supermarket own 0.25-0.45: branded 0.80-1.20
Advanced options
The gas exchange price is the whole economy: a 60L cylinder swap runs ~GBP 15 at full retail but the "60L" assumes gentle fizz: heavy-handed carbonators get 40-45L, pushing real cost to ~35p/litre: barely beating supermarket own-brand. The fixes: exchange at the cheapest retailer (prices vary GBP 5+ between shops for the SAME swap), fizz once not thrice, and refrigerate the water first (cold water carbonates far better: warm water wastes gas). Against BRANDED sparkling it's a landslide either way: against 25p own-brand bottles, it's a convenience-and-plastic decision, not a money one.
What The SodaStream vs Bottled Calculator Works Out
- Verdict: your yearly bottled-water spend minus the yearly gas cost of making the same litres, with the months the machine takes to pay back from that saving. Against branded sparkling at 80p to GBP 1.20 a litre it is a landslide; against 25p own-brand bottles there is often no money saving at all.
- Cost per litre compared: a GBP 15 cylinder swap nominally carbonates 60 litres but realistically 40 to 50 under normal fizzing, so gas lands around 30p a litre of tap-sparkling, beside your bottled price per litre.
- Making the numbers better: exchange where it is cheapest (the same cylinder varies GBP 5 plus between retailers), chill the water first, use one long press, and count the plastic bottles you no longer carry home.
- Cylinder exchange price and litres per cylinder (advanced): the two numbers that are the whole economy. Edit them for your shop's swap price and your own fizzing habit; heavy-handed carbonators get 40 litres, gentle ones 60.
- Years kept, bottle replacements and syrup (advanced): the carbonating bottles have pressure-safety expiry dates (a new one every three years is about GBP 10), and flavoured drinks add syrup at 20p to 60p a litre. The machine is spread over the years you keep it.
- True cost per litre (advanced): gas plus syrup plus bottles plus the machine's share per litre, the figure to compare honestly with the shelf price.
- Break-even bottled price (advanced): the bottled price per litre below which the shop wins on money alone. If your own-brand bottles are cheaper than this, the machine is a convenience-and-plastic decision.
- Total over the machine's life (advanced): machine, gas, syrup and bottles over the years against buying bottled for the same period.
- Plastic bottles avoided (advanced): the number of shop bottles of your usual size not bought a year and over the machine's life. For many buyers this is the actual rationale, with the gas maths as reassurance.