Not limited, but I am interested in trying cfl for this grow. I have read much about HPS but they seem really expensive and hot. I am planning on 2 small boxes 2' X 2' X 3' tall. I would like to try the SoG method so I am guessing a small box will not be a problem. I am also considering getting some more LEDs ,I have one it seems to be doing the job for now as I am only about one month from seed.