GPW? Should we start focusing on GSQM instead?

Hi.
Thought I'd give my 2c. Got this idea from the 4lbs per 4x4 thread.
Let's face it. Most growers aren't limited by the power available, but the grow space available. Another thing most growers chase is yield.
LED tech has become efficient enough that the lmc561 and 301 make a difference to your power bill by like what $10 (depending on your grow size of course).

Us as growers must ask ourselves this question. Do you want to be the most efficient in the forum with
2gpw , 4lbs yield in a 4x8 or be the guy that gets 1.5gpw with 5lbs yield in a 4x8 but paying an extra $50-200 in power for that extra lbs?

Sure, GPW is a great benchmark for benchers and potential goals ( like computer/cpu benches). But is it a realistic goal for most of us here?

We should all be focussing on grams/sqm just like in the hydroponic tomato industry.

In saying that, grams per square meter will help us improve a lot more as a grower than just upgrading to better LEDs ( although nothing wrong with having the latest and greatest ).

I hope i haven't caused too much drama here and will be interested to know what the SOG guys get per sqm size.

Anyone ever wonder what the most efficient pot size is for x weeks of veg?

Looking forward to the future of new growing techniques used.

All of the metrics are really only good at comparing your own grows against your goals. With as much variance in grow techniques not to mention strain and pheno variety it’s nearly impossible to use one metric across the board for everyone.

Maybe total dry yield, total cost (electrical, nutes etc) and total time? Some sort of factoring of those variables? Then again, genetics plays a big part as mentioned.

Hi! Yes it is very difficult to compare yields! And as you mention grower skills genetics and nutes are big factor!
There is guys who pull 1.5gpw using a/c co2 dwc coco with bottle nutes after 3 month vegg...and there's guys who pull the same in soil using organic amendments a fan and an extractor with 4 weeks vegg! Who is better?
So yes in a way you are right but in fact there is so many parameters to take into consideration that if you really think about it it is almost impossible to compare our respective grows!
To be fair we should test every setup in their basic form!!! The lamp(diodes COB HPS CMH t5 plasma...) should be used with only the basic equipment so the same fans and the same cuts and the same vegg time...only way to compare different light!
I get about 1.5gpw on average...from seeds in soil solid amendments water all along I have a fan inside the tent 1 intake 1 outtake that's it! No co2 no a/c nothing else and I vegg 4 weeks plus 7/10 days seedling! Do you believe that a guy who pull the same amount but with everything money can buy and 2 or 3 month vegg is really pulling the same???
Everything should be taken into consideration!1 vegg time 2 used nutes 3 watts involved(all the watts not only the lamp) 4 clones or seeds 5 gr/ft2!
So yes we should find another "scale"!!!
Have a lifted one and lots of good vibes from France growers

Overgrow had a good tool app that measured grams per watt from seedling veg to finish and seemed like a really good way to measure yeild pity they got taken down.

Well as with any math problem, we first need to identify the variables. I also forgot water. I think CO2 could be part of a variable including nutrients and would be expressed as a $ cost figure. Basically anything that costs you money in the grow that is not a one time expense like your lights or tent. (sorry for the metric, but it makes more sense)

So we know we need variables for:
Total yield (I suppose wet yield is actually the best measure, grams)
Total water consumption (Litres; as a side note 1 Litre of water weighs 1Kg)
Total consumables costs (nutrients, co2, etc expressed in $)
Power consumed (easy, watts, everything including AC, fans, lights etc)
Time to harvest (easy days)
Total grow space or 'area" (easy square meters)

Then the tricky one, genetics, lets assume we go with DLI which is mols per meter square per day. That would help calculating efficiencies for various plant species, ie low light vs high light species, but doesn't really help us with strain differences of the same species much. Alternatively we could use 4 different integers, 1=indicas, 2=hybrids, 3=sativas, 4=autos (or something like that,but then you are limiting the equation to only one species of plant), I am not a mathlete by any stretch of the imagination, so maybe someone with better math skills could chime in on building an equation.

goofy81 said:

Sure, GPW is a great benchmark for benchers and potential goals ( like computer/cpu benches). But is it a realistic goal for most of us here?

