Grams per watt

I see a lot of posts where people are talking about yield, as in grams per watt. From what I gather, 1 gpw is good and 2 gpw is awesome. I really feel like this is more applicable to people who have decent juice from their lighting system.

Since my light is only 38 watts (LED) I somehow feel like the scales are tipped in my favour when looking at gpw's. With 5 plants in flower at about day 36 it looks to me like I already would exceed 38 grams and likely will exceed 76 grams by the time it is finished.

Although my investment has been next to nothing I still feel it takes far to long to produce a decent crop. I am looking at convincing my wife that putting some money into a proper grow room with not only pay for itself with the output ($ saved by not having to buy it), but it will also help with the smells. I find the smell very minimal inside the grow room, and almost never noticeable beyond 10 feet away.

Unfortunately the smell of flowering cannabis seems to give my wife a headache sometimes. I assured her that for a minimal investment we can eliminate that issue altogether. Does that make sense?

Makes perfect sense.
If you have a decent filter and fan exhausting straight outside you could eliminate most of the smells.
An onabucket or an ionizer would easily handle the rest.
Grams per watt is geared more toward the commercial setting or on larger then average from rooms/areas.
Smaller area with low wattage can make even a hack like me look like I know what I'm doing.
A gram per sq foot equation would make more sense or a gram per sq watt somehow idk

torontoke said:

Makes perfect sense.
If you have a decent filter and fan exhausting straight outside you could eliminate most of the smells.
An onabucket or an ionizer would easily handle the rest.

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I completely agree with what is quoted.

As for the Gram/watt, forget about it. There are too many factors that play with the yield. It is a vague reference and you should try to focus on your grow and try to get the most of it.

Here are some factors that may influence the yield; The type of light(HPS, CFL, LED), the type of strain, the growing medium(soil, soilless, hydro),the nutrients and more.

gpw is only a rough measure of output, use it as a guide for yourself but it's not something to be used to compare to other grows as there are too many variables. Genetics is one of the biggest variables, there's strains I've grown which would pull 2 oz. with another right beside it pulling 4 oz. But if you've grown the same plant and continue to grow it through clones, and your environment/equipment doesn't change it can be a rough calculation of how efficient your grow is going for you. I personally use ounces produced per gallon of medium, my medium hasn't changed since I started growing indoor so it's the only constant. I don't compare strain to strain, but I always run some clones which I've run before under different conditions so I can compare how well I'm doing in different pot sizes or lighting conditions for example.

I used to be really into grams per watt. I calculate all my grows to keep track of my progress.

At this point in time though, grow area is my limiting factor. So I'm leaning more towards grams per square foot now. I grow very efficiently either way so wattage isn't as big of an issue as it used to be. As I increase my lighting over a given area, my grams per watt will drop in numbers, but my yield per area will go up. Highest yield per area is much more important to me now then gpw, but only because of my limiting factors.

Thanks, great feedback form everyone. I did not think gpw made a lot of sense since the playing field is so diverse. For me I need to hit a decent enough number to validate continuing this venture, to my wife at the least. It really bothers me that my wife gets a headache so I am going to work on a solution to that first and foremost.

grow1620 said:

I used to be really into grams per watt. I calculate all my grows to keep track of my progress.

At this point in time though, grow area is my limiting factor. So I'm leaning more towards grams per square foot now. I grow very efficiently either way so wattage isn't as big of an issue as it used to be. As I increase my lighting over a given area, my grams per watt will drop in numbers, but my yield per area will go up. Highest yield per area is much more important to me now then gpw, but only because of my limiting factors.

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Yes what you and torontoke say about grams per sq.ft. makes sense. I know I need to up my game where lights are concerned if I want to produce a bigger yield. Smell first though, as I am sure that will only get worse with more juice from lights.

If smell is an issue, you can look into low smell strains such as cinderella 99 or northern light. Both low smell strain and easy to grow.

Thanks. I have some NL seeds so maybe I will try that in run #3. If my GSC turn out as nice as the bud they came from I will run a few more of those as well. Since I am currently doing nothing about the smell, anything would be an improvement.

zoic said:

Thanks. I have some NL seeds so maybe I will try that in run #3. If my GSC turn out as nice as the bud they came from I will run a few more of those as well. Since I am currently doing nothing about the smell, anything would be an improvement.

