Quote Originally Posted by GanjaRobPDX
1000w lights are a waste of energy IMO. I started out growing with 1000w lights for a few years and when I switched to 600w lights I was suprised to see my yields actually increase
and my energy bill dropped significantly.
The reason my yield increased is because I was able to put 600w of light over each plant and, because heat was much less intense, I was able to move the lights closer which made better use of the
light I already had.

600w lights also create less heat overall, which cut down on cooling costs in the room environment.

so...a 600w light is what you want...hands down.

in a 4'x4' space I highly recomend not going above 600w because cooling the light will be nearly impossible.
also, 1000w lights will significantly cut down on the height you can grow your plants because the heat they put off ( even when 1000cfm fan is pulling through 6" hoods) prevents you from allowing the plant to get closer to the light than 16-18".
So with that in mind you can cut 18" from your usable plant height for the light, 12-20" are gone for container height, plus hood (16"). So if you use a 1000w light you will lose roughly 4ft of vertical grow space.
600w: you will gain 1ft or more of vertical grow space because the foliage can almost touch the hoods when using a 600w light in a sealed, well ventilated hood.

hope this helps...
Ok my question in im wondering weather to use a 600 or 1000 HPS light for a 5x5x5 room...Thinking im going to flower maybe 6-8 plants at one time....So if you say a 600 watt is better for a 4x4 room would you agree im better off energy wise to suffectently bud 6-8 Plants?