The growroom: Grow lights

An important aspect of a succesfull grow is using the right grow lights. It can literally make or break the quality and amount of cannabis you are able to yield. Cannabis uses light for photosynthesis, to grow bigger and become more potent. Without light, life for a plant is impossible.

Not every light is suitable to grow plants with and not every light is powerfull enough to imitate the sunlight. Another important aspect is the colour spectrum of the light that is needed for a plant. Luckily there is many choice when it comes to good working grow lights and they all have their own benefits. Based on your personal needs and growing method you should choose one that fits best. On this page we’ll describe all kind of growing lights and their pro’s + cons.

Different kinds of lighting:

First of all: Sunlight

For outdoor growers there is one light thats free, powerfull and very effective to grow cannabis with: The Sun! Depending on where you live you can take full advantage of this free light source but it’s required to have the possibility to grow outside. If it’s not legal to do in your area or you have cannabis hating neighbours, it might be a good idea to look for other ways to grow. We don’t recommend to grow cannabis behind a window as the lighting coming through is just too weak.


Next to ordinary sunlight, there are 3 main types of lights for growing cannabis:

-High pressure light (HPS)

-Metal halide (MH)

-Cermamic metal halide

-Compact fluorescent lights (CFL)

-T5 lights (and other tube lighting)

-LED lights come in many different forms and strengths and there isn’t really one standard type. However some work better then others to grow cannabis with. We;ll explain the differences!


High Intensity Discharge light (HID)

High Pressure light (HPS)

These lights use a technique where sodium is being pressured in the bulb while connecting it to a certain voltage. This will result in a very bright yellowish light source. Lot’s of commercial growers use these as they are pretty cheap to buy and produce enough light to grow proper cannabis.

However there are some negative aspects when using HPS: First of all the power usage is pretty high with these lamps. So make sure you are not “over lighting”  your growing space. (Using more light then is nessecery) This will cost you money that could be sved. Next to that, these lights produce lots of heat which makes it easier to detect for law enforcement and harder to create a good environment (depending on the temperatures where you live). It also requires a front panel for the light to work safely which cost some money and experience to install.

The burning hours of a HPS light varies around 8000-10.000 hours. So you are able to use the same light for +- 7 grows which is quite good.

Metal halide lights (MH)

Metal Halide lights are around for quite a while now. This type of lighting is very similair as the HPS lights as it also works under pressure, need it’s own front switch and produces lots of bright light! Users report that the results of their grow were VERY good when using this type of lightning. They produce a high intensity discharge (Just like HPS) and they use mercury vapor to create a very bright light. Next to that they contain halide salts to add some colour to the light.

Despite very positive sounds and results, these lights are better to be used in the vegatative period of the plant because they produce a soft blue light (Growing plants love that). Once they are turned on they become very hot and thats why some growers avoid them! They must be high enough not to burn your plants. Next to that you can use them to regulate the temperature in the growroom.

 Ceramic Metal Halide light (CMH)/ Light Emitting Cermamic

LEC (Light Emitting Ceramic) or CMH (Ceramic Metal Halide) lboth refer to the exact same kind of lamp and they are pretty similair as the normal MH lights. The big difference with normal metal halide lights is that part of the lamp is made of ceramic (Just like HPS). This makes them more efficient then normal MH lights.

CMH lighting has some major benefits compared to HPS:

  • The colour spectrum is way more suitable to grow plants with which is noticable on the quality of your product (especially in the vegatative phase).
  • They produce the perfect UV levels for a plant.
  • More efficient on electricity usage (better energy efficiency. Same energy, more light)
  • They emit way less emi (electric magnetic interference) Then HPS which makes it less detectable.

In summary a very good light! You could check out some grow reports with LEC/MH and HPS lighting and compare results!


Fluorescent grow lights.

Household light (CFL’s)

Compact Fluorescent Light Bulbs (mostly known as CFL’s) and household LED’s are the types of lights that people use to light up their house. So they are not really ment to grow plants with as they mostly don’t offer the right colours spectrum and intensity.

However it could be a great way for starters to learn about growing and lights. I personally started with using CFL’s and it will do the trick eventually. The positive thing is that they are very cheap and easy to find (almost any home depot store will have them).

These type of lights or often used for micro grows in computers, containers,closets or space buckets. They don’t produce much heat or use lots of electricity and a few of them could produce quite some intensity for your plants.

T5 growlights + other fluorescent tube lights

If you have never heard of T5 lights, you probably still know what they are. The come in long tubes and are used everywhere! Thats why you can find them easily in any home improvement store or garden center. Their low price makes it perfect for growers with a low budget.

In the beginning, these kind of lights were only used as an addition light (For certain supplements) or for seedlings/clones. However last years these kind of lights evolved and high-light-output versions were created that made is possible to use them the entire vegetative stage (some growers even flower their plants with these lights). A great thing about these kinds of lights is that they don’t produce lots of heat and won’t burn your plants quickly.

In the flowering phase we recommend to use different kind of lights. Think about LED’s/HID’s as they give a way better yield per Watt then T5 lights. Simply because they produce better (colour) and stronger (Brightness) light for a plant to start producing buds.

If you keep your plants short and small it might be possible to finish them with only T5 lights. Another great idea if you don’t want replace them with LED/HID is adding a few CFL’s to improve the brightness and colour. Try placing them in the darker areas of the growroom (where there is lot’s of shadow).


Led grow lights

Last years there is a improved trend on growing lights: LED’s. More and more growers are turning to these powerfull and very effective lights. They look very modern, shine bright purple light without using lot’s of electricity and they won’t emit lot’s of heat. These aspects makes them very attractive for home growers!

LED’s also offer other benefits compared to other lighting. Next to the fact they have put a lot of research in LED’s and growing plants, it’s possible to create the perfect colour spectrum thanks to the difference in the colours of individuel LED’s. Another great thing is that some of the LED lights have the possibility to switch from “grow light” to “flower light” (the colour spectrum changes to the plants needs). They are also easy to set-up (plug in and ready!) and won’t produce any heat.

Probably the biggest benefit of LED’s is the extreme low amount of electricity it uses. It uses less then half the electricty compared to a HPS while the light intensity and results are the same or even better.

The sad thing is that it’s pretty hard to find the right information about LED growing lights as you have many different lights and some brands use misleading information to promote theirs. Luckiliy there are also brands that have proven their quality and are already known under growers. A great tip is to read grow reports from other LED growers and compare their results/lighting with each other.


Now you know more about the different lighting thats suitable to grow cannabis it’s time to choose one! You have to do this step for yourself based on the conditions in your grow project. Keep things like this in mind:

  • If you live in a hot climate, try to avoid lights that emit lot’s of heat (like HPS)
  • Want to cut down on electricty, also avoid lights like HPS and look for LED’s or CFL’s
  • Are you doing a micro grow? Then a normal HPS or LED light could be too much and you could go for household lights (CFL’s) or T5 lights.

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