Why GPW?

[timmur]

Wouldn't it make more sense when measuring yield to express it as Grams Per Lumen (or some other measurement of light) per some unit of time rather than per watt? I realize that a commercial grow cares very much for the cost of the light, but couldn't that be measured separately?

I work in an industry where yield is absolutely critical, but energy is not directly part of any yield formula. Anyone competing on the basis of the metric that I suggested would obviously be aiming for the highest possible yields while minimizing all other overhead costs. This may in fact mean accepting less than the very highest yields if the costs outweighed the benefit from a financial perspective.

A total yield formula would probably account for all nutrients and water as well. Just sayin. Am I thinking about this wrong?

 

[DoubleDDsNuggs]

I suppose it could be a more accurate way

only because each 1000w has a separate lumen rating which varies on brand. 600w bulbs also produce more lumens per watt than a 1000w bulb which would make it easier to get a higher gpw if what you're suggesting is correct. A 1000 watt hortilux hps has 135 lumens = 1 watt while the 600 watt has 146 lumens to each watt.

 

[mojave green]

and for another twist:
https://www.icmag.com/ic/showthread.php?t=286177

 

[ganja_guru]

Lumens are irrelevant, lumens are a measurement of total amount of light visible to the human eye. Plants see things differently, it's all about par or micro-moles when your talking about plants, not lumens.

GG.

 

[pinkus]

GPW works fine. You could research and parse but it wouldn't yield much IMO...plus you would really have to nail down a standard spectrum, and some would perform better outside that standard. good luck with that. Not a bad idea, but there are better places to concentrate IMO.

 

[hush]

The more you grow and harvest, the more you realize that there really is something to the GPW standard. It's not perfect, of course, but I have yet to see anything come closer to being a better benchmark. I take that back, back in the day there was a movement to start focusing on "grams per watt per month" which takes into account the fact that people can totally yield LOTS more when they veg longer, which throws the numbers off.

It's arbitrary in a sense, but it still works. Much in the way that measuring TDS in ppm is also arbitrary, but it still works because it creates reference points.

 

[timmur]

@ganja_guru

it's all about par or micro-moles

Agreed. That's why I said lumens or some other measurement of light. My thought was that a yield metric should measure how much biomass is produced given certain inputs such as micro-moles of light, etc... That was my original thought, but it seems things get overly complicated with that approach.

@hush
You hit the nail on the head with GPW as a metric of growth efficiency: it fails to take time into account. Consider two grow operations in a very competitive market with large annual production. Using the standard GPW metric both operations claim identical performance on the metric. Suppose further that one of the operations produces 5000 lbs of dry product annually and the other produces 6000 lbs annually. Our metric seems to indicate that they will produce similar quantities though they don't. One explanation for the discrepancy could be that the longer vegetation cycles for one of the grow ops gives them parity with the GPW metric as it excludes time. When we look at total yield over some defined period of time we see the reality.

 

[SeedsOfFreedom]

The real measurement should be grams per watt per day. This is the way I figure out my yields. If people did this more, many would stop growing 55-60 day commercial strains thinking only they yield well. G/W/D is perfect to figure out the output of any area annually, or monthly.

 

[pinkus]

The thing is IMO, many sativas will yield as well or better given the time element... BUT the longer flowering time makes it more of a gamble. especially when legal issues can force a quick shut down. Like I just had happen with some 12-14 week plants :/

 

[Jhhnn]

GPW does not properly account for power usage. Grams per kilowatt hour does. For home growers, modern tiered billing methods & all the little adjustments in an Xcel bill make the math more complex when translating that into dollars per gram.

For example-

18 hrs/day x 30 days veg = (540 hrs) + 12 hrs/day x 70 days flower= (840 hrs) for a total of 1380 hrs.

A 1000w lamp actually draws ~1100w, 1.1 kw, so that's a total of 1518 KWH.

with a yield of 550 dry grams, that's .36g/KWH. With an effective electric rate of $0.18/KWH, that's also $0.49/g.

Edit- it's fairly easy to add in the cost of running fans & circulation pumps in DWC. The cost of A/C would need to be figured from actual power consumption over time due to varying load & compressor cycling.

 

[Ttystikk]

The real measurement should be grams per watt per day. This is the way I figure out my yields. If people did this more, many would stop growing 55-60 day commercial strains thinking only they yield well. G/W/D is perfect to figure out the output of any area annually, or monthly.

This is a good metric, but only if we include all the watts, not just those in the bloom room.

