hey,, i think others may agree it all varient on your grow condtions and if there optiumal or not. see if you say use that one 1000w light with one plant then your grams per watt per 30days wont be any good.and 1000w without more than 4 plants isnt worth it and a waste of lumens and £$
Also will the plant be topped?will you be LST-ing???,cause that will make her yeild more but take longer to finish. Im sorry but your questions abit vauge, are you growing in soil/hydro? whats your grow exp. first time,30th time.
anyhow also when you harvest that wieght will be 75% rouglhy more than when dryed and cured,,so 80g can become 12g ish,,my math is awful..
anyhow so i cant tell you sorry,,take it easy.