That's a fantastic Q re: the ceiling after which there is no additional gain.
I can't give a specific answer but I CAN say that the best youcan hope for is to find what your limiting factor for growth would be, and work on improving it. It is USUALLY light for indoor growers. Once you have lots of light, you will want to look at other factors... soil moisture, atmospheric CO2, carbon availability in the medium, and of course your nutrient load. This is why many growers who use CO2 are not getting as much additional oomph from it as they could.

600w light is more efficient in lpw than a 1000. That's one thing to think about.

Your big thing is going to be temps when you really crank up the light.
stinkyattic Reviewed by stinkyattic on . Too much light - is there such a thing? I've seen the numbers for suggested light amounts per square foot of actual growing space, but I'm wondering if there is in fact a ceiling for this? So long as you can keep the plants temperate and not allow them to get burned, is their a ceiling beyond which the light can still hurt the plant or at the very least be of no benefit whatsoever? I recently read an article by a fellow who claims to be using a 1000w HPS for a 3'x3' grow area, but can swing it because of the other measures he's Rating: 5