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What are compact fluorescents and how can I use them for growing?

Find out why these lights are useful, but are not as effective as HID's for high yield growing.

Compact fluorescents are close relatives of the 4ft tube fluorescents, commonly used in shops and schools for their white, soft light that does not cast any defined shadows. These lights are long tubes, usually 4ft long, filled with a gas that releases a photon of light when excited by electricity. The electricity is passed through the tube from the metal sections at either end, thus exciting the gas within and releasing photons of light. These lights must have a 'starter' which gets the light going initially, unlike incandescent which can just be turned on and off without one. Regular fluorescents usually emit 18w of light per tube, and cannot be plugged straight into a wall socket.

Compact fluorescents, on the other hand, are made for use in regular light sockets, and can easily be installed by anyone with basic handyman skills. Compact fluorescents are usually around 8inches long (not including the ballast, which usually adds about 3 inches to the total length) and emit minimal amounts of heat from the globe itself. Most of the heat emitted from a compact fluorescent comes from the ballast. These lights are usually between 8w and 27w, although some variation may occur between brands and uses.

The main reason people choose CF's over regular fluoro's is their compact ability! They are very 'movable' and can be positioned almost everywhere. They put out MUCH more light than their bigger cousins, while using only a fraction of the space.

Some of the many varieties of compact fluorescents.

Image contributed by: Locutus


If you're running a large grow setup, and you're concerned about the spike in electricity, replace your regular light bulbs with compact fluoro’s around the house! They give off the same light, using only a fraction of the electricity. If you're running a HID light, and the electricity increase could kill you financially, or you're just worried about LEO, it might be a good idea to replace incandescent with compact fluoro’s. As an example, a 100w incandescent uses most of its energy giving off heat. If you replace all these 100w incandescent bulbs with ~20w energy saving compact fluoro's, you can dramatically reduce your energy bill, and help the environment at the same time. In fact, I recommend changing all your lights to CF's regardless of your growing situation, as they will save you $$ in the long-term, and save the environment.

The advantage with these lights is that the conversion from incandescent isn't complicated! Simply un-screw the old bulb, and screw in a compact fluoro! Done! You're on your way to energy saving paradise!


Every grower has, or still uses these lights. Although they don’t even come close to the results from a HID light, they do however provide a cheap alternative for a newbie 'dabbling' in the fine art of growing. Instead of spending hundreds of dollars on an HID light, a newbie can purchase a compact fluorescent for a few bucks, and still have money for a coffee on the way home.

These lights are also excellent for starting seedlings and clones, as their cool light will not dry out the soil as fast as an HID. They have a low intensity, and are gentle on newly germinated seedlings, and are great for clones as they wont dry them out or give them too much of an early blast.

Compact fluoro's are also great for stealth grows, as they can be kept about 1 inch from the plants, and do not require extensive heat ventilation due to their warm operating temperature.


Most lighting stores will sell them, but watch out, prices are very different depending on what type of shop you get them at! As lighting shops only sell lighting equipment, their prices can either be high or low, it really depends on the type of lighting shop it is. A designer lighting shop may end up being much more expensive, as they tend to be more directed towards the upper-class designer type customer, which extra $$ to spend. Hardware’s sell them, but their variety of lights is usually limited. Electricians, and assorted electrical shops will sell them, and this is most likely where you will get the best range and the best prices. My advice to you is, shop around! You wont regret it when you can save around 30er light.


For anyone growing cannabis, it is pointless to buy a weak light. Given the option of 8w, 15w and 27w, you would be stupid not to buy the 27watt, as they are more or less the same price. Compare the lumen output of each of the bulbs, different 27w bulbs may have different lumen outputs (depending on the manufacturer) and as with everything, the more lumens the better. You will also be given 2 options, the screw method of fitting, or the bayonet method (push and turn). My preference is the bayonet fitting. Make sure that you choose the right one for your socket! Also, do not choose a regular compact fluoro. Pick the one with the energy saving feature (will be explained why later on in the document). Now, for vegetative growth you should choose the 'cool white' light. This is also acceptable for flowering, but a 'warm white' light will be better as it is stronger in the red end of the light spectrum which is more suitable for flowering.


Now, this is extremely easy. As these bulbs fit normal light fixtures, you can just dismantle and old lamp to get the cord, plug and bulb fixture. This is ready made, as all you have to do is plug the cord into a wall outlet and screw in a bulb (with the power turned off, of course). This requires no electrical knowledge at all, and is the easiest way to get a cord suitable for a compact fluoro. The cord is simply removed from the lamp, and you are ready. If you feel you are not up to this task, or you do not have an old lamp ready to be destroyed, you can easily make one of these cords with basic electrical knowledge. Hardware’s and electricians will sell you the cable (you'll need at least 1 meter) and the fittings for the wall socket and the light. Just tell them you're making a lamp for pottery and need a few cables to make up yourself. The parts are cheap, and you can save $$$ this way. If you have any queries, the electrical store will know exactly what type of cables you need etc, and will be more than happy to give you instructions on how to put it all together.

