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Cannabis Cultivation Tips: How To Set Up Indoor Grow Lights

Excess light can damage your cannabis plants as much as too little light. Learn all you need to know about light as it relates to cannabis, and how to properly set up your grow lights for massive indoor harvests.

Learn to assess and position your cannabis grow lights for maximum effectiveness.

  • 1. The 3 most common types of modern grow lights
  • 2. Light spectrum, PAR, and lumens
  • 3. PAR and PPFD in watt computation
  • 4. Sun, bulbs, and proper photonic pressure
  • 5. How much light does your grow room need?
  • 6. The watts per square metre rule: how many plants can you grow?
  • 7. HID (MH, HPS): rules for the right distance
  • 8. LED: rules for the right distance
  • 1. The 3 most common types of modern grow lights
  • 2. Light spectrum, PAR, and lumens
  • 3. PAR and PPFD in watt computation
  • 4. Sun, bulbs, and proper photonic pressure
  • 5. How much light does your grow room need?
  • 6. The watts per square metre rule: how many plants can you grow?
  • 7. HID (MH, HPS): rules for the right distance
  • 8. LED: rules for the right distance

THE 3 MOST COMMON TYPES OF MODERN GROW LIGHTS

Contemporary indoor cannabis cultivation usually involves at least one of three artificial light sources: HID, CFL, and LED. Frequently, growers use a combination of grow lamps. Of course, there are other, more antiquated lighting technologies, but they are all pretty much “Betamax” lamps. This blog will focus on the most common lighting used by the 21st-century cannabis cultivator. We are going heavy on the practical grow room advice without relying on the pseudo-scientific stats.

HID or high-intensity discharge lamps have been the grow lights of choice for every kind of indoor grower from beginners to pro cultivators since the early 1990’s at least. Over the years, lamps have become more efficient, ballasts have gone digital, and reflectors have gotten bigger and better. Growers that favour HID are big believers that lumens are the only output statistic that matters when it comes to lights.

Sure, CMH or ceramic metal-halide has come on the scene and the 315W CMH bulb is impressive, but a rather expensive upgrade for a standard MH or metal-halide lamp. Moreover, 315W CMH is not quite as high performance as a high-end dual spectrum/agro 600W HPS or high pressure sodium lamp. Similarly, CFL shows some promise, but always runs a distant second to the tried and trusted HID.

LED or light-emitting diode is the up-and-coming breakaway technology that looks to end the reign of HID for cannabis cultivation. The latest generation of LED systems are now capable of producing comparable, and in some cases, superior quality marijuana than the average HID set-up. PAR or photosynthetically active radiation is the metric that LED zealots consider most important.

It’s best not to get too obsessed about the various new measures of light and modified light spectrums. Keep it simple. Think of light in terms of watts and electricity bills. Next is the question, “How much power consumption?” Followed by, “How much heat will the lamp produce and how much light will it emit?”

OLD SCHOOL HID

In ordinary decent stoner terms, HID has gotten some new bells and whistles, but the core principles of cultivating cannabis with this kind of artificial light remain the same. MH for vegetative growth and HPS for flowering. Although, the dual spectrum HPS lamps are a popular alternative and probably even better for autoflowering strains.

400W and 600W bulbs are the most suitable for indoor cannabis cultivation. Lights need to be hung level. The optimal light height or OLH is between 30-50cm above the plant canopy. This means carefully fastening the reflector to the ceiling or roof of the grow tent with either easy roll hangers or rope ratchets.

It’s best to use fixtures that can be easily adjusted and repositioned as the plants mature and grow taller. However, seedlings and cuttings may find a 600W MH too intense and a 60cm+ distance overhead might be more appropriate.

Don’t mess with light rails unless you’ve got the engineering credentials. Stationary lights that don’t wobble with a level, horizontal bulb housed in a clean, open reflector is professional, standard cultivation. Ideally, use a large reflector, or as big as will squeeze into the grow space, with a wide spread to utilise the entire area.