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Easy and relatively cheap fix as already posted (ona, carbon filter).

For your conversations with your wife. One thing I always keep in mind when deciding whether to spend/invest in my grow is the alternative cost at $8-$10/gram for what can be questionable quality without a reliable hook-up. The spend is always justifiable when comparing it to spending $200-$300/oz. for questionable quality flower in thew BM or LP's.

Thanks GroErr, looking into that now. I plan to evaluate this on $/g for sure, and since I have one grow in flower and one soon to be there, I really need to produce 80g from both grows to come in around the $5/g mark, hard to imagine I cannot get at least that much, even from the first grow alone. I guess in 3-5 weeks I will find out.

OK, I read up on this ONA gel stuff and if I get the jist of it, you use this away from your grow area or in the end of the exhaust tube to completely replace the smell with a new one, the ONA smell. This would certainly remove the occasional distinct odor at the front door quite well I believe. My only concern is that both my wife and I are odor sensitive to many perfume smells. The information I read suggested ONA gel had a perfume smell. Is that correct in your opinion?

zoic said:

OK, I read up on this ONA gel stuff and if I get the jist of it, you use this away from your grow area or in the end of the exhaust tube to completely replace the smell with a new one, the ONA smell. This would certainly remove the occasional distinct odor at the front door quite well I believe. My only concern is that both my wife and I are odor sensitive to many perfume smells. The information I read suggested ONA gel had a perfume smell. Is that correct in your opinion?

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It's available in different scents.
I wouldn't have it in the grow room at all.
Make one of these and put it somewhere central and it will mask any remaining odour.
The main plain ona smells like fresh clean linen

torontoke said:

Makes perfect sense.
If you have a decent filter and fan exhausting straight outside you could eliminate most of the smells.
An onabucket or an ionizer would easily handle the rest.
Grams per watt is geared more toward the commercial setting or on larger then average from rooms/areas.
Smaller area with low wattage can make even a hack like me look like I know what I'm doing.
A gram per sq foot equation would make more sense or a gram per sq watt somehow idk

Click to expand...

If you have any odor at all when using a carbon filter then you do not have it setup correctly. A proper carbon filter with either a negative air setup or an air scrubber setup will 100% eliminate smell.

Only the uneducated would choose an ionizer or ona bucket... I have linked professional industry documentation on how to figure out CFM and ACH required for any space in the odor control thread.

Trust me dont use chemicals to mask and cover up your smells, do it the same way large industry like sewage treatment plants or HAZMAT professionals do it. Its not expensive either.

https://www.rollitup.org/t/the-ultimate-odour-control-thread.90893/page-48

If budget is a concern just buy aquarium grade activated carbon and make your own filter.

haze010 said:

If you have any odor at all when using a carbon filter then you do not have it setup correctly. A proper carbon filter with either a negative air setup or an air scrubber setup will 100% eliminate smell.

Only the uneducated would choose an ionizer or ona bucket... I have linked professional industry documentation on how to figure out CFM and ACH required for any space in the odor control thread.

Trust me dont use chemicals to mask and cover up your smells, do it the same way large industry like sewage treatment plants or HAZMAT professionals do it. Its not expensive either.

https://www.rollitup.org/t/the-ultimate-odour-control-thread.90893/page-48

If budget is a concern just buy aquarium grade activated carbon and make your own filter.

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In a sealed perfect grow you are 100% right except for when you actually open the area to do anything in there.
And if the exhaust is going directly outside.

I always thought an ionizer charges the air with electrons but perhaps there's a chemical involved I've not heard of.

torontoke said:

In a sealed perfect grow you are 100% right except for when you actually open the area to do anything in there.
And if the exhaust is going directly outside.

I always thought an ionizer charges the air with electrons but perhaps there's a chemical involved I've not heard of.

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Actually not really, it depends on the volume of the area and how much CFM you have going thru it. If your fan is beefy and your space a 2x4 or smaller it being sealed near airtight shouldnt be a problem. When i said chemical i was referring to the ona im not that familiar with ionizer.

