HPS or LED for Flowering

Currently have 4 NL with a 600w LED for veg. Should i add another 600w LED or switch to a HPS lamp for flower?? Thanks for any help. Please advise on wattage for HPS also.

I love my LED and I am not an experienced grower, but climate would impact my decision. If you live in a hot area, then LED should run cooler. For me it is all about location and season.


Please define your “600w LED” as the variation between different models is phenomenal.

As Vexer says, one consideration is temperatures, and obviously an HPS generally fires out more heat which has to be managed. You’re also talking about how much height you have in your grow space, and so on. Plus a single HPS in the middle will have more concentrated light in one area whereas with a second LED you can have a more even spread of light with one LED above 2 plants.

So more info is needed on which LED light you have, your grow space, environment, and so on so you can get the best advice possible.

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I use two 600w Mars Hydro leds in flower in a 3x3 and the yield is decent.


Tent height is 78” I’m using a 600w Mars hydro. I live in the Midwest, so summer heat is always an issue with temps right now at 90 degrees. Tent is 2x4 and I have a 190 cfm odor extractor and a fan going in the tent.

What is considered decent if you don’t mind sharing??

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I use 2 of the same lights as @Noctis420 in a slightly smaller tent. My first grow yielded almost 1/2 lb dry from 3 plants. Not the biggest harvest but for the first time out, I was pretty happy. :v:


So that’s 6’6" total height, knock off a foot for the height of pots, another 2 feet for space between the HPS and the plants because of the heat, space between the HPS and the top of the tent for ventilation around the light, so to go HPS you’re going to be scrogging like hell because you’ll need to keep the plants 2.5 feet tall at the max by my guesstimates. Does that sound about right to those with more experience with HID lighting?

You need 400 actual watts of the Amazon lights like Mars or viperspectra for 2x4. The Mars 600w is 130 actual watts, so you’d need 3 of them to get a decent yield. Decent meaning 2-4 oz per plant from my experience. That’s why I built my own diy lights. I want 6-10 oz per plant if I’m going to all that trouble to grow them @Familyman

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I can do two more mars lights. I really don’t want to deal with the heat. I’d be more than happy if I got a pound out of my 4 plants total.

It’s pretty unlikely you’ll get a pound dry out of a 2x4. If you’re looking for big numbers I wouldn’t invest more money into mars lights either. Look at the 3 board qb 320 kit, that would put you on the upper end of yield potential for a 2x4.

I’m thinking of upping to a 4x4 tent also

How much, given good husbandry, what is a reasonable yield??

I’m not sure what that means?

If things go well with a single mars 600, I’d probably expect somewhere between a couple of ounces to qp of decent buds.

Husbandry is a term used for using good techniques for growing etc. it’s an aquarium people term. I have a background in farming salt water fish and corals.

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I measured the watts of the Mars 600w with a meter and it’s pulling 264 from the wall. So that’s 528w in the 3x3 . I measured it with this.


Gotcha. With a background like that, I’m surprised you didn’t end up with a more fancy light. There are a couple of coral guys that I work with, they are more picky than horticulture people usually.

When Kessil starts making grownlights for weed I will look into it. They are the best. If you think lighting debates are intense here…


I think they do, but I wouldn’t buy them. Light spectrum is semi important here, but takes a backseat to intensity on almost all accounts. Same thing with spectral tuning. You can do some neat stuff with it, but you definitely want your money going towards photons first.


Very true. My aquarium has a spectral controller and I can do some cool things. They even have lights that simulate storms and cloudy days.

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