I used to be a member of the old Cannabis World and there were many very experienced growers there and a number of breeders too. Some were fairly big name but not the most famous, though some have since gained more fame, and some were very talented hobby/basement breeders and some were basically pollen tossers but the consensus opinion there was CFLs are a terrible choice to make for grow lights. CFLs have improved some since then but not dramatically and many that are mentioned by people here were available then and they have not changed in the least since.
I have been a member of numerous pot growing sites and am a member of four right now and I have never seen a site with so many people in love with CFLs like I see here.
If used correctly, if the proper lighting, as in wattage to cover the full area needed to be covered is used, and all other conditions being equal HID lighting will beat CFLs every day of the week, month and year when it comes to plant growth and bud growth/yield and the quality of the bud, as in density of the bud. For some reason many here do not believe that or just refuse to believe it and claim otherwise but that is just how it is, that is how the mop flops.
Many people hear write terribly about LED lighting but if high quality LEDs are purchased and purchased in large enough numbers and if used properly they will beat HID lighting and leave CFLs so far behind in the dust that it is ridiculous but due to people having purchased low quality LEDs and not having enough of them and not knowing how to use the properly they have had poor results and then blamed LEDs for their own failures when it came down to not making the best choices and not knowing how to use LEDs.
There is a place for CFLs when it comes to growing. If someone is growing in a PC case or small cabinet or something and they are incapable for some reason or reasons to supply adequate ventilation for the heat HID lighting will produce and they cannot afford high quality LEDs then CFLs are their only other option. In any other growing scenario where there are other options CFLs are the worst option to pick if someone wants the most from their plants.
I sometimes chuckle to myself when I read threads and messages where someone is all excited about the ultra-expensive high quality beans they just received in the mail and then they go on to tell what their lighting is and it turns out to be CFLs and often times small amounts of CFLs and they write as if they will be getting some super great crop of super killer weed. Well it just is not going to happen, at least not when compared to the results they would get if they used HID lighting.
I tend to believe that what has happened is many people who got into growing went into it with low budgets and others with what they believed were constraints that where they could not use HID lighting and what they ended up with to them appeared to be great results and they were impressed and they were happy so they then told others that CFLs are the way to go. But then they never saw the results of HID lighting to go by and compare to so they do not know that what impressed them would have been far more impressive had they used HID lighting.
Unless HID lighting is positioned to low and it cooks the plants it is much more forgiving than CFL lighting. It puts off much more light and penetrates much better so if someone is off a little with the positioning of their HID lighting, again as long as it is not to low, the amount of light they put off is still enough that they do not see any problems unless they are way off with their positioning.
If someone does not believe that stop and think how many threads are seen here with pictures of stretching plants and then how the person says what they use for lighting and it is always CFLs. The responses are usually lower your lights 2 inches or lower your lights 3 inches. Well if 2 or 3 inches will make that much of a difference in plant growth when that 2 or 3 inches is totally unobstructed how well will CFL lighting penetrate when plants grow taller, far more than that 2 to 3 inches, and have foliage that will obstruct light? What happens is every time you grow 2 to 3 inches you have created another 2 to 3 inches on the lower portion of your plants that does not receive adequate light.
Of course the answer to that is buy more inexpensive CFLs and put them around your plants at lower levels and that will fix things. Well if CFLs penetrated like HIDs do there would not be a need for that in the first place so right there you find evidence of how inefficient CFL lighting really is when it comes to putting off usable light and penetration.
Roughly 50% of the total amount of usable light that is created by CFLs never leaves the tubes, it does not penetrate the coated glass. So while some say they only use a small amount of electricity compared to HID lights what they do produce in total only half of it makes it out of the tubes so if someone wants to talk about efficiency you have to ask if they mean efficiency as in low electricity usage or high output of usable light per watt used and if it is the later then HID lighting wins hands down every time.
The major disadvantages of compact fluorescent light bulbs are their inefficiency and poor light penetration. A bank of several compact fluorescent light bulbs can use as much energy as one HPS bulb, but will not produce anywhere near as much usable light for your grow. CFLs will never equal the efficiency or output of HID lights. HID lights are the most efficient source of light a grower can use. HID lights produce five times as much light energy per watt of electrical energy than any incandescent lights.
You see messages that say lumens, lumens, lumens and some that say PAR lumens but what you have to do is figure out lumens per square foot.
Distance from Source to Meter: d (feet)
Light Source Output: Lo (Lumens)
Light Meter measures Illuminance: I (foot-candles)
Area of Sphere: A = 4 p d2
Illuminance is the measurement of how bright a point source of light appears to the eye. It is measured in foot-candles (or lux). The foot-candle is defined as the illuminance on a uniform surface one-foot away from the light of one candle and is equal to one Lumen/ft2. Which means a light source's output of 1 Lumen flowing through a sphere with a surface area equal to 1 ft2 would produce an illuminance of 1 foot-candle on the surface of the sphere.
Example: What light source output Lo (Lumens) would be required to produce an illuminance of 1 foot-candle at a distance of 1 foot?
Illuminance: I = Lo/A where Lo is the Light Source Output (Lumens) and A is the surface area (ft2) of a sphere centered around the light source.
At a distance of 1 foot, A = 4 p ft2, and so when I = 1 foot-candle, Lo = IA = 4 p Lumens (approximately 12.57 Lumens)
In other words, for a light meter to read 1 foot-candle from a uniform point source of light that is 1 foot away, a light source of about 12.57 Lumens is required.
In general terms: I = Lo/(4 p d2) assuming the light can be considered a uniform point source (no reflector).
From this, one can determine a light bulb's minimum peak illuminance (foot-candles) when one knows its specified initial output rating (Lumens) and the distance (feet) to the observer.
For a light bulb with an output rating of Lo (Lumens) and a code limiting illuminance to less than I (foot-candles), the minimum allowable distance from property line to the bulb would be d, where:
d = sqr_root(Lo / (4 p I))
When you do that you find that HID lighting is by far the better option.
When someone growing pot considers efficiency what they really should be considering the most is grams yielded per watt. The gram/watt ratio is lower with CFL's than with HID's. Since that is the case where is the most important efficiency factor for pot growers found, in using CFLs or using HIDs?
