r/Homebrewing • u/BlizardLizardWizard • May 14 '26

Help with low efficiency

Hi,

I've been brewing for a bunch of years now, but more recently started actually calculating out my efficiency for all grain brews. I've noticed that for the few I've done this for, my calculated efficiency has been unexpectedly low. I was hoping r/homebrewing might be able to help me figure out why.

As an example, my most recent recipe was a DIPA. I used 12lb pearl malt, 1lb wheat, 1lb, caramel 20L.

Mash water: 14lbs/grain x 1.4qt/lb = 4.9 gal
Water temp: 167F
I preheat my mashtun (large blue Igloo) with 175F water, which I then discard.
I add the 167F water to my mashtun and slowly stir in the grain.
Temp check reads 154F.
Steep 120 mins. Temp remains relatively stable, but at 85 mins, the temp dipped to 148, and I added 1/2 gal 175F water to bring it back up to 151F. Temp check at mashout was 149.5F.
I vorlauf and lauter, then fly sparge with 170F water to bring the pre-boil volume to 7 gal.

I measured a brix of 11.1 with a refractometer, which I converted to a gravity of 1.048.

Efficiency Calculation:
PPG = (Vpreboil x gravity points)/lbs grain = (7gal x 48)/14lbs = 24
Efficiency = PPG/PPGmax = 24/37.7 = 64%

I used table on typical malt yields in How to Brew to estimate the PPG max.

Wondering if it's the extra 1/2 gal used to temp adjust or if I'm not calculating the value correctly. Any input is appreciated.

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u/spoonman59 May 14 '26 edited May 14 '26

Generically, crush size can impact efficiency. Not sure how you source your grains or what you know about the crush.

Is the gravity reading after boiling? You don’t want to calculate efficiency off pre-boil gravity since boil off hasn’t happened yet.

ETA: I realize now it doesn’t matter if you calculate it prevoil. It’s simply actual gravity versus expected gravity, volume is irrelevant.

1

u/BlizardLizardWizard May 14 '26

I get my grain from MoreBeer pre-milled. Haven't invested in the equipment to do it myself.

The gravity is pre-boil. The calculation uses post-boil gravity? Interesting. In HTB, it says PPG is the "yield in terms of volume and gravity of wort collected from the mash and lauter before the boil." The equation there specifically uses pre-boil volume, though I guess it doesn't specify for the gravity.

2

u/spoonman59 May 14 '26 edited May 14 '26

  1. Grain crush can actually matter! So consider that nothing is wrong with your process and it’s the crush.

  2. I guess I’m wrong and it does use preboil. My mistake. I re read the equation now and it makes sense. I used brew father so don’t really calculate it myself.

  3. How do you confirm your water volumes? I tested the volume markings in my AIO and they were off enough to cause my numbers and consistency to be off. If you have weighed or used a known accurate measure than you are good, but if your volumes aren’t what you think they are then that could impact it.

1

u/BlizardLizardWizard May 14 '26

3) is an interesting point i hadn't considered. I'll double check it. Thanks

1

u/spoonman59 May 14 '26

Good luck! I’m sure you will figure it out.

1

u/Questionable_Cactus May 14 '26

You're asking about mash efficiency, so once you have extracted the sugar from the grain, that value is constant. In my calculation sheet I have that as "Gravity Points" which is PPG x volume.. This number doesn't change because it represents an absolute value of sugar dissolved (technically I think it should be "Gravity Points per Pound," but the weight of grain is fixed at this point as well so I don't care about it). After boiling, your PPG and volume both change, but the Gravity Points do not. So you are fine to calculate mash efficiency right after lautering.

Some thoughts on your efficiency: how sure are you about your refractometer? Are you allowing the wort to cool down to ~70F before measuring and also correcting for temperature calibration? Have you ever considered batch sparging, it can help with efficiency? Also, 64% is low, but not crazy low. 70% is pretty standard for most brewers, I can sometimes get into the mid-70's, but that's about it.

1

u/BlizardLizardWizard May 14 '26

The refractometer i calibrated recently so should be accurate. Im allowing it to cool to room temp before measuring.

A few people have suggested batch sparging, so that may be the next thing I try. Thanks.

1

u/PM_me_ur_launch_code May 14 '26 edited May 14 '26

There are two different types of efficiency, mash efficiency which you're describing and brewhouse efficiency, which is based off of what goes into the fermenter.

Mash efficiency is measured in the kettle and it = conversion efficiency (%) times lauter efficiency (%).

Brewhouse efficiency is measured in the fermentor and is mash efficiency (%) times your efficiency (%) in knocking out to fermentor. If you have 80% mash efficiency but only get 80% of your wort into the fermentor due to trub and other system loss, then your brewhouse efficiency is 64%.