year high-end LED’s advanced over HPS. The gap has only grown wider in 2020.

Illumenedge is Canada’s premier horticultural lighting agency, specializing in lighting design-builds (both HPS and LED) for licensed producers.

LED vs HPS Grow Lights: In 2018

Since the introduction of the Light Emitting Diode or LED in to grow technology, there has been arguments and aversion to the modern alternative.

At first, LEDs seemed to fail to accurately pinpoint and perform the in necessary section of the light spectrum. Not only did they seemingly fail to perform, but also came at a much greater upfront cost. HPS systems were much more reliable, being tried and tested for years in the agricultural industry.

This is another reason that growers and horticultural professionals are opposed to LED, as many live by the mantra of “If it ain’t broke, don’t fix it.” However, issues began to arise when LEDs became more engineered towards horticulture.

As time progressed and technology was further perfected, LEDs caught up to the performance of their HPS/MH counterparts.

Now, in 2018, we here at Illumenedge wanted to take another look.

In this post, we will conclusively compare the specific benefits and detriments to each grow light technology.*

I will go over the following areas in detail and highlight where each respective technology excels and fails:

* This is a general view of HPS vs LED. Each grow room, tent, or facility requires different components and specifications. This review is based primarily on the general differences in purchasing and implementing a grow operation.

  • Yield
  • Energy
  • Heat
  • Area & Spacing
  • Photosynthetic Photo Flux (PPF) & Density (PPFD)
  • Upfront Costs
  • Lifetime
  • Safety
  • Honourable Mentions & Conclusion


Here is a photo of a study conducted by DelviroGrow.

In this study, they compared ten 1000W HPS vs ten 600W LED fixtures ability to grow and effectively produce cannabis.

In Variety 1 of the case study, 8 plants were utilized to conduct the comparison.
The HPS plants had a yellow-y tinge and produced a total of 14.10lbs of wet cannabis (equivalent to approximately 9.85lbs dried)

The LED plants had a much healthier dark green colour, as well as resulting in a total yield of 17.65lbs wet (12.4lbs dried).

There are many advantages to growing cannabis under LEDs, including safety, yield, cost, and maintenance.


……..Arguably the most controversial topic (aside from iv. Quality), yield seems to be a factor that depends primarily on the grower’s abilities and knowledge rather than the type of light the plants are receiving. The HPS industry minimum would be approximately .5 or half a gram per watt used. That means one 1000W HPS fixture would produce a total of 500g per harvest, or just over a pound.

……….From outside sources, many claim that LED technology can produce up to or more than 1.0g/watt. In the study conducted by Delviro, we saw the LED technology growing cannabis at 1.55lbs/plant (dried). That would be about 695 grams of cannabis, averaging out at an impressive 1.16g/watt. The fact of the matter is that yield per watt is the most important aspect for many growers and many retailers. This is the main reason why I have covered it here first.

……….Although yield is not the only important factor, it is the initial identifying catalyst that will determine whether or not LED technology is a suitable adversary to traditional HPS solutions. A two-year academic study presented at the Cannabinoid Conference in Cologne, Germany, in September 2017 entitled The Effect of Light Spectrum on Cannabis Sativa Morphology and Cannabinoid Content’ showed that not only were yields slightly higher, but the LED fixtures produced more internodes on plants. LEDs also produced better compound accumulation and compact growth habit, meaning higher levels of THC and CBD in each plant and more clusters of bud. In the conclusion of their study, the LED produced cannabis had THC levels 26% to 38% higher than the HPS product.

ii. Energy

……….Here is where LED and HPS lights seem to differ the most. The massive 400W difference between a standard HPS set-up and modern LED is not the only area where one will find a reduction in energy usage. Although the 40% savings of light-energy output is definitely remarkable, it is clear that there are more areas where savings can be found in such aspects like ballasts, exhaust fans, temperature and humidity controls, HVAC, and maintenance.

……….Many growers find that, following the switch to LED, their AC usage is reduced by approximately 75%. One of these units can be the biggest energy-guzzler in your entire operation, so this switch is critical to your energy bill. You reduce your operations overall energy usage as ventilation and exhaust fans are rendered obsolete and maintenance is drastically reduced.

Compare for example a 10-plant grow operation for HPS; you would need at least 3 fixtures (3,000 watts), an exhaust system for each, an AC unit of at least 10,000BTU, and temperature, humidity, and Co2 controls. This could rack up to upwards of 7,000 watts!

……….In comparison, an LED system would still require HVAC and environment controls, however, the usage of these systems are reduced heavily. There is far more math I could get in to here but each grow operation is so specific that even an anecdotal example would not be of much use.

iii. Heat

……….Whether you’re dealing with 1, 10, 50, or 100+ HPS lamps, you’re going to see a massive influx of heat in to your environment. The heat produced by a 250W HPS lamp is so great even that needs ventilation. These fixtures typically don’t have any solution built in for the ample heat provided so you must work around this. That means catering your environment to HPS with fan-powered exhausts for each light, large AC units that run while and after your lights are on. This can cause even more issues if your area is not equipped or suitable for growing.

……….The reason HPS lamps generate so much heat is because the light is created by the ignition of gas within the lamp. LED fixtures utilize very thin layers of semiconductor material. These materials either have an excess or a deficient amount. This disparity between layers causes electrons to move therein generating light. The heat per watt is far greater with an HPS fixture compared to LED. This technology is far more efficient in transferring energy in to light, as it produces less heat and has a higher wattage equivalency to HPS (600w vs 1000w).

