Brewhouse efficiency standard deviation, low, high, average

[max384]

I'm a bit of a nerd and keep track of my brewing on an Excel spreadsheet. I've brewed about 50 batches since I decided to start an Excel spreadsheet. I just did an analysis and found that my brewhouse efficiencies:
High: 87%
Low: 70%
Average: 79%
Standard Deviation: 5%


Anyone else keep track of these statistics? Care to share?

I wish my efficiency was more consistent... But I do find that if I rebrew a recipe, I'm usually within 1 maybe 2% of the efficiency of the other one. I wonder if it varies so much because I brew so many different styles with such vastly different OGs?

 

[IslandLizard]

How about grouping them by gravity range and see if the SD is closer to your 2%? I'm sure it helps to get the tails in check. Try with 3 or 5 gravity ranges.

 

[max384]

How about grouping them by gravity range and see if the SD is closer to your 2%? I'm sure it helps to get the tails in check. Try with 3 or 5 gravity ranges.

This is a great idea. I don't know if I have enough data points, but I'll run some numbers and get back to you.

 

[dmtaylor]

I have oodles of data on all my batches (at least 60 or 70). I'll be back when I can get to my real computer.

 

[max384]

Okay, when I group them by OG I get:

<1.050: avg 80.1, stdv 6.4, hi 87, lo 70

1.050-1.059: avg 78.9, stdv 4.0, hi 86, lo 72

1.060-1.069: avg 79.8, stdv 3.2, hi 84, lo 76

&#8805;1.070: avg 78.0, stdv 4.2, hi 83, lo 74

 

[brewcat]

I wonder if it varies so much because I brew so many different styles with such vastly different OGs?

Probably efficiency of different grains.

 

[IslandLizard]

Okay, when I group them by OG I get:

<1.050: avg 80.1, stdv 6.4, hi 87, lo 70

1.050-1.059: avg 78.9, stdv 4.0, hi 86, lo 72

1.060-1.069: avg 79.8, stdv 3.2, hi 84, lo 76

&#8805;1.070: avg 78.0, stdv 4.2, hi 83, lo 74

Very interesting to see all 4 groups have an average within 2.1% efficiency of each other. And as expected the lowest and highest gravity ranges show the largest difference, but relatively smaller than we would expect. Could have something to do with number of data points.

I'd say your efficiency is nicely predictable except for the lowest gravity range, which shows the largest spread with deviation over 5%.

 

[max384]

Very interesting to see all 4 groups have an average within 2.1% efficiency of each other. And as expected the lowest and highest gravity ranges show the largest difference, but relatively smaller than we would expect. Could have something to do with number of data points.

I'd say your efficiency is nicely predictable except for the lowest gravity range, which shows the largest spread with deviation over 5%.

I went back and looked further, and it seems as though my efficiency with wheat beers are always low 70s. And these are always sub 1.050 OG. If I exclude the wheat beers in that category, my average is 83.7 with a standard deviation of 4.2.

It appears that @brewcat is correct in that different grains have different efficiencies. I never really heard of wheat having lower efficiency... But it sure does for me. Hmm.

 

[Oginme]

Very interesting to see all 4 groups have an average within 2.1% efficiency of each other. And as expected the lowest and highest gravity ranges show the largest difference, but relatively smaller than we would expect. Could have something to do with number of data points.

I'd say your efficiency is nicely predictable except for the lowest gravity range, which shows the largest spread with deviation over 5%.

What is the number of observations for each of the ranges listed? With the standard deviations for each subset and the averages being so close, I would guess that the averages are not statistically different from each other.

 

[doug293cz]

I went back and looked further, and it seems as though my efficiency with wheat beers are always low 70s. And these are always sub 1.050 OG. If I exclude the wheat beers in that category, my average is 83.7 with a standard deviation of 4.2.

It appears that @brewcat is correct in that different grains have different efficiencies. I never really heard of wheat having lower efficiency... But it sure does for me. Hmm.

I believe wheat has a smaller kernel size than barley, so needs to be crushed at a smaller mill gap to get a good crush. Do you crush your wheat finer than your barley? If not, that may explain your lower efficiency with grain bills heavy on wheat. The lower efficiency would be due to lower conversion efficiency (mash efficiency = conversion efficiency * lauter efficiency.)

Brew on

 

[dmtaylor]

Okay, I'm back as promised.

Following is a graph of my efficiency out of 59 all-grain batches. You can see that my efficiency was mediocre when I first started out many years ago and has since leveled off and even reduced slightly because I have a concern that too high of efficiency can reduce malt flavor, so I actually opened the gap on my mill when my average efficiency approached 90%. By opening my mill gap, my average efficiency immediately dropped by about 8%, from about 90% to about 82%. I guess you could say that I have the ability to dial in my efficiency wherever I want, within reason. Also included on the graph is the sum of gravity points and efficiency for each batch, which I find to be almost constant. After the graph, see a table that shows the non-constant "constant" and efficiency that I will typically achieve for any given goal OG. I use this table for every single batch and with it I am able to nail my OG every time within a couple gravity points. Questions? Ask and maybe I'll answer.

OG, Efficiency, Sum OG + Efficiency
1.045 86 131
1.050 84 134
1.055 82 137
1.060 79 139
1.065 76 141
1.070 72 142
1.075 68 143
1.080 63 143
1.085 58 143

By the way..... I notice no difference in efficiency using this table when brewing wheat or rye beers. With an adequate crush, you should get a good enough crush of smaller wheat kernels and still achieve good efficiency and be able to ignore the grain type as a variable. If you see big swings with wheat, you really should crush harder / set the mill gap tighter.

 

[IslandLizard]

I believe wheat has a smaller kernel size than barley, so needs to be crushed at a smaller mill gap to get a good crush. Do you crush your wheat finer than your barley? If not, that may explain your lower efficiency with grain bills heavy on wheat. The lower efficiency would be due to lower conversion efficiency (mash efficiency = conversion efficiency * lauter efficiency.)

Brew on

Absolutely this ^

Wheat and rye have indeed much smaller kernels than barley, and you definitely need to set the gap narrow enough to crush them, or most will simply pass through. On my MM2 (1.5" rollers) 0.026" is about the maximum for those size kernels. I also run my flaked goods through that gap. Barley gets crushed at 0.032-0.034". Mash efficiency is around 85%.

I don't have any exact data, but my 50-60% wheat beers have the same efficiency as those with all or mostly barley. That is, if I wait long enough to lauter the tun dry. I always do 2 batch sparges of equal volume. W/G ratio 1.33-1.50.