i have 2 sq. ft. box 3.5 ft. tall. whole interior (top, bottom, and all sides) lined with 2mm foil tape (its almost like im growing in a box lined with mirrors), with 1 intake and pc exhuast fan. i have 5x 23w cfl bulbs 800 lumens each. SO... is 4000 watts enough for my one plant it seems to be...