Need some help!


There’s so much to learn! :thinking:

What’s the difference between watts and lumens? What is HID?

My tent is 4.75x4.75 feet and 6.75 feet tall. Does that mean my sf is 22.56?

I have a 1000w HPS and am considering switching to LED because of the heat. What specs will I need for an LED for my tent size?


I’ll answer for you.

Watts is the product of voltage times amperage (P=I TIMES E) in a DC circuit (yes, yes, phase angle and so on in an AC circuit I know). This is a measure of actual power output and is what the electric company charges you.

Lumens is one of many measures of light output. There’s also PARR, candle power etc.

HID stands for High Intensity Discharge.

22.56 square feet is your working footprint yes.

Led’s will be cooler but they are misleading in their marketing. A typical 1,000 watt led sold on Amazon actually draws about 220 watts. So effectively you would need 4 of them but wait! They do run a bit more efficiently so you might not need as much led as you do MH or HID. The usual minimum wattage for HID is 50 watts per square foot but led’s are around 35 watts per. More is better, and that’s wattage at the plug; NOT what the seller is quoting as “equivalent”.

If you are electronics savvy yout can build a superior led setup and there is a section on ILGM that talks about just that. "Let’s talk about DIY lighting ".

Hope that helps.

ps, my grow box is 24 square feet and I have 1,340 actual watts of led’s on them.


Thank you so much for the reply and info!!
I wouldn’t consider myself electronics savvy but with half decent instructions I’ve been fairly successful at figuring things out. I’ll take a look at the ilgm posts on the topic and will keep learning before making a decision and investment.
I’ve had to bump my light down to 750w due to too much heat. I’ll have a better location for the tent in a couple months but if I can’t keep the temp down at 1000w then I’d really rather go with LED. Would 750w be enough for veg in my tent size or is it 1000w regardless of growth state?

Is HID similar to HPS?

Thanks again for your help! :sunglasses:


HPS is a type of gas (high pressure sodium) and delivers in a particular wavelength. MH (metal halide?) is typically used for veg. I’m an led grower so my knowledge on this system is academic.

Where you really want all the light you can get is during flower. If you want dense nugs you gotta be up there in the watts per square foot to do it.

There is another metric that’s used which is grams per watt or g/w. This would refer to the overall efficiency of your system over time. Really it ought to have a third leg like per month or per year to be truly meaningful.

Sorry if I got off the track there. I’m gonna call in @dbrn32 and @Niala to help further with your lighting q’s.


I may be able to help, thanks for the tag @Myfriendis410!

First things first, like he was explaining, high pressure sodium is a type of high intensity discharge lighting. Metal halide and light emitting ceramic typically fall into that category as well. Just like there are different types of led’s, or fluorescent. But we typically say you are an hid grower, led grower, fluorescent, or use some combination of the 3.

So you have a dimmable 1000 watt currently running hps? Are you using a cooled hood? That could help a bunch!

We can get into comparing an led if need be. But if you’re happy with the hps outside of the heat, let’s start there.


You were in the right track @Myfriendis410 :grinning::+1::ok_hand::innocent:, thanks for the tag…

I let @dbrn32 take the lead… @GreenThunder

Tag me if needed :innocent:


My light is dimmable with a ballast and it does have a cooled hood. Temps are high 80’s and up to 90 on occasion. Right now the tent is against a wall on one side, due to space constraints. I’m hoping the heat won’t be an issue once I can move it (about 6 wks)
Right now there’s just one gal that we’ll be harvesting this weekend. I have 4 in veg state I want to move into the tent after the other is harvested but I’m concerned about the heat. They are currently under a T5 florescent and just over 3 weeks old.
Thank you so much for your help! :sunglasses:


Thank you!! :sunglasses:


When you put your little ones in there I’m assuming that there will be a bulb change to MH. As young as they are you can probably turn the light down and lower it to best cover little ones, which will greatly mitigate your heat problem.


Ok. Assuming you have your cooling fan and filter sized correctly, no air leaks, and your ductwork is clean without a bunch of unnecessary bends? Are you pretty comfortable that stuff is all in order?

Please don’t feel like I think you’re stupid or anything. I just want to cover the obvious stuff before overwhelming you with led stuff. Assuming if you’re going to to move to led, you’ll want a lighting system that’s competitive with the 1000 watt hid, yet runs cooler? It’s plenty doable, but not just any old led is going to do that. You’re 1000 watt is typically considered the cats ass in a 4x4, but a little light on what is essentially a 5x5. What you plan on doing there will kind of dictate which way to go.

I don’t like to use seller descriptions to qualify lights. Spectrum, par, and efficiency are much better. You’ll have to decide if you want to veg along with flower, as that will potentially change the spectrum you want to target. After that, a good solid led fixture that’s actually more efficient and can match or exceed the par of a quality 1000 watt hid light is going to start around $7-800. And if you wanted to actually fill that 5x5, probably close to twice that. If you’re ok with that, we’ll get down to business. If not, there are a few other options as well.


I don’t know what MH is… I hadn’t planned on changing the bulb - do you think I need to? It’s only about 6 wks old.


