Inconsistent Efficiency

From brew to brew, my efficiencies are all over the place. It's driving me nuts. I'm using Beersmith, and knowing your setup's efficiency beforehand comes in handy when creating recipes. Differing efficiencies can significantly alter the end result in relation to what you were expecting.

Here are some examples:

My 1st batch of Altbier, brewed on 11/16/11, had 69.18% brewhouse efficiency.
My 2nd batch of Altbier, brewed on 3/17/12, only had 66.29%. The only difference that I know of is the 1st batch was 5.5 gallons and the 2nd batch was 5 gallons, however I did adjust the grain bill to reflect this difference.

My Bourbon Barrel Porter, on the other hand - had amazing efficiency: 83.10%! Also I brewed an Octoberfest on 4/24/12 that had 82.65% efficiency. And a Cream Ale brewed on 4/30/12 had 77.80% efficiency. These were all 5 gallon batches. My grain crush is the same every time, I use the same brew process every time (I batch sparge, by the way).

As you can see - they vary widely. It's kinda difficult to formulate a recipe when I can't predict these inconsistencies. Is this normal? Does anyone have this issue?

Thanks.

For me the biggest sticking points in consistency were making sure I had complete conversion in the mash, and making sure I had a good drain in the MLT.

I started doing an iodine test for conversion. If you're batch sparging, make sure you're not leaving a lot of first runnings in the tun (ie deadspace). And of course stir like mad.

My efficiency is consistent batch-by-batch at 70%. A few points difference could be a measuring error, but 20 points difference shouldn't be happening. When you say the crush is the same, are you crushing it yourself or at a lhbs?

Pappers_ said:

My efficiency is consistent batch-by-batch at 70%. A few points difference could be a measuring error, but 20 points difference shouldn't be happening. When you say the crush is the same, are you crushing it yourself or at a lhbs?

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I crush my own. I bought the 2-roller Monster Mill last October. I checked the setting on it when I got it and didn't see the need to change it, as the crush looks really good.

I am also not sure if I should be paying more attention to "brewhouse efficiency" as opposed to "mash efficiency", or if they're equally important.

Northcalais40 said:

If you're batch sparging, make sure you're not leaving a lot of first runnings in the tun (ie deadspace).

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My mash tun has a deadspace of .3 gallon. Of course, there is grain absorption to account for, but it seems my beers with bigger grain bills are producing higher efficiencies.

Northcalais40 said:

And of course stir like mad.

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I do - every 15 minutes I open up the tun and stir and take temperature readings in multiple locations. I've been pretty good at hitting my numbers as far as temperature goes.