How much light do I need?

F

FrankMJ

Member
I apologize for possibly asking a stupid question. It's been years since I've grown and now that I am able to get back into it I was looking into using LED for lights.

I will have a 2x4 tent that I was thinking I'd grow 3 plants and SCRoG them. I found a nice DIY kit with RapidLED, the 2x4 which is around my price range for lights at the moment. I was thinking of getting the 75w version which would put me altogether around 375 watts. One thing about these two kits available for the 2x4 size is that one is using CXB3590 and the other Vero29SE's, I honestly do not know the difference between these two COB systems.

Previously I was using a 400w HPS in a 2x2 tent instead and am curious what the differences are I can expect besides around the same amount of watts being drawn from the wall and it being cooler.

I'm also open to suggestions if there are other brands that have these DIY kits. My main goal is to push these plants as much as possible for my tent size. Thank you for your help!
 
JavaCo

JavaCo

Well-Known Member
2x4 is 8 square feet 25 watts per a square foot would do well. So 200 watts is all you need and that is in flower you could veg that area with 100 watts. Veros are not any better then the cree's they are just cheaper and grow the same in my opinion.
 
jimihendrix1

jimihendrix1

Well-Known Member
If possible, I wouldnt use anything less than 50w sq/ft. Minimum recommended is 37w Sq/Ft for Veg. 40 for flowering, but Haardcore Sativas need at least 50w for reaching full genetic potential, and not take forever to finish.

I use 1000w Hortilux, at 18 inches in a 4 x 4 area which is around 60w Sq Ft. But Im in an open area, with tons of airflow.

I also use 1000w for seedlings at 24-28 inches. Closer after seedling stage.

4 x 2 area Id suggest 2 x 315w Ceramic Metal Halide for blasting them, and growing them to their maximum potential.

Actually the 2 x 315 are good for 5 x 2.5. At 4 x 2 that's 78w Sq/ft, which will allow you to grow taller, bigger plants, and/or put the lights a bit more off the canopy, and not hurt light penetration.
 
F

FrankMJ

Member
My tent will likely be stored in a walk in closet so I was planning on using LED's to keep the temps down. Good information though, thank you for sharing.
 
K

kushedy

Well-Known Member
I grow in a 2x4 space with 8 x cxb3590's. 200w would do it (25w psf). On the grow I have going at the moment I did start of running 300w in flower (37.5w psf) & after a couple of weeks started getting light burn on the top most leaves. I have since played around with various wattage settings & found that 200w is the sweet spot, for the strain I am running at least.

Depends on your budget. If you are going for a lower number of cobs then yeah you would want to run at a higher wattage & you would need sufficient vertical space so that you don't burn your plants. If you can afford 1 cob per square foot you have amazing coverage so don't really need to push the wattage. Think about the layout of 8 cobs in that small a space. If laid out evenly over that space you are placing one cob every 20-24cm (roughly) in each direction. Yeah you could hang them high & pump wattage through them but why waste the electricity when you have that level of coverage.

All that said it is nice to have extra wattage to future proof yourself just in case you at some point are able to grow in a larger space.
 
Last edited:
canadian1969

canadian1969

Well-Known Member
Go 50 watts a square foot on a dimmable fixture, that way you have a little extra overhead and some room to play with light levels.
 
JavaCo

JavaCo

Well-Known Member
This is 210 watts in a 4x5 but the plant is about 3 foot by 3 foot so that is about 23 watts a square foot. day #33 so it has at least another month to go. They are also Vero 18 gen 5's so they are 25% less efficient then the newer gen 7's and SE's. You would be getting 25% more light out of the newer ones. 0202181200.jpg
 
Humple

Humple

Well-Known Member
jimihendrix1 said:
If possible, I wouldnt use anything less than 50w sq/ft. Minimum recommended is 37w Sq/Ft for Veg. 40 for flowering, but Haardcore Sativas need at least 50w for reaching full genetic potential, and not take forever to finish.

I use 1000w Hortilux, at 18 inches in a 4 x 4 area which is around 60w Sq Ft. But Im in an open area, with tons of airflow.

I also use 1000w for seedlings at 24-28 inches. Closer after seedling stage.

4 x 2 area Id suggest 2 x 315w Ceramic Metal Halide for blasting them, and growing them to their maximum potential.

Actually the 2 x 315 are good for 5 x 2.5. At 4 x 2 that's 78w Sq/ft, which will allow you to grow taller, bigger plants, and/or put the lights a bit more off the canopy, and not hurt light penetration.
Click to expand...
Welcome to the wonderful world of modern, white-light LEDs, where 30w/square foot (sometimes less) is common, often recommended (by veteran LED growers), and highly effective. It's a very different thing from growing with HPS, and you can't really apply the old HID standards across the board.
 
jimihendrix1

jimihendrix1

Well-Known Member
I grow trees inside. 5 feet tall, and in 20 gallon containers. 20oz- 24oz a plant every 63 days. Or 2lbs a light with 2 plants vegged a bit smaller, but still in 20 gallons Promix BX.

