Grams per watt vs grams per square meter

Basic Growing Info
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#1

What is the difference?

Grams per watt tells you the amount of dried cleaned material you can get from any lighting combination. Simply add all the watts and divide the total amount of dried material to get your G.P.W. Grams per watt is important if you have to worry about electricity costs.

Grams per square meter is the amount of dried material you can harvest from a 1m x 1m space. When breeders use this term in their descriptions it gives me a idea of what I can expect from a strain.

A issue I have constantly is plant layout in a large room.
-How is the most efficient way to set up a room to achieve maximum g.p.s.m? The question is so dynamic that it can only be answered by defining the projected plant height style etc. For example my rooms next set up, I will have stationary buckets so I will need to have 2 isles to be able to attend the plants. (I am going to try a room with rolling tables soon) my isles are 2 feet wide and I have two of them. I use netting and train the plants toward the isle to maximize space.

My isles are full of light and take up area. Lets say that I wanted to total my g.p.s.m how would I do it in a large room?
Would it be

LxW/dried mass

or LxW- area of passageways/ dried mass??? :thinking:

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2018 light efficiency ultimate battle
#2

Over,…many moons shall we say I have consistently yielded more per “square foot” than my friends or others. A rectangular room was best and you stager pots down both sides and grow across the width. Plant grows up, tie down, continue until flowering begins and if down right every branch will be a huge cola, no magic, simple.planning. As always, the more light power you have the better so my retaliatory question :stuck_out_tongue: is if it comes down to lights, power, energy saving and heat are ceramic metal halides the answer OR LED’s??? :smile:

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#3

They just released a Double Ended Ceramic Metal Halide that I am waiting to test an see how it compares to a standard CMH.

I would rather pay more electricity and have a better quality product:stuck_out_tongue_winking_eye: It is a joke

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#4

Salutations Viva_Mexico,

My input is purely hypothetical. Lets assume the blue/red spectrums invert while space vanishes gradually around growing plants, as illustrated schematically below:

Does it have to be rectangular at all? Why not surround each cell with 3 lamps only instead of 4, with each triangle side being shared with other similar cells around? E.G. 3 lamps for 1 cell/unit/plant, 4 lamps for 2, 5 lamps for 3, etc.

Then, how might this affect the g/W count, comparatively to a cartesian layout?..

…

Good day, have fun!! :peace:

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#5

I have done hydro circles before. One vertical bulb in the center with the same distance from the bulb to each ebb and grow bucket.

If I had a cool animation I would ad it here. :point_down:

cool animation

with led lights and and some hid lighting you can do that. I just ordered a new lighting controller that has soft start with sunup and sundown that I will have start on one side of the room and finish on the other side as they gradually increase in brightness. This round I will be supplementing with Cmh to see how it compares to pure de hps.

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#6

I have used the Gavita controller before. I like the sun up sun down option.

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#7

We’ve used so many 1000 watt super metal halides way back we blew the lines off the mainline and the transformer blew up. I witnessed it walking the dog. Have you ever heard hydro wires sing, run,…so, yea, power “was” everything but not now. I think the issue is LED’s need more lights than ceramic metal halides footprint.

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#8

I don’t believe it matters which metric you use as long as you improve with every harvest.

The trays on trolleys is a good idea then you can cut down the amount of walkways to 1.

Another idea is to drop down some ‘walls’ next to the lights closest to the walkways so that minimal light spills out from your grow area onto your walkway and the maximum photons can be used as they were intended.

The metric I use to measure against my own grows is grams per square metre per day.

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#9

LED guys use umoles per square meter per second.
How about grams per square meter per kilowatt hour?
Not easy to calculate like grams per watt.

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#10

Something like that is whats needed. Grams/watt and grams/sq Meter both on ly tell part of the story.

You have to have enough light or it wont matter how large your room is. At the same time, a super bright light in a super small space wont work well either.

I think it would be much better to combine the metrics in some way like you suggest. It could probably be simplfied down to grams/watt/sq meter. Thats going to make for small numbers, so you probably need to have a multiplier in there - maybe times 100.

Another alternative would be to use both at the same time in some way. Maybe add them together or multiply them for a combined total? I lean towards adding them together. if your grams/watt is hi but your grams / sq meter is low, you didnt do as well as you could have. You had good growth for the amount of light, but poor use of space. The total will reflect that - maybe. Im slightly buzzed, so my math skills are not at their best :smiley:

The problem is, the two different “standards” have become “the agreed upon way to do it”. You’re going to have a very up-hill battle convincing everyone to change over to a new system :slight_smile:

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#11

We LED growers are very aware of what our gram per watt is :sunglasses:… I’ve seen some amazing numbers being grown with LEDs in the last year… blows away most anything or anyone I’ve seen using HPS on product per watt bases… so good that the LEDs are producing more product than HPS on a per square meter bases as well… we are getting a superior product as well.

