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Blipstir
Human



Registered: 05/05/14
Posts: 437
Loc: CO Mountains
Last seen: 1 month, 4 days
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Question about Grow Light and Wattage.
#28503851 - 10/13/23 10:24 PM (7 months, 1 day ago) |
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Hello, I ordered a 1000W Phlizon Full-Spectrum LED grow light for a cactus during the winter months. One thing I noticed in the item specs is that it says.
Power Consumption: 100 W
Wattage: 1000 W
I don't think I fully understand what is being listed here. Does that mean this light is able to put out 1000 watts worth of light but really only does 100 watts? I feel like I might be wording this question wrong too, but I would greatly appreciate some clarification.
Edited by Blipstir (10/14/23 10:03 PM)
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Kryptos
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Registered: 11/01/14
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Re: Question about Grow Light and Wattage. [Re: Blipstir]
#28504989 - 10/15/23 12:09 AM (7 months, 6 hours ago) |
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Wattage is referring to two things: power and radiant flux. Radiant flux is the sum of all electromagnetic radiation coming off of an object. Which is technically also power, but in a different form. Electromagnetic radiation, instead of electron flow.
For incandescent lights, this is very simple. A filament converts power to radiant flux using resistance. Electron flow becomes heat+light+other em radiation, which is radiant flux.
Since filament performance was pretty universal, you could use wattage to accurately estimate light output.
However, with the discovery of other forms of light, like, for example, LED, things changed. An LED is much more "efficient" (if the goal is light, an LED is a terrible source of heat compared to a filament), and gives off more of certain types of electromagnetic radiation, and less of others. So, less heat, more light.
So, they came up with a new unit, the lumen. Lumens measure luminous flux, i.e. only the visible light band of the EM spectrum. Useful for lights, since that's the point of a light.
But the old system still kinda stuck around. Like how you can go to the store and buy a "60W" LED, which actually pulls like, 9W of power, but gives off the same luminous flux as a 60W incandescent would have. Technically this should be expressed in lumens, but old habits due hard.
So, I'm guessing your 1000w bulb that consumes 100w is giving off the light equivalent of a 1000W incandescent bulb, but only using 100W of actual power.
This is somewhat oversimplified to the point of probably not being 100% correct.
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koraks
Registered: 06/02/03
Posts: 26,729
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Re: Question about Grow Light and Wattage. [Re: Kryptos]
#28505526 - 10/15/23 01:05 PM (6 months, 30 days ago) |
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Quote:
Kryptos said: So, I'm guessing your 1000w bulb that consumes 100w is giving off the light equivalent of a 1000W incandescent bulb, but only using 100W of actual power.
Yup, that's most likely it.
It's basically just misleading and confusing. And I don't think that when it comes to grow lights, a 100W LED unit is really equivalent to let's say a 1000W HMI. How the equivalence works out exactly will depend on a host of factors, particularly the emission spectra of the light sources that are being compared and the sensitivity and conversion efficiency of the receptor (in this case a plant). When it comes to plants, it will furthermore depend on what kind of plant and perhaps even what part of its growth cycle.
So there's really no quick & dirty way to equate X Watts of LED power to Y Watts of some other form of lighting.
Btw, about lumens: for applications like these, they're basically useless. The problem with lumens is that they are based on the sensitivity of the human eye, which peaks very strongly in the green part of the spectrum, i.e. around 525nm with a very broad bell curve tapering off to about 390nm (where UV starts) and about 680-700nm (where IR starts). Ironically, this green part that's weighed very heavily in lumen specs is exactly the bandwidth where photosynthesis virtually doesn't happen. For plant growth, particularly red and blue are relevant.
This means that if you would compare a 1000 lumen bulb that emits mostly green light will be pretty much useless for a grow light, whereas a source that emits only blue and red light and is also rated at 1000 lumens will be very much appropriate. If you plot out the spectra of these imaginary light sources and do some rough paper napkin calculations to work out how these two 1000 lumen sources compare in terms of absolute power radiated, you'd very quickly reach the conclusion that the lumen scale is totally unfit for choosing or designing narrow-band lighting systems for plant growth.
Not to mention that lumens are indeed a measure of flux and flux depends on (1) distance to the light source and (2) irradiance pattern of the light source (e.g. beam angle).
So lumens only sort of work if you compare broad-spectrum light sources intended for the human visual system with a similar irradiance pattern.
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Kryptos
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Registered: 11/01/14
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Re: Question about Grow Light and Wattage. [Re: koraks]
#28505580 - 10/15/23 01:47 PM (6 months, 30 days ago) |
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koraks said: So there's really no quick & dirty way to equate X Watts of LED power to Y Watts of some other form of lighting.
I mean...Watts is the "quick and dirty" way--because Watts can be used to measure the electromagnetic flux coming off a bulb.
To go back to my example of incandescent vs. LED bulb--filament are extremely efficient at converting electrical power to blackbody radiation, which is also a form of power. But it's very non-specific. So, 60W incandescent is giving off like, 50W IR and lower energy flux, 9W visible flux, and maybe 1W high energy wavelength flux. A 60W "equivalent" LED consumes 9W electricity and gives off 9W visible flux.
Hence, to the "quick and dirty" measurement of visual comparison, a 9W LED is the same as a 60W bulb.
But you're correct in that this breaks down for grow lights and such, since plants don't use human visual spectra.
(pretty sure we're saying the same thing in various ways with varying amounts of detail, but that's okay because this discussion is meant to...illuminate...the subject for anybody that's passing by with a question!)
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koraks
Registered: 06/02/03
Posts: 26,729
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Re: Question about Grow Light and Wattage. [Re: Kryptos]
#28506337 - 10/16/23 03:11 AM (6 months, 30 days ago) |
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Quote:
Kryptos said:
Quote:
koraks said: So there's really no quick & dirty way to equate X Watts of LED power to Y Watts of some other form of lighting.
I mean...Watts is the "quick and dirty" way--because Watts can be used to measure the electromagnetic flux coming off a bulb.
I see what I mean, but I think the issue here is that Watts are used inconsistently, and deliberately so. They're used as a way to express electrical power supplied to and dissipated by the LED or the incandescent bulb, and at the same time as a (very gross) approximation of the luminous flux emitted by the LED source. Since Watt is basically a unit that expresses an amount of energy per unit of time, it's a really flexible measure to use - but that also makes interpretations specific to contextual factors. Especially for consumers, this makes the whole thing kind of convoluted and confusing. Sadly, there's no good solution to it!
Quote:
To go back to my example of incandescent vs. LED bulb--filament are extremely efficient at converting electrical power to blackbody radiation, which is also a form of power. But it's very non-specific. So, 60W incandescent is giving off like, 50W IR and lower energy flux, 9W visible flux, and maybe 1W high energy wavelength flux. A 60W "equivalent" LED consumes 9W electricity and gives off 9W visible flux.
Yeah, in principle at least. Although LEDs aren't quite that efficient. For most high power LEDs, the efficiency is maybe 50% or so AFAIK; the rest is still dissipated as heat in the semiconductor junction itself.
Quote:
(pretty sure we're saying the same thing in various ways with varying amounts of detail, but that's okay because this discussion is meant to...illuminate...the subject for anybody that's passing by with a question!)
Sure; this discussion is not so much about disagreement but more about elaborating a couple of key points.
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