Efficiency vs. OG Questions

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Well-Known Member
Nov 20, 2012
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Hi All,

I had a nice brew day yesterday. I made the 5 gallon version of this Imperial Pumpkin Ale. It ended up smelling great, and the yeast is going nuts right now. Good stuff.

My question relates to efficiency vs. OG. I’m a fairly new AG brewer and I’m still tweaking my equipment. My last brew came in at 75% efficiency, which I was very happy with. However, my OG ended up significantly lower than expected (I didn’t boil off as much as I thought I was going to).

With yesterday’s brew, I used a different LHBS to crush my grains, and I believe the crush was quite different than my normal shop. Also, I assumed the mash was for 60 minutes, but the recipe made no mention. I think i should have mashed longer. I only ended up at ~62% efficiency, but I nailed my OG.

1) I’m having a little trouble understanding how efficiency relates to OG. After I measure the pre-boil efficiency, would I need to make any adjustments for the boil? For example, if my pre-boil gravity is lower than expected (lower efficiency), does that mean I’ve extracted less sugar from the grains, and should boil longer/hotter to evaporate more water to hit the estimated OG (even though that would potentially reduce the overall wort volume and throw off the hop bitterness ratio)?

2) How does a low efficiency affect the taste? Is hitting OG more vital to a successful brew than having a high efficiency?


Well-Known Member
Feb 14, 2014
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I suggest reading Kai's work on this: http://braukaiser.com/wiki/index.php?title=Understanding_Efficiency

That should help clarify a lot of it. To boil it down though (pun most definitely intended), (kettle) efficiency describes how well starch was converted to sugar and transferred to your kettle. OG is both a measure of the sugar in the kettle and the volume of the liquid it's in --- therefore you can have high efficiency and low OG, or any combination of those two parameters for a given final volume.

If your efficiency is low (as measured pre-boil) you can get the correct OG by boiling longer as you said, but alternatively, you can keep some "oh ****" DME on hand to gain gravity without messing up your hop schedule.

Efficiency won't effect taste, OG will. For example, if you plan a DIPA for an OG of 1.075 and it comes out 1.050 then it probably won't be balanced and it may tough to drink.

I think most brewers here will agree that the efficiency you get isn't as important as consistency. Crushing at your LHBS can detriment consistency because the mills are used so frequently and a lot of places don't allow you to adjust them. I've had good luck crushing at the LHBS by running the grains through twice. My efficiency is still a little inconsistent (70-80%) but it's good enough for my purposes.

Lastly, brew more. That's probably the most important step for better process control and understanding.

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