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Grams-Per-Watt is an erroneous measure of productivity

toohighmf

Well-known member
Veteran
these are our opinions. don't see where anyone is really trying to dominate the thread. I think a lot of cool different discussions kinda started from the orig. topic. it happens when people are thinking.. Who's not making sense?
 
Realistically, this is the best way to measure your grow room efficiency going forward. When we all have to start thinking about carbon credits for the power to offset our usage, this g/kwh will make TONS more sense. After all, we pay for it in kwh.

So at 0.52 g/kwh.. I have some room to improve. However, no veg, no co2, 55 day cut downs right now make for 6 per year. So effectively I'm at 0.52 24/7 365.
 

ItsGrowTime

gets some
Veteran
Just made 2230 Grams on 1800 Watts (3 x 600W)
Vegged 5½ week
Bloom 8 Weeks :smokeit:

My last harvest was 2072 dry grams but only 8 days of veg from clone and 9 bloom weeks. Strain matters a lot here I think. I can flower early and get solid yield in less time, but way more plants (36) than you probably.

For awhile I thought gpw was the "holy grail" but now I just try to outdo my last crop. If I can't then I did something wrong or different that hurt yield and I take a note of it and change it next round. Im always striving to get better, not hit some subjective goal.
 
Y

YosemiteSam

Once you have chosen what and how you are going to grow (and that might very well have been influenced by g/kwh) then all you really need to measure is lbs per harvest and inventory turns (or crops per year if you prefer). Those two things will tell you how much product you will produce a year.

The rest depends on your goals. If you are growing for personal use I would think quality would be your main goal with yield only mattering in that you want to produce enough for personal use...maybe at the lowest cost possible, maybe not...definitely going to depend on the individual. If you are a commercial grower then quality is going to be determined by the market you are in (if you don't meet minimum standards you ain't gonna sell it for a decent price...and if you are smart you are going to set your standards well above the market minimum). Beyond that your main goal is going to be lbs per year cause that is what you are in business for.

Comparing g/kwh or any other arbitrary productivity measure against other people with other goals and different methods is about as worthless as arguing about who has the biggest dick.

It has been said before but what is really important is continuous improvement from crop to crop or year to year.

Least that is the way I see it. I could be wrong.
 
I agree completely. This would also solve the issues dealing with comparing HID to CF and LED grows.

And it would give you a more accurate way to gauge approximately how much it cost to produce X number of grams of pot.

i.e. 600 watt light ran for 12 hours each day for 8 weeks (672 hours) and produced 1/4 lb (113.4 grams), lets also assume our average cost for electricity is $.095 a KW/hr. Therefore .6*672(.095)= $38 therefore $38 = 113.4 grams or $0.33 a gram.
 
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MeanBean

Member
I just bought 25 of these on wholesale!!

Got em all strung up and plugged in.. Not the bananas.


picture.php


Can you tell me how many GPW and How many GPKWH I can expect with a bagseed strain??
 

MeanBean

Member
there only 4" wide, think of how may watts per foot I could get if I put them close together!!! Huge yields!
 

toohighmf

Well-known member
Veteran
If you are growing for personal use I would think quality would be your main goal with yield only mattering in that you want to produce enough for personal use...

Least that is the way I see it. I could be wrong.

YS: the higher the quality, usually comes better yields with that particular strain. every strain has it's peak performance. While most 2+ strains out there might lack overall quality, but yield great. The better the pot, at least from my experiences, yield suffers. when grown correctly though, the low yielding "elite" strains will yield better. I guess what I am trying to say is that with quality, comes more quantity. while sometimes you sacrifice 1 for the other in genetics, no matter what, the better the pot is grown, the bigger it will be.
 
S

secondtry

I have only been a member for a month or so, but I keep reading people using the gram-per-watt as a measure of productivity. Grams-per-watt is an erroneous measurement! What you need to do is use Grams-Per-Kilowatt Hour used.

If two growers growing the same pheno and both using a 600w HPS get 600 grams from their harvest, it would sound like they are both equal in productivity, right? But if the first grower did it in 60 days and the second in 83 days, it's obvious who the most productive grower is.

