SodaStream tries everything they can to stop people competing with them to refill their gas cylinders or supply competing gas cylinders for use with the equipme

SodaStream tries everything they can to stop people competing with them to refill their gas cylinders or supply competing gas cylinders for use with the equipment they sell, and have largely succeeded, allowing them to sell carbon dioxide at a significant mark up. For comparison, considering only the cost of obtaining carbonated water, and assuming water is free (since it isn't a significant cost), in New Zealand dollars: 1 L of store bought carbonated water: ~$0.99 1 L of water at the lowest Sodastream carbonation: $0.20 (assuming $12 / 450g of CO2, 450g makes 60L). 1 L of water using market rate food grade CO2: $0.0032 (assuming a 3.5 kg cylinder makes 467 L and costs $15 to fill). Note that if you do buy a cylinder, there are additional costs (in NZ, a cylinder must have a safety warrant of fitness issued in the last three years to be filled, which costs ~$15 - so that is an additional $5/year to add to the cost of ownership). This article provides information on the DIY approach: http://m.popsci.com/diy/article/2012-06/how-make-your-own-home-carbonation-system http://m.popsci.com/diy/article/2012-06/how-make-your-own-ho...