Hard to say, I would guess it depends on your desired plant size. I have two 600 watt HPS lights in my grow room, each with a 32 in. X 32 in. shade and I grow my plants in two groups with 3 gallon and 1 gallon pots. I have pineapple express and sensi star that I like to do sea of green and I keep those in 1 gallon pots, about 10 at most under a 600 watt light and they get up to about 16 inches tall and yield around an ounce per plant. The others in the 3 gallon pots I let get about 3 feet tall and I grow 4 of those under a 600 watt light and get about 3 - 4 ounces per plant depending on strain. I'm no pro so I couldn't even tell you if these are ideal yields or not, but I have no complaints.