LED Watts per Sq. Ft.??? Unanswerable question?

DankDave420

DankDave420

Well-Known Member
Hey guys. Just trying to get an answer on this. The sources online range from 25-60 watts of LED per sq ft for flowering optimally. I don't have a par meter and I am just looking for a general goal. I know that LED should be measured in Par umols. I know LED's aren't that far off though that nobody can give a decent range. Somebody out there knows a good wattage to aim for. I just want a good up to date answer from someone with experience. If it matters much I am not using any COB's. Is 25-60 watts per sq. ft.the best answer I can get? Is this question unanswerable? If it is, what is the question I should be asking to get the answer I am looking for? How much light? Seems like a very important question that shouldn't be too hard to answer for anyone with experience. Even a link to a reputable source that isn't a light dealer would be helpful. But I really would like some first hand experience, I know it is out there. How much LED light is optimum through flowering?
 
GroErr

GroErr

Well-Known Member
I've found ~30w sw. ft. in flowering and 20-25w in veg to work well, that's with COBs, likely applies to the newer strips as a guide. With older diode based tech you need more like 40+w sq.ft. in flower for any decent numbers. So the answer varies a bit depending on the tech which is likely why you've seen wide ranges. Some like to use more, some less. I did a run at 22w/sq./ft. and that produced well, but added more than a week to a few phenos.
 
DankDave420

DankDave420

Well-Known Member
Awesome guys. Thanks. Those are good answers. I guess that range is always going to be wide with the range of quality these things are made. I'm at 28 watts per sq ft now with a Viparspectra 400w (200w actual), I believe that falls into the less efficient category. I am thinking of just getting a second one then and if it is too much I can mess with alternate timing maybe to act as like a light mover. Wonder if anyone has done that. Wonder if those light movers are legit. I am not trying to be the failed experimental grower. I wonder how much light would be too much. 56w per sq ft pushing too much? I have plenty of ventilation. Thanks again guys. Anyone else? Experience with this particular light would be fantastic. Also I can not give likes or anything yet, your input is very much appreciated.
Also I am not growing 4 sq ft plants. I have about 2 foot of plant space vertically and will likely just do a small SOG type. I never calculate number of plants, only sq ft of canopy. Im stuffing as many small untopped plants(9 max) in there as I can at first to see how it works out. I can always take some out if there are problems. I want a fast harvest then I'll work on a high yield next time. This is all just for personal use and I don't smoke that much. I'll give away any extra to friends. Thanks again guys.
 
S

Seshwaan

Well-Known Member
Hey man. I am actually in the process of building my own LED board for my 1sqft PC case so have been looking into this extensively. Obviously I am new to this but feel I have a pretty decent basic understanding.

You cannot really use Watts per sqft as a general measure for LED's due to the fact that depending on which LEDs/COB's you use they each have different lumens per sqft.

For example, off the shelf LED bulbs may have under 100 lumens per watt, Most CFL's you will see have only 60lm/W.... I am using some bridgelux BXEB-L0280Z-35E1000-C-A3

And they have 156 lm/W. There are some samsung strips for 3-4x the price that have 189lm/W. So you may have 3 different LED setups all giving 50W per s ft but the each of them can range greatly with how many lumens they each provide to the space.

I have found multiple places stating that the between 4000-6000 will suffice so I have gone for 6000 by using 5 of those bridgelux strips above.

Beauty of DIY is that you can tailor the light to exactly what you need. I haven't done the math but I am sure that you wouldn't get anywhere near 6000 lm/sq ft with a viparspectra or UFO
 
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S

Seshwaan

Well-Known Member
Budget Buds said:
Lumens per watts dont mean shit, u got the right idea for umol's....I use 50 watts per sq foot with vero 29's , using a Dimmer for less intense light in veg, works great for my testing and main rooms:)
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Could you expand on why lumens per watt don;t mean shit? Genuinely interested.

I always thought lumens per were an indicator of efficiency and the more efficient an LED the more photons you get out of the same wattage
 
DankDave420

DankDave420

Well-Known Member
Seshwaan said:
Could you expand on why lumens per watt don;t mean shit? Genuinely interested.

I always thought lumens per were an indicator of efficiency and the more efficient an LED the more photons you get out of the same wattage
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I am asking for a goal Watt per Sq. Ft. assuming that most grow LED's would be similar PAR and efficiency. I know there is a range, I was just hoping to get a smaller range since most of the info is outdated and the tech is changing quickly, and there is much more experience with them now. I realize it is not the best way, but I don't have a PAR meter and do not plan to aquire one. So I figured it would still get me close because alot of the sources still recommend a wattage per sq. ft. as a goal.

I am no expert yet, but from my understanding. The reason we use PAR in umol's for LED's is because it is the amount of useable light reaching the plant. Some of the spectrum of light that is unusable to the plant is often reduced, as they focus on only the usable spectrum. Also they focus on specific colors like reds and blues because they are the ideal color for growing. This would make using the full spectrum lumens insufficient as you can reduce the lumens without reducing the amount of usable light your plants receive. Some colors like green are not used as efficiently, considering our green plants tend to reflect most of the green light hitting them. So the green can be reduced, reducing lumens. Not having a complete understanding of all of this is another good reason I didn't build. I relied on someone else to do the engineering and went on user feedback to make the purchase. This is still a top rated light anywhere you look even though it is cheap. Definitely not the best money can buy. I will certainly document my experience with it.
Thanks for the input guys. It is truly appreciated.
 
