It depends on your space,a space maybe 1.5x1.5x4 would work ok with 4-5.When i used cfls my objective was to get as close 75w-100W per Square foot and 4 of those 23x4=92 close enough.If only 1 plant go for it if 2 or more you may need about 10.I just read a post with only 46w of cfls and they yeilded 43.4 grams so anything is possible depending on your space tho.