# grams per watt

Discussion in 'Growing Marijuana Indoors' started by blindbudsmoker, Oct 12, 2010.

1. #1
Last edited by a moderator: Oct 12, 2010
Hi...

been reading here for a while and i keep hearing these numbers for GPW that seem a little nuts, like trying for a 1.0gpw. i guess i didnt search but was curious how these numbers are being calculated. from my math even you only counted bloom time of 2 months , 1gpw would equal almost 4.5 pounds off a 1000watt. i have yet to see a room that even comes remotely close to these numbers. can some one expand on how these numbers are figured. thanks.

2. there's no way to put Grams pre watt in a science, so many factors play rolls in how juicy your buds get.

3. After your harvest you weigh out your bud in grams. Take the dry cured weight and divide it by the total watts used for your lighting. You will get your gram per watt ratio.

With your 1 g/w and 1000 watt light scenario you would expect 1000 grams at the end of your harvest which would be roughly 2.2lbs. A more common number for the average grower is the .5 g/w mark which would mean more around a pound for a 1000 watt light.

4. so how is this goal of 1gpw made then? thier is sort of a science as well, imo. we figure it out and from what ive come to know is the best i have ever seen is almost .45 YTD.

5. oh shit, lmao, i was thinking of something completely diff, sory bro, imr eally baekd atm, and there's always posts about people saying "how muany Ounces can ig et from my plant?"

6. so no time is factored in? that seems like sort of a big flaw in this idea. seeing as how time is the most valuable asset. if you dont include time then really the 1.0gpw that high times used to say was standard should/is easy to achieve. if no time is factored in then whats to say u dont veg for 6 months and bloom for 3 and end up with 3 gpw? doesnt it seem like all time/energy would need to be factored to make the gpw into a real number?

7. i guess the reason i am asking any of this is because reading some of the threads and a person says some thing like. first grow got .5 gpw hopeing to hit 1gpw on my second try. in my head im thinking wtf, been at this for years and have a hard time holding .35 gpw. so wanted to see how the math was being done.

8. 1 gram per watt of electrical power is used as a benchmark for an efficient grow, as far as your 6 month veg 3 month bloom scenario goes plant size and number are insignificant. If you veg a plant for sevral months you are obviously only gonna be putting 1-2 plants under your light why not veg for 1 month and put 4-6 plants under that one light? You would save time and have the same growth potential its all about how much lighting you can provide when you are not growing under the power of the sun, light not time is the most important factor in indoor growing...

And as far as you .35 gpw after years of growing i would be interested to know what kind of equipment you are growing with because obviousy its crap or you are not utilizing it properly.

9. so under this idea then a 2000w sog set up that pulled 3 pounds every 2 months would be = 2000w dirt setup that pulled 3 pounds every 4 months? seems that the sog setup would be a bit more effeciant due to the time factor.

in the gpw that makes sense to me the sog setup would be pulling 1350grams/2000w/2months=.33 gpw/ytd and the soil would be pulling 1350grams/2000w/4months=.16gpw/ytd

not 100% but seems time is far more valuable then the amount of lights u can hang, the amount of lights you can hang is infinite but your time per year is set.

10. #10
Last edited by a moderator: Oct 12, 2010
I fail to understand why the second grow would take 4 months seems as though 3 would be correct, and i also fail to understand why both grows are yielding the same amount when one is growing for 2 extra months?

I understand what you are saying as far as time goes in this scenario but you weren't talking about sog in the post i was replying to you were talking about a 6 foot tall monster plant, and i never said growing medium or techniques were not important i simply said in my opinion light is the most important factor.

11. #11
Last edited by a moderator: Oct 12, 2010

was just a scenario, and even with that i did the math wrong since if you went strait 12/12 on the sog and 18/6 soil. for every light you run at 18/6 needs to be counted as 1.5 lights to make all things equal.

as far as what medium or technique used that is used it seems to me that the time has to be factored in no matter how, why or what way you do things.

the blanket statement is of gpw to me is the same as the guy who says they get 2 pounds per 1000watts. it really doesnt amount to much with out a time frame in which they did it. 2 pounds a light is nothing to be proud of if u did it in 4 months. but to pull it off in 2 months u can pat yourself on the back.

12. How many plants would be needed to achieve 1 g/w in a 600W scenario? Everyone keeps talking the ratio and not the standard number of plants needed.

