Brewhouse efficiency is a term that causes some confusion for first time all grain brewers. I previously covered how to improve your brewhouse efficiency, but we frequently see questions on our discusssion forum from brewers who don’t understand what brewhouse efficiency is or how it is used in recipe design.
Brewhouse efficiency is defined as the percent of potential grain sugars that are converted into sugar in the wort. Typically this includes losses for a given brewing setup, and these losses are taken in aggregate rather than accumulated individually. It is therefore a measure of the overall efficiency of your brewing system.
Brewhouse efficiency is a key input when designing all grain recipes, as it determines your estimated original gravity. If you don’t have an accurate brewhouse efficiency number for your particular equipment, your original gravity estimates will be way off and you will miss your target gravity.
Every grain in an all grain recipe has a potential yield, listed as the dry grain fine yield on the malt sheet. The dry grain yield is determined in laboratory conditions, by powdering the grain and extracting as much as possible and then extracting maximum potential from the sample. Yields vary from 50%-87% depending on the type of grain used. You can also express yield as a potential such as 1.038.
The actual brewhouse efficiency is measured for an entire system. Unlike the dry grain yield or potential measured in a lab, real brewers achieve only a percentage of the ideal number due to real considerations such as efficiency of the mashing process, and losses due to boiling, deadspace or trub. This percentage of the potential, as measured across the whole system into the fermenter, is the brewhouse efficiency.
A related term is mash efficiency. Unlike brewhouse efficiency, mash efficiency measures only the efficiency of the mash and sparging steps. Mash efficiency can be through of as the percent of potential fermentables extracted during the mashing process that actually make it into the boiler.
Programs such as BeerSmith will calculate the brewhouse efficiency from a given recipe, volume and original gravity. However it is important to understand what’s going on under the hood. Lets look first at how to calculate the total potential of the grain for a batch of beer:
(potential_pts) = (grain_pts) * (weight lbs) / volume_gals
Each grain has a dry grain potential, which you can find from our grain listing or from the malter’s web site. The grain_pts is calculated from the grain potential by subtracting 1.000 and multiplying by 1000. For example, a grain with a potential of 1.035 becomes simply 35 points. 5 pounds of this grain in a 5 gallon batch would add 35*5/5 = 35 potential points to the beer. If we sum all of the potential points from the various grain additions we can get the overall potential. If we had no losses in the system, the 35 points above would give an ideal starting gravity for our beer of 1.035.
I mentioned that the potential points represents the gravity under ideal conditions. In practice one gets much less than this, usually around 70-80% for brewhouse efficiency overall. Therefore the actual original gravity is determined by the potential points times the gravity:
(batch_pts) = (potential_pts) * (brewhouse efficiency)
So if we consider a recipe with 40 potential points, and a 75% brewhouse efficiency we get 30 batch points or an original gravity of 1.030. This is how original gravity is estimated.
Reversing the calculation we can calculate the efficiency from an ideal recipe potential estimate (potential_pts) and actual measurement (measured_pts).
(efficiency) = (measured_pts) / (potential_pts)
So for example if we had a recipe with potential_pts of 80 and measured the wort into the fermenter 1.050 we get an efficiency of 50/80 = 62.5%. Note that this assumes we hit our target volume. If we don’t, we need to consider the target and actual volume as follows:
(efficiency) = (measured_pts * actual_vol) / (potential_pts * target_vol)
The formulas above give us the overall brewhouse efficiency, but can also be used to calculate the mash efficiency into the boiler. For efficiency into the boiler we simply use the boiler volume and measured boil specific gravity into the boiler as opposed to the fermenter. In BeerSmith you can click on the “brewhouse efficiency” button in any open recipe to perform more detailed mash or overall efficiency calculations.
Now you know how to calculate the two key all grain efficiencies: brewhouse and mash efficiency. For additional reading, consider our article on improving all grain efficiency.
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