I don’t feel like you think I’m stupid :blush: instead I realize I know less than I thought I did and am super grateful for the help. I am in awe of the generosity of those like you who freely share information and knowledge! :sunglasses:
I’m fairly sure my cooling fans and filter are the right size. My ducts are clean but there are a few bends… 3 in the exhaust and one in the intake (though I don’t have an intake fan yet… that’s probably a lot of the problem I guess)
My interest in LED is for lower temp but also less operating cost. I had hoped they would be a little less than what you say but I also realize ‘you get what you pay for’ and quality generally comes at a higher cost. I certainly don’t want anything less than comparable to the 1000w HPS for light output. I’ve read a little on the Perfect Sun Goliath and really like it but am not sure if I’m swayed by the seller description :thinking: Which is why I’m reaching out for advice :smile:
The tent was advertised as 4x4 and I wish that’s what it was. The actual size is 4.75x4.75 and I do like that I can get in there with the gals :wink: My plan/goal is to use it for veg and flower stages, growing up to 4 plants at a time. Although I could just continue to veg in the bathroom closet with the T5 florescent.
My son is moving out next month so the tent will be moved soon. The setup should include fewer bends and thinking about an external exhaust for the room.
I’m about to put up my first grow journal… I’ll tag you if you don’t mind :hugs:
Thanks again for the help, I can’t fully express my gratitude :innocent: Growing is legal in my state but being so new to it, I haven’t found anyone local to learn from.


I’m close to putting up my first journal… Do you mind if I tag you? I think I’m going to need all the help I can get :thinking::wink::grin:


Do you know what cfm rating of fan is? Also, are all of your passive vents around bottom of tent open?

As far as your growing style, you wouldn’t really need to fill a tent from wall to wall with light. I think one of the fixtures designed to do a 4x4 would plenty. That would require you to mostly keep the plants together though in the middle of the room. Your best light will be there, as opposed to at the edges where that slightly bigger tent would probably be quite a bit weaker. Is that a problem? And don’t sweat wanting to veg and flower with the sane light. You just pick a middle of the road color mix.

An alternative would be to go with 2 long and narrow fixtures. They would probably be a little cheaper individually, but overall cost would maybe be a little higher. But them you could essentially treat it like two 2x4 areas within the same area. Would give you more freedom with spacing. I’d probably go with the one fixture, but that’s just me. We want it best for your application.

I really like to recommend the Pacific light concepts plc-6 for a 4x4. It’s not the best light, more like best bang for your buck. Problem is they’re currently out of stock. But if you have time, go and check them out. There is independent test data, and actual ppfd numbers to compare. In my opinion, it’s the cheapest real world 1000w hid replacement. Comparing par data, efficacy, and cost. Drawing 600 watts at $800, it will alleviate some of your heat issues and energy cost without giving up yield potential.

Another option is going to be the hlg 550 from horticulture lighting group. It’s normally around $1050, but they are currently running 20% off. This one uses the latest in mid power technology. Instead of having a few high powered cobs, it uses 4 pcb boards that contain 304 Samsung diodes each. This doesn’t have quite the light intensity in the middle that you’d be accustomed to, but probably more even. With 20% off, it’s one to give a good look. There’s lots of buzz about it too, so a quick Google search should give you plenty of grows to see it in action. This is probably one of the coolest running led fixtures of the size as well.

If you don’t want to spend that kind of money, you could throw a few amazon lights in there as well. But competing with the hid, it probably wouldn’t be all that much cheaper. Last I looked the viparspectra was kind of holding down the amazon light title. Two of the bigger ones will set you back $500, and I still don’t think they would be quite as good.

Timber grow lights has a few that would do the trick as well.


Wait… maybe I get it. Do you mean a bulb of a different wattage? Should the wattage veg state be set lower?
The more I learn, the more I realize how little I know! :smile:


Hahaha, at least you have a good sense of humor about it!

Metal halide is another hid bulb. It produces a much more blue or white as you will see it light spectrum. Most growers using hid lighting will use the metal halide bulb for veg stage, and then hps bulb for flowering. The mh bulb will keep the plants short and bushy, as opposed to the hps bulb where they like to stretch a bit toward the more red light spectrum.

A lot of the ballasts will run both types of bulbs, that’s why the guys were asking. You could probably pick up a mh bulb and screw it directly into your hps socket. Buy DEFINITELY double check that your ballast is OK to do this with.


There’s so much to consider :thinking:

My passive vents are mostly blocked because of where I had to put the tent until my son moves out. I probably should have waited but my girl was asking to get out of the closet :wink:

I don’t know the cfm rating (or what that means) but here’s a pic of the label.

I don’t plan to have more than 4 at a time and don’t think it’s a problem to keep them together in the center.
I hadn’t thought of having two separate but out of necessity I’m going to hang the two T5 florescent lights until I can move the tent into the spare room. It’s only 6 more weeks. I think the timing will be good; my 4 girls should be just about ready to make the switch to flowering then.

I appreciate your recommendations, it gives my research more focus and I feel a little better armed against compelling advertising :wink:

Thanks again for sharing your knowledge.


The hurricane 6" should move plenty of air, I suspect those vents being blocked is your biggest culprit. Any possibility of pulling the tent maybe a couple inches from the wall? I would imagine any little bit would help.

Getting a little more air moving in there should help. If you have lower outside temps, you could try cracking a window. Or anyway to get some cooler air wherever your tent is.


I feel like a sponge, soaking up all I can reach :hugs::smile:

I will check on the ballast and if it’ll take it then I’ll check out the different bulbs. This is all so exciting to me! I always thought, it’s a weed so it’ll grow with minimal care. But now that I’m doing it, and learning and seeing what others produce, I want to do better than just minimal. Three years ago I grew a plant in the closet with a cheap florescent and rain water. It produced buds but I can see how you kinda get out what you put in. I want more and better :wink::sunglasses:


And definitely do plenty of research on the lights, feel free to tag me with any questions. It seems every grow light is “the best” in the manufacturer’s eyes these days.