What is the Perfect Wattage for a Grow Light

Hey Forum Friends. I gots a quick question… Haha! Y’all know better by now, huh? So my 5x6 tent is overflowing, and I still have 5 clones about to be needing forever homes if they all root up. I am now ready to purchase a new tent and equipment. I plan to stick with ViVoSun for my Lights and I intend to get one of the tents with the divider. My question has to do with Wattage. I know for the propagation area I need a smaller light with less wattage, and really the VS1000/100Watt is the only one that will fit in the side section of any of the tents I’ve seen, so I gotta get it for that part. I currently use a VS4000 and I do see some light burn at both 50 and 75%, so I figure I don’t need 400 watts from whatever new light I get. But how many watts DO I need? 300? 200? The ViVoSun’s are full spectrum LED’s. The attached pics are of each lights output, I guess, and the link is to the VS1500/150Watt because their descriptive photos are different from the others.





Removed unauthorized link

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A good rule of thumb is about 35-40 watts per square foot ie 1’x1’
If your needing to cover a 4’x4’ space that is 16’ square
16x40=640 watts
16x35=560 watts

One thing you want to consider is what the light is putting out in the center of it at a particular height. The most you’ll want to hit the plants with PPFD is maybe 1000 ppfd. I strive for around 850-900 ppfd.

The design of many lights are very strong in the center and that can be a challenge if they are all tall. Rotating the plants so that the shortest parts are in the center of the light and the tallest are out on the sides/edges helps when lights are concentrated in center.
I circled what I mean from your pics in post above and with those numbers they can negatively affect the tops of the plants.




The physical dimensions of the VS4000 for example is just under 2’x2’ in size yet covers up to 5x5 per their web site.

I tend to prefer the bar style strip lights that spread the lighting more evenly across the tent. The fixture size being closer to the actual coverage size…this one says 5’x5’ coverage in flower.

You could also consider multiple smaller fixtures to cover the larger space that won’t have such an intense middle PPFD

Hope this helps

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Ok. Yes, this helps. I do rotate and turn them every other day and I do try to keep the shorter ones in center. Although I do move them out of center about every 4th rotation just because it feels right to do so. I use the meter each time to get as close to the same reading at each plant that I can and tilt of move the light to get it closer to even, at the tops of each plant anyway. I will look into some bar lights. What you say does make sense. The 4000 came with my kit and so I was trying to jeep everything as close to possible as the same.

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@Skydiver Hey, so if I got one of those divided tents with the larger main section and 2 smaller ones on the side, for my seedlings and/or clones would just a normal kind of lamp with a grow bulb or some special kind of bulb


and/or those little stick LED’s with the alternating red and blue things that I have be sufficient for the small side?

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You will need more light than that.

Clones really need a lot of light as they are basically mature plants.

HLG offers some 150 watt lights which is what I use.

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Something that you need to think about is how much wattage your receptacle can handle before it kicks the breaker. Lights, fans, etc. can add up quick

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I personally would go for an HLG 100w-200w for the clone/seedlings. Not too expensive. Much more efficient. Super customer service.

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Hps/mh pull much much more wattage/amps than any led you grab. 200w led can match a 600w hps/mh with 1/3 the power draw. Can drop 1000 true watts in without blowing breaker. That will cover a 4x8 just about.

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@Myfriendis410 You hit on something I been wondering about there. Someone else told me they are the same as the plant they’re from. Dies that mean I should be giving them the same Nutrients as I’m giving the others even though they are so small?

@John7 Yes, yes. Believe me when I say that I know the electric iny house. To get to my breaker box I have to go outside, unscrew the little door and duck walk back 25’ wielding some kind of stick in front of my to clear out whatever creepy crawlers there are. Ick! Yes, idw to be blowing any breakers so i know what all is on each breaker. Blew one today actually. Not because of too much on one but because I let 2 wires for a lighting fixture to touch qhen I was pulling the ground. Sucks! I am without any outdoor lights and no kitchen light tonight. Now way I’m going under there after dark though.

@Myfriendis410 @Skydiver What about one like this? Thenonly thing comes up when I google
HLC Light is some kind of power unit???

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HLG as in g for george lighting company. Big lights they have competition but I believe the single board small lights are so far above everyone else its unfair. Best diodes available. 53v vs 48. Lifetime clone/seedling light. 10 years easy.

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Again depends on the space your looking to cover
The vivisun 1500 you posted above will cover a 2x2 in flower.
Same concerns with the middle PPFD and hanging height.
It can cover a larger footprint for veg just like pretty much all light fixtures.
They have conflicting data on the site regarding PPFD and coverage.
Says 2x4 and also says 2x2 for flower plus the PPFD charts shown at top and then lower down show different footprint sizes.


The light will work you just want to be aware of its characteristics and go from there.

As far as power draw the math is 120 watts = 1 amp
So if your using a 15amp breaker all things on that breaker could mathematically run up to 1800 watts total (120x15) but you want to allow about 2 amps as dead space so up to about 1550 watts max less if you can swing that.

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Clones are fed as adult plants.