Please note that this is a guide for regular compact fluoro's. There are some outdoor varieties (which are rare) that need to be fitted specially. This FAQ is written for the regular compact fluoro’s, the ones that are most accessible to the general population. Other varieties of compact fluoro's are hard to find, but may or may not be better for growing. As I have little experience with these rare lights, I cannot comment on them. The reason I haven't seen them before, is because they are almost non-existent where I live.


To build this reflector you will need a regular soda can, any brand will do, which you will need to rinse thoroughly until no residue is left inside. You will also need a good pair or scissor and a robust kitchen knife to cut the metal accordingly. An alternate method to remove the lid, would be to use a can opener. The lip of the lid can be used, and it will cut it cleanly. These tools should be chosen carefully as they will determine over failure or success of this construction. A lack of caution and a sharp metal edge can be fatal to your fingertips so think twice if your tools are capable of doing the job.

How and where to cut:
Firstly, draw a plan of your cutting path on the outside of the can using a permanent marker or a wax crayon. This will aid you to get a better overview of you plan and to avoid silly mistakes on the way.

Cutting the top part of the can out needs to be done first, adjusting the opening according to the size of your bulb. You do not have to cut it exactly to shape as glue (super or high-temp hot glue) can be used to stick the reflector to the bulb ballast later on. A can opener is the preffered tool for this job. The reflector is purposely not covering the ballast to ensure good aeration and to avoid damage to the ballast components, resulting in a short circuit.

Next, you will need to cut the main part of your soda can in half using your scissors. A hole may need to be drilled first using your kitchen knife to get a good starting point for the scissors.

The inside of the can is coated with a thin plastic layer that should not cause any trouble cutting through the sheet metal. The bottom side of the can does not have to remain in place but leaving it will add stability to the reflector and enhance the reflectivity. An extra hole can be cut into the bottom as well to improve ventilation along the bulb or to connect a 50mm pc-fan to the end.

Lastly, two more cuts have to be made into the sides of the semi-circle reflector to ensure that the sides do not reflect the light back to its origin but rather focus it to where it is needed. The reflector can now be bent according to your light requirements thus making it possible to focus it directly on your plants. If your reflector does not quite fit the bulb yet you can now use glue to stick it to the ballast.


The main advantages of modifying your compact fluorescent are:
· Reduced length of compact fluorescent
· Reduced heat build up (increased air-flow)
· No need for pre-made light sockets, saving you money

There is an even cheaper and more compact solution than to spend the extra cash on unnecessary light sockets and to end up with less usable space due to clumsy fixtures. All these problems can be avoided easily if one knows how to skips wiring a bulb socket and instead going straight to wiring the bulb itself. This requires some adjustments and modifications of the bulb casing but it can be done by simply following the steps provided.

For this example I will use a 23W Phillips fluoro bulb which is ideally used in confined spaces due to its compact size. The following pictures will illustrate the process of re-wiring this bulb and modifying it to meet the requirements of compact size and low cost.

This is the bulb I was referring to (23W, 1500 lumen)
Notice the upside-down “U” shaped tubes. These will require less airflow to cool the bulb as the air can move freely in between the tubes unlike those of conventional stick-like coils.

First, get a good pair of bending or clamping tongs and squeeze them tightly to the round connector plate of your CP fluoro and gently twist it off.

Never twist it off in a COMPLETE circular motion as the wires inside are still attached to the receptor plates and can sometimes break/rip if you apply too much pressure by twisting. Pulling is better than twisting. You will end up with two different wires sticking out the end. In this case, I cut the remaining plastic bit off in order to reduce the overall length of the bulb.

You will need to open the bulb ballast in order to make 2 separate holes in the plastic casing of the bulb for the two wires. This isn't hard at all, you simply need to drive a screwdriver in between the upper and the lower part of the casing and gently push them apart. There will be no glue required to stick them back together as the bulb has a push-slide-lock mechanism that simply snaps them back together. When you open the bulb, you should something similar to this even though not all ballasts are the same, depending on the manufacturer.

Now you need to drill two holes at the appropriate height for the two wires to be pulled through. Since its plastic that isn't all that hard either and can even be done with a pair of scissors.

After that, its just about putting the pieces back together and making sure the wires come through their designated hole. You can use hot glue to hold those wires in place but this is not recommended as the heat in that area of the bulb casing is very intense. Use only High-Temp glue!

If you are short of space or simply want a rigid construction, you can cut the bottom plastic part of the bulb of and use a bigger piece to distribute the weight more evenly. I used med-high temperature translucent hot glue to fit a piece of a 2” black PVC pipe onto the end of the bulb thus completely eliminating the need for a socket. This is just an optional step, as the bulb will hold without the extra support by simply gluing the sawed-off end to the predestined wall.

(ATTENTION: DO NOT USE the regular LOW TEMP Hot glue as it will melt at temperatures above 130 degrees Celsius which the bulb is capable of generating. ONLY, when gluing something DIRECTLY to the bulb casing, USE THE MEDIUM-HIGH temp. Hot glue, which will withstand significantly higher temperatures.)

