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 Home Brew Forums > How do you measure efficiency?
04-20-2010, 03:51 AM   #1
earwig
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 How do you measure efficiency?

Can someone explain how to measure efficiency? I cannot find anything that actually explains the method on how to measure efficiency.

Thanks.

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04-20-2010, 04:41 AM   #2
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There's a ton of explanations out there including the wiki page that goes into great detail.

But the easiest answer is this: If you know what your gravity should be (either from software or kit instructions or looking it up) you can measure your gravity and divide it by what you're supposed to get.

i.e If you're supposed to get 1.069 (theoretical maximum, best case scenario yield) but you physically measure 1.062 then you do the math: 1.062/1.069, or 62/69 which equals 0.89 and when you make this a percentage 0.89X100 = 89% which would be your efficiency.

Now if you measure your gravity when all wort is in your pot and before the boil and then do your calculation, this is called your measured efficiency.

If you measure gravity after boil is complete and when you dump into cooled fermenter and then calculate, this is called your brewhouse efficiency since it takes into account all of your individual brew equipment steps into the process.

Hope this helps!

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04-20-2010, 05:17 AM   #3
earwig
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That helps a lot! Which is considered more accurate, before or after boil?
Thanks again.

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04-20-2010, 07:28 AM   #4
SPLASTiK
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04-20-2010, 09:57 AM   #5
duffman2
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It's not as much a matter of accuracy as it is consistency. If you can dial down your efficiency then you know how to adjust your grain bill accordingly (add more/less grain per brew). If you have great efficiency you can buy less grain. If not, no biggie, but you'll know your brewing process better

Cheers

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04-20-2010, 02:37 PM   #6
WickedLB
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Quote:
 Originally Posted by earwig That helps a lot! Which is considered more accurate, before or after boil? Thanks again.
If you measure after the boil you are not going to get an accurate measurement.

To use more specific numbers, lets say you want to make a SMaSH using 10 pounds of 2-row pale ale malt and you want a preboil volume of 7 gallons.

The maximum yield of 2-row is 38 points/pound/gallon (see John Palmer) so that means the highest pre-boil gravity you get is:

1.054 = (10 pounds * 38 p/p/g / 7 gallons)

Now if you end up with an actual pre-boil volume of 1.042 then your efficiency is:

1.042/1.054 = 78%

Your beer gravity will still be higher because you will concentrate the wort in the boil. If you go down to 5.5 gallons you will end up with 1.053.

My point here is that if you calculate efficiency AFTER the boil, you would be getting 98% efficiency (1.053/1.054) which is WAY off.

To really calculate efficiency you need to know exact volumes.

Hope that helps a bit.
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04-20-2010, 02:53 PM   #7
earwig
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Thanks again for the replies, they DID help.

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04-20-2010, 04:26 PM   #8
nebben
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If it wasn't obvious already, efficiency only applies when you are doing an all grain batch or a partial mash batch. Extract batches are already 100% efficient in theory since if you want 1.070 SG, you can dial it in exactly by measuring the weight of your extract added.

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04-20-2010, 06:36 PM   #9
dcp27
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Quote:
 Originally Posted by WickedLB My point here is that if you calculate efficiency AFTER the boil, you would be getting 98% efficiency (1.053/1.054) which is WAY off.
Just a correction, those pre- and post-boil efficiencies are the same since the max would now be 1.069, not 1.054.

Quote:
 Originally Posted by earwig Which is considered more accurate, before or after boil? .
Whichever time you have the most accurate volume and the wort is sufficiently mixed. Ideally, you should check it pre-boil though so you know if you need to add extract, sugar, etc to make up for bad numbers.
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04-20-2010, 06:44 PM   #10
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When I saw this thread I thought... good question. After looking at that Braukaiser link I think I need a review my college chemistry courses... yikes!

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