How efficient is your grow?


Does anyone pay attention to this? How do you even measure?

I’m thinking it would be something like grams per square meter per kilowatt hour. Anyone see something better or different?


I am not sure about the square meter per kilowatt but I would be interested in figuring if I should set my lights in my room a different way, currently I have a mish mosh of lights, 5 LED total. I have them staggered to look like the 5 side on a dice. I have a 600W in the middle and the other 4 on either side, not sure what the other 4 are, maybe 300W from each light, I would have to check on that tomorrow. Also I would like to know how many plants can I put in my grow space. My grow room is 10x12 but I have a walk space around the entire room, so I might have an 8x10 grow space. Years ago I had 2 big Raptor HID lights, I grew 10 plants in 5 gallon buckets, they were monsters. I no longer use those lights and went to LED, I no longer grow in 5 gallon buckets, I have moved down to 4 gallon pots and 3 gallon pots, I am also growing Autos at the moment. I will be watching this post.


Hi @doodlebug and thanks for posting!

You’ll want to hang your lights however you feel they provide the best coverage. How many plants you run and spacing between plants will determine that. It’s best to tackle with an open mind. A lot of times growers will space their lights to their room size, but that makes little sense if you’re not using the edges of your room. You’ll want to space them so as to provide the best intensity to your plant canopy, sometimes this means being a little weak at the edges. It’s better to be weaker there than have potential weak spots in the center of your canopy where you should have the most hearty growth.

As far as number of plants, that depends solely on your growing method. If you choose a sea of green grow, you could easily fill that space with 6-8 plants on a long veg time. Or probably fit 100 a more if you’re using small pots. But your best bet would probably be somewhere in the middle.

Since that’s a lot of square footage, and you’re growing autos, have you considered maybe starting something like 3 plants a week? It’s a rough guess, but by my math, you should start to harvest about 3 per week about 10-12 weeks in. 30-36 plants would be a lot, but they should fit. Will also keep you from harvesting a ridiculous amount of plants at once. Keep in mind that 30+ plants is a lot to tend to, for anyone. So you may be better off starting with less and seeing where it takes you. But I figure 3 maximum would fill that space.


My goal would be 20 at any given time. Currently I have 8 ladies and just put 5 new seeds in Saturday. My room is pretty bright. I did the measure way when I hung the lights. I looked up how many feet each light should put off and I figured about 3x3 area each light and like I said, the 600W is smack in the middle.I don’t dseem to have an dark edges, the entire room seems to be bright Yes I would love to plant something every 3rd day, I didn’t think about that as I just put in those 5 seeds. Next time.


With normal LEDs you want 25-35 watts per ft². These are going to be true watts of course and not the advertised wattage on the box.

Normal LEDs haven’t been able to achieve what a normal HPS usually achieves, which by a professional grower can be up to a gram/watt, but new LED technology promises to change this. Chip On Board LEDs or COBs will bring LEDs to the next level of growth while changing what we pay on our electric bill per gram.

In the next 5 years, grow efficiency will reach a new level all together, so they say…:roll_eyes:


Out of curiosity, why are you trying to grow so many plants? you can get a slightly quicker turn around but have to work an awful lot, Especially in comparison to one large plant. I don’t know if your in a legal state or not, but if your not, then you need to know when cops are sitting around planning on who to bust, and they are looking through their papers at perpetrator X and you, and Perpetrator X has 10 small plants and you have one large one. The police don’t know the size of your plant, who do you think they are going to go after, the grower with ten or the grower with one. Plus the work that goes into taking care of one plant in comparison to taking care of 8 or 10 in the same FT2 is substantially different…



Great topic. Variables include electricity costs equipment costs water costs and harvest results.


I hadn’t really considered initial investment. But yeah I would say that it should be taken into consideration. If you’re growing even a small amount from recycled items that didn’t cost much or anything, I think that should be taken into account.


To be fair one would need to account for the cost of the space as well. My mortgage is X for so many square feet so one would have to figure that in as well. No?


I figure I am paying the mortgage whether or not a grow tent is in the basement.

I, too, would like a metric to go on to determine if I am using my space, lights, etc the best I can.

I have the numbers from my first grow. I will definitely be comparing how this grow goes as well. I have to figure in a time element to my overall calculation as well. Fewer plants, longer veg, more time invested, but nearly the same grow space as when I did 6 plants.


@Bogleg, if you had a home business, the square footage would be a tax deduction. If you bought or rented space to grow that would be an upfront cost. I think it should be noted as a fixed cost and broken out as a line item.


All good stuff! I’m with bogleg here @Myfriendis410. Unless you’re maybe renting/paying on a separate space or cash cropping. I suppose it really depends on what’s important to you. My thought behind this post was maybe start a conversation where different growing methods and/or grow room designs could be considered. All in all, a 4x4 tent has the same capabilities in a one bedroom apartment that it will have in a million dollar house. Calculating that cost would create an extremely biased result that wasn’t really the scope of my intentions.


Okay, I’m with you. It’s an interesting exercise!


No I disagree that would mean you need to justify being productive to offset the mortgage for EVERY sqft of the place. How good is your cooking? Good enough to justify the sqft of your kitchen which would add to the cost of making it (utilities and ingredients
So no. :stuck_out_tongue_winking_eye:


No no no. It’s a valid point. All @dbrn32 wants to track are consumable costs. As a former business owner I understand.

If you had a home business using your kitchen you for damned sure WOULD count the cost of the kitchen square footage! So my question wasn’t quite as stupid as you make out.

If you were growing cannabis for money as a business, the square footage would be factored. @Fever


Electricity is the biggest expense indoors. So, Grams/Watt would be the measure.


If we were talking about a business anywhere in this conversation I would not have even responded (as well as I did lol).


I disagree. My current light would run a long long time before I exceeded it’s cost in power consumption. Granted, I’m currently at $.06 kwh. If I spend $600 on a 300 watt light to exceed a gram per watt, that doesn’t automatically make me more efficient than someone pulling slightly less with a $100 light. But if I can do it in 5 square feet vs 9 square feet, that should count for something.

That situation won’t apply to everyone. But here’s one that will. You have 1000 watt hid in 4x4, use advanced nutrients, grow from seed, and pulls .8 gpw. Another grower grows in 3x3 with 300 watt led, uses gh nutes, grows from clone, and pulls a gram per watt.

Gram per watt is gram per watt right? But who yielded more per square foot? Who had highest cost per gram? Who had excess that their buddies may throw some cash for?

If you change any of those variables, one way can and will be ahead of another. Gram per watt will kinda sorta tell you how efficient your light is. But even that has potential to be easily skewed.


So yes the least amount of sqft might be advantageous for a quality of life perspective. More habitable space. Not sure how to measure that, and all the other funny implications that can be made about other areas in the dwelling and what fills up those spaces.


I have a history degree and this smells like calculus. But I wouldn’t know for sure. :slight_smile:

So we need to start with a basic calculation that combines cubic feet of occupied plant space, wattage of lights, and time required to equal N number of grams. The question is do any of those factors get weighted or could we do something like:

4x4x3 = 48 cubic feet
1000 actual watts
105 days

Yielded 280 grams.

For example.

Then you could do the other calculus functions for cost of space, watts consumed, and how much time it took to total cost up over the grow. You could get a a dollar per gram equation this way. Some how.

Let’s talk about The Battle of Agincourt or something instead…