Possible to gain 15 pts. eff. by increasing to 12 gallons?

I brewed my second 12 gallon batch on saturday.

It was supposed to be a special bitter (1.050). I did everything as usual, but i had my intended OG at the *beginning* of the boil, i.e., I collected 14 gallons of 1.050 wort. This calculated out to 89% efficiency! Oh, and I'm a batch sparger. My special bitter is now technically an ESB, I guess.

My first big batch was an IPA (1.065) it was only a ten gallon, and I got typical efficiency 77%.

So, assuming I didn't mismeasure the grains (and I'm sure I didn't), is it possible to get this type of efficiency bump, by virtue of the larger batch size? (please also assume that my hydrometer works and my calculations are correct, etc.) Thanks

Normally a larger batch size is less efficient for us homebrewers

lowlife said:

Normally a larger batch size is less efficient for us homebrewers

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My experience is different, but I think it has more to do with how I sparged than anything else.

I normally do 5 gallon batches and use batch sparging. I just dump one big load of water in for the sparge, stir, let rest, and drain to BK.

I did a couple of 10 gallon batches earlier this year and did not have enough room in my 10 gallon MLT to dump all my sparge water in at once, so I split the sparge into two equal volumes and did two sparges.

My efficienty went from my typical 75% up to about 82% on those two 10 gallon batches. I believe it was due to using two sparge additions instead of just one.

I keep meaning to test this by doing a 5 gallon batch with split sparge water, but I always forget and just dump it all in at once.

You should have slightly higher efficiency just because it's a lower OG than the IPA, but not that much higher. How are you measuring your volumes, and are you correcting them for temperature? If your process was the same, I'm guessing one or more of your measurements may be off somehow, as increasing batch size shouldn't have much effect on efficiency. Here's a good explanation on how measurement accuracy effects efficiency calculations.