1000 watt a 5x5 grow area up to 30 plants, my set up is 4 and half and 2 and half grow tray , i got 18 plants in that bitch with a 1000watt light i get alot of popcprn bud because there in so tight but i get at least 1000grams if not more of big budz, so im happy with that its all about trail and error if you do decide to go with a second light i think 2 600watts is better than one 1000watt imo, idk good luck fellow grower