Wattage vs Space vs Yield - how much do I really need?

Shaded_One · Sep 10, 2022

Shane over at MIGRO just put together a really cool video that I thought I would share with you all as I see this question/discussion being brought up a lot in random threads. What he did was polled his social media communities and gathered information based on peoples experiences and combined that with his data to give us an easy to follow guideline that tells you the "optimal" plants to run in a given space, tells you the optimal amount of light for the given space, and also gives you a rough estimate on expected yields (obviously there is huge variance to this, and should only be used as rough estimates). What I will do is go through the vid and gut out the infographics so you guys don't have to watch the video if you don't want to but I will still include the link down at the bottom.

Dried Flower Yield Estimate - these are rough numbers of what you can expect with many variables

Number Of Plants - photoperiods on the lower end of the scale, autoflowers on the higher end

Optimal Light Intensity - he explains this better in the video but it has to do with ROI and reduction of invested light increases. At a certain point the curve heads downward and that's at around 800 umol

Recommended LED Wattage per Space - with good quality diodes you can get by with about 30w per square foot of grow space

Here's a link to the full video if you'd like to watch and get more info:

BigBlonde · Sep 10, 2022

Thanks for this @Shaded_One!

When I was looking at reviews and recommendations for LED lights, I noticed that the older articles had higher values of wattage/ft^2. That I interpreted as being attributable to improvements in LED technology. It seems to have stabilized at 30 watts/ft^2. It wouldn't surprise me, however, if that number were to decrease somewhat as newer and better technology becomes available.

Aqua Man · Sep 10, 2022

Yeah id say that fits the bill pretty well. Seeing these recommendations for 40w per sq ft. Makes me cringe

Observationist · Sep 10, 2022

Currently I have 600w of led in a 5x5, I can’t even use all 600

Lol

growsince79 · Sep 10, 2022

Aqua Man said:
Yeah id say that fits the bill pretty well. Seeing these recommendations for 40w per sq ft. Makes me cringe

I think 40w is great if you have extra height. Even the best bar lights are weak in the corners, and a higher light makes a more uniform canopy. I need at least 35w/ft.

Aqua Man · Sep 10, 2022

growsince79 said:
I think 40w is great if you have extra height. Even the best bar lights are weak in the corners, and a higher light makes a more uniform canopy. I need at least 35w/ft.

Yeah i should add that its ppfd that matters. Light style also plays a role as the further you keep then the higher the wattage you need to run.

Madmax · Sep 10, 2022

Observationist said:
Currently I have 600w of led in a 5x5, I can’t even use all 600

Lol

You should b able to brother ..how highs your ceiling..i keep the lumatek pro 600 between 20-24" at 625 watt..some grows i will get one closer and get a little fox tailing..im running the se 7000 now between 20--24 ' at 85% which is 620 watts and tops are very uniform..

Madmax · Sep 10, 2022

I should of said over a 5x4 area..

MIGrampaUSA · Sep 10, 2022

Madmax said:
You should b able to brother ..how highs your ceiling..i keep the lumatek pro 600 between 20-24" at 625 watt..some grows i will get one closer and get a little fox tailing..im running the se 7000 now between 20--24 ' at 85% which is 620 watts and tops are very uniform..

I've been running an ROI-E720 in a 5 x 5 and have no issues running the light at 100% (800 watts) @ 18".

One thing I have not seen mentioned is if you're growing in a tent with reflective mylar walls, you can get away with a bit less wattage because the light off the tent walls is reflected back into the grow space.

Madmax · Sep 10, 2022

My lack of experience wont let me push the plants lol..i have white tips on my gals suggesting they are getting plenty of light..id like to know the reflectability of white melamine chipboard that has a low sheen.i have gotten very good penetration right down through the canopy...this is most likey the answer why i havent tried lower height as the yields are very high..

BigBlonde · Sep 10, 2022

Dispersion of the light, I think, may also be worth considering. I started thinking about this while thinking about how the sun provides light at different angles throughout the day. We don't move our lights to mimic that, but we can spread the light by using a wider span of lights. That, in addition to watts per area was the reasoning behind why I decided to use two light panels.

MIGrampaUSA · Sep 10, 2022

BigBlonde said:
Dispersion of the light, I think, may also be worth considering. I started thinking about this while thinking about how the sun provides light at different angles throughout the day. We don't move our lights to mimic that, but we can spread the light by using a wider span of lights. That, in addition to watts per area was the reasoning behind why I decided to use two light panels.

Good choice. In many situations, 2 smaller lights will provide better coverage than 1 large light. Total wattage being equal in both cases.

Peat_Phreak · Sep 10, 2022

Confucius say - buy brighter light than needed and turn it down. When the light loses brightness over time, then turn it up.

Shaded_One · Sep 10, 2022

MIGrampaUSA said:
I've been running an ROI-E720 in a 5 x 5 and have no issues running the light at 100% (800 watts) @ 18".

One thing I have not seen mentioned is if you're growing in a tent with reflective mylar walls, you can get away with a bit less wattage because the light off the tent walls is reflected back into the grow space.

I hate to plug Shane like he's some guru or whatnot but he did a good video on that and touched on the inverse square law for LED's in grow tents with reflective walls as well :)

MIGrampaUSA said:
Good choice. In many situations, 2 smaller lights will provide better coverage than 1 large light. Total wattage being equal in both cases.

+1

growsince79 · Sep 10, 2022

I didn't watch. Did he touch on why it doesn't work figuring leds?

Shaded_One · Sep 10, 2022

You get about a 13% loss in light intensity over 2x the distance when in reality with the inverse square law there should have been around 75% loss.

So yeah the inverse square law for LEDs in grow tents is

PerfecTrader · Sep 10, 2022

Shane is the sheet and thanks for the thread @Shaded_One I have followed him since before my 1st grow and the dude is legit af. I love when the person is unquestionably matrix-like knowledgeable but also humble to boot and easy to understand

MIGrampaUSA · Sep 10, 2022

PerfecTrader said:
Shane is the sheet and thanks for the thread @Shaded_One I have followed him since before my 1st grow and the dude is legit af. I love when the person is unquestionably matrix-like knowledgeable but also humble to boot and easy to understand

Shane is good, but so is Dr Bugbee. Personally I like them both.

growsince79 · Sep 10, 2022

PerfecTrader said:
Shane is the sheet and thanks for the thread @Shaded_One I have followed him since before my 1st grow and the dude is legit af. I love when the person is unquestionably matrix-like knowledgeable but also humble to boot and easy to understand

Shane probably reads the farm. We figured it out years ago. Lot of know it alls wanted to argue. lol

Shaded_One · Sep 10, 2022

MIGrampaUSA said:
Shane is good, but so is Dr Bugbee. Personally I like them both.

Yep - like tools in your belt to be called upon and utilized in times of need. Shane is a little more specialized in the LEDs/lights themselves whereas Bugbee is more involved in overall/general plant based knowledge. Shane actually had Bugbee come on one of his videos to chat and it was a good one, that's where I learned about the importance of the green spectrum in relation to leaf penetration!

Wattage vs Space vs Yield - how much do I really need?

Wattage vs Space vs Yield - how much do I really need?

Shaded_One

BigBlonde

Aqua Man

Observationist

growsince79

Aqua Man

Madmax

Madmax

MIGrampaUSA

Madmax

BigBlonde

MIGrampaUSA

Peat_Phreak

Shaded_One

growsince79

Shaded_One

PerfecTrader

MIGrampaUSA

growsince79

Shaded_One

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