R

Ryante55

Well-Known Member
DankDave420 said:
Hey guys. Just trying to get an answer on this. The sources online range from 25-60 watts of LED per sq ft for flowering optimally. I don't have a par meter and I am just looking for a general goal. I know that LED should be measured in Par umols. I know LED's aren't that far off though that nobody can give a decent range. Somebody out there knows a good wattage to aim for. I just want a good up to date answer from someone with experience. If it matters much I am not using any COB's. Is 25-60 watts per sq. ft.the best answer I can get? Is this question unanswerable? If it is, what is the question I should be asking to get the answer I am looking for? How much light? Seems like a very important question that shouldn't be too hard to answer for anyone with experience. Even a link to a reputable source that isn't a light dealer would be helpful. But I really would like some first hand experience, I know it is out there. How much LED light is optimum through flowering?
Click to expand...
Your question is too broad if you are using old blurples you need alot if your using 200lm/w white led you probably only need 30w/sf if your running 150lm/w white led you might need 35w/sf in my experience you don't need more than 45w/sf for optimal growth with led that have been released in the last year or 2
 
Rolla J

Rolla J

Well-Known Member
155 watts max and 30watts the lowest i can dim down on just these 2 bars. All 4 bars 36 chips should run atleast 345 max in flower. Will hook it up tomorrow. And also check out my other diy light see what that pulls. Was alll so curious to see what im pulling from the wall, so i ran out and got a P3 kill a watt today
20171020_143250.jpg 20171020_143312.jpg
 
mauricem00

mauricem00

Well-Known Member
DankDave420 said:
Awesome guys. Thanks. Those are good answers. I guess that range is always going to be wide with the range of quality these things are made. I'm at 28 watts per sq ft now with a Viparspectra 400w (200w actual), I believe that falls into the less efficient category. I am thinking of just getting a second one then and if it is too much I can mess with alternate timing maybe to act as like a light mover. Wonder if anyone has done that. Wonder if those light movers are legit. I am not trying to be the failed experimental grower. I wonder how much light would be too much. 56w per sq ft pushing too much? I have plenty of ventilation. Thanks again guys. Anyone else? Experience with this particular light would be fantastic. Also I can not give likes or anything yet, your input is very much appreciated.
Also I am not growing 4 sq ft plants. I have about 2 foot of plant space vertically and will likely just do a small SOG type. I never calculate number of plants, only sq ft of canopy. Im stuffing as many small untopped plants(9 max) in there as I can at first to see how it works out. I can always take some out if there are problems. I want a fast harvest then I'll work on a high yield next time. This is all just for personal use and I don't smoke that much. I'll give away any extra to friends. Thanks again guys.
Click to expand...
that viperspectra 450 uses 206 watts of power but only produces 27 watts of radiant power. a high end white C.O.B or 561 strip light will give you close to 45 watts or radiant power for 100 watts of input.you would need over 340 watts of those cheap LEDs to match the output of a high end cree or osram LED. how much power you need depends on the quality of LEDs you are using.
cheap LEDs are not worth the money.
 
ChaosHunter

ChaosHunter

Well-Known Member
GroErr said:
I've found ~30w sw. ft. in flowering and 20-25w in veg to work well, that's with COBs, likely applies to the newer strips as a guide. With older diode based tech you need more like 40+w sq.ft. in flower for any decent numbers. So the answer varies a bit depending on the tech which is likely why you've seen wide ranges. Some like to use more, some less. I did a run at 22w/sq./ft. and that produced well, but added more than a week to a few phenos.
Click to expand...
This
 
Rolla J

Rolla J

Well-Known Member
@horribleherk has a CLS blurple grow as well as a cob setup. I believe he runs more watts with the CLS led light.

I run a cree and osram blurple led, the unit farm Ufo80 led in a 2x2. The draw is 175w +-5 182watts in my kill a watt
Here r some specs of that light.Screenshot_2017-10-20-15-08-06-1.png
I also run that diy flower light with full potential which runs 2x as much power in a 2x2. Like 90w sq ft lol compared to about 44w sq ft with the high end blurple
 
Tim Fox

Tim Fox

Well-Known Member
Rolla J said:
155 watts max and 30watts the lowest i can dim down on just these 2 bars. All 4 bars 36 chips should run atleast 345 max in flower. Will hook it up tomorrow. And also check out my other diy light see what that pulls. Was alll so curious to see what im pulling from the wall, so i ran out and got a P3 kill a watt today
View attachment 4029792 View attachment 4029793
Click to expand...
oh yea man looks great,,, here is my current citi panel, i am adding a couple of cree 3070's to get up to around 60 watts in flower next runIMG_0604.JPG IMG_0628.JPG
 
Rolla J

Rolla J

Well-Known Member
Tim Fox said:
oh yea man looks great,,, here is my current citi panel, i am adding a couple of cree 3070's to get up to around 60 watts in flower next runView attachment 4029902 View attachment 4029904
Click to expand...
Got you a nice frame there! Thats a killer light right there. Have ubhad a harvest yet with the light?
The other diy one i have is for veg runs 6000k yeah yeah looks like a phoney qb haha
Guna hook it up tomorrow and see what im pulling from the wall. I dont think anymore but 110w at max. But we shall see20171001_194750.jpg
 
horribleherk

horribleherk

Well-Known Member
I have an osram diode light (200w.) I run a 2x2 Scrog inside a 3x3 tent so I pretty much use 50w=1sq.ft.with this light my other light is cob@340w. it is over a 30 x 30 Scrog which comes out to about 45.3w=1sq.ft. these terms & numbers for leds are mind boggling & im on my first run in this configuration the top pic is the cob light bottom pic is the osram blurple light the plants are sisters from same mom same batch of clones I flipped the cob tent 3 weeks ago today & the blurple tent 2 weeks ago this seems to be working out for me these are single plant growsIMG_3051.JPGIMG_3056.JPG
 
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