What does efficiency mean in brewing?
Brewers often talk about efficiency on brew day. In most cases, this is about how much beer you actually get out of the raw ingredients. Now, let's take a closer look at the terms we use when talking about efficiency in brewing.
The sugar content, i.e., the starch, in the grain is constant, and it is this sugar that you want to extract from the malt. In short, efficiency is a term that defines the concentration of sugar in the wort, compared to the constant amount of sugar in the malt.
Now we will take a deeper dive into the two most important concepts used when measuring efficiency: mash efficiency and brewhouse efficiency.
Mash efficiency
All malt for brewing contains a specific amount of sugar that you can potentially extract. This figure is what we refer to as 100%, and it can vary between different malt types. Here you can see an overview of the potential of various malt types. Neither homebrewers nor professional breweries will be able to extract absolutely all the sugar from the malt, and we use the amount you have actually extracted to calculate mash efficiency.
For an average homebrewer, mash efficiency will be around 75 to 80%. This figure tells you what percentage of sugar you have extracted from the malt.
Measuring efficiency
To measure mash efficiency, this must be measured after mashing and sparging. Stir the wort thoroughly, so that any sugar that has settled at the bottom of the brew kettle mixes well with the rest and gives a correct reading. Take a sample from this and cool it down to room temperature, before measuring with a hydrometer or refractometer.
This is pre-boil gravity (also called SG or Specific Gravity), and shows how much sugar you have in the wort before boiling. With this figure, we can calculate the mash efficiency. To make this simple, the calculation is integrated into programs such as Brewfather or calculators like the Brewhouse Efficiency Calculator from Brewer's Friend, where you select "Efficiency For: Conversion".
Brewhouse efficiency
Now that we know what mash efficiency means, we can move on to brewhouse efficiency.
If, in addition to looking at how much sugar we have extracted from the malt, we also count other places where wort is lost on its way to the fermenter, we can calculate brewhouse efficiency. This includes how much is lost at the bottom of the brew kettle, absorption by hops and trub (more hops bind more liquid), evaporation during boiling, and wort that, for example, remains in hoses when transferring to the fermenter.
Brewhouse efficiency, in other words, is the unit of measurement used to describe how much you actually end up with from the raw ingredients, and how much has been lost along the way. If you use Brewfather or similar programs, this will be calculated automatically for you when you enter the OG (Original Gravity) and the amount of beer you have in the fermenter.
What do we use efficiency calculations for?
For homebrewers, mash efficiency is perhaps the most important concept, because it tells you how much sugar you have actually extracted from the mashing process. OG plays a role in how much alcohol the finished product will end up with. If this figure is significantly lower than expected, something is wrong somewhere, and you might want to take a closer look at the process during mashing and sparging, and possibly water adjustment. How the grain is crushed is also important. If it's crushed too coarsely (many whole grains), you won't get access to the sugar in the malt. If it's crushed too finely, it can hinder good circulation in the mash (stuck mash). What is right varies from brewing setup to brewing setup, and we therefore recommend most people to have their own malt mill.
For most, mash efficiency is not the most important in practice, as long as it is consistent. In comparison, a commercial brewery will look more at brewhouse efficiency, since it's then about how much beer is actually produced on a brew day. While a homebrewer can easily add 5-10% extra malt to a brew without significant expense, a professional brewery that brews over 1000 liters at a time will see a dramatic increase in raw material costs if brewhouse efficiency is low.
If you really want to delve into this topic, we recommend How to brew by John Palmer or Malt: a practical guide from field to brewhouse by John Mallett.
