interesting... its really not complicated. we just use the gpw as a yardstick of sorts... its nothing to get heated over- except when ppl start getting personal- although some ppl take accusations more seriously(as do i), esp considering how they would react in actual life to such a challenge(=honesty).
IMHO it is COMPLETELY IRRELEVANT if you are using HID, fluoro's/cfl's or LED's- the same applies as a yardstick to all light systems BUT CAN BE MODIFIED to suit individual set ups or systems, grow space etc.
the 1 gpw device is simply something of a universal measure of what is possible and is GENERALLY measuring the dried weight(grams) against the wattage OF THE LIGHTS BEING USED NOT the total watts of every appliance and device being used to compliment the grow, as these GREATLY vary from grower to grower and grow room to grow room- depending on specific needs-THE WATTS REMAIN THE ONE CONSTANT across the board that contributes to dried weight!! it is measuring how much dry bud one can achieve from a certain amount of watts. this SHOULD be quite clear. as an upcoming grower myself i want to know how much dried weight i can achieve from a 400w, 600w or 1kw light- if i want to strive for a pound per plant, how many LIGHTS will i need to accomplish this?? ah, here is the crux of the matter right here.. other factors such as co2 enrichment can add to weight of course but is not included in the base result more an addition/compliment to the base result