Glass filters, light, and air-cooling lamps are expensive. Therefore, cool tubes are really only suitable for closet grows as they have some of the worst reflective properties of any reflector on the market. Adding more lights and more fans means higher power bills.

LIGHTING AND GROW SPACE

Generally, 400-600W per m² is plenty of light for a home grow show. Commercial growers may push this to 1000W+ for maximum yield. Packing as many lamps as possible into the grow-op is not a fast track to a heavy harvest. More HID lamps means more light, but also a lot more heat. These babies run hot. 250W lamps are for micro-growers only.

The only advantage the 250W lamp offers is that plant tops can get as close as 20cm to the bulb. Heat output is far less than a 600W, but light will not penetrate as far. Limited light will reach the lower branches of taller plants.

The addition of just one extra 600W HPS can massively increase grow-op temps. It’s often a less costly and more effective solution to invest in upgrading the grow room instead. Maybe cover the walls in Mylar or upgrade from a magnetic ballast to a dimmable, digital ballast, or go all the way to LED.

HOW MANY PLANTS?

The answer is as many or as few as the grower prefers. You can pack 16 cannabis plants in 11l square containers into a 1m² grow space in a SOG. Alternatively, a grower can fill the same space with one large plant using the ScrOG method. Either way, the yield will be comparable. Again, it’s all about how you make use of the light and the grow area.

SUPPLEMENTING WITH CFL

CFL or compact fluorescent light is really effective in the cool white spectrum as an alternative to an MH bulb. A 250W CFL can deliver comparable results to a 400W MH lamp. This is achieved by hanging the CFL as close as 10cm above the plant canopy. CFL runs cool and can get really close to plants without burning foliage. Plus, CFL lights will only marginally increase grow-op temps. This makes CFL perfect for seedlings, cuttings, and for use during vegetative growth. CFL lights are sometimes the only option for micro-growers.

Unfortunately, CFL boasts neither impressive lumen nor PAR output figures. Worse, CFL lights are not very effective for flowering marijuana. Cannabis plants need far more intense illumination during bloom than CFL can supply. Expect lightweight yields and loose buds from CFL lights in the flowering phase.

NEXT-GEN LED

The latest LED systems have finally achieved parity with traditional HID lighting systems. At present, the situation is similar to when flat screen televisions first became available at the turn of the century. The benefits and advantages were plain for all to see. However, the limiting factor was prohibitively high prices by the leading manufacturers.

High-performance LED kits that draw 350-400W and can outperform a 600W MH and HPS configuration with a full spectrum array don’t come cheap. There are some models that really can do it all. The very best systems can run cool and are incredibly economic in the long-term. Hanging distances vary widely, so buyer beware and make sure to check the manufacturer’s instructions.

Below, we dig into the science behind light output so you can assess the ideal wattage and placement of your cannabis grow lights. We’ll cover terms like photons, lumens, and PAR, as well as the main types of grow lights and how they differ.

LIGHT SPECTRUM, PAR, AND LUMENS

Light is made of photons, which are tiny particles that inevitably travel at the speed of light. Photons in light beams vibrate with different frequencies and wavelengths. Humans can see photonic radiations within wavelengths from 380–680nm, while plants’ sensitivity to light ranges from 200–800nm. Not all wavelengths within this spectrum produce the same effects on photosynthesis; those that most activate biochemical processes in plants are called PAR (photosynthetically active radiation), which has a spectral range of 400–700nm.

Light can be measured in photometric quantities derived from the human eye’s sensitivity to colour, or else with radiometric quantities related to the energy transported by light beams. Lumens and lux are commonly used photometric units that refer to light perceived by the human eye.

However, photometric measurements do not indicate how much light energy a lamp sends to a plant for photosynthesis because they don’t include the PAR variables. Despite that, lumens and lux can provide an initial indication on a specific bulb’s output, and we can compare different products by measuring their photometric efficiency with the lumen:watt ratio, regardless of the eventual differences in light spectrum output at different wavelengths.

Lux and lumens work well in measuring MH, HPS, CFL and T5 lights, but they won’t accurately measure the efficiency of an LED light when growing cannabis.