Voila the final product of which you can wire as many in series or parallel as you desire. You can place these bulbs literally anywhere due their compact size and the low heat production, keeping in mind that the bare minimum between leaf tips and bulb should be 1cm (2/5 of an inch). Anything closer will result in prompt or delayed leaf burn.

This is just an example of how well suited these bulbs are for small spaces such as stealth boxes and small cloning chambers. It also illustrates the importance of ventilation as the smaller the box, the stronger the ventilation has to be to exchange the hot air buildup sufficiently.

This method is ideal for those who wish to wire a number of bulbs without spending even more money on bulb sockets. These might seem cheap when compared to the pricing of the bulb, but in the log run it is better to save a few bucks here and instead invest them in another area of growing or even another bulb. There is no need to have a possibility of replacement as the average lifetime guarantee on these bulbs lie between 10000 and 15000 hours, which means nearly two years of continuous use.

Wiring in CF's parallel:(Image by tipzijuana)


It all depends on what light you are using, if it’s HID, standard fluoro or compact fluoro (I assume you're not using halogens!). For HID (HPS or MH) lighting, use roughly 30w per square foot, and for flowering use around 60w per square foot. This is merely a guide, your plant, light height; reflective surfaces etc make a huge difference on these numbers. For a small plant, below 1ft tall, I’d say you would need at least 25w of fluorescent light. I find that it isn't at all practical to use tube fluoro’s for the vegetative stage past 6 inches, as only the top of the plant is receiving enough light to carry out photosynthesis properly.

Using an energy saving compact fluoro will help 'push' the light to the base of the plant, assisting photosynthesis. If the plant indicates it needs more light by growing slowly, and with small leaf petioles, you may need more light. Go with the basic rule of keeping the fluoro’s very close, and using roughly 20-30w per square foot for strong vegetative growth. If you can afford to over-light your grow room, why not? You wont regret it when your plant is bushy and healthy. If you feel that you need to only purchase a minimum amount of lights, you probably shouldn’t be growing.

Growing takes effort and money, and if you can't support a plants needs you might as well just forget growing until you can afford a proper setup. Skimping on lights is the biggest mistake a grower can make, because photosynthesis is so important to for a health plant.


When purchasing a compact fluorescent, you will notice that nearly all of them have a larger number on the box, than what it actually is. This number is the lights comparison to the brightness of a standard incandescent globe. Do not be fooled, this does not mean that the light is 100w! It is most likely around 18w.

Now, here is where the myth behind these lights is uncovered. Most people will say that you should totally discard the brightness rating. This is wrong! The brighter a light is, the more penetration it has. With a usual, run-of-the-mill compact fluorescent (say, 15w) it emits only 15w of light with poor penetration. An energy saving compact fluorescent with 15w of light, which is rated to 100w of light, will only emit 15w of light. The difference between the two is, the energy saving light has a much stronger light penetration of the normal one, while still only emitting 15w of light.

This is beneficial to growers because with a larger plant, a normal 15w compact fluoro will sufficiently light one part of the plant, and by the time the light has reached the other side of the plant, so much of the light has been lost that it is barely worth having. With the energy saving compact fluorescents, the light will travel to the other side of the plant, and still have enough intensity for reasonable results.


Keep these lights under a reflector all of the time to concentrate the light onto the plant. Hang them horizontally, as most of the light is given off by the middle of the tubes. Keep them close to the plants. As a general rule of thumb, 1 inch away from the top of the plant is perfect. Any more, and you're wasting your time, and less and you risk burning your plant (although these lights are very cool, it is possible to burn your plant if it touches the light or ballast for an extended period of time). If you're given the option, go for a few compact fluoro’s positioned around the plant, as opposed to 1 strong light at the top. Positioning lights around the plant help stop vertical stretching, and encourage the plant to bush out.


HID lighting is generally accepted as a better light for growing cannabis for a few reasons...
· It has much better light penetration
· It is much more powerful (higher lumen output)
· It is stronger in light spectrums suited for growing plants

What can we do to combat these problems to make the most out of our fluoro’s?

· Use a good reflector. Desk lamp reflectors are perfect, along with coke cans (cut in half from top to bottom).
· Purchase lights with high energy saving capabilities (e.g. high watt ratings)to increase light penetration
· Purchase lights with suitable spectrum strengths for each phase of growing (eg warm white, cool white etc.)
· Keep the lights close to maximize intensity


· For good results, these lights must be used with a good quality reflector. They give of 360 degrees of light (in a 2D cross-section) but you will only really need 90 degrees of light (maximum). Building a reflector will help concentrate all the light to the area needed, instead of wasting it lighting up the ceiling of your grow room!

· Although you can successfully grow and flower a cannabis plant under a fluorescent, your results will be poor and you will most likely be disappointed. Use these lights only for seedlings and clones, and perhaps the vegetative stage of the cycle. A HID light is recommended for flowering.

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