The US beer business is booming, thanks to a growing number of craft beer bars.

And they’re helping sell a lot of drinks packaged in barrels or kegs. Those beer shipments jumped 88% to $2.4 billion from 2007 to 2012, almost three times the rate of total beer growth, the US Census Bureau reported.

Keg beer now represents 8.6% of all beer sales, up from 6.1% in 2007, the Census Bureau reported, and beer wholesale shipments topped $28 billion in 2012, or 33% more than in 2007.

While pop culture tends to associate kegs with drunken college parties, they are crucial to the growing number of craft beer bars, some of which have 40 to 61 different styles of beer on tap, and a few 100 taps or more—which mean 100 kegs on-site.

The Census report shows the number of US breweries more than doubled to 869 from 2007 to 2012. This may be a conservative number, and other data sources put the number at around 2,800. The Beer Institute said the Census report considerably underestimates the beer business, because it does not count all the brew pubs. American brewers, importers and their suppliers create 2 million US jobs, and pay $49 billion in taxes.

The increase in production is mostly due to small local or regional breweries. Craft breweries such as Bell’s near Kalamazoo, Michigan, and Lagunitas in Petaluma, California, have more than doubled their shipments over five years, while major brands are generally flat though. Of course, some of those small craft brewers end up stocking up a corporate giant’s liquor cabinet.

Craft beers show up in beer-only bars and a growing number of places that sell beer on tap, Jessica Daynor, managing editor of Draft Magazine, told Quartz. ”There are simply more points of consumption for draft beer: grocery stores, liquor stores, pop-up beer gardens, zoos, museums, skate shops and even flower shops are hosting taps, not to mention the restaurant sector, which is wholeheartedly embracing beer,” she said.

Growlers—reusable glass or ceramic jugs that pubs fill and individuals take home—are becoming more popular too, she noted, for the drink-at-home or throw-a-party people. Generally containing four pints each, growlers come in smaller sizes too, known as howlers or growlettes, and are filled from kegs. Their popularity is on the rise, so much so that some bars have installed filling stations.

And for those who want a beer on tap in their kitchen, plenty of devices are being developed and marketed to keep draft beer cold and fresh. Then the buyers will have to roll their barrel or keg back to the shop once it’s empty.