PAR AND PPFD IN WATT COMPUTATION

Broadly speaking, the minimum amount of wide-spectrum light needed by a cannabis plant is around 9,000lm per square metre, while the optimal is over 20,000lm/m². However, a vigorous indoor plant’s growth and flowering depends on the light thresholds reached at specific wavelengths that trigger photosynthesis. That’s why LED grow lights use radiometric systems in order to measure the quantity of photons irradiated in the PAR colour frequencies we mentioned before.

The most widely used radiometric measurement in horticulture is the PPFD (photosynthetic photon flux density), which measures the flow of PAR photonic micromoles per second in a square metre (μmol/m²/s). Assuming the PPFD of a grow light is provided, we can calculate its radiometric efficiency and compare different lighting systems using the PPFD:watt ratio.

SUN, BULBS, AND PROPER PHOTONIC PRESSURE

Midsummer midday sun reaches the Earth at latitudes of around 45° with a photosynthetic power of 1,200–2,000 PPFD. Yet, cannabis seedlings, clones, and mother plants are happy with a PPFD of just 200–400μmol/m²/s. Cannabis plants in their vegetative phase will need 400–600μmol/m²/s, and flowering plants normally require 600–1500μmol/m²/s PPFD with atmospheric levels of CO₂. A study found that the most productive PPFD for cannabis is 1500–2000μmol/m²/s at a temperature of 25–30°C with natural CO₂ increased to 750ppm.

Even if cannabis is a demanding plant, irradiation above the limit threshold for each variety, stage of life, or environmental conditions doesn’t necessarily increase yield. Conversely, an excess of photonic pressure can cause damage to leaves and flowers. In other words, flower production increases when the cannabis plant receives 20–30 moles of PAR light per day, then levels out between 30–40 moles, and reduces at over 40 moles.

HOW MUCH LIGHT DOES YOUR GROW ROOM NEED?

To establish the correct amount of light for your crop, you need to multiply your grow room length by its width to obtain the growing surface, then multiply the obtained figure with your desired PPFD level.

If your grow box is 250cm long and 80cm wide, your grow space will be 2.50m × 0.80m = 2m². If you aim for a flowering plant canopy of around 2 square metres and you want to experiment with a PPFD level of 500μmol, you simply need 1,000μmol/m²/s. This result should then be divided by the PPFD per watt of light to ascertain the wattage needed.

THE WATTS PER SQUARE METRE RULE: HOW MANY PLANTS CAN YOU GROW?

LED systems produce higher PAR than MH, HPS, and other kinds of lamps. Despite that, your plants will need about the same amount of watts per square metre to achieve a harvest similar to that of traditional HID bulbs. Also consider that LED light systems are often advertised as being more powerful than their actual electrical power draw, but this doesn’t mean that a 400W LED can cover the same square footage as a 1,000W HPS bulb. Here are some general charts of the power needed to grow vigorous cannabis plants using different lighting systems. During the early vegetative stage, they will need around half the power.

As a reference, HPS lights can approximately cover the following canopy areas:

250W ≈ 0.5–1m² ≈ 2 plants
400W ≈ 1–1.5m² ≈ 4 plants
600W ≈ 1.3–2m² ≈ 8 plants
1000W ≈ 1.8–3m² ≈ 10 plants

LED lights can approximately cover the following canopy areas:

120W ≈ 0.5m² ≈ 1 plant
200W ≈ 0.8m² ≈ 2 plants
280W ≈ 1m² ≈ 4 plants
350W ≈ 1.5m² ≈ 6–8 plants

To get an idea of how much light intensity you are providing to your plants, you can buy a lux meter and measure the light intensity over different points of the canopy. Alternatively, you can do a theoretical calculation that considers the lumens emitted by the lamp in relation to the grow surface. In order to calculate the lux pressure on the canopy, just divide the lumens of your lamp by the square metres of the illuminated surface. If you position a lamp that produces 100,000lm at a distance of 1m from the plant’s top, it will illuminate an area of 1m² with an intensity of 100,000lx (100,000lm ÷ 1m = 100,000lx). If the lamp is only 0.5m away, it will receive 100,000lm ÷ 0.5m = 200,000lx.

