Theory about why CFLs don't work as well as HPS etc

I've been scratching my head about why people often seem to find that CFL doesn't yield as well as other lighting sources e.g. HPS, as peoples' usual explanations about light not penetrating etc etc don't make much sense to me. Well, I've been trying a CFL grow and I think I have a pretty good answer for everybody now: I bought two types of CFL lights: ones which were advertised as 30W and ones which were advertised as 105W (that's real watts, not equivalent watts). They didn't seem that bright to me so, feeling a bit suspicious, I spent a tenner on a nice german power meter. That told me that the 30W CFLs were actually drawing 25W each, which is not great. But far worse was the larger lights explicitly advertised as grow bulbs. They came out as 41W each rather than the advertised 105W! That's not even half!

Consequently, my CFL grow which should have been running on a total of 300W real power has actually been getting a measly 157W! My calculations were based on getting about 18 to 20 thousand lumens, but in fact I've probably been getting more like 9 or 10 thousand.

In my opinion a CFL grow should be the match of HPS watt for watt (maybe a little in HPS favour), so I should have been about comparable with a ~200W HPS setup. If I'd not done these measurements I would have been scratching my head why I only got half the yield compared with a 200W HPS setup and would probably have concluded that, for whatever reason, CFL is just not as good for growing cannabis.

Has anybody else tried measuring the power consumption of their lighting setups, especially those based on CFL? I've a feeling that many grow lights in particular, which are often made by smaller companies many from china with no reputation to go before them, really have light outputs far far less than those that are stated.

I think it's the light penetration from the HPS. The CFL's lumens drop off sharply when the light meter is taken away from the CFL.

This is why it is advised to keep CFL's very close to the plants. The HPS is hung much higher and retains the lumens over greater distances.

In my first grow in my signature I used a cheap light meter to measure the output from my LED light.

Hope this answers your question.

Take Care

S.L.

Hello just read your post and I can see what you are saying with regards to the issue of CFLs, I have used CFls for vegging and found they worked brilliantly so I scrapped my HID lamps, I also switched from HID on the flowers to flourescent tubes I used Phillips MASTER TL-D Reflex 36W/840 tubes (warm red tubes) built into an array of 8 tubes per light I used 2 light arrays (16 x 36w) for a total of 576w Best yield I had was with Ak 47 @ 732g.

The beauty with these tubes is that you can have the array positioned to the point that it is touching the plants, when you factor in the inverse square law and how far you have to position a HID lamp away from the plant plus the fact that those Master Reflex tubes are in a better suited spectrum to plant growth (hardly any yellow lots of red per se HID) then maybe you can understand why they work.

I always found that the tubes need a run in, on new tubes 2nd crops tended to be better than 1st ones, and tubes should be replaced every 6 crops, but as they are cheap enough to buy, produce very little heat (no detection worries) and yield very well on that basis I would never use HIDs again.

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Originally Posted by Johnnycannaseed

Hello just read your post and I can see what you are saying with regards to the issue of CFLs, I have used CFls for vegging and found they worked brilliantly so I scrapped my HID lamps, I also switched from HID on the flowers to flourescent tubes I used Phillips MASTER TL-D Reflex 36W/840 tubes (warm red tubes) built into an array of 8 tubes per light I used 2 light arrays (16 x 36w) for a total of 576w Best yield I had was with Ak 47 @ 732g.

The beauty with these tubes is that you can have the array positioned to the point that it is touching the plants, when you factor in the inverse square law and how far you have to position a HID lamp away from the plant plus the fact that those Master Reflex tubes are in a better suited spectrum to plant growth (hardly any yellow lots of red per se HID) then maybe you can understand why they work.

I always found that the tubes need a run in, on new tubes 2nd crops tended to be better than 1st ones, and tubes should be replaced every 6 crops, but as they are cheap enough to buy, produce very little heat (no detection worries) and yield very well on that basis I would never use HIDs again.

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I'm glad to see that you mentioned the inverse square law as this is indeed the law that governs the decrease in intensity of EM radiation such as light. This includes light from HPS and from CFL. As per the poster above you, there seems to be a strange view going around that photons from CFLs are somehow weedier and less well-travelled than identical photons from HPS. I'd like to see the evidence for the view that light intensity drops off quicker for CFL than HPS as this would have to mean that one of them was violating the inverse square law.

