Lights, power/watts, heat and ventilation, HID and LED


While I have you here for a moment…I took down my 1000watt hps lights and replaced them with the 400 watt hps for vegging the heat I believe was a big problem with yeild. The temp dropped a good 25 degrees I was thinking of using the 1000for last day 3 weeks of flower…what do you think of that…a ok
Or should I switch to led

An interesting article about LED lighting for your grows
Two 250 watt cfl one at 6400lum one at 2700 lum
No nutrients yet in soil from seed 25 days
Monster cropped clones

I don’t have any real experience with HID lights, never really felt the need to use them. Most of my knowledge on them is book-smarts – practical theory. A ton of my friends use them, I see what they have to go through using them dealing with the heat. I continually match or exceed their yields, watt per watt, with my (by now) mostly home-made LED system.

However I do know a thing about the parameters, and if you are having a hard time keeping the room’s temps and the temps at the canopy near ideal, you might be able to make better use of lower powered lights and still have about the same intensity or lumens at the canopy by moving the lights closer, and using the lower powered lights.

Because of the inverse square law, moving the lights to half the distance does way more than double the intensity of the light.

So if you are having a hard time keeping the canopy below about 80F, ideal temp indoors is about 26C/78.8*F and slightly below, not including higher temps for CO2 enrichment, then lights with closed hoods that do not add as much to the temperatures in the room or lowered powered lights might be your only alternatives besides going to LEDs.


This is awesome just over night my girl’s look so much better. The leaves are reaching for the light and I could smell them to. What a difference over night.

The temp is steady 78 degree and you can see they are loving it.
I also don’t have to water them every day. From yesterday to this morning the soil was still moist.y new tent came yesterday.
I’ll be palacing 1/2 my plants in there and keep them in there until there ready to be placed in the flower tent.

I’m looking at this LED 300 watt system. Can anyone tell me if this would help or be better than the two 1000 watt I think it will.



Honestly man I would go a little bigger if your gonna get a led,my 300 watt seems to be just enough for my tent and it’s only 4x2x5,so you would probably be better off and a lot happier it you went a little bigger than a 300 watt


Hey…Cash Thank You for your input.
My tent is…4x4x80 inches. So 400 or 600 will do.
What do ya think cause I dont know.



Well I would probably see if one of the more knowledgeable guys chimes in but if it were me I would get the 600 watt as long as it had the separate veg and bloom switches and if I remember right,I believe Macg said he only uses the blue spectrum through the whole grow which would be just the veg my tent with both switches on it brings the temp up about 3* compared to just the veg switch on,hope this helps a little man


Ok, do you have one tent or two with those dimensions?


One 300 watt LED will not replace one 1000 watt HID, much less two.

Industry standard for HID is 50 watt per square foot and for LED it is 30-35 watts per square foot, so you need a 600-700 watt LED light, minimum, to replace the 1000 watt HID.

A 4x4 foot tent is 16 square feet, so you want 800 watts of HID minimum, or 480-560 watts with a good LED, for one tent, that will allow for the plant or plants to have a 16 square foot canopy.

Also be wary, I would never pay the full price of some of the better name brand LED manufactures out there. And Advanced LED is one of the best that I believe gives you the honest info on their light’s stats. And I still wouldn’t pay their prices.

I would buy a few different LED lights I’ve seen online at reasonable prices made from some of the more reputable Chinese manufacturers. It is true some of these manufactures are building some of the name brand lights in the same factory, or manufacture the LEDs – themselves, for some of the name brand lights. Not necessarily Advanced, however.

The thing to look for is the actual watts the LED light actually uses, not the watts in the lable name of the light, as well as making sure the light has a balanced spectrum including both the high and low of each of the reds and blue.

Chlorophyll absorption peaks are 430 nm (blue) and 662 nm (red) for chlorophyll a, and 453 nm (blue) and 642 nm (red) for chlorophyll b. Chlorophyll b is not as abundant as chlorophyll a, and merely help in increasing the absorption range.

So you want a light that has about a mix of LEDs that cover those nanometer spectra and is about 30% blues and 70% reds, as well as some white LEDs, because the truth is plants respond to lights of varying colors because there are several different plant pigments which are capable of absorbing light and transferring the energy to chlorophyll which catalyzes photosynthesis. Plants may grow in green light, but efficiency in the use of the total light energy will be small because plant absorption of green light is very small.


The other tent is 76x76x76



Ok, so I’m still not following, how are you using your lights?

Do you have closed hoods with ducting? That might be cheaper than buying LEDs.

Using only one 1000 watt in the 4x4?


yes I used two
1000 watt in the 76x 76x76 It got to hot even with two exhaust fans and one stand up fan so I took them out and now useing two 400 watt hps and temp dropped to 78 degrees.



Wow is all I can say. I went shopping for LED lights and all I can say is WOW!!! Can’t believe the prices… I’ll just stick with the hps lights and not use high watt’s
Just got to do a little home work and SToner has put me in the right direction and not to for get Cash.
Stoner you have giiven me a wealth of info on this lighting problem… and I Thank you so much for taking your time to explain in detail the way you do awesomely some sir.



Great page MacG. Jey guys; Sorry I am so late to the party. Having had a nice 8’x10’ room to grow in for so long, I got spoiled. When I finally got a tent; I had to buy the 400 watt MH/HPS lamp for the tent 4’ x 4’ x 7’

I cannot imagine using a 1000 watt HID in my tent, and I have one sitting on the shelf, well 3 actually.

In order to use a 1000 watt HID in a small tent; You would need an Air conditioner in the room. This would allow you to constantly replace hot air with cool air. Ice bottles will not do it. Good Luck. :smile:
Oh yeah; You all can send me some of all this extra cash you have lying around, LOL


I was useing two in a 76x76x76 tent.
With two exhaust fans air conditioner and stand up fan and could not control heat. So now I have two 400 watt hps lights in there and the temp is a steady 78 degrees when I flip to 12/12 I’ll switch to 600 watt hps I shouldn’t the 600 watt would put out much heat.

Now my 4x4 tent will use one 400 watt hps for vegging only that’s what this tent will be used for and the other big tent will be for flowering only.
I also have two 3x3x76 tents that will be used for my small seedlings and starter clones. I’ll use my T5s 14 watt for them.
Well that’s what I have going on any input would be awesome. Thank you guys for all your help



? Posting late my tent is 32"x 32"x 60" and I have a 300 watt led was thinking of getting something bigger so I guess I should be good with what I have


DS XTE 300 or a spectrum king by sunlight is my next light


Check out Ice mud with advance LED lights , that would give you a more renounce decision .


One important idea to comprehend when using a tent. Reflectivity!

In an open room I might use a 600-1000 watt lamp. In a tent with 6 reflective sides; Not necessary. :smile:

In a tent; The ability ti control temps and humidity is key and will produce the most healthy and productive yields. :slight_smile:


So Stoner… iem usering 400watt hps at 50000 lumens with 12 square feet of growing space if iem doing this right thats 4167 lumens per square ft.
So I don’t need two lights in there for vegging correct. It just don’t look right.
Here is a pic so you have a better idea.

<img src="/uploads/growingmarijuana/original/2X/f/fb663c588e18b51f75fdc6dee8d9a9e5276a2188.jpg" width=“283” height=“500”



@garrigan62 How do you get 12 square feet? I see what looks like a 4 foot by 8 foot canopy area minimum. I think those scrogs look like 4 ft’ x 4 ft’? The two sectioned off pvc areas look like two 4x4 sections end to end?