Unfortunately, the luminous intensity decreases by a factor equal to the square of the source distance from the illuminated object, therefore your same lamp placed at two metres will increase its beam width, covering 4m², but with only 25,000lx. Consequently, you would need four lamps to reach your hypothetical 100,000lx target on your whole grow area.

HID (MH, HPS): RULES FOR THE RIGHT DISTANCE

HID bulbs come in a metal halide (MH) version with cold light suitable for the vegetative phase, and a high-pressure sodium (HPS) version with a much wider spectrum for the flowering stage. These lamps run hot and require a proper cooling and exhaust system. They also emit less light over time, thus new bulbs should be kept further away than older bulbs, and after a couple of years, you should consider replacing them.

The proper distance for both MH and HPS bulbs depends mainly on wattage. Always begin with the light at the upper end of the range and gradually lower it. Assuming the ventilation in your grow room is properly set, with a smaller 250W bulb you can start at a distance of 35cm, progressively descending toward the canopy until you reach 25cm from the buds at the end of the flowering stage. With a 600W bulb, you might start at 50cm, descending down to 30cm; if you picked a 1000W lamp, you better allow at least 80cm of distance.

Common practice has you hold the back of your hand facing the light just above the top of your plants; if it feels comfortable, so will your plants. But don’t trust general rules too much. Always check your plants for any signs of overheating or excessive photonic pressure.

How High Should You Hang MH and HPS Grow Lights?

Popular, widely used, and arguably the best for higher yields, many growers are committed to their MH or HPS grow lights.

While MH and HPS are suitable for different stages of the growing cycle, you can generally hang them at a similar distance from your plants. Both lights function best when closer to the crop, but it’s good to test them out if it’s your first time.

Whether you’re a novice grower or are switching things up, we recommend starting at the upper end of the light’s range. This way, you can gradually lower it until you’re satisfied your plant is getting enough energy. We recommend keeping your light at least 30–38cm (12–15″) away from the top of the canopy at all times. Remember, looks can be deceiving, and you don’t want to heat up the leaves too much.

If you’re unsure how much heat the plants are getting, do a quick hand test. Simply place your hand at canopy-height under the light and see how hot it is. If it feels too hot for you, it’s also too hot for your plants. Therefore, just move it further away.

One last thing to take into consideration are your bulbs. Not unlike those in your home, a bulb’s functionality decreases over time. Since bulbs give off less energy as they age, an older bulb will need to be closer to your plant than a newer one. Similarly, a brand-new one should be kept as far away as possible without sacrificing plant development. Most people replace their MH bulbs at least once a year, whereas HPS users can replace them once every couple.

MH/HPS Grow Light Distance Chart
STRENGHT DISTANCE
150W 20–30cm (8–12″)
250W 25–35cm (10–14″)
400W 30–48cm (12–19″)
600W 35–64cm (14–25″)
1000W 41–79cm (16–31″)
MH/HPS Grow Light Distance Chart

LED: RULES FOR THE RIGHT DISTANCE

LED systems run cooler than HID bulbs, but they still need some cooling to prevent accidental burning of your plants. LED lights give off a great amount of light pressure, even at relatively low temperatures. This amount of light itself, not the heat, can cause light burn and leaf bleaching.

Different models of LED grow lights have different optimal distances from plants, and manufacturers usually include recommendations alongside their products. Just start at a medium distance within the recommended range and observe your plants over the coming days. Back the lights off if you notice any leaves turning pale or with burned tips. If your plants are happy, move the LED panel closer, but never to the point where the upper leaves start bleaching, yellowing, or turning brown.

High-wattage LED panels with more than 300W should be kept at least 70cm away from the canopy, then eventually moved closer during the flowering stage. As a general reference, 200–400W LED lights should be positioned 30–70cm away from plants, while 450–600W lights require a distance of 50–80cm. Higher wattage systems must be located even further away. Remember to keep a close watch over your plants whenever you start using a new light.