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No, it isn't.

GPW is used by licensed large scale, volume growers as a means to ascertain their overall costs and productivity.

For the average grower like me and most folks, it's completely irrelevant.

For me it's the price it cost me from start to harvest, per lb produced. That includes everything but my labor for my grows.
As long as my indoor grows cost less than $200 per pound produced, I'm a happy camper.

what if you grow in layers?

Most breeders have quoted grams per sq. Meter since the beginning.

You still have to know wattage and veg time.

My breeder used to have info on his website that said 600 watts per sq. meter and some strains are 450 grams and some up to 600.

He said minimum 5 weeks veg.

These are very close to my results after a lot of practice with the same Seeds.

I do both. What is more important to you depends on if you are bound in watts or bound in grow area.

Usually there is an inverse relation between the two. You need more intense light to get higher g/m2 and that usually means somewhat lower g/W.

IDK guys, like @torontoke says, they are completely subjective and only good for comparing your own grow to your following grow and barely acceptable for that. If that's all you are going to do then grow area is unlikely to change and is not needed for your own comparisons, but total electrical use is, (as is time, which should be reflected in total wattage). I think both measures are pretty irrelevant at this point. g/W was really just a way to get a 'very general' indicator of the efficiency of grow lights. g/m-2 assumes the same amount of time and power are going to be used each grow which we know varies from one strain and method to another.

Lets say this is a hypothetical example of a small scrog
$0.12/kWh electrical cost.
Total wet yield at harvest is 400 grams
Area, 0.5 square metres
Consumables, lets say soil + fertilizer $15
Time to harvest: 16 weeks

We need to look at inputs vs outputs.
kWh (75 watts veg 8 weeks 18h days, 150 watts flower 8 weeks 12h days) = 75.6 + 100.8 = 176.4 kWh @ $0.12 = $21.17
plus consumables = total cost of grow = 21.17 + 15 = $36.17
Then lets say as an expression cost per gram 36.17 / 400 = 0.09 $/g
Since time is already expressed in the total cost of power calculation we can ignore it going forward, longer grows will simply result in larger electrical bills. In a hydro grow, larger electricity usage, but shorter time to harvest, its a level playing field when using kWh.
Now the only variable left is area. So in this hypothetical example we have an end result of $0.09/g over 0.5 m-2 for an efficiency of $0.18 per metre squared. We can drop grams from the expression as it doesn't matter at this point, but we are actually expressing "cost per gram per meter squared". Which I think is what @wietefras was driving at above, but you still need to factor time into the equation.

I think this kind of expression is much more meaningful in comparing one grower to the next as well as within your own grows. No? It allows each grower to experiment and have confidence that they are considering everything not just yield from grow to grow.

https://www.rapidtables.com/calc/electric/watt-to-kwh-calculator.html

p.s.
The reason I used wet yield is because not everyone is going to use the harvested material in the same way, some will cure for smokable product, some will simply dry it or freeze it for extractions, some will incur losses during these processes, plus it's just easier to weigh it right as it comes off the grow imho. Of course there is nothing stopping you from using dry weight instead. If you also wanted to include water consumption and CO2 you would have to express them as a cost inputs.

Cheers

Both.

canadian1969 said:

IDK guys, like @torontoke says, they are completely subjective and only good for comparing your own grow to your following grow and barely acceptable for that.

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I don't get why people keep saying that. They are perfectly comparable metrics even with other people's grows.

It's like a car manufacturer quoting a 0-60mph or 0-100km/h figure and then complain about how the fuel mileage is not incorporated in that measurement. Or the Cw factor of the car for wind resistance can be different. Or grip of the tyres and road. Or whatever other detail you can come up with. Who cares that you could look at much more details when you have an easy to check metric which really says a lot about the performance of the car in one figure (as opposed to the list of individual parameters incorporated in that figure).