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#12

YES exactly @reiko
An accurate equation has to include time.

for example; a 60-day SOG grower will have less gram per watt than one who’s growing 6’ trees with a long vegetative stage. But that doesn’t mean they were less efficient with electricity.

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#13

Salutations again Viva_Mexico,

Hummm… I should have added a legend i guess. Maybe next time, when the opportunity repeats once more.

Good day, have fun!! :peace:

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#14

wow :sunglasses::sunglasses:

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#15

Yes! Time is the missing element. Thank you for pointing that out. I knew he was onto something but you made it clear :smiley:

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#16

measure them all … grams per watt, grams per sqf, grams per kwh, and grams per kwh per sqf. could also chart out your room on paper and record stats for each individual plant, table, light, quadrant or whatever you like.

growmau5 season 3 results were 1.52 g/w, 20 g/sqf, 2 g/kwh, and 0.1 g/kwh/sqf

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#17

I’m pleased to read the time’s injection (wich is crucial imho) in the equation, to judge the productivity off course. But also the cost ! During all the life of the plant, you use nutrients, electricity, your own time, mediums etc …

I’m personnally always extrapolating on a year the stats (for real, a “breeding-software” do that for me lol), the variations are more easy to judge when it can be tricky to do that on a single session then compare with offspring of the same direct line (by example).

To stay on the subject, there is my habits :

  • For SOG style i use the grammer/sqm and aside i note the maximum number of specimens/sqm than the strain can handle. You can do pretty dense SOG with jack herer and all strains than produce “baseball bats” flowers, and outperform with ease the breeder’s datas. Not the case of a vintage nothern light and all strains than grow with “side branching”, you’re forced to reduce the number of specimen to don’t increase drastically the cost per grammer (yield concentrated on the main cola and less sexy than a “tree grow” in term of cost ratio …)

  • For classic style (one month veg, one to twos gals medium) i use the grammer/specimen.

Then i take each ratio and i inject the watts inside. Not so critical in my case in term of costs but it give me an idea on how the line is eating lights.

example with the same line :

  • Lets say i’ve a net dry 20gr/clone in SOG with 30 specimens, wich give 600gr/sqm, 70 days from scratch (total) with 0.5 Kw/sqm
  • And a net dry 300gr/specimen in classic with 5 specimens per sqm (wich give 1.5K/sqm), 120 days from scratch (total) with 0.5 Kw/sqm

In the first case, “each day” will be worth ~8.5gr/sqm/0.5Kw and in the second ~12.5gr/sqm/0.5Kw.
But the first case cost only 720 hours (elec, nutrients, human time etc ) and the second 1680 hours [720(veg)+960(flo)]

The line react in tree mode with a +47% pure yield, but cost +133% more to produce. In this vein, i will choose for this line the SOG way.

In another hand i’ve a zamal hybrid than totally reverse this (real) example in costing more in SOG than in tree mode (because the low yield in SOG make the grammer very expensive without so much difference in the total time in the crop).

I’ve ignored the gr/watts intentionnally because i use it to judge the plants more than anything else, but it stay a cost and with sodium’s crop it will barely lead the price of a weed.

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#18

Hahahaha nice! I was at a friends house once when the power lines coming from the street that passed over the garage started to short, caught the garage roof on fire, snapped in two and the live half of the wire was laying in the street. I had to go move it so nobody would get hurt.

#19

Thats great! What kind of averages would a led grower get in Grams per square meter?

Yes, I use a 1 year time period for my average.

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#20

Im running a SOG now. 6” pots, 4pots/sq ft.
Vegged clones 2-3 weeks.
4x8 room. 2x 600W hps and 1x 315W cmh.(1515watts)
8 diff phenos/strains
So far ive harvested 32 clones, trimmed about a dozen but only 2 phenos. Yield so far is 8-12g/clone.

If I average 10g/clone I will pull pull 1200grams whats ch equals about 0.8g/watt.
Or ~40g/sq ft (~400g/sq metre)

The next 56 clones vegged about a week long nger, hoping to pull 14g/clone on those ones to get the average up.
If I used only the best yielding clones for SOG im pretty sure I could pull ~1.5g/watt

Shot of how i access them- drip trays on casters.

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