How High Should You Hang LED Grow Lights?

Go-to grow lights for gardeners, LED lights take a lot of fine-tuning to find an ideal hanging height. However, with so much power, under the right circumstances you can get some amazing yields.

LED lights are tricky. There’s so much variety on the market that there’s no one-size-fits-all option. As a result, there’s no standard distance for them. Basically, whichever unit you choose, manufacturers will provide recommended heights and you’ll still wind up fine-tuning.

Another way LED grow lights can trip you up is they don’t always look as powerful as they are. Lights appear dim, so it’s easy to think they’re not emitting enough energy. On the contrary, they’re deceptively strong, and you’ll need to keep an eye on things. If you don’t, your plants could end up bleaching, or you’ll end up with an underwhelming crop.

Although every LED grow light is different, as a general rule, hang them further away than you would other lights, and adjust. You can then keep adjusting throughout the plant’s grow cycle, moving them closer to the plant as it flowers.

LED Grow Light Distance Chart

Again, all LED grow lights are different, but the following chart should help with some general rules.

The simple guide on how to hang your grow lamps that you’ve been searching for. Illuminate your indoor cannabis grow-op like a pro.

Grow Light Breakdown: Heat, Cost & Yields

For the many growers who are unable to cultivate cannabis outside in the free abundant sunshine, grow lights are necessary to successfully grow cannabis indoors. Grow lights take the place of the sun, and power the growth of your plants and their buds. Light is like “food” for your plants, so without a lot of bright light, even a healthy cannabis plant won’t produce much bud at all.

More Light = Bigger Yields!
(up to a point, it is possible to give your plant too much light!)

3 Main Classes of Marijuana Grow Lights

There are lots of options for grow lights that work well for growing cannabis indoors but in the end they boil down to 3 major types:

  • (LEDs come in a huge variety of sizes and form factors. There aren’t really any “standard” types yet, though some lamps get better results than others.)

Note: Some growers may have heard of “Induction” grow lights, which are pretty rare these days but still pop up from time to time. There are two types: “Magnetic Induction” grow lights do okay for growing cannabis but they’re pretty much glorified fluorescent lights. “Plasma Induction” grow lights actually perform pretty poorly at growing cannabis.

Some types of induction lights are well suited to stadium lighting but honestly they just aren’t that great for growing cannabis and they come with huge price tags. Even a lot of LEDs are cheaper and you’ll get better results with them. You can learn more about induction grow lights here.

Note 2: Incandescent light bulbs (old fashioned light bulbs) are NOT suitable for growing marijuana!

Compare the Pros and Cons of Each Grow Light

1.) Fluorescent Grow Lights

Fluorescent grow lights come in many different shapes and sizes, from twisty bulbs to long tubes. Fluorescents are popular because they make efficient and pleasant lighting for humans, and also work great for herb gardens and other types of low-key indoor gardening without using a lot of electricity.

CFL Grow Lights

CFL grow lights are the twisty-looking bulbs you can find anywhere you normally buy light bulbs. They produce a great spectrum for growing cannabis and can be used in tiny spaces where no other grow light would fit such as the inside of a cabinet.

Keeping CFLs close results in the best yields and growth

T5 Grow Lights

T5 grow lights are one of the most easily available types of grow lights and are used to grow many different types of plants. As a result, they’re available in many garden and home improvement stores.

T5s are much bigger/wider than CFLs and usually come as part of a panel, but they can still be kept mere inches away from your plants without worrying about burning them.

These cannabis plants are thriving under T5 grow lights

Pros of Fluorescents

  • Cheap to buy
  • They don’t use a lot of electricity or make a lot of heat unless you have a lot of them packed together in a small space
  • Great light spectrum for growing cannabis
  • Since lights can safely be kept just a few inches away from plants, they’re a good choice for short spaces
  • One of the best lights for clones, seedlings and young plants. Big lights must be kept far away from young plants to avoid burning them, which ends up wasting a lot of light and energy. By using smaller lights like fluorescents while plants are still short, you can save quite a bit of money on electricity during those first few weeks compared to using a high-powered grow light.