Anyways, you're probably having more success because you're using good quality name branded CFLs which actually produce the amount of light they're supposed to. I was thinking maybe a lot of people made the same mistake as me and bought from one of the many cheaper grow light makers which, it now seems, produce far less light than they are supposed to.

Maybe CFL is getting a bad name because of this - a lot of people seem to be against it or say it is for 'noobs' or whatever. But I've a feeling that if you get good quality CFLs it should be as good as any other source.

I use the GE brand 23W and they work good. I'm using 6 when in flower I'm going up to 12. For two plants. The lumens are 1610 per bulb for 6500 k and 1760 for 2700k. I think people may have problems because they don't make a hood to focus the lights or they try to grow too many plants with too little light. 6 lights per plant is good. I almost bought a huge 6500k cfl from home depot , I forget the name of the brand.

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Originally Posted by Powernoob

I'm glad to see that you mentioned the inverse square law as this is indeed the law that governs the decrease in intensity of EM radiation such as light. This includes light from HPS and from CFL. As per the poster above you, there seems to be a strange view going around that photons from CFLs are somehow weedier and less well-travelled than identical photons from HPS. I'd like to see the evidence for the view that light intensity drops off quicker for CFL than HPS as this would have to mean that one of them was violating the inverse square law.

Anyways, you're probably having more success because you're using good quality name branded CFLs which actually produce the amount of light they're supposed to. I was thinking maybe a lot of people made the same mistake as me and bought from one of the many cheaper grow light makers which, it now seems, produce far less light than they are supposed to.

Maybe CFL is getting a bad name because of this - a lot of people seem to be against it or say it is for 'noobs' or whatever. But I've a feeling that if you get good quality CFLs it should be as good as any other source.

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Here is the thing a lot of this stuff put out by HID companies is a myth and marketing to protect their own vested interest at the end of the day once you know the science then you come to realise that certain things do not add up, as far as I am aware a photon is a photon, different wavelength photons have different amounts of energy, shorter blue wavelength photons have more energy than longer wavelength photons if my memory is correct.

So HID lamps are only supposedly better because they are belting out more photons than the CFLs not that their photons are stronger than CFLs because that is not the case, but that is not the whole story as a good percentage of what HIDs are belting out is not usable light ( it is delivering large amounts of a spectrum that is only absorbed in small amounts by the plants).

Now these HIDs deliver lets say in old money terms 95000 lumens for a 600w Hps @ its source, but a plant cannot sit that close to the light so if you move the light 1 foot away now its lumen count has dropped to 23750 lumens, move the light 2feet away and from the plant and the story gets worse for HIDs those lumen figures now drop to 10555 lumens.

So you have a light that runs hot delivers large portions of its light in a spectrum that is not really catering to the plant and has a lowish light output when hung at a usable growing distance, well when you do the maths and compare that watt for watt to an array of flourescent tubes that can be hung at source to each plant, that give off a more usable spectrum of light for plant growth and that can distribute that light equally over a growing area, produces way less heat and consumes less on the electricity it becomes a no brainer as to why I chose this route what I fail to understand is why so few have cottoned onto this I can only put it down to being set in their ways and falling for the marketing hype and brightness of HIDs, but that is a human eye response to their brightness, to a plant those lights would look adequate but kind of dullish and nowhere near as bright as we perceive them.

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Originally Posted by jiggsaw

I use the GE brand 23W and they work good. I'm using 6 when in flower I'm going up to 12. For two plants. The lumens are 1610 per bulb for 6500 k and 1760 for 2700k. I think people may have problems because they don't make a hood to focus the lights or they try to grow too many plants with too little light. 6 lights per plant is good. I almost bought a huge 6500k cfl from home depot , I forget the name of the brand.

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I think the other problem is that they do not place the flourescents close enough to the plants and that they do not use quality flourescents as stated by powernoob, if they did then they would see the results for themselves, the tubes I use have built in reflectors so all the light is focused downward

I thought HPS lights put out more lumens/ watt than cfl is this not true?

They put out more lumens but think of it this way if 60% of those lumens are in the wrong spectrum then that means its PAR value is around 40% of total light output and do not forget you need to factor in the distance those lights will be away from the plants so you have to apply inverse square law and when you do that you will find HIDs are worse on a watt for watt basis than a decent set of T5 or T8 tubes.