Similarly both g/W and g/m2 can say a lot about your grow performance and they are reasonably easy to obtain. Even if people don't calculate them specifically, they do tend to report grow size and used watts for the lights in their grow report and usually at some point the yield.

You can compare those as a ballpark figure to those of other growers and for yourself to track if you improved things or not after you change something in your grow. Like I said I, would compare both because they are somewhat interchangeable.

Or look for grows with a similar ratio between g/w and g/m2. For instance If you get 1.5g/W and 600g/m2 and someone else gets 2g/W and 300g/m2 it's clear you are using completely incomparable grow styles (light levels).

Also try to look for similar lighting. Not much sense in comparing g/W of a highly efficient led grow to a the low efficiency CFL bulb grow.

So yeah there are some caveats, but there is such a wealth of these numbers easily available that you can find grows similar to your own and compare their g/W and g/m2 figures to see how yours compare.

On the other hand adding more parameters to "improve" the quality of the metric really only make thing less comparable to others anyway. Electricity price won't be the same. Ambient temperatures won't be the same (leading to extra cooling or warming costs for some). All that data says nothing about your grow performance either. The climate in our tents should be similar in the end and how much electricity or money that costs isn't that relevant.

I also don't really care about other functions of time.

Weeks of flowering is not that relevant since it's mostly determined by genetics and perhaps a tiny bit by light spectrum. At best you would use that to see if a certain strain is more efficient or not. It doesn't say anything about your own performance in controlling aspects of the grow.

Weeks of veg is similarly irrelevant since it's mostly a function of how many plants you use. If I grow a lot of plants per m2 I veg for a shorter period and vice versa. In the end you end up with a grow area full of plants and you start flowering. From that point onward it doesn't really matter how you got there. It's only when I flip to 12/12 that I start counting. The rest is simply overhead. For which you could use other metrics if you insist on measuring performance of that segment of the grow.

If you want more detail then you should record those, but since no one else is doing that (or publishing them) you won't have any data to match it to other than yourself.

Got my work cut out for me this morning.

wietefras said:

They are perfectly comparable metrics even with other people's grows.

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You say that then immediately contradict yourself

here

wietefras said:

For instance If you get 1.5g/W and 600g/m2 and someone else gets 2g/W and 300g/m2 it's clear you are using completely incomparable grow styles (light levels).

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and here

wietefras said:

Not much sense in comparing g/W of a highly efficient led grow to a the low efficiency CFL bulb grow.

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and here

wietefras said:

So yeah there are some caveats, but there is such a wealth of these numbers easily available that you can find grows similar to your own

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I shouldn't have to dig for similar grows, thats not a way to fairly compare different grows which is the whole point of what I am illustrating, and of this thread, that doesn't make sense.

wietefras said:

Electricity price won't be the same. Ambient temperatures won't be the same (leading to extra cooling or warming costs for some)

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Yes, you are right, the total cost of grow may or may not be important to people and would lead to discrepancies due to geography and electricity rates, in that case just back out that portion of the calculation, which results in
0.88 kWh/g/m-2 , which still takes power and time / area into consideration.

wietefras said:

Weeks of veg is similarly irrelevant since it's mostly a function of how many plants you use.

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Or how big you grow your plants, i.e how long; and during veg we don't use as much power, as we discussed in the post on optimizing height/power of lights that can be dimmed; its not irrelevant when designing a method of fairly comparing any grow to any other grow, which is my objective and which you contradicted yourself on in your opening statement, g/W + g/m-2 are not "perfectly comparable metrics even with other people's grows". It could be argued it's irrelevant to you personally. It could be argued its irrelevant to a commercial grower as they have set production runs, where 't' (time) is the same from grow to grow (presumably). As is their power consumption so probably why they use g/m-2.

goofy81 said:

We should all be focussing on grams/sqm just like in the hydroponic tomato industry.

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For us time varies widely between grow methods and impacts the efficiency of each grow. If a person can get to harvest 10% faster than me with the same grams per watts and space, that is of interest and begs me to ask why/how.

goofy81 said:

In saying that, grams per square meter will help us improve a lot more as a grower than just upgrading to better LEDs

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wietefras said:

but since no one else is doing that (or publishing them) you won't have any data to match it to other than yourself.