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Ermahgawd I just so confused about it all. I just want a new tent. Something not as big as the 5x6 I already have. Looking at a 4x2 now because this whole light thing has me down in the dumps. I don’t need separate chambers. At the end of the day I am a good ole West Virginia chick that wants to grow some dope but am running out of space for the few I’ve got going now so apparently space is going to be an issue if I don’t add something. When I got this one I have it was a kit and I got everything up to and including Nutes and meters and even bags and timers and fans, EVERYTHING, for under $700. Now I can’t come close to that. Once these Tangies start growing something will have to be trashed if I don’t have a 2nd set up by then. So I’m quickly running out of time. I would like to have a bar light because what @Skydiver said makes sense for a 4x2 room, but gawd they are high dollar. So are the ones @Myfriendis410 and @Storm recommended. And those have separate power units! Idk? I’m stuck right here at this juncture and dk which way to go. The whole lighting thing is what is confounding me. There’s no way I’m going to understand the science behind it. I suck at science. Sometimes a gal just needs somebody to say, ‘ok
Stfu and get this’. But I got nobody to tell me that. I don’t expect anybody in here to. Y’all can just recommend and I get that. I will just have to figure it out. I don’t need the exhaust and such as I don’t use the one I have really, so a kit is not feasible. I am rambling. Sorry. Thanks for all y’all’s input. After cleaning up last night, this is what I have…


Question: if someone threw a rock and knocked you off your donkey, would you be considered stoned off your ass?

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Ps, sorry about the link. I didn’t know it would be considered unauthorized. Does ilgm sell lights?

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Maybe look at it from a different perspective: how much flower do you use per year? For me it’s less than a pound. I give most of it away. Based on that i could grow 2 plants and have a surplus.

I like to grow and I like bigger plants so end up with way more flower than I need for personal consumption. But realistically I could produce enough for my needs in a 2 X 4.

Lighting is tough and made harder by outrageous claims. The company i recommended builds solid lights with the most efficient diodes and provides no false claims. I like them as they do save money over time.

When i started i ran 1,300 watts of crappy LED’s. Decided to build my own and now i grow in a bigger space with only 800 watts from the meter.

My current grow.

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Tell me how much you want to spend to set up a 2x4 tent with light and whatever else you deem necessary like humidifier and dehumidifier or whatever and I’ll send you a list that would best fit your budget.

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You built your own light??? That’s cray. For real. I am smart on a lot of things, but when it comes to Science people mayaswell be speaking Greek to me. I have decided on a smaller tent and some kind of bar light. Whether an HLG or a Mars, idk? Depends on who much cash my ex is willing to chuck out to me. While I’m sure they are top notch, given all the stuff I’ve read the past few days, but they are pricey. Whether in the long term or not, he doesn’t care about my power bill, only about what he can get by with today. Now you see the largest part of my predicament. Lol! But hey, he’s willing to do SOMETHING, so I’ma take what I can get before he changes his mind.

Hey, while I have you here, will you change my handle to ‘ShureGreen’? I think that’s a good one in this world, don’t you?

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@Skydiver That’s just it. U til my ex gives me a number Idk what he’s gonna put out. I just know it’s got to be soon. I been trying to find the best quality at better rates and making up my list. I had planned on $500 by myself and then he said he’d get everything I need for a 2nd setup. Heck, all I need is the tent, light, a couple of fans, Temp and Rh Monitor, Timer, Dehumidifier, some bags, seeds, and a good meter and I refuse to get any of it from Amazon or eBay. I’m an eBay Reseller myself, but I know all their stuff is cheaply priced and also cheaply made. Amazon is the same. The meter I want is $200.! Lol! But I think it’s important to have a good one because I’m unable to get mine to calibrate at 7. Had that with the last 3 I’ve gotten off eBay. Junk is what I’m trying to say. Lol! A 4x2 tent is 100. There’s a Mars light for 200. Everything on my list except seeds totals $680+. Those are at the best deals I can find. If you can find better then I’m all ears. Like a GSD’s ears. See photo of my Capp before he grew into his. Lmbo!!!

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@Myfriendis410 Ok. So the HLG’s, there are so many ‘businesses’ with those initials, and USING those initials, that I am having trouble finding the ones y’all are talking about. Could you possibly link me up?

@Skydiver @Myfriendis410 Ok, so I saw a couple that while idk much about all the coverage area info that is what has me befuddled, still look like they might be decent lights at a price I could pitch. I suppose since I’m choosing to go with either a 4x2 or 5x2 tent that a Bar light would be the best. But I wonder if the Drivers and ‘bulbs’ are included in prices or if they’re extra? I tried to ask the Mars place and they sent an email thanking me for my feedback. I wasn’t giving FB, I was asking the question. So that in itself, just cause I’m such a *itch makes me not want to buy from them. The Spider place is kind of a joke, imo. AC Infinity seems professional, at least. They have an IONboard S24 that looks interesting. Then the Mars place has a TSL2000 and I see people discussing how wonderful their SP3000 is for the sizes of tents that I’m looking at. But with y’all being the guys that seem to always be there on many of my threads, I’ve come to somewhat trust in your words. I’ve also read some of your stuff and you are both obviously informed individuals and that means a lot. So I found out that I’m not allowed at link websites here in our forum, so maybe if y’all have a spare minute over the next day or 2 you might check these 3 sets out and give me your opinions? And let me know where to look for the HLG and about the drivers etc being included or separate. Please? If not that’s cool too. Just asking. Thanks a bunch for y’all’s time. Heck, that alone means the world to a stuck someone. -K

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A hot setup IMO is a 4x2 veg tent and a big flower tent like you already have. Well I’d like that. If veg only and not flower the 4x2 lighting doesnt have to be George’s lighting company. Someday youll take that light to use somewhere else and wish it was George’s tho.

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