HPS wattage for area of 3' X 3'

I'm pullin a pound or so (at best) from a 600 in a 2x3 space. 5 ft high. If i had 3x3 i'd def. use the 600. Then again maybe it's overkill but my theory is the 600 has better intensity / better canopy penetration than a 400 even though it could illuminate a larger footprint area.

 

^^^Agreed. If you can control heat issues with a 600 than go that way. I used a 400 in a space similar to yours and had good vents so could have probably went with 600 and upped my harvest. Oh well, live and learn.

 

On paper, that space is just about perfect for a 400w. But as others have said, I don't know if any of us at some time or another hasn't wished we had gotten the stronger light.

If you want to grow all the way out to the very walls then get the 600w assuming you can manage the heat. If you are talking about 4-6 plants then you could get away with the 400w very nicely but would not regret, other than when the electric bill arrives, upgrading to the 600w even then.

 

Go the 600 mate, but you'll def. need some kinda sealed air cooled reflector... fuckin make one like i did... 600 has a biiiiig sweet spot for intensity if you can suck that heat away. And a tip with shielded reflectors (glass or whatever) is have a fan pointing towards the outside of the glass in addition to the heat removal through the inside. There's so little radient heat with this done right that big fat colas can be within 12 inches of the side of the bulb, while the rest of a V shaped garden still receives the top notch lumens of a 600.

 

1 plant mate