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Yeah no one else is doing it, because I am figuring it out in real time here in this thread, doesn't mean we shouldn't. That's circular reasoning. The whole premise of this thread is to question if there is a better way as approached by the OP...

goofy81 said:

Us as growers must ask ourselves this question. Do you want to be the most efficient in the forum with 2gpw , 4lbs yield in a 4x8 or be the guy that gets 1.5gpw with 5lbs yield in a 4x8 but paying an extra $50-200 in power for that extra lbs?

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Again the objective (for me at least) is to find a way to fairly compare any grow to any other grow and the only thing I have really added to the "I do both" expression is time, which is undeniably valuable.

Of course the proof is in the pudding. Let's try comparing some radically different grows to each other like a CFL to a QB or CMH to F strips. Or say hypothetically I wanted to change from soil to hydro while simultaneously dropping the scrog method but without changing my lights; how could I possibly come up with a way to compare my results? In my light I can tune to a variety of colour temps, how can I compare vegging under 5000K to veg under 3000K with all other things being the same? g/W and g/m-2 isn't going to cut it if I do not also consider time. I think this deserves some consideration and experimentation. Most people that keep logs know how long their individual grows took, they also know their wattage, it's therefor fairly simple to figure out kWh then divide that by yield then divide that by m-2. Lets take a look at the results and see if this hypothesis holds water.

At the end of the day, I am glad I went through this mental exercise as from now on I will be using this method for comparing my grows. Dead easy actually as all I have to do is reset my Watt meter as it can calculate kWhs. I dont have to worry about tracking power levels through veg which I tend to increase incrementally as the grow proceeds. this makes much more sense to me than simply making changes in my grow and hoping to see a difference in yield/power without considering time.

Everyone gets a participation trophy for best yield.

canadian1969 said:

You say that then immediately contradict yourself

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No I did not and I explained why not immediately below that.

Besides, even if I did, I also explained that adding extra parameters makes it even less useless to compare figures to those from other growers. So it's still less worse than a new convoluted metric with more parameters included would say. Especially parameters which mean nothing for your actual performance anyway and are actually incomparable on their own.

Who cares what the color of your car is when you compare 0-60mph figures? Or that someone added 0-60mph figures on ice and then demands that the figures are corrected for friction coefficient of the road? Or that we measure our fuel use and correct the 0-60mph data for fuel use. Because it's better to get to 0-60mph on less fuel.

All of that is just as useless as incorporating veg phase kelvin figures in your grow cost metric. You're really just making things worse for comparing to others by adding those insignificant and highly incomparable details.

Also, even if the type of grow isn't identical, g/W and g/m2 are still comparable as benchmarks. If you are looking to improve g/W or g/m2 and another type of grow does that, then you could switch your grow style. You can still learn from g/W that you can easily increase your g/W on average by switching from HPS to a decent led light. Doesn't mean that you are a better grower perhaps, but it does change the g/W.

My point was, that if you want to know if certain aspects of your grow have an impact then you compare to grows with mostly just that aspect different. That will never be any different whatever metric you use. If you spend $100 on a grow or $120, you still won't know if that was because of the nutrients. Unless you make sure all aspects of the compared grows were the same apart from nutrients.

The only "improvement" I made myself was to use g/umol/s instead of g/W. That makes HPS and led grows with different efficacies more comparable. But then again that's less easy to do with other people's grow. Especially if you want to use g/umols/s which actually reaches the plants (ie after reflector and wall losses)

Doing that I actually got pretty similar g/umol/s figures with my HPS grows as I later got with with COBs.

The most important way to every grower is to measure by the limiting factor.

That being grams per square meter/foot if real estate is the limiting factor, grams per watt if electrical is the limt, or yield per plant if that is the consideration.

lol you guys make harvesting sound way too complicated.

WeedSexWeightsShakes said:

lol you guys make harvesting sound way too complicated.

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kWh/g/m-2
not complicated