 

[Ttystikk]

One of these days we will hit upon a metric that accurately depicts monster single successive crops vs perpetual with short cycle times relative to one another- and I believe that's the day inefficiencies in monster crops during veg will become clear, just as vertical vs horizontal growing is already beginning to do now.

 

[Drek]

GPW are relative to the conditions in which they're grown.

About as good as they are.

 

[Bueno Time]

GPW does not properly account for power usage. Grams per kilowatt hour does. For home growers, modern tiered billing methods & all the little adjustments in an Xcel bill make the math more complex when translating that into dollars per gram.

For example-

18 hrs/day x 30 days veg = (540 hrs) + 12 hrs/day x 70 days flower= (840 hrs) for a total of 1380 hrs.

A 1000w lamp actually draws ~1100w, 1.1 kw, so that's a total of 1518 KWH.

with a yield of 550 dry grams, that's .36g/KWH. With an effective electric rate of $0.18/KWH, that's also $0.49/g.

Edit- it's fairly easy to add in the cost of running fans & circulation pumps in DWC. The cost of A/C would need to be figured from actual power consumption over time due to varying load & compressor cycling.

Nice post, I was also going to recommend the G/KWH method.

Most people just go by GPW of the lighting wattage only, out of simplicity I would think.

 

[FRIENDinDEED]

ive read all the responses and you guys are some of the most intelligent around but no matter how smart you are you cant beat the sun so stop tryin

because your talking about something you have to pay for you want to find the best way to maximize what you have but if you take the money out of the equation, or rather the constant paying out thereof, then your concern about how much power you use becomes a fleeting thought

and I think only one person mentioned the factor of plant response which is key no matter how much power you manage to utilize or under utilize. some plants in the same situations and under the same conditions will yield more than others

imo the only real way to get the most out of the energy that you use is dealing with a high/yielding strain to begin with; it then leans into the argument of soil vs. hydro and what yields more (since we are talking about maximizing how great of a final weight you get from what you grow right?) but that all comes down to personal preference eventually

someone did mention the point of does this calculation factor in the amount of veg time given and since bigger plants yield greater final weight then it has to be considered into the initial calculations I would think.

the OP's question was pertaining to the consideration of a better measuring rod but to me it just sounds like someone trying to find a better way to cheat.

imo ultimately due diligence and common sense will yield you more in the end everytime more than trying to fool yourself with a different configuration of given numbers ; lol, "you got to use what you got, to get what you want"

but hey that's just me and please don't beat me over the head its late, insomnia is chillin with me, im a virgo so I have to get these thoughts out since its all I have.

 

[pinkus]

some people CAN'T use the sun

 

[timmur]

One of these days we will hit upon a metric that accurately depicts monster single successive crops vs perpetual with short cycle times relative to one another- and I believe that's the day inefficiencies in monster crops during veg will become clear, just as vertical vs horizontal growing is already beginning to do now.

You won't have to wait. All that is needed is total KWH used until harvest and total yield of dried bud. As long as you look at strains that have the same or similar potential the GKWH metric should tease out the differences between different grow styles.

 

[Ttystikk]

I think you start at the meter and subtract only the stuff that is not directly related to the grow op. I would cast the net widely; if a microwave is needed to keep the peeps on-site happy, fed and productive, then it's included.

 

[GrowerGoneWild]

Wouldn't it make more sense when measuring yield to express it as Grams Per Lumen (or some other measurement of light) per some unit of time rather than per watt? I realize that a commercial grow cares very much for the cost of the light, but couldn't that be measured separately?
A total yield formula would probably account for all nutrients and water as well. Just sayin. Am I thinking about this wrong?

Lumens is irrelevant, I buy based on wattage. 1KW can create close to 1gpw, same with a 250. So we can kinda say that HPS HID lighting makes ~1GPW if done right.

Water cost is minimal, I worry on cost per tank. You could create a formula for cost per gram including nutrients to produce.

Watts is watts... and same with dried, cured, trimmed product. Grams are grams. IF you used 100 watts of lighting to produce 100 grams of produced. That would be a good setup.

 

[timmur]

Lumens is irrelevant, I buy based on wattage. 1KW can create close to 1gpw, same with a 250. So we can kinda say that HPS HID lighting makes ~1GPW if done right.

GPW is a lousy metric. It doesn't factor time into the calculation. GPkWh or grams / kilowatt hour is much better. I suggested using gram / unit of light / unit of time as a more pure metric as plants don't consume watts to grow they use photons. The devices that emit photons consume the watts.