As an indulgence, seltzer isn't that expensive; I can usually find it on sale for 50 cents a liter or less. (The two-liter bottles are cheaper still, but when I buy them the seltzer invariably goes flat before I use it all up.) However, I do feel a tiny bit guilty about all the packaging waste my seltzer habit produces. I've never bought any other kind of bottled water, and I've written repeatedly about what a silly waste of money and resources it is, but here I am, still tossing a plastic bottle into the recycling bin every few days (or an aluminum can every day). But unlike plain water, the fizzy stuff isn't available on tap, so what's the alternative?
It might seem like the obvious ecofrugal choice would be to buy one of those newfangled home-carbonation machines, like the SodaStream. Unfortunately, my research indicates that these devices, while they may reduce waste, don't necessarily save money. The most basic SodaStream machine, the Fountain Jet, costs $80 and comes with one 60-liter carbonator. Replacement carbonators cost $15 each. Assuming I now pay 40 cents a liter for seltzer on average, I'd have to consume 420 liters of the stuff to reach the point at which my homemade fizz was as cheap as the store-bought variety. If I go through 3 liters of soda per week, or 78 liters over the course of a summer, it would take over 5 years for my soda machine to pay for itself—assuming it didn't break before then.
The main reason the SodaStream is not particularly cost-effective isn't the initial cost of the machine; it's the high cost of the CO2 refills. There are lots of places to have CO2 tanks refilled: one reviewer of the Fountain Jet on Amazon.com notes that "most paintball shops and some grocery stores" provide this service, and so do many sporting goods stores. The problem is that SodaStream's machines use a proprietary cartridge that won't work with the refilling equipment. A SodaStream competitor called the Primo Flavorstation could take a standard-sized CO2 canister, but it's no longer on the market. There are a few other soda makers on the market, but they all appear to use proprietary CO2 cartridges as well. Cuisinart machines use tiny 3-ounce cartridges that cost $20 a pop and carbonate only 16 liters of water; the Hamilton Beach Fizzini takes single-use CO2 chargers that cost 70 cents each and are good for only one liter. It can also take the standard-sized chargers used in an old-fashioned seltzer bottle, which can be bought in bulk, but even these come to 43 cents each with shipping. In every case, the cost per liter is actually higher than that of the store-bought seltzer, which means there's no way the machine will ever pay for itself.
I'm not the first person to notice this problem, of course, and various companies sell products designed to circumvent it. A company called CO2 Doctor sells a $35 adapter ($40 with shipping) that will let you fit a standard 12-ounce paintball tank into your SodaStream; another company sells a similar adapter called the SodaMod for $60. A 12-ounce CO2 canister can be refilled for about $3 and, extrapolating from the size of the SodaStream canister, should be able to carbonate about 50 liters of water. However, once you factor in the cost of the adapter, plus the cost of the machine itself, you'll still have to drink 360 liters of seltzer before it becomes cheaper than buying it from the store.
So it looks like there's no good way to make a home soda machine truly cost-effective. However, there are other ways to carbonate water at home with less equipment. The My Pop Soda Shoppe system, for instance, skips the CO2 canister altogether and produces its own fizz the old-fashioned way, through fermentation. You just put a cup of sugar and two teaspoons of yeast into one bottle, and as it ferments, it will produce 10 liters of CO2 that are stored in a separate reservoir. From there, you transfer it as needed into a bottle of cold water. Unlike other home soda machines, this one can also carbonate other types of liquid, such as fruit juice or wine. The system costs $75, and the seller claims that the materials needed cost only 2.4 cents per liter. However, if you use organic sugar, as we do, the cost for materials shoots up to 95 cents per batch, or 9.5 cents per liter. That's still a much lower cost per liter than the SodaStream; it would take only about 250 liters, or a little over 3 years, for this system to pay for itself. But during that whole time, we'd go through sugar awfully fast, which would mean making more frequent trips to Trader Joe's. Moreover, this system requires quite a bit more work than most home soda makers (filling, cleaning, and so on).
Another alternative is to put together your own "home carbonation system," as outlined in this Instructables article. The author provides a condensed explanation of how it works right at the start of the article:
Take a 20lb CO2 Tank and regulator, attach a tube, and stick a 99 cent locking ball air chuck (tire inflator) on the end of the tube. Pop a cheap snap-in tire valve (schrader valve) into a plastic soda bottle cap and you're ready to carbonate any liquid in about 30 seconds. Colder liquids absorb more CO2 carbonation.
He estimates that you can get all the parts you need for "around $100, plus the deposit on a CO2 tank," which is another $100 or so. By his reckoning, a 20-pound CO2 tank can carbonate over 1,000 liters of water, which he says works out to less than 2 cents per liter (which presumably means that it costs around $20 to refill the tank). Unfortunately, because of the high initial cost of all the parts, the system wouldn't break even until it was halfway through its first tank of gas. At the rate I drink seltzer, that would take over 6 years—longer than the SodaStream. (This site has testimonials from several users who were able to put together home systems for less, but the cheapest system was $95 total, which means it would still take just over 3 years to pay for itself.)
What I'd really like is a machine like the old FlavorStation, which could work with a standard 20-ounce paintball tank. That way I'd be able to get the tanks refilled at any local sporting goods store, and the whole thing would take up less room (and be less work) than a big 20-pound tank. And the thing is, it's still possible to buy the original FlavorStation from various vendors for around $32.50. If the 20-ounce tank it comes with is good for 85 liters (once again extrapolating from the size of the SodaStream cartridge), then this machine would actually pay for itself on its first tank of gas, or just into its second year of use. And even if my local sporting goods stores refused to refill the Primo CO2 canisters (a problem mentioned by some users on amazon), I could just buy a paintball tank for an extra $20 and still be ahead of the game.
The only reason I hesitate is because, with the product being discontinued, I know I can't expect to get service or parts for it if it breaks. So is it worth a $32.50 gamble on a product that, if it lasts, could only save me around $100 in its first five years of use—as well as keeping around 400 plastic bottles out of the recycling stream? Or does it make more sense to just assuage my guilt by buying my seltzer in aluminum cans, which are more cost-effective to recycle?