Honestly, creating a neg air condition is easier than you think. If your carbon filter is venting outside thats a non-issue, you should have absolutely no smell at all being vented out, if there is any smell at all you dont have the right balance between airflow cfm and the size of the carbon filter or the carbon is worn out and needs to be replaced. More than once ive used the existing dryer venting as an exit exhaust without an issue. For that kind of situation id go with an air scrubber over an neg air build anyway, and then opening the door shouldnt matter. For a closet where venting out is a problem you'd want an air scrubber over negative air anyway.

Ive helped build and ran air testing on neg air containments for hazmat stuff like aesbestos where its whole apartment building thats condemmed and due to be torn down. All the hazardous stuff needs to get disposed of before it can be destroyed and we create a neg air environment for that where part of the roof was even caved in. We use rip-proof tarping to try and cover holes and gaps but its Faaaar from air tight. It just means you need a stronger fan to maintain that negative air. If your space is small it doesnt really take that much of an oversized fan but if its for like a closet, when you open the door you may have some odor escape to the room, other than that it should be a non issue.

This is just honest advice from someone whos job it is to deal with decontaminating air (i work in HAZMAT) for odors the absolute 100% best thing is carbon.

The industry guide i linked in other thread if u want to read how the numbers are gotten and real info about air scrubbing and negative air setups.
https://www.drieaz.com/uploads/deca/gtas.pdf

Any questions you have id be happy to answer, this is the one area i can help contribute back on RIU where ive recieved tons of help from others on things i dont know. I can dig up even more in depth documentation if anyone is interested in further reading.


Edit: i forgot to mention, that ona bucket is basically an DIY air scrubber but for some reason he is using ONA instead of a carbon filter. Carbon is so much better....

Something like this in general idea but using a homemade carbon filter instead of a hepa filter is an air scrubber for odor.

GPW is too vague a number. The reason I say that is if grower A get 0.9gpw has a big commercial grow where he grows a lot of plants at a time with short veg times but grower B gets 1.5gpw with a small plant count and very long veg times how do you compare all the other factors? Something like gram per $ spent on variable costs(labor, nutrients, electricity, rent, taxes, etc)would be good but hugely complicated to work out.

mjinc said:

GPW is too vague a number. The reason I say that is if grower A get 0.9gpw has a big commercial grow where he grows a lot of plants at a time with short veg times but grower B gets 1.5gpw with a small plant count and very long veg times how do you compare all the other factors? Something like gram per $ spent on variable costs(labor, nutrients, electricity, rent, taxes, etc)would be good but hugely complicated to work out.

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Yes, but it is useful when youre talking about 1 grower doing the same exact grow and is trying to compare two different lighting systems. IE: a controlled experiment.

Otherwise id agree but if its one person testing light a vs light b like so many side by sides, or how growmau5 uses it to compare lights, nutes ect, in those cases gpw is valid.

zoic said:

Thanks GroErr, looking into that now. I plan to evaluate this on $/g for sure, and since I have one grow in flower and one soon to be there, I really need to produce 80g from both grows to come in around the $5/g mark, hard to imagine I cannot get at least that much, even from the first grow alone. I guess in 3-5 weeks I will find out.

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Once you get things flowing and fully utilize your space you can get down to $1/g or so all-in. Every time I've calculated my costs I fall in somewhere around $1/$1.25/g including all expenses and depreciation on equipment. Add labour if you want, I don't count my labour, it's my hobby and I'd be doing it regardless of costs.

On the ona stuff. If your room is never opened and you never take your plants out you don't need anything other than the carbon filter. Of course, shit happens and you'll open the area, unless you have spaces within your grow area to also hang, trim etc. you'll end up brining plants out of the tent/room at some point. That's where the Ona comes in handy. I trim/chop in the basement in the open are where I have lots of space. That's when I open my bucket and a couple of hours later smell's gone. Nowhere near my grow area, I just keep a bucket in the basement area I use for trimming and open it when I'm working on plants outside the room. I use like 2 buckets a year and it keeps the smell at bay, cheap insurance and no questions about "that smell".