Here is the link to the latest BIABacus; http://www.biabrewer.info/viewtopic.php ... 375#p32306

In that example a 76.7% 'Efficiency into Fermentor' is estimated.

It depends on the gravity beer you make and so many more variables. Some of us, like me, try to measure down to the mm and one thousandth of a point. Some don't do math or measure and make fine beer.

On a 1.065 beer with as careful as I could take measurements and readings, I got a 72.6%


MS

This question is a good one and there is a wealth of info on the site regarding it but, atm, that info is quite buried. The question raises a lot of issues as MS has hinted at above and I'll try and address some of these later today sd as well as the question you asked on sparging in another thread.

In the meantime, here is one post that might get you started. An advanced search of posts done by me that include any of the terms "brewhouse efficiency" "kettle efficiency" "fermentor efficiency" "coffee" "washing machine" or "sweet liquor" should dig up some sort of info, possible enough to answer your question completely. When I do write here later on, I'll only have time to summarise the major points so bear these search terms in mind for later.

The first point I'll make is that fermentor efficiency is of almost no value without knowing your kettle efficiency as well. Unfortunately fermentor efficiency is often used as a base in the most common brewing software. I think the post I linked above probably expands on this major problem.

Later

A bit rushed for time so I'll just try and write some stuff in point form (no particular order) for the moment. sdsratm, let us know if you need more info on any point or whether it has helped.

1. There's only one useful efficiency figure for home brewers and that is a "kettle efficiency". This figure tells you if you have a problem with your mashing/sparging process. (These two things occur simultaneously in a pure BIAB). To obtain a kettle efficiency reading, you will need to take a volume and gravity reading at some stage during the boil.

2. To record a "fermentor efficiency", you need to measure the volume you were able to transfer to your fermentor and the gravity reading. If you ended up with a low "fermentor efficiency" all that would tell you would be that you either had a problem in your mashing and sparging process or you had a problem in your trub management. It would not tell you which one of these was your problem.

3. Most commercial software copied the original commercial brewing software and base themselves on fermentor efficiency. This is bad for reasons stated in 2 above.

4. Commercial software also leads users to believe that efficiency (kettle or fermentor) is a constant. It isn't. A high gravity brew, regardless of the brewing method, will always be less efficient than a low gravity brew. If you washed a pair of filthy jeans in 6 gallons of water, they will come out cleaner than if you wash them in 3 gallons of water. (They will also come out cleaner if you let them soak for longer.)

5. The BIABacus auto-estimates both your kettle and fermentor efficiencies. A beginner who does not want to get stuck int the traps above is best to learn how to use the BIABacus. It will teach you what is important to concentrate on first and will tell you if you are not doing things right.

6. Efficiency terminology in other software has become useless. For example, existing software is often manipulated by users (very often for excellent reasons) so that "brewhouse efficiency" can mean either a fermentor or a kettle efficiency. Reports from these programs usually make it impossible to tell what type of efficiency the original brewer is talking about.

7. Finally, to put things into perspective, the only difference between a kettle efficiency and a fermentor efficiency is how much kettle trub you have and how much wort you spill or lose on transfer from kettle to fermentor. For example, let's say you had a kettle efficiency of 80% and let's say there were 25 L of wort in your kettle after chilling. If after transferring to the fermentor, you only got 20 L into your fermentor, then your fermentor efficiency would be 20/25*80=64%. Some brewers after brewing this will tell you they had an efficiency of 80%. Others would say 64%.

So, in summary, anytime you hear someone say, "My efficiency is..." or "My brewhouse efficiency is...", even though you will see these sentences written almost daily on almost every brewing forum except this one, these figures tell you nothing. Or, if you read, "I always get the same 'whatever type' efficiency on all my brews," you'll know the poor brewer has been brain-washed, thanks to existing software, into the, "efficiency is a constant" myth.

It's not an easy thing to get educated out of the brainwashing. It took a few of us here several years. Our hope is that we can prevent other brewers falling into the same trap.


PP