The expense adds up, though, at nearly a dollar a bottle, and the packaging and transportation bother us. So we've been doing a little research into home carbonation. From pre-packaged to homemade, here's a range of options with pics and links for those of us who can't get enough seltzer.
• Do It Yourself: For those comfortable working with things like regulators, tubing, and clamps, here is a great Instructables tutorial for building your own bar tap-style setup for carbonated water. He takes most of his process from this very thorough article. Final cost: about $100 setup and $.02 per liter.
• The 1-Touch Method: The system offered by Soda Club USA is an easy, streamlined way to make soda water at home. You buy a Fountain Jet soda appliance along with a startup kit that includes gas chargers, flavors, and bottles for about $80. The chargers give you about 110 liters, and charger refills cost $20.
Read a review of this system. This leaves you with one more big, one-use appliance sitting on your countertop, but the cost is not bad - $80 startup, then about $.18 per liter.
• The Old-Fashioned Way: In the past, soda water was made at home and the bar with a seltzer bottle - you can still find vintage glass versions of these on eBay and in antique shops. They're often very beautiful. It's a simple system: a soda siphon with an attached gas canister carbonates water. It's a similar system that is used in whipped cream dispensers, and you can buy these through Fantes and other online shops.
There's some danger with these; you need to follow instructions precisely or the bottle could explode. Also, with the cost of cartridges you're still looking at about $.50 a bottle.
Here's a review from a blogger who uses a seltzer bottle, with a helpful chart comparing storebought seltzer and homemade, contrasting cost, fizziness, liberal guilt assuaged, etc.
• And for Bay Area dwellers... You can also buy your seltzer water from the Seltzer Sisters - they'll deliver straight to your door.