I remember some people talking about grams per watt in a thread somewhere and usage overall came up. I now just ran into this. Thought it could be a good post to have. Copy and pasted,I take no credit.



GARDEN EFFICIENCY RATING - Online Calculator

How much juice you burn to grow a gram..

Standard methods of reporting garden yields are imprecise and don't take the factor of time into account. This is a summary after discussion on a new standard formula for reporting yields and efficiency.

The GE Rating is based on the amount of kilowatt hours used to produce one gram. This factors in how long your strains flower and the resulting number makes it simple to compare 4000 watt gardens with 400 watt gardens. The calculations are easy, here is an example:

2000 watt flowering area
60 days of flowering
12 hours on light cycle
total yield: 49.5 ounces

1) Divide the total wattage of your lamps by 1000 to determine the kilowatts per hour:

2000 / 1000 = 2 kw/h

2) Multiply the previous result by the hours of the light cycle (usually 12):

2 x 12 = 24

3) Multiply the previous result by total days in flowering to determine how many kilowatt hours you used:

24 x 60 = 1440

4) Make sure your yield is in grams, so:

28.4 x 49.5 ounces = 1405.8 grams

5) Now simply divide grams by kilowatts:

1405.8 / 1440 =

0.97 grams per kilowatt hour, or a GE Rating of 0.97! Good job to the hypothetical grower, approaching a GE of 1 is the first plateau to be reached and is a sign of an experienced grower.

The secondary additions to the GE formula would be for the "Whole Garden GE Rating" which must include time spent in cloning and in veg. Figure it out the same way, with days spent under cloning lights, hours per day, and add those totals to the watt usage before dividing. This will give you a much lower rating than the standard Bloom GE Rating, but is more accurate for SCROG gardens, and anyone who is involved with extra vegetation time.

this is wonderful but I am a hillbilly that doesnt own a calculator. lol

Lol! I guess you broke your abacus too eh?

Does this mean my slide rule is obsolete ???

When one calculates grams per kilowatt hour, does one not also include the kilowatt hours used by all of the ancillary equipment involved, such as multiple fans, blowers, pumps, air conditioning, etc., in the equation?

This calculation includes the power that the lights alone use and leaves the rest out.

ahh very true 52 I should have added that, but you mentioned it for us! Thanks. In my personal calculations I did cause of curiosity awhile ago, I have all my fans and exhausts added in my equasions.(382 watts going basicly 24/7, Nothing too huge)

Defintely takes abit of figuring out If you want to try and see what you're spending! Always good knowledge to have in hindsight. For me I want to see how well my 600w lights do vs 1000w, It was a bold move for me switching, spent a good 750$ on digi 600 ballasts >.< I can tell already with my past energy bill, Glad I made the switch over.