GPW Vs Gram per KWH

[Vadim]

I've seen many discussions, brags and harvest posts about GPW. The problem with a straight GPW reference it doesn't take into consideration time, so it's hard to compare what's real or not. Some grows go for say 10 weeks whilst others might in fact be 4 months. However if we used Gram per Kilowatt Hour then that would be more a comparative analysis than the straight GPW model used. I realise it's a little more difficult to calculate but in reality not that difficult:

• "Light KWH draw" x hours/day on (This for photo's would need Veg and Flower calcs)
• "Fans KWH draw" x hours/day on
• "Inlet/outlet exhaust draw" x hours/day on
• "Heater/cooler KWH draw" x hours/day on
• Add them up for total KWH consumed and divide into Harvest Total

Example:

• Light - 0.63KWH x 18hrs x 90 days = 1020.6KWH
• Light - 0.63KWH x 12hrs x 70 days = 529.2KWH
• Fans - 0.2KWH x 24hrs x 160 days = 768KWH
• Inlet/outlet exhaust draw - 0.35KWH x 24hrs x 160 days = 1344KWH
• Heater - 0.9KWH x 12hrs x 160 days = 1728KWH
• Total = 5389.8KWH Consumed
• Harvest example = 600grams
• GPKWH = 0.1113

Wouldn't this provide a better comparison of input to output? It would also keep one very mindful as to what is the most efficient light type. We then have other factors like substrate, nutes, room/tent type. However IMO, this would enable growers to really determine the absolute best method from a weight to cost which could also then include all the costs of grow room, lights, fans etc etc. Could even do a GP$. Mmm, best have another and ponder this!

Just a thought!

 

[Marzbadrock]

Yes, I actually argued this point years ago on a separate thread. I was figuring gram per watt, per day, per sq ft.

 

[Vadim]

Yes, I actually argued this point years ago on a separate thread. I was figuring gram per watt, per day, per sq ft.

Yep, that'd work too.

 

[gr865]

It's all a gift from the God's!
It is still cheaper and the product is better than buying recreational.

 

[Dan Dark]

I appreciate the engineering brains here. More of an artist I prefer to know my ladies, I name them, baby them (yes, probably too much). Sometimes I keep plants that look like shit just because I like them. I clone, use seeds and trade genetics all I can because the art of growing is what floats my boat.

Thank said, thank you engineers for the learning that supports my more fluid and organic thinking!

 

[Heraldo]

I bet a lot of us nerd out with the numbers and stats.
I just plug in a electricity usage monitor, keep track of how much I spent on "hardware" (soil, nutes, etc.) and duration of the grow.
The only practical aplication I have for the resulting numbers is to get less bummed out when I have a bad harvest.

 

[Weaselcracker]

It does make sense to count the time, and the electricity, and all the costs of the equipment, and all that....if you’re going to go all out.
I’ve seen a lot of different propositions on the forum for reworking the ol grams per watt formula. Probably the easiest is what Graytail does -grams per day.
Something like that can be handy in your own grow for some way to compare harvests to each other, Or just for fun. Personally I just go by eye and rarely ever weigh anything before smoking it.

But no matter what you do it’s always a bit subjective. If I get 1 gram per watt on a good run, somebody else comes along and says they got 1.5 grams per watt.

1.5 grams of what though?

 

[NorthernCosmos]

Wouldn't this provide a better comparison of input to output?

Been thinking the same thing, and yes, of course it would. The total energy put in tells it all, whereas instantaneous energy used tells a lot less in a cost analysis.

(BTW, I take it you mean mean e.g. "Light - 0.63kW x 18hrs x 90 days = 1020.6kWh" - sorry, don't mean to nitpick, but units are important, or your spacecraft WILL get lost or crash...)

 

[Auggie]

Legal commercial grows have been using metrics to analyse output since the beginnng.
You should see the spreadsheets I have to use, populate and monitor.

We follow closely:
- weight divided by the sum of cost of electricity from public utility plus cost of generators including depreciation
- weight divided by total cost of labor including all benefits

Plus about fifteen other metrics.
When one metric goes off the tracks, it can be a leading indicator of trouble and save a lot of grief down the road.

Just a quick rule of thumb, I think of lbs per light.
I like to see 2+ lbs per 1000 watt light - meets expectations.
I have gotten as much as 3 lbs per 1000 watt light - and 'the third floor' smiled upon me.
And, embarrassingly, as low as 1.2 lbs. (third floor was ominously quiet)

 

[bobrown14]

Interesting to see folks starting to finally "get it".

The weight/time is one factor.

The most important factor "to me" is quality which is much more subjective.

How do we measure quality with science?

"I vegged my plant for 8 months and killed it, I got a pound off 1 plant." Meh...

Another metric besides time and weight is space.

Then there's me I grow with solar power indoors so my KWH thing blows all the calculations outta the water. I do pay some electric (geothermal heating to go with).

I wood think the fact that I can grow with lighting and its almost no cost to me throws a wrench in the calculations.

 

[Auggie]

The weight/time is one factor.

Yea, that's another thing that we monitor.
We turn a room every 60 days.
I know, I know ... that's not enough.

But ... If you turn a room in 60 days and get 25 lbs, or wait 70 days and get 27 lbs, or wait 80 days and get 30. Which should you do?

Answer: It depends on your goal. Is the goal to satisfy a specific customer who wants it cut early? Are they willing to pay for that special order? It is to maximize profits on a yearly basis? Doing a harvest every 60 days gets one more harvest per year than if you do it at 80 days. Is that one extra harvest worth more than the extra weight for the longer harvest time?
It's all metrics. And having a clear 'mission'.

The most important factor "to me" is quality which is much more subjective.

Right.
And that's where 'customer satisfaction' comes in. Everybody is different, we all have different tastes - that's why they paint cars different colors.
Know your customer. Ask them what they want, and if they're unreasonable, then you know you have a customer that your competition needs.