Hello Hapa, :tiphat:
Really thank you for your stopping by. You asked a very good question, I would like to answer you also I think it is a good informaiton to share with other growers here. Here below is a requirements watt for per sft of HPS, CFL and LED need, summerized by a very professional grower and many of our customers say it is very useful.

"How much light should I use?The following is a MINIMUM light requirement for productive growth in the vegetative stage:
CFL: 42.25 watts per square foot
HPS/MH: 32.5 watts per square foot
LED: 22.75 watts per square foot
The following is a MINIMUM light requirement for productive growth in the flowering stage:
CFL: 65 watts per square foot
HPS/MH: 50 watts per square foot
LED: 35 watts per square foot"
From what I know, you will need 22.75~35watt/sft during veg and you need 35~50watt/sft during flower under LED. Also please notice the watt is actually watt. For your space, 4x8x6.7, I would suggest you go with two of our 1200w lights, to get your space well covered and also get around 37.5watt/sft at 18 inches hight. :Gold:
For the advantage of our lights?
-Less heat, less power waste, therefore in the long run, you can save a lot.
-We use the light spectrum you plants will need so they will grow more healthy under it.
-You will get more denser and bigger buds with our lights. Also they will taste better.

I am glad I can help, if you have any more question, please post here

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