Cannabis plants under a T5 grow light – when plants are trained (like these ones in a Scrog setup) you can get pretty decent yields from fluorescents.

Cons of Fluorescents

  • Fluorescent grow lights get smaller yields per watt than the other types of grow lights if you use them in the flowering stage while buds are forming. With fluorescents you can expect about 0.25 grams of buds for every watt of electricity (using the true watts out the wall, not any type of “equivalent” watts), while LEDs and HPS get 2-4 times as much yield per watt of electricity.
  • The light from a fluorescent lamp doesn’t penetrate far down into the plant so they are best suited to plants that have been trained to grow short and flat; they aren’t powerful enough to support tall plants in the flowering stage.

Fluorescents are a great choice for clones, young plants, supplemental lighting and can save you money on electricity in the vegetative stage compared to using high power lights when plants are too young to use it all anyway. They can also be used to flower plants in spaces that are shorter than what’s possible with other grow lights (aka ‘stealth growing’).

That being said, when it comes to the flowering/budding stage, if you can fit a bigger light you will get significantly better yields/watt by using an HID or LED grow light!

2.) High Intensity Discharge (HID) Grow Lights

HID grow lights are much more efficient than fluorescent lights and are powered by large, oddly-shaped bulbs. They are usually screwed into a reflector or hood to reflect more light down onto the plants. HIDs are great at growing cannabis, but they also get very hot and are usually hooked up to an exhaust to help vent out heat.

Full tutorial on MH & HPS grow lights
(most common grow light combination for cannabis)

Full tutorial on CMH / LEC grow lights
(LEC stands for “Light Emitting Ceramic” and is a type of Metal Halide bulb that is built with ceramic like an HPS – basically it’s sort of like a blend between MH and HPS bulbs)

Metal Halide (MH) Grow Lights

Metal Halide grow lights are generally used for the vegetative stage because they produce a bluish light that vegetative plants love, though this type of light can also be used all the way to harvest.

The light from a Metal Halide appears a little bluish, and is well suited to growing cannabis plants in the vegetative stage

High Pressure Sodium (HPS) Grow Lights

High Pressure Sodium grow lights are often used during the flowering stage because they are very efficient and their yellow light stimulates bud production. HPS grow lights in the flowering stage get better yields per watt of electricity than any other type of grow light available today, which is a big part of why they are so popular.

The light from an HPS appears yellow, and is great for flowering plants because the light spectrum stimulates bud production

Ceramic Metal Halide (CMH) & Light Emitting Ceramic (LEC) Grow Lights

These are actually just two names for the same thing. This type of metal halide bulb uses ceramic as part of the lamp just like an HPS. As a result, CMH bulbs are more efficient than regular MH lights (though still not as efficient as HPS bulbs).

“LEC” and “CMH” both refer to Ceramic Metal Halide grow lights, which is a type of HID light that is a bit more efficient than a regular Metal Halide light

Pros and Cons of HID Grow Lights

  • HIDs are the most efficient type of grow light (gets the highest yields/watt).
  • Of all the HIDs, HPS grow lights are the most efficient and the best for the flowering stage. When using HPS grow lights in the flowering stage, you can expect about 0.5-1 gram/watt if all goes well.
  • HID lights are simple to use because they can be hung the right distance from the plants with no guesswork on your part (unlike LEDs), and no need to adjust the lights all the time (like fluorescents).
  • HID bulbs get really hot and generate a lot of heat. Because of the concentrated heat production, you will almost always want to put the bulb in a hood and also provide some sort of cooling to prevent heat from beaming down onto your plants and driving up the ambient temperature of your tent/grow room. This is especially important for the bigger lights with power above 250W.
  • Additional setup – As a result of the heat mentioned above, most growers use an exhaust fan with ducting to vent out heat. Unfortunately, the prospect of having to deal with the fan and ducting scares off many growers from HID lighting.
  • More parts – HID lighting means a few more parts than other types of lighting. Fluorescents are just the bulb and a fixture and most LEDs are just the light itself. But most HID setups have at least a bulb, fixture, an external ballast and an extra cable if you don’t count the exhaust systems parts, too.

