900 watt LED into 4x2 tent

Starting my first tent grow… dimensions are 4’x2’x6’
I bought a 600 watt LED grow light but they sent me a 900… I’m worried about the size of the tent against the size of light I will be putting in. I have been told I should be ok if I keep the light 24” higher than the tops of my plants. Is it totally pointless to use this light in this tent? I just had a very successful outdoor grow this summer and wanted to try inside. Any suggestions!!! Rather not have to send back the light but if it’s just gonna kill the plants than I will.
Any thoughts??? Thanks guys!

What is the brand of LED. Not all LEDs are equal, nor do the “label watts” always equal the real watts.

Generally you want about 35 watts per square foot with quality LED systems.

With economy LED systems, you can often use up to 50 watts per square foot, the same as what is recommended with HID lights like HPS.

A 4 x 2 foot floor space means you want about 280 watts at 35 watts per square foot, and 400 watts at 50 watts per square foot.

The most common LED systems out there only use about half the watts they advertise in their label.

And so I wouldn’t be surprised that your LED actually only uses closer to about 400 to 500 watts, and so you will probably be fine.



Well that’s rather awesome isn’t it! What brand is the light? You need the “true watts” means what it draws from the plug :+1::wink: then you want 35-50 watts per square foot. You said you have a 2x4, which equals 8 sqft, and 8x50 is 400watts for your space. Is the space 5’ height?

Sometimes more light is better but you do need head clearance.

Edit @MacGyverStoner has you covered as I already typed this. Like I said you just want to be concerned with height when your plants are fully mature. You will need to scrog your plants


You should be fine, I am running 7.1 180 watt leds . I run 6 in a 10 x 6 ft area. Watch you lighting distance you be good. If you got 900 for 600 price, shhhhh…grow in peace my friend


The brand is phlizon…

I’m trying to attach a picture… thanks for the quick replies folks… I’m setting up the tent right now!!

The sticker on it says input voltage 85-265v power:900watts


From what I researched it’s a 450 true watt LED. Should be good for your space. I have a 2x4 tent as well.


Sweet thanks! I found something saying it’s only 180true Watts… maybe just a poor review?

If you look at the bottom description it says:

Core Coverage at 24" Height 2.5x2.5ft


Recommended Height to Plant: 12”-50”according to different growing stages

And so…

2.5 ft. x 2.5 ft. = 6.25 sq. ft. at 24", at 50 watts for 6.25 sq ft you’ll need 312.5 watts

It probably does have more than that, and around 400 - 450 watts sounds about right for what this light would truly be using.

And again, it sounds like it should be fine for your space.



Here is what I found. Sounds about right too.


That one says it’s only 180 max…

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If you have a watt meter or know anyone who does, you can plug it in and find out for sure.

But I think I’d trust @HJL’s research more than one random “review” post. But even the person claiming only 180 watts max seems to be pretty happy with the purchase with 4 out of 5 stars.

Something like this:



Thank you! I appreciate all the input I will try to remember to update this feed with how it went otherwise I’m gonna figure out how to start a journal on here. Cheers!

I agree, killawatt best way to know for sure.

The problem comes in with where they come up with the 900. Just because there’s 90 diodes doesn’t mean anything. They’d have to be driven at 3 amps to be 900 Watts and 1.5 amps to be 450 Watts assuming fv is around 3. I’d be willing to bet drive currents are betweem 500-700ma, as that’s what most of these fixtures use. Calculate led watts and add driver efficiency losses, and it’s right in the neighborhood of what reviewer posted. If I had to guess, a killawatt is probably what the reviewer used.


Absolutely! 90 x 10 watt diodes does not mean they use 900 watts.

Most LED’s peak efficiency is usually driven near or just under or over half the max wattage. Generally the 10 watts means these diodes will run up to 10 watts without burning out immediately. But they will burn out much sooner than they normally would, even if the temperatures are kept very low.

LED’s work quite a bit differently than other light sources. And the efficiency of turning electricity into photons is generally much more efficient than most other light sources, but the efficiency is directly connected to the temperature they are running at, the cooler, generally the better and the more photons per watt they will put out.

And so most of the time, the true watts will be about 1/3 to maybe about 2/3 the label watts.

And yes, when using something like the kilowatt, you are not measuring just the LED watt consumption, but also the driver’s or drivers’ consumption, as well as the fan’s or fans’ consumption, but these generally do not use as much as say a HPS’s ballast, and so a kilowatt measurement will get you a pretty good idea of what the LEDs are actually using or being run at…

And of course you could send a message to the manufacturer on Amazon to see what they say, they should know, and according to the question section the seller does respond to questions and not just fellow purchasers.



It’s sad that every single light manufacturer thinks they have to make false claims. And it is sad that Amazon lets them get away with it. You think it is 900 watts and will burn your plants but it is really 180 watts and is not enough to flower in an 8 square foot tent. We’re trying to do something here that requires real facts, and they are just making it harder than it has to be.

If they want to claim something other than the actual watts drawn from the wall, they should also add PAR watts. That is the useful radiation that can be used by a plant. Some lights might be better than others (depends on the spectrum), so buyers could make a rational choice.


Good point about the fans, I didn’t mention them. Almost all of these fixtures use them, and the difference between a good fan and a cheap fan in terms of power draw is probably only a couple of Watts max. A bigger difference would probably come in a fixture that uses four fans vs a single fan.

There’s really a lot that goes into designing these lights. Quality leds, drivers, fans, and heatsinks all cost a pretty penny. But can be a major boost in the performance of the fixture. It should be kept in mind any time someone is looking at purchasing one of these pictures. A low price doesn’t always mean a good value, it could just be an inferior product.


I get that… I got what I could afford. My next grow will have better equipment.


Actually this company did do that:



If you cut your tent’s lighted are down to 4 square feet, you would have enough light to raise great big fat buds. You can do that with something as simple and cheap as a piece of cardboard painted flat white with wall paint. Just an idea of how to make the most out of what you have.


Always have to work within your means, that’s a given. You see that pic that @MacGyverStoner posted? That tells you it’s par level at 24” height. 400 umols is great for vegging plants not as great for flowering. To get ideal par levels for flowering it needs to be closer to the 12” height. You’re effective footprint will also be smaller as you lower the light, so keep that in mind.

It’s not to say that you couldn’t run the light higher than 12”, you certainly can. But your buds will be smaller and not as dense. So for this particular fixture 2-3 of them would probably be ideal to create good light coverage for an entire 2x4. I’m definitely not suggesting you go buy more of them. But price wise how it stacks up against a single fixture that could do the same area usually isn’t much different. Those par numbers are a much better indication of what you’re getting for your money than anything else.