Do CFLs produce more heat/W or more light/W than HPS?

Hi all,

Something been confusing me about the old HPS vs CFL issue: it seems to be the view that HPS produces more heat for a given grow and therefore you have to have extra ventilation etc. But it is also the view that HPS produces more light per watt than CFL (i.e. you maybe need 50% more CFL watts to get the same result as HPS).

The problem is that this violates the laws of physics. Since neither bulb is converting energy into sound, or into movement, or anything else, there is only heat and light coming out of both of them. So if an HPS bulb produces more light per watt than a CFL, then it would have to achieve this by producing less heat per watt (i.e. converting more electrical energy into light than heat vs the CFL). Or if it produces more heat per watt, it has to produce less light per watt.

So I was wondering which one people think it is: Does HPS produce more light per watt or more heat per watt?

It doesn't violate any law of physics. The only law it seems to be breaking for you is the conservation of energy, which I believe you have a very basic understanding of. HID lighting will create more heat and INTENSITY of lighting for every watt used but fluorescents will create better QUALITY of light. This means that the spectrum of visible light from a HID will be generally lower than a fluorescent, however, the intensity of the HID will be higher at (a) specific wavelength(s). You're missing the fact that HID and fluorescents work in a very different matter and cannot be compared head to head. I do mean no offense by my explanation, and I hope you learn something.
-Lay

Well that was enormously condescending, especially when you take into account the bewildering ignorance of physics manifested. I'll break it down for you to make it a little easier to understand:

1) CFL and HPS lighting systems generate only heat and light.
2) For every watt of electrical power you give to such a system, it must therefore generate a total of 1W of heat power and light power combined.
3) But the proportion that is heat vs the proportion that is light may vary.
4) Therefore the CFL system must either produce more heat per watt than HPS, or more light per watt, or the same.
5) It is commonly said that HPS produces more light per watt than CFL.
6) It is commonly said that HPS produces more heat per watt than CFL.
7) This is impossible.

Talk of nebulous concepts like light quality is completely irrelevant to the above argument. The breakdown of light energy across the spectrum is also irrelevant to the above argument. Finally, the law of the conservation of energy IS a law of physics - in fact the first law of thermodynamics is essentially a conservation of energy law.

I don't believe that was condescending, I was trying to explain to you in the most truthful way possible. If you think about it, I could have ignored your question completely and just treated you like a utter beginner. Now, I really don't want to bring that out more anyways, but I'll try to explain a little more.

I'll break your thought process down, and I'll show you where you're going off about this.

1) CFL and HPS lighting systems generate only heat and light.
(Yes, but you also got to account for ballast inefficiencies, and even sound output if you wanna be accounting for every single energy type. Also, you got to factor in the inefficiencies caused by the phosphor/fluorescent coating inside the CFL's.)
2) For every watt of electrical power you give to such a system, it must therefore generate a total of 1W of heat power and light power combined.
(Look above)
3) But the proportion that is heat vs the proportion that is light may vary.
(Yes, you are right. This can be affected by which ballast, wire, or even socket you use. All inefficiencies are accounted for, in every source of waste energy)
4) Therefore the CFL system must either produce more heat per watt than HPS, or more light per watt, or the same.
(Yes, and no. Like I said, the way HID's make light is very different from how CFL's create light.)
5) It is commonly said that HPS produces more light per watt than CFL.
(This is where intensity and spectrum come into relevance. HPS will create a higher intensity of light in (a) specific wavelength(s), which means that the energy used for creating light will be towards creating that/those wavelengths with the other wavelengths it may create (at a lower intensity), rather than a whole spectrum of light, like the CFL's (which also have peaks, but not anywhere near as high in intensity). Just think about it. If hypothetically, all the energy in a light bulb is used to create one single wavelength, that intensity or power of that specific wavelength is going to be massive. However, if the energy is dispersed over a whole spectrum, then obviously the highest intensity of any wavelength in the whole spectrum will be lower than the hypothetical bulb creating one wavelength. This isn't a concept, it's reality.)
7) This is impossible.

Now I'll break down your final comments.

The breakdown of light energy across the spectrum is relevant, because it's characterizes how the light "manages" its available energy to the spectrum. So do HID's create more light? Depends on how you look at it. If you're talking about intensity, then yes, they do create a higher intensity light. But if you're talking about quality, CFL's will mostly have more light across the spectrum. The law of conservation of energy is indeed a law of physics, but never did I say it wasn't a law of physics.

CFL's are no doubt more energy efficient, but the plants don't take in the amount of lumens or luminous flux, they have a strict spectrum to absorb.