Is it enough to want to purchase something for a hobby for the hell of it because it is shiny and new or a neat thing to have? There are pieces of equipment that I would like to have that will make only marginal improvements to the quality of the beer or the brewing session but are sexy (a stainless steel conical fermenter comes to mind). Buying a specialized grain mill, however, will actually improve the consistency and efficiency of the beer, save money and incrementally save time. It is a purchase that I have been weighing ever since we went to all grain brewing a few years back and I think it is time.
I went through my brewing records for 2009. We used just over 160 lbs of 2 row malt last year. It is our base grain, in which all of our recipes use a majority of. My local homebrew shop's (LHBS) cost on that grain is a reasonable $1.40/lb. (other local shops sell the same malt for more). So, we spent a little over $224 on a majority of our grain bill. My LHBS also offers to sell 50 pound bags of that malt for $49.99 or roughly $1.00 per pound. So, buying in bulk and grinding our own will save approximately 40 cents per pound ($6-$8 per batch, or 3 to 8 cents per bottle).
If last year is a baseline year (which is more than we ever brewed, but less than I hope to in 2010) the savings is about $64 per year. At this estimate, three years is our break even point for a mill. Not bad. If we can find bulk savings on one or two of our specialty grains that we use often, we can increase that savings. We do, however, also need to invest in storage and a scale to store and weigh our grains. I will ignore that for the time being, as I can probably use bins I have here for storage and also the bathroom scale for gross weighing of grain.
Another advantage to milling our own grains is increased mash efficiencies. The mash efficiency refers to how much starch is converted to sugar during the mash and how much is extracted (rinsed) from the grain into the wort during the sparge. 100% efficiency is a theoretical maximum based on the amount of starch that actually exists in a grain of barley, and would be impossible to actually achieve in actual brewing conditions. Again, referring to my 2009 brewing records, our mashing efficiencies varied from 58% to 72% last year and the most efficient mashes were from grains milled at a different homebrew shop. My LHBS's mill was giving us efficiencies averaging in the low 60's. Many homebrewers get efficiencies in the high 70's and even high 80's. It is a balance between the milling process, the mashing procedures, and the amount of time it takes. I spoke with people at my LHBS about their mill (and my crappy efficiency). Their mill is a 2 roller factory non adjustable unit, but it wears out over time. They replace it a couple times a year from such high volume use. They showed me one that they replaced, and you can actually see that the middle of the rollers are worn so that there is a visible difference between the gap at the end and the middle of the roller. It looks like the rollers are bowed outward in the middle and as a result they are barely cracking the grain. This explains the crappy efficiency numbers (but also the easy mashing/sparging). I was considering offering to buy their used and worn mill until I found out that it can't be adjusted. The efficiency would stay the same and eventually get worse. A new mill is likely to last us a lifetime.
It is not a stretch to say that we can get a consistently higher efficiency if we can control our own grind. A 20% improvement would likely be achievable, but even 10% would save us $16 per year using bulk pricing. So, the total yearly savings comes to over $80/year on the two row malt alone. Including a 10% savings on specialty grains that require mashing (Munich and Victory malts are the main ones we have been using), we could easily save another $10 per year.
We could spend less on a mill. Most two roller mills cost about $45 or so less than the 3 roller unit I want. The theory behind a three roller variety is that the grain passes through twice (the first pass is a wider gap than the second) which is more efficient and a little gentler on the grain's husk and thus less flour is made....supposedly better. I am sure it probably doesn't matter. You could spend more with larger diameter rollers or stainless steel rollers, too, for more durability and longer life, but the upgrade I chose supposedly makes a difference on the quality of the grist.
Of course, buying in bulk (including malt and hops) won't save me many, if any, trips to the LHBS. I will still be buying select specialty grains, hop varieties that I don't or can't buy in bulk, and periodically new and different strains of yeast. It may save us time spent at the shop, however (which is nice), as grinding the grains can happen while waiting for water to heat or even the evening before a brewing session.
Mostly, a grain mill will allow us to reproduce beers with a level of certainty what our starting gravity will be. That alone would be worthwhile if only to reduce my own aggravation and ensure the beer meets a profile we are shooting for. If you add in the cost savings (break even point being 2 years or less) and a possibility to spontaneously brew a simple beer periodically (with all of the raw ingredients sitting around and a couple extra hours time), this purchase becomes a no-brainer.