All you do is fill a bottle with water, chill it, stick it in the machine, and press a button a few times, or more if you like more fizz. You can also add flavorings, like cola and lemon-lime. The CO2 carbonator is easy to install once you get the hang of it (well, except for a geochemist friend of mine, who claimed to have "extensive … argh! … experience in the lab … ugh … with these devices … ack!"). Each carbonates about 100 bottles, and when you order new ones, Soda-Club picks up the old ones. Sometimes that swap goes smoothly, sometimes not, but I feel this appliance is worth it.