Ive done about 8 grows under a 400 watt, its adverages 3 - 4 oz.
Depending on strain and vegtime and If I didnt shock the hell out of them at one point in the grow.
I had an aeroponics (20 gallon) 7 - 13 plants setup in a 2X3 closet
I took very little care of these plants other then changing...