I understand anything over 100 watts per square foot is a waste. I'm working with 8 cubic feet of grow space, I figure that should be about 75 watts per square foot would should be better than average bud right. So far I'm still curing what I've grown which seems to be getting much better. Just trying to do the best the cheapestRealy depends on wat your trying to do i generally run one plant per sq ft under a 1000 watt hps in a 4×4 area or 2 1000 over a 4×8 ft area yeild depinding on strain is rite around an oz a plant or 1 lb per light easy number to achieve for novice grower