Brew House Efficiency of Double Bogey

By scot in Home Brewing on Wednesday, April 4th, 2012

brew house efficiency

I never check my efficiency when I brew from the ground up. What I mean is that I usually compare it to what the brew sheet says I should get (which I set at 72%). I am happy if I am close and/or above those marks. Not all that scientific. In my defense if I miss my gravity and the beer tastes good, does it matter? To a point, yes. I want to understand why I am coming up short but at least the beer is good.

To figure out the efficiency, I first tried an online calculator: it would/should be quick and simple. I didn’t believe the numbers it returned (turns out it was wrong but then again my calculations below could be wrong), there had to be another way. Of course a search of the net produced tons of results with the first couple being from places I had been in the past. The first is a link to John Palmers’ online version of his book: How To Brew. The page highlights how to do manual calculations of the mash efficiency. Unfortunately those calculations cannot be one without know the amount of potential sugars your grain will add in one pound increments. Beer Smith has that information.

The two combined gave me enough to do my calculations. The calculation is simple, having three values:

  • Formula: PS x G# / WV
  • PS – Potential sugar contributed per pound
  • G# – Pounds of grain in the beer for that particular grain
  • WV – Volume of wort collected

Below is the grains I used and the calculations for each grain.
2Row 36 x 25.0 / 8.25 = 109.1
Roasted Barley 25 x 1.50 / 8.25 = 4.5
Chocolate 28 x 0.75 / 8.25 = 2.5
Special B 30 x 0.75 / 8.25 = 2.7
Crystal 120 33 x 0.50 / 8.25 = 2.0
Wheat 40 x 0.50 / 8.25 = 2.4
Flaked Oats 37 x 0.25 / 8.25 = 1.1

Total 124.3 (number of potential gravity points contributed if efficiency was 100%)

I actually achieved a starting gravity of 1.098 or, for the case of these calculations, 98. Now it is easy to divide the starting gravity achieved by the possible gravity points:

98 / 124.3 = 78.8% efficiency

I think that is pretty good efficiency, especially for a large mash. This leads me to two last thoughts. One, did I make a mistake in my calculations? And, two, are the gravity readings I am taking off? I will continue to keep an eye on this and do these calculations until I see a pattern or more suspicion is raised. Enjoy!

Useless Fact: At birth barnacles look like water fleas. In the next stage of their development they have three eyes and twelve legs. In their third stage they have twenty-four legs and no eyes. Barnacles stay fastened to the same object for their entire lives.


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