actual watts needed

Ok i have a question, i have 66sq ft ,for growing math says about 3300 watts of lights to be used in this space. IF your using Hps lighting and its says that its 1000 watts , now Led lights say 420 watts of equivalent power too the 1000 watt HPS lighting.

what is actual wattage am i going to use ? do i still need 3300 watts of light, or do the leds reduce the amount of light wattage i need because of better light system

I am no pro by any means but I hope this helps ...


I am running an 8x8 canopy with 2350 actual hps watts and I am underpowered although my plants are decent and healthy budsites are small and yeah big mistake on my end I suspect my yield will be 30% less or more due to insufficient lighting .

If I did another 8x8 I would definitely re position my lights and get rid of the 1000w and run all 600w 6 of them ...

Also dont underestimate an old bulb I have a plant 9 inches away from a 400w mh all my other hps lights are 14 inches away roughly anyway I feel like my distance would be 18 to 20 inches with newer bulbs another mistake on my part .


But I am learning I have 30 plants and expect to hit 3lbs I know that's not great lol but just goes to show you dont under power your room/tent I thought oh it will be fine well really wasnt worth it at the end of the day ...

To answer your question I wouldnt do 60 sq ft without at least 3000 actual hps watts

Using power as a metric to calculate lighting levels requires you to know how efficiently your light source converts electricity into photons of PAR. That's why you see anywhere between 30-50 watts/ sq ft.

but that doesn't answer my question , if hps and other lights say 1000s watts , and led say equivalent too , am i getting 3 -1000 watts hps or 5-600 watt led lights to make up the difference . or am i just over thinking this and 3000 watts is 3000 watts regardless led or hps.

ssgeddy420 said:

but that doesn't answer my question , if hps and other lights say 1000s watts , and led say equivalent too , am i getting 3 -1000 watts hps or 5-600 watt led lights to make up the difference . or am i just over thinking this and 3000 watts is 3000 watts regardless led or hps.

Click to expand...

Most good leds are around 35w per sq/ft. Cheaper ones require closer to the same wattage as hid per sq/ft.
Dont trust when they say "equivalent". Look at power draw of the fixture.
Any led that is actively cooled is using some of that draw to power the fans, not produce light.

Ive ran 4k in the same sized space...HPS...spendy so i run 2k now HPS...inwas right at the limit(was expeirencing light bleach)

Hell i ran 4k vert in the same space

But idk LEDs limits, i hear they light bleach more but thay could have been an older LED problem

Boatguy said:

Most good leds are around 35w per sq/ft. Cheaper ones require closer to the same wattage as hid per sq/ft.
Dont trust when they say "equivalent". Look at power draw of the fixture.
Any led that is actively cooled is using some of that draw to power the fans, not produce light.

Click to expand...

yea i am not looking to buy a cheap set , thats where i am lost is it better to buy , 3 -1000 watt lights or 6 -600s daisy chained. plus one light for a 4x4 veg room for 8 plants .

brands im looking at is kind, black dog or vrr something samsung, i need to figure out my amp draw on all electronics in shed to continue my wiring . any suggestions

ssgeddy420 said:

yea i am not looking to buy a cheap set , thats where i am lost is it better to buy , 3 -1000 watt lights or 6 -600s daisy chained. plus one light for a 4x4 veg room for 8 plants .

brands im looking at is kind, black dog or vrr something samsung, i need to figure out my amp draw on all electronics in shed to continue my wiring . any suggestions

Click to expand...

going to be installed in shed, shed will be done right with specs to perform .max 8-9 plants 3000 watts 6x11 room 12 ft ceilings .

Just my $0.02...

HPS (~1.95μmol/J)
50W/ft2

High efficiency LED (>2.4μmol/J)
30W/ft2

Avg efficiency LED (<2.4μmol/J)
35W/ft2

EDIT:
Most HPS are used in big areas and hung high, most LED are used in confined spaces and hung lower, these characteristics are reflected in my opinion above. I wouldn't recommend sticking more than a 600W HPS in a 4×4 tent, but I would also recommend higher wattages for LED if using in open areas and hanging higher, perhaps 4-8W/ft2 more for each type of LED if hanging high and in open areas.

I start seeing photoinhibition around 40W/ft2 of midpower LED, but this is in tents where most light is reflected back. 35W/ft2 is currently where I'm at but I drive them hard (143W/QB304). The same PPFD can be achieved at 30W/ft2 if I'd buy more lights.

50W/ft2 is what we ran for HPS but that was in bigger areas without immediate reflection and hung higher, we'd get heat stress and light bleaching at 62.5W/ft2 (1000W-ers at 75%) so we switched to 600s and the plants seemed to respond better.

ChiefRunningPhist said:

Just my $0.02...

HPS (~1.95μmol/J)
50W/ft2

High efficiency LED (>2.4μmol/J)
30W/ft2

Avg efficiency LED (<2.4μmol/J)
35W/ft2

Click to expand...

I’d agree with those LED numbers, as a minimum target.

With HPS lighting you want 50 - 60 watts per square foot.

With quality LED 35 watts per square foot. Cheap LED probably more like 40.

Hust17 said:

I’d agree with those LED numbers, as a minimum target.

Click to expand...

Some people here are getting by with as little as 25w/ft2. Probably the source of the high gpw some pull with leds.
My older cob fixture starts doing damage around 50w/ft2. Newer tech is more efficient.

so which leads to this question, do i buy 4 600watt lights or 2 -1000s qnd a 400 w led

Boatguy said:

Some people here are getting by with as little as 25w/ft2. Probably the source of the high gpw some pull with leds.
My older cob fixture starts doing damage around 50w/ft2. Newer tech is more efficient.

Click to expand...

I’m using 33 with meh Cobs, you’re right, I just mean people should aim for those numbers ideally.

ssgeddy420 said:

so which leads to this question, do i buy 4 600watt lights or 2 -1000s qnd a 400 w led

Click to expand...

All depends on what you are trying to do. Take a look at @Renfro he makes different use of his space.

Thing is, as @Boatguy hinted at, these figures are basically just lighting from the top. If you grow large plants then side lighting may be beneficial allowing the sides to grow buds like the tops. Of course this doesn't work in every grow. In mine it allows me access between the plants, down the rows and it allows me to get the most off a limited plant count. Having pulled in the mid 50 pound range off 12 plants indoors I would say it's a great way to go for some growers. If plant count wasn't an issue I could run no veg SoG with 600 plants and I wouldn't have the same yields, probably more like 25 pounds per run but with no veg time.

Renfro said:

Having pulled in the mid 50 pound range off 12 plants indoors I would say it's a great way to go for some growers.

Click to expand...

I would say that about 50% of my yield is side canopy and 50% is top canopy. It's crazy because I can walk down aisles between my plants but actually get more yield out of the room because of the walls of buds on the sides. Just have to not burn yourself on the vertical lights lol. But rolling in there on a mechanics stool with a 5 gallon bucket dolly to water keeps me under the lights.

100w/ft^2 for chinese blurple lights
50w/ft^2 for HPS
30w/ft^2 for the white LEDs of a few years ago
25w/ft^2 for modern efficient LEDs that came out this year or older LEDs dimmed down.

My last grow was 22w/ft^2 with dimmed down V2 boards.