Well the question is then, if all things being constant in your grow including: strain, light, space and power consumption (running same veg and bloom period for all growth cycles ex. 3 weeks veg @ 24 hours then 9 weeks bloom @12 hours). If you dont use gram per watt (GPW) to obtain your yields and output then how can you tell if you are dialing in a strain and getting better results between grows?
GPW is a precise measurement that everyone globally uses to pinpoint how much a strain is yielding indoors and 1 GPW is a standard that you should shoot for. Even seed companies when you look at their descriptions and yield content regards that a particular strain can yield between 0.8 gpw and 1.0 gpw under 1000w lamp fixtures.
How is GPW a bullshit unit of measurement? Given all things are constant: strain, lamp/bulb size, room, containers and light cycle. Assuming these are the basic factors heres 2 examples..
So my grow room is a 10x10. Im running exactly 6 plants per light or 24 plants. Im running 4 weeks of veg @24 hours per day and 9 weeks of 12/12 hours per day. Im using 5 gallon containers and the same cuts from the same mother plants on all my grows.
Example on my first run #1:
I harvested this run and I was able to get 7 lbs or roughly 3100 grams or 0.78 GPW. OR an average of 775 grams per bulb.
OR
Example on the next run #2:
This time I harvested 8.25 lbs or roughly 3700 grams or 1.08 GPW. OR an average of 925 grams per bulb.
Example on the next and final run #3:
I was able to harvest 7.5 pounds or roughly 3360 grams or 0.84 GPW. OR an average of 840 grams per bulb.
How is using GPW to monitor how well you are growing and yielding on a particular strain bullshit? IMO GPW is a basic platform that everyone uses to measure their yields and if they are dialing in their grows and moving forward using the measurement of GPW will tell you how well you are growing that particular strain and if adjustments need to be made. 1 GPW is the gold standard thay everyone for most part grows tries to obtain (strain dependent obviously some wont ever do that). But seed packages and strain information is easy to obtain and will also tell you how much that particular strain can yield some are expressed in GPW while others are measured in Grams per sq./meter. So assuming that you continue to grow in the same space, same containers and using the same wattage of lights in veg and bloom, and the same exact phenos from mother plants; IF you arent gonna measure your output or total yield in comparison to total numbers of grams per wattage then what other measurement would you want to use?
Some measure a gram per sq meter which breaks down like this: a 10 x 10 room = 100 sq ft. OR 9.2903 meters squared. For its purpose we can round to then tenth and make it 9.3 meter squared. So using 4 lights
@1000W per bulb using them in an area covering 9.3 meters squared, then you are left with roughly 2.325 sq meters per 1000w bulb. Since, most strains on average yield approx. say 350-450 grams per square meter (just using a average of what I found on seedbank site I dont know if this is true just using as an example!!)
So taking this assumption you can then multiply that estimate times the 2.325 sq meters that each 1000w bulb covers for space and you get a range of 813 grams to 1050 grams per 2.325 sq. meters. At the end of the day grams per square meter and in comparison to the examples above using the grams per watt (GPW) measurement are roughly the same give or take a few grams. This is because the light and your output or wattage is a constant variable that covers a specified area of growth. So no matter what size room you have or how many containers or whatever other factor you want to change, the ONE thing thats ALWAYS constant is the size of the bulb and the output of watts. So measuring in GPW is in reality the best unit of measuring the output and yield for harvesting to monitor how well you are running a particular strain.