Starting from rooted clones:

Grower one would have a productivity level of 1.388 grams-per-kilowatt hour: 600 grams divided by .6x12x60.

Grower two would have a productivity level of 1 gram-per kilowatt hour: 600 grams divided by .6x12x83.

Ideally one needs to calculate all the kilowatt hours used in the whole process from cloning, vegging and flowering to give a true picture of productivity using the same strain. The above example just used the 12/12 cycle for simplicity and to give you an idea of what I'm talking about.

Use the Grams-Per-Kilowatt Hour measure when comparing your growing technique to others; you may be doing better than you think!

I agree, but you should use system wattage (ballast + lamp) not just lamp wattage. Reason being there is more and less light emitted (PPFD) and at different wavelengths (SPD) from one ballast to the next (different brands) with the same lamp. So to normalize your equation you should add the extra wattage from the ballast.

nice thread BTW
 
S

StealthyStalks

I just bought 25 of these on wholesale!!

Got em all strung up and plugged in.. Not the bananas.


picture.php


Can you tell me how many GPW and How many GPKWH I can expect with a bagseed strain??

Mr. MeanBean, you really need to read up on lighting. You would need to run five of those bulbs just to equal the lumen output of one 250w HSP. Incandescent lights are the most inefficient lights of all; they convert more energy into heat than they do light. That is why they are used in EasyBake ovens!
I think the earlier commenter was correct: you would be better off using the banana. :smoke:
 

MeanBean

Member
I well I found some light bulb paint. I am going to paint some bulbs red and some blue so I can hit the exact spectrum for plant growth!
 
S

secondtry

Okiedope, my original post was for simplicity reason only. If you read through my comments you'll see I agree one would need to take into account all the energy inputs: fans, pumps, lighting, air conditioners, dehumidifiers, etc. as well as prorated energy use for the mothers. Also it is important that any comparisons be strain/pheno specific and the use of clones would give the best measure of efficiency comparison.

I knew an engineer would get it!

Quick note:

It's not easy to use phenotype expression for quantitative comparisons. Phenotype is 50% genetic and 50% environ which means unless each grow has the same environment the pheno expression of the same strain will be different. Also, I think you are using the term strain correctly if I read that sentence accurately, but in case not here is a golden nugget: The term strain is commonly misunderstood and often misused term used by cannabis growers. A strain is the same thing as a cultivar, a strain must be living. NL#5 is a variety while NL#5 Elite is a strain, that is, "Elite" is a strain of the variety NL#5.

I like your posting style BTW, keep it up
 
S

StealthyStalks

I well I found some light bulb paint. I am going to paint some bulbs red and some blue so I can hit the exact spectrum for plant growth!


You aren't serious, are you?

It doesn't work the way you are thinking and all you are going to end up with are some high wattage Christmass bulbs. Take em back to the store and get your money back. Really.
 
S

secondtry

OP:

One more thought, please poke holes in it if you see any:

The most ideal method would probably be using PPFD weighted to Quantum Yield (QY). Then replace the kWh datum that QY datum because it's much more accurate to compare grows or evaluate grows (energy/time/yield) with photons plants use (PPFD) verses the kWh used by the lamp+ballast (where much of the energy is lost as non-PPFD quanta and heat). But, to use QY one needs at least a quantum senor, data logger and good math skills, so using kWh is the most feasible, if not the most ideal.
 
S

StealthyStalks

Quick note:

It's not easy to use phenotype expression for quantitative comparisons. Phenotype is 50% genetic and 50% environ which means unless each grow has the same environment the pheno expression of the same strain will be different. Also, I think you are using the term strain correctly if I read that sentence accurately, but in case not here is a golden nugget: The term strain is commonly misunderstood and often misused term used by cannabis growers. A strain is the same thing as a cultivar, a strain must be living. NL#5 is a variety while NL#5 Elite is a strain, that is, "Elite" is a strain of the variety NL#5.

I like your posting style BTW, keep it up

I just upped your rep because I did not know that... :smoke:
 
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