LED Wattage per One Plant

indicahacker said:

I'm curious if anyone in this forum has identified an accurate calculation for LED wattage per one plant.

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az2000 said:

I think in similar terms as you. But, I think of one plant as a 3gal container in a 2x2 space. Using Cree lightbulbs from Home Depot (I hear purists hissing), I do well at 20-30w/sq ft.

One factor is vertical height. I.e., are we talking sq ft of a short or tall space? Maybe the better measurement should be cu. ft? Using those Cree bulbs I use 20-25w/sq ft in a 4' tall space. 25-30 in a 7' tall space.

They're not the most efficient lights. But, I think what adds to the efficiency which I realize is that they are placed around the plant (close, distributed, bathing the plant. Not a single powerful source at a greater distance.). That's why your post caught my eye. I think of my side and top lighting as a "per-plant" method of lighting (instead of a monolithic fixture concentrating light into a single source). It's more labor though. It's barely worth the effort in a 4x4 space with 4 plants.

Anyway, it depends on the quality of light. Those Cree "lightbulbs" are at the level I mentioned. Lights using epiwhatever diodes would be higher (say, 35w/sq ft in the short space, 45 in the tall). A T5HO would be 40w/sq ft in the short space. A CMH would be 35w/sq ft in the tall. (I don't think they are suitable for the shorter or taller space, respectively).

I posted an example of using that distributed low-wattage light. It has links to my blog showing how I rig up that kind of per-plant lighting.

There is also LED strip lighting. Search this forum for "SMD 5630" to find some threads. I've been intrigued with this because it's 12v and you can shape it to the contour of your plant. I was thinking of some thin aluminum sheets as panels, hinged so it could fold around the plant. Those diodes are a little more efficient than the Cree lightbulbs I like.

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Rahz said:

The LED has a fixed lumens per watt of 126 @350ma but not all LEDs operate at the same efficiency. In fact there is no light source as diverse as LED in that regard. Also the 400w HPS is being rated at less than 50 LPW which seems odd to me.

At any rate I think a good method of determining light levels needed is from PPFD calculations. 1 plant is a variable that doesn't describe the size of the plant. Having the size of the plant one must still decide how much light to give it. 500 PPFD? 1200 PPFD? Both are legitimate targets but one will require over twice the wattage of the other.

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az2000 said:

I think in similar terms as you. But, I think of one plant as a 3gal container in a 2x2 space. Using Cree lightbulbs from Home Depot (I hear purists hissing), I do well at 20-30w/sq ft.

One factor is vertical height. I.e., are we talking sq ft of a short or tall space? Maybe the better measurement should be cu. ft? Using those Cree bulbs I use 20-25w/sq ft in a 4' tall space. 25-30 in a 7' tall space.

They're not the most efficient lights. But, I think what adds to the efficiency which I realize is that they are placed around the plant (close, distributed, bathing the plant. Not a single powerful source at a greater distance.). That's why your post caught my eye. I think of my side and top lighting as a "per-plant" method of lighting (instead of a monolithic fixture concentrating light into a single source). It's more labor though. It's barely worth the effort in a 4x4 space with 4 plants.

Anyway, it depends on the quality of light. Those Cree "lightbulbs" are at the level I mentioned. Lights using epiwhatever diodes would be higher (say, 35w/sq ft in the short space, 45 in the tall). A T5HO would be 40w/sq ft in the short space. A CMH would be 35w/sq ft in the tall. (I don't think they are suitable for the shorter or taller space, respectively).

I posted an example of using that distributed low-wattage light. It has links to my blog showing how I rig up that kind of per-plant lighting.

There is also LED strip lighting. Search this forum for "SMD 5630" to find some threads. I've been intrigued with this because it's 12v and you can shape it to the contour of your plant. I was thinking of some thin aluminum sheets as panels, hinged so it could fold around the plant. Those diodes are a little more efficient than the Cree lightbulbs I like.