……….Another key aspect for many LED fixtures is that they use the metal frame as a heat-sink, further decreasing and dissipating any heat output.

iv. Area & Spacing

……….Every grower knows that your environment is one of your most crucially important factors that must be perfect. When you remove your hot HPS fixture, you will immediately make your environment more stable and far easier to maintain. Your area will be less humid and will rest at a more stable temperature. You’re also able to remove many additional physical components with the traditional HPS system after introducing LED fixtures, such as fans, environment control systems, and larger AC units.

v. Photosynthetic Photo Flux (PPF) & Density (PPFD)

……….With many LED fixtures, more light is emitted because the source is larger and more dense, therefore we’re getting better canopy penetration. LED grow lights also typically have better PAR and higher PPF & PPFD levels, ranging from 700-1000.From most lights, you’ll want at least 2.0 μmol/s.

Another advantage of LED is that these lights generally have higher levels of PAR deeper into the canopy because of the dynamic light source. It is a wider and longer fixture, also allowing you to be able to grow a larger number of denser, stronger plants.

Because of the nature of how an HPS lamp is limited in size and light distribution, it creates hot-spots on plants as well as on the photosynthetic photon flux density map. This means it’s PPFD is generally very high in the center of the ray but deteriorates as it expands outwards towards the ends of the area. This does not occur with LEDs as diodes are clustered and placed specifically to space the PPFD accurately from all points of the fixture. Another issue seen is that the strong yellow light emitted from HPS fixtures does little to fuel photosynthesis.

vi. Upfront Costs

……….Here is the only category where LED could be considered the “loser”.

………………..In fact, it’s clear that within the last few years LED grow technology’s immense upfront cost has decreased as competition increased, engineering furthered, and users have become more familiar with the change. Although this cost has certainly decreased, it’s clear that LED start up cost is significantly higher than HPS.

……….An HPS fixture, bulb, and ballast has a lower start-up cost compared to the standard Full Spectrum LED fixture. All major grow rooms, greenhouses, and facilities need HVAC regardless of whether HPS or LED is used. The difference is in the size and usage of these auxiliary components. Upfront there is an investment, but these fixtures are going to last you a minimum of ten years versus having to buy two new bulbs for every fixture once a year.

……….When considering your lighting solution, remember that with LED, you’ll save on essentially the rest of your entire lighting system.

vii. Lifetime

………………………………….Quick Maths!:

………………..You buy an LED fixture and look at your warranty. It is 100,000 hours, the industry standard. Although your fixture was a lot more expensive up front compared to an HPS setup, here is why it is worth it.

……….HPS lamps must be changed every 2-3 cycles (6-9 months) because they lose efficiency and PPF. A standard 3 month grow cycle requires 16 hours of light a day for the first month in the vegetation stage (480 hours) and 12 hours of light a day for the second and third month in the flowering stage (720 hours). That means you’re getting approximately 2,400-3,600 hours out of your standard HPS bulb.

So, in the end, the number you are paying per hour for your fixtures are:

LED: .015¢ per hour

HPS: .83¢ per hour

That means you’re paying more than 55x * less per hour for your LED fixture versus your HPS.

*note: The numbers are based on a $1,500 LED fixture over a 100,000 hour warranty and a $200 HPS industry standard bulb over a two standard 3-month cannabis grow cycles.

The fact is clear that HPS last 2-3 cycles while LED lamps would last approximately 83 cycles or for about 30-40 times more.

viii. Safety

……….Last but certainly not least, but usually the most underrated. Safety for your operation and your own well being are increased drastically removal of HPS systems eases upkeep and relaxes your environment overall.

……….Firstly, as covered previously in this post, the heat from a 1000W HPS lamp is incredibly high and requires ventilation. Not only is this a fire hazard for your room, tent, plants, or otherwise but it is also a burn risk for you as you move through your facility or replace your bulb. Even after waiting for what seems like long enough for the bulb to cool, it can remain extremely hot. An LED, plainly said, will not burn you or start a fire if it falls or is damaged. Replacing these bulbs is also a fall hazard for many growers and operations managers as some facilities are not equipped as extensively as others.

ix. Honourable Mentions & Conclusion

Throwing out old lamps: You can be proud you are supporting a far more energy efficient solution with LEDs as well as one with no waste production.

Cost Confusion: Although you may be paying more for an LED fixture or setup, you’ll see the return of investment within the first two years. Many growers idolize the ‘low cost’ of an HPS fixture and lamp but they disregard so many other costly factors.

Trial and Error: Many growers are willing to make the change, increasingly so as technology advances and fellow industry peers change their styles and systems.

In conclusion, LEDs are better in essentially all categories so, if you are willing to put down the money at the start, you’ll see your lights start to pay for themselves. They are safer, more engineering, far more modern, and bring practically no maintenance after initial install. Much research on the topic of LED vs HPS is biased as it’s conducted and reported on by LED grow light companies, however, there is accurate empirical evidence. This evidence leans heavily in favour of LED grow light technology which is enough to convince us.

This article was Authored by Illumenedge in Jan 2018. This is the year high-end LED's advanced over HPS. The gap has only grown wider in 2020…. Illumenedge is Canada's premier horticultural lighting agency, specializing in lighting design-builds (both HPS and LED) for licensed producers. LED vs HPS Grow Lights: