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**OldManGrower** · 02-12-2023, 01:43 PM

Ok, interesting question. I will bore you with my own ideas and welcome all any other viewpoints. Firstly on LST, the answer is yes you will increase your yields significantly. However, I do not know how the 25% increase number was derived. Secondly, a one gram per watt yield is my holy grail. I have yet to achieve it but I'm working hard on it. More light does equal higher yield to a certain point, then it, like most things can become harmful. It doesn't make sense to have a very large light if you have to keep it dimmed. You are paying for unusable watts.

**bboyfromwayback** · 02-12-2023, 01:59 PM

1g per watt should be your goal regardless of the type of light you’re using. If you over achieve great, just don’t buy into the manufacturer’s description when they say 2-3g per watt. They’re lying to sell their product.

**Franklin** · 02-12-2023, 03:56 PM

The grams per watt, in my view, doesn't mean anything without also knowing the length of time the plants were growing. If someone grew one gram per watt in three months it is certainly better than 1.2 g per watt in 5 months. I think we need some sort of standardization like gram per watt per day growing or something. LST will get you closer to a gram for a watt only because it creates a bushier plant, but it takes a lot longer, you could get roughly the same effect in a sea of green without any LST and it would be much faster

**AGH** · 02-15-2023, 02:09 PM

I think there is a difference (and a balance between) yield and efficiency and as growers, we all get to decide the balance between them. The measurement of grams per watt is more of a general rule of thumb comparison for different kinds of lights.

You can measure yield as the total grams per watt of the fixture. This is a pretty easy way of doing it and it factors only the final harvest compared to the strength of the fixture.

However, if you want to measure a Cost of your grow, aka efficiency, you would need to add the total amount of electricity used for the entire grow. You could limit this to just lights, but to truly measure the cost per gram, you would want to take into account your lights, exhaust fans, circulation fans, as well as any heaters or dehumidifiers that might be used to control the environment depending on how detailed you want to be.

With the above distinctions, if cost of electricity doesn't matter, you could veg until your tent is completely full by using LST and other training techniques. Different training techniques temporarily slow growth for different amounts of time (depending on technique used, strain, and 'art' of the grower) which will add days or weeks to the vegetative stage. This adds to the final harvest (up to a point) but also adds costs since you extend the amount of time you're using lights, fans, etc.

So really, they're two different measurements that measure two different outcomes. If one is looking to grow larger harvests, it takes time. While that increases grams/watt at the end of the grow, it may not be the most efficient (total grams/total amount of electricity used). If one is looking to be efficient with energy use, you might settle for a lower final yield grams/watt.

Here is a great calculator where you can play around with different lengths of time in veg to see the difference in costs: https://www.growweedeasy.com/electri...owing-cannabis

Using the above calculator at the default settings and not adding in the cost of anything other than lights, adding a week of veg at 18/6 adds an extra $1.50 per 100w of light.

Really, it all boils down to the different goals of different growers. Some may say the extra time in veg (with the goal of increasing yields) is worth the electricity costs. Whereas others may find that a few extra grams (or more) isn't worth the extra time paying for electricity.

In your case, if you can increase your yield by 25% (using the numbers you mentioned) and assuming that most LST will add an extra week or two (let's assume somewhere in the middle - 1.5 weeks) then:

Your lights are total 350w (if I'm reading your original post correctly)
Previous yields with NO LST: 690g
Expected yield with LST: 690*1.25 = 863 which is an additional 173g
Extra cost for lights for extra 10 days (assuming defaults in above calculator): $8.32
This means that the extra cost per extra gram is $8.32/173g = $0.05 per gram

Now this is leaving out all the extra electrical devices so it's not REALLY only 5 cents per gram, but even if you quadruple the cost, 20 cents per gram seems pretty worth it. Now these are based on several assumptions, namely that without LST you get 690g and with LST you get a 25% increase in yields and that it delays the flip to flower by 10 days. But you can see that LST is often worth it.

Let's see if it were only a 10% increase in yields:

Additional yield (based on 690g with no LST): 69g
Additional cost: $8.32
Extra cost per gram: 12 cents

Again, even quadrupling that cost it's less than 50 cents per additional gram achieved by LST.

The above math is why many growers who aren't in a rush to get to harvest often use some sort of training to increase yields. While it does increase total time and total electricity and costs, the additional yields are very worth it when broken down by cost.

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