From my experience I harvest 2.5 lbs per 16 sqft with 18-25 watts/sqft of double ended hps lights on a semi-large scale (110 lights). It sounds crazy but it’s true. My plants are usually 35-45 inches tall when finished and roughly 2-3 feet from light bulb. No cal mag, no fancy nutes, just micro...
Exactly, I don’t know what and how these people are growing but I do 18-22 watts/sqft with double ended hps and hit 2.5 lbs/per light consistently on large scale (110 lights)