grams per watt is the equation your looking for. if 1 gram of bud can be achievedfor each actual watt used( 300w led panel is actually only bout 180w) then your looking for about 350-400w REAL draw. Also there will be a learning curve and you will not hit a gram per watt your first few time learning how to best care for yourplants. Honestly if you want to get close to that number I would suggest 2 of the Mars 600w units(300+w actual draw each) at around 600 watts actual draw and 2x2 footprint each u should be able to flower 6 healthy plants and get to or above your numbers your looking for
Following up to what he said, .5g/w is AVERAGE for LED panels. Mars 300w lights are guaranteed 140W+ actual draw. I think you could pull off 6 smallish/medium plants with 600W's (wouldn't get 12oz though), but also look into running HPS instead if you're really trying to pull some O's. It's a lot more set up, and significantly more money to run, but the results are worth it as you can definitely pull 1g/W with experience. HPS will require a lot of ventilation as well.
I used a Mars 600 278 draw on my first run in a 36x20x62 inch tent with inline cf, clip fans etc. used Femmed seeds from Nirvana got 6 ounces of dank bud. The light was $130 then. The 300's pull 140 true draw like mentioned. It depends on your budget and Grow area for Hid. higher temps and electricity tho, I think a 2x4 with 3x300's IMO. Btw for 6 Femmed seeds you would need a 4x4. Sent from my iPhone using Grasscity Forum mobile app