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indicahacker said:

Hello,

I'm curious if anyone in this forum has identified an accurate calculation for LED wattage per one plant. Presuming I want to grow only a single plant, most LED light solutions are overkill. It may be more cost effective to have LEDs on a per-plant basis for people with constrained environments, or who simply want a micro-grow.

There are a lot of use cases for this type of lighting style, including nutrient research, individual breeding plans, tissue/plantlet research, and more.

Any thoughts? One option is to use the Howard Lighting HID to LED conversion chart[1] to get a decent estimate. Since the average marijuana plant will take up at least one square foot, we can presume the 50W/sqft estimate is sound. Using the conversion chart, we can see that the average 100W HPS HID equates to approximately 33W LED. This could be used to conjecture that 16W LED is adequate for 1sqft, and thus, a single plant.

Are there other thoughts regarding this? Thank you!

[1] http://www.howard-lighting.com/Documents/ProductLiterature/HIDToLEDCrossReference.pdf

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dandyrandy said:

It's about density, or is it destiny? Sorry been smoking some blue dream and I'm a bit blitzed. Anyway I run ~ 800w in an area approx. 11 sq ft. I have a cola on one of my tga's that is humongous. It has 4 mains. I have run the area using 600. I find 800 is better. My lower buds are also larger. I guess it depends on your needs. I need to post a picture of that bud. It's taken a while to type this. Been a long day at work.

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ttystikk said:

The problem with this statement is that until you tell us what efficiency your LEDs are running at, we have no way of quantifying how much light you're talking about.

That's why I'm always including PPfd when discussing irradiance on the plants, like this;
24 ft² trellis
4 200W modules with 56% efficient CXB3590 COB chips, for 800W.
Each module delivers 824 PPfd to an area 2x3=6ft²

In order to test the high end of that range, I'll simply add two more 200W modules to the first four;
1200W, same efficiency, 1247 PPfd.

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Abiqua said:

I never really replied about LED and is it time....

And one thing I wanted to ask, even though I think you have mentioned what you actually do in the past....But I keep hearing that you have to change your HPS bulbs every other run or so, or they lose like 5% or more and drop fast after that with 3-6 months....

I have a small small exposure to HPS, but I was the same and didn't change out bulbs and recommended every 12 months or so, when asked. [Which was ignorant on my part, because I have never ran the same HPS for 12 months]

But I keep hearing this repeated over and over. I don't know what conclusion to come to

Anyhoo..I think waiting is still of the essence...I ran about 4 hours of #'s for the Citizen LED cobs and posted last night in the LED threads....The future is looking bright for LED's, but we still aren't quite there, let alone big time commercial grows....

Again, I think if you sat down and penciled out everything that goes into the equation and compared HPS vs LED, that they come out about equal. But the LED costs are VERY front loaded and still really only realistic if you DIY...which many just aren't ready for, or won't ever

I still think it might be a year or two before cost matches an HPS, up front...But then, it kills it later on down the road, with increased efficiency, less heat, yaddah yaddah....

One example of the Citizen is 117 watts from one chip and 42-43% efficient.

I believe that two of these would match a 400 watt. But again, I am looking at $2 watt to build...and no 400w I know of is $450.... But if I could maintain the same output as a 400 watt, while using less wattage and emitted heat, especially over a year or more, that has to be factored into the equation...If you keep an HPS long enough, you will have to do a bulb change....at some point and that has to factor into your end cost, if we wan't NO bias....for the LED, barring good working function, bulb changes are eliminated from the cost....

Really only price fixing is keeping the LED from wiping out Bulbs in general imho.....The power, the end results, it can't be denied anymore, but the PRICE alone is keeping people from being curious, not the tech

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indicahacker said:

That's definitely interesting, @Rahz. I like the idea of using PPFD, but that may be hard to calculate given availability of information on component datasheets. Is there a standard for doing this?

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