Lots of stuff works, not saying that. Hell back in 74 I grew with multiple 8ft SHO Fluro, with a mix of Daylight, and Cool White. This was before HID.

No atmospheric control, and I can get a 1000w light 18 inches from the canopy, and blast the crap out of them with photons. Hortilux HPS is over 1600 Umole. Gavita is 2100. BUt you have to have a lot of ceiling height for Gavita.

I also use the heat from HID, and is not a negative for me, and is an asset.

LED from my experience uses way less water, is slower, and doesn't produce as much, and start up is insanely unrealistic, and they aren't truthful about Watts.

Ive got3 1000w flowering lights, and 1000w Veg light.

How much is it going to cost for 4000w REAL WATTS of LED/COB? ALOT.

My buddy paid almost $3000 for a 1000w PhytoMax 2, and it not as good as 1000w Hortilux, noto mention a 1000w Gavita, or 1000w CMH DE, and it has been very unreliable.
 
Last edited:
Humple

Humple

Well-Known Member
jimihendrix1 said:
I grow trees inside. 5 feet tall, and in 20 gallon containers. 20oz- 24oz a plant every 63 days. Or 2lbs a light with 2 plants vegged a bit smaller, but still in 20 gallons Promix BX.

Lots of stuff works, not saying that. Hell back in 74 I grew with multiple 8ft SHO Fluro, with a mix of Daylight, and Cool White. This was before HID.

No atmospheric control, and I can get a 1000w light 18 inches from the canopy, and blast the crap out of them with photons. Hortilux HPS is over 1600 Umole. Gavita is 2100. BUt you have to have a lot of ceiling height for Gavita.

I also use the heat from HID, and is not a negative for me, and is an asset.

LED from my experience uses way less water, is slower, and doesn't produce as much, and start up is insanely unrealistic, and they aren't truthful about Watts.

Ive got3 1000w flowering lights, and 1000w Veg light.

How much is it going to cost for 4000w REAL WATTS of LED/COB? ALOT.

My buddy paid almost $3000 for a 1000w PhytoMax 2, and it not as good as 1000w Hortilux, noto mention a 1000w Gavita, or 1000w CMH DE, and it has been very unreliable.
Click to expand...
You're talking about a completely different and MUCH poorer class of LEDs, though. PhytoMax are overpriced and overpromised. I definitely agree with you that your buddy got ripped off. Take a look at COBs and Quantum Boards. Read some of the journals here in the LED section and you'll discover that GOOD LED lights most certainly don't produce less, and most certainly don't drink less. It's a new age, and the old-fashioned LEDs that you're talking about will get every bit as much scorn here as you'll find in the HID section of the site. And there is just no way you'd need 4,000 watts of good LED to replace your 4,000 watts of HID. The norm here is around 60% of HID wattage. Send your buddy our way as well, and we can give him some tips on modern LEDs.
 
jimihendrix1

jimihendrix1

Well-Known Member
We'll stick with the HID. Thanks.

Also tried the Black Diamond 675w Perfect Sun COB, and didn't get as much vs 1000w Hortilux, in a 4 x 4. No less a 1000w Gavita, and I can buy 4 1000w Hortilux with ballast, and fixtures for $1000
 
Humple

Humple

Well-Known Member
jimihendrix1 said:
We'll stick with the HID. Thanks.

Also tried the Black Diamond 675w Perfect Sun COB, and didn't get as much vs 1000w Hortilux, in a 4 x 4. No less a 1000w Gavita, and I can buy 4 1000w Hortilux with ballast, and fixtures for $1000
Click to expand...
Hey, if you need the heat, I don't blame you. But judging LED by these cheapo pieces of shit is a mistake, man (Black Diamond isn't any better than PhytoMax). If you ever feel like taking the time, peruse the grows in this section and you'll see that people are growing more weed with less power. Or don't, as it pleases you. As for me, I'll take more bud for less money spent on electricity any day.

Edit: when I say cheapo above, I'm talking quality, not cost.
 
Krytend

Krytend

Well-Known Member
jimihendrix1 said:
We'll stick with the HID. Thanks.

Also tried the Black Diamond 675w Perfect Sun COB, and didn't get as much vs 1000w Hortilux, in a 4 x 4. No less a 1000w Gavita, and I can buy 4 1000w Hortilux with ballast, and fixtures for $1000
Click to expand...
You can't compare a commercial grade light like a Gavita against a Bpurple and say Leds don't produce the same.
 
You must log in or register to reply here.
Top