Most homebrewers brew in five gallon batches. Any brew day will run you 3-4 hours, and most people wouldn’t want to get less than a case of beer out of that much effort. However, when you brew that large, you pretty much have to brew extract or at least partial extract batches, if you plan on brewing in your kitchen. If you’re willing to move to your garage, and drop some serious dough, you can do all-grain.
There are a lot of things that get cheaper when you go larger. Brewing isn’t one. The more grain and liquid you’re moving, the harder it is for one person to do the work, and the more you rely on tubing and other methods to move the wort around. You can’t very well lift a ten gallon kettle by yourself and transfer wort carefully. So, the equipment cost goes up exponentially when you brew larger. The materials, meanwhile, you generally buy in bulk, so 1 gallon worth of grain costs 1/5 what five gallons worth of grain does.
One drawback of one gallon brewing is that it is generally wise to pitch a bit more yeast, and every batch will have leftover yeast and probably hops. A single vial or packet of yeast will usually do the job for a 5 gallon batch, but can be separated out into 2 or 3 one gallon batches. The yeast won’t keep very long after it’s opened, so it’s important when brewing on a one gallon scale to try to plan recipes with the same yeast back-to-back. Hops also start to lose freshness after packaging and more so once they’re opened. Keeping them in the fridge or freezer can help, but it is wise to try to brew recipes with similar hops in succession so you don’t end up with countless bags of a few fractional ounces of hops in your freezer getting stale.
I can fit all of my equipment (except for my carboy collection, which is almost constantly in use in the fermentation closet) in a large cardboard box in my closet. I can’t say the same about larger equipment.
When brewing one gallon, I can just pick up pots and tuns and move them around, using strainers, and just pouring while trying to minimize oxidation to transfer wort. In larger batches, you end up needing to purchase kettles or tuns with bulkheads and valves, or DIY them onto your equipment. You’ll also need some sort of false bottom or manifold for your mash tun. If you’re brewing all grain or otherwise have left the stove, you’ll also need burners.
Now, none of this is impossibly difficult or cost-restrictive, it’s just a huge jump from the needs of one-gallon brewing. I hope to buy a house in 2017, and will almost certainly start building up a system for brewing larger batches. By the time this is possible, I should have some excellent recipes I’ll want to put together in large format, which brings me to my next point:
While cost and the sheer size of equipment can make the choice of one versus five gallon batches easy to decide for some brewers, there are other advantages for one gallon brewing as well. If you want to try some new, even risky techniques, it’s much easier to do on a smaller scale. And any time a beer turns out bad, well, its just ten beers that turn out bad. For example, I’ll soon be pitching a Brett culture propagated off of a store-bought bottle into a gallon of saison. It’ll be at least three months until the beer is done. At that time, if it is terrible, I’ll be upset, but not nearly as upset as I would be if it were five gallons of terrible three month ferment beer.
The obvious flip side is that when a beer turns out fantastic, there is only ten of them.
Brewing in one gallon format has allowed me to indulge my crazy experimental side, on a budget, with my space restrictions, and to put out a new beer every week.
Some people might loathe spending three hours per batch for so few beers, but for me the fun is in the process, and I honestly don’t think, even giving it away to friends, that I could go through enough beer without getting bored of it if I were brewing larger.