Example of MH/HPS Setups That Yield 1-5 Ounces/Month

  • 1-2 oz per month
  • Electricity: $69/month (including electricity for fans)
  • Initial Setup Cost: $605.00
  • 1.5 – 3.5 oz per month
  • Electricity: $96/month (including electricity for fans)
  • Initial Setup Cost: $744.00
  • 2.5 – 5 oz per month
  • Electricity: $128/month (including electricity for fans)
  • Initial Setup Cost: $780.00

There is a larger size MH/HPS grow light available (1000W), but at that size it starts going outside the scope of a “hobbyist” grower as far as ease and yields. In addition to needing a lot of extra cooling which costs electricity, a 1000W HPS grow light is less efficient compared to a 600W grow light (as far as how much light is put out for electricity used). I think most hobbyist growers would be happier with a 600W, or even two 600W lights, over a 1000W 🙂

HIDs are very well suited to growing cannabis and very easy to use once they’re set up. If your main goal is to get the highest yields possible, then HIDs are the way to go! However, they do require extra setup compared to the other grow lights because chances are you will need a fan to vent out heat from your grow space.

3.) LED Grow Lights

LED grow lights are very popular among cannabis growers as an alternative to HPS grow lights. They tend to run cooler and also usually come with built-in cooling. They can often be plugged into a wall and simply hung over plants which is definitely easier than setting up an HID grow light. LEDs also have great penetration so they don’t need to be moved frequently like fluorescents.

Simply hang an LED light over your plants and start growing!

  • LEDs almost always have built-in cooling that pushes heat up and away from the plants (unlike HID bulbs which beam heat down on your plants and need to be cooled separately). As a result LEDs run very cool and many growers are able to get away without venting heat at all.
  • The smaller size LEDs can be plugged directly into the wall and hung up over your plant, without needing to do anything else. You can just plug them in and start growing!
  • Some growers believe LEDs produce more resinous bud. Combining LEDs with HPS grow lights seems to be getting some growers really great results, though more testing is needed.
  • Although the LED lamp itself usually does run a lot cooler than a similar wattage HPS bulb, they still produce heat and the bigger sizes like 300W+ may need to be vented with an exhaust fan to prevent the grow space from getting too warm.
  • Despite what some sellers may tell you, LEDs get slightly smaller yields per watt than HPS grow lights on average (LEDs commonly yield about 0.5g/watt, though some growers and lamps get better results than others!). There is a learning curve when it comes to getting the best yields from your LEDs, partly because each lamp is different and there are no “standards” to go by yet. A little experience with a specific lamp can improve your yields by a lot!
  • LED grow lights tend to need a lot of space between the lamp and your plants, which means you need a tall grow space to get the best results. This is actually the main thing holding me back from trying LEDs more. Smaller LED panels should be kept 18″ or more away during the second half of the flowering stage to avoid light burning your buds (buds can be burned from too much light even if the temperature is cool), and some of the bigger models need to be kept 30″ or more away from the buds. When in doubt, contact the manufacturer!

If you get very high-wattage LEDs, you may need to vent out heat to keep the grow space cool

For growers who are looking to harvest 1/2 to 1 ounce of cannabis a month, LEDs may be your best choice. At this size, they are super low on electricity, run cool and need almost no setup! They get better yields than fluorescents but don’t run as hot as an HPS of similar wattage.

Note: When shopping for LEDs, make sure they contain some amount of green or white (full spectrum) light. Plants grown without at least a tiny amount of green or white light are very prone to nutrient deficiencies and simply don’t grow as well. Learn more about how light spectrums affect cannabis growth!

Now that you are familiar with all the most common cannabis grow lights I hope your choice is a little easier. I wish I’d had this information when I first started growing indoors 🙂 Happy growing.

There many grow lights that work well for growing cannabis indoors, but they boil down to 3 popular types: fluorescents (CFLs, T5s), HIDs (MH, HPS, LEC) and LEDs. Learn the differences so you can pick the best option for your setup!