13. imo the amount of plants needed for most any thing is not that crucial. plants will grow to grab every spec of light they can get. so more plants really just = less time since they will not have to grow as far to fill the canopy area.

and 1gpw off a 600 would be insane by my math, that would not be possible by anyone besides nasa growers or someone with that kind of finacial backing and schooling.

by the math i read here you really only would need one plant and veg it for 6 months and turn it back for 2 and im sure you would get 2 pounds off it.

14. Ok, so 1 g/w with a 600W is not possible but what is then? .35 g/w more like it?

15. I've seen well documented examples of people getting 1 GPW with a 400, and a 1000, but I'm sure a 600 watter would be just as possible.

16. #16
Last edited by a moderator: Oct 12, 2010

well.. heres some numbers i put together for some friends who wanted to get ideas. its alll based on 1000s but you can get a idea

GPW GPM Total per year Pounds per year
1.0 = 1000 = 12000 = 26.6
.5 = 500 = 6000 = 13.3
.3 = 300 = 3600 = 8
.2 = 200 = 2400 = 5.33
.1 = 100 = 1200 = 2.66

this is the math for a year per light. and this is why it seems a gram per watt is insane, i dont think its possible to pull 26 pounds a year from 1 light. when we count our days out we start from the day they show roots and come out of the dome/easy cloner.

the idea to not include time is like giving you a formula for a feeding program like 500 mil of this 500 mil of that and its perfect, the vital key thats missing from that is to how much water. same idea.

if u do .35 your math would look like

.35gpw x 600watts x 3months = 630 grams/1.4 pounds

i have really never used 600s so im not sure how well they work but from 90% of the math ive did on this, the average dirt grower is pulling between .12ish to .25ish and average hydro is .2 to .3. every room that ive seen go passed .3 is usally dialed to the tits and has had all the kinks worked out.

17. hold on a minute, dude, where in GRAMS PER WATT do you see a reference to time? This is per harvest. This figure is with unlimited veg time: it only includes grams and watts...

You could veg a plant for 2 months under a 150w hps and get 5 ounces (roughly 1 GPW) or you could veg it for 2 years and not get any more. That is why this is an important benchmark. There comes a point where extra veg time doesn't get you any more yield because the amount of light can only support so much plant.

An expert grower with good genetics can pull around 1 GPW per harvest with HID lighting, but when you start talking about GRAMS PER WATT PER MONTH you are talking about something completely different. No one claims to pull one gram per watt per month...

18. imo thats kinda the problem if you are try to be productive and learn to get better each round. if the only info you know is that u pulled 2 pounds off of a thousand then lets say the next round you did 3 you honestly would have no idea if you did better or worse without the time. if you had a car that got 50 MP? that wouldnt do u any good cause what if the ?= a liter and not a gallon. same idea. u have to have some sort of perspective on it. where we live its vital to know your time frame of power is being used since we pay so much for it.

the way you say that thier 2 differnt things, is that a way of saying one is accurate and one is a guess?

a dumb story but fits this model.. when we first moved we set up a room. took almost 3 months to finish it. the day we got here a friend gave me some 15 babies, they sat in my closet under a 400 the next 3 months, and i got when them they were allready a foot tall probably a 4-5 weeks or so old. we finished them under 2000 watts and got almost 6 pounds. does that mean that i got 1.4 GPW?

also as far as im concerned was shit all genetics. blueberry or some thing.

19. I agree that GPW certainly doesn't tell the whole story. It is just a benchmark of comparison.
There comes a point where people just have to simplify things in the name of comparison, because if the benchmark was grams per watt per month per dollar per ounce of nutrients used per inch of plant height, no one would take the time to calculate it out. There are so many variables that go into any grow that it would be impossible to include them all when comparing harvests.

No one really claims that grams per watt tells the whole story, though, it's just a simple way to compare harvests.

20. thats about what ive come up with reading today, its more or less a guess of about how well some one did. to do all the rest of the math isnt quite that hard. we take our matha ll the way down to the day they come out of the tray/easy cloner and from that day forward we know what and how long all lights have been on. a side note on power, where we live its now 46cents a kilowatt.... so we pay very close attention to time on that fact to.

also thinking on it, it makes sense for any one who wants to just pull down a crop and be ok with it. most i know seem to keep very good records to strive and improve on every round so that might also be why we keep track of time. with us it even comes down to how much down time we have, why we track it by the year and not the cycle. over the course of 3-4 years if you take a week for turn around thats another full crop you have given up.