Tap Water Calculator
See how much money, plastic and CO2 drinking bottled water costs compared with tap water, based on your daily habit.
🚰 What is a Tap Water Comparison?
A tap water comparison puts a number on what most people already suspect but rarely calculate: bottled water costs vastly more than tap water for the same volume, uses plastic that a tap glass never touches, and carries a far heavier carbon footprint per litre. Every bottle purchased carries the cost of the water itself plus manufacturing the PET container, filling it, labelling it, refrigerating it and shipping it, costs that a pipe network delivering water in bulk simply does not incur at anywhere near the same scale.
People run this comparison when deciding whether to invest in a refillable bottle or a home filter, when a household is trying to trim a recurring grocery expense, or when an environmental educator wants a concrete, personally relevant example of how small daily choices scale into meaningful annual totals of money, plastic and emissions.
The scale of the gap is what usually surprises people. Tap water in places with safe municipal supply typically costs a small fraction of a cent per litre, while bottled water routinely costs the equivalent of two to four dollars per litre once broken down from a single-serve bottle price. That gap alone, before plastic or carbon are even considered, is usually enough to justify the switch on cost alone.
Where tap water genuinely is not safe to drink directly, the fair comparison is not bottled water against untreated tap water, but bottled water against filtered or boiled tap water, both of which remain dramatically cheaper and lower in plastic waste than buying bottles day after day, even after accounting for the cost of a filter.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 — A Typical Daily Drinker
2 L/day, 0.5 L bottles at $1.00, tap at $2.50/m³, 12 g plastic, 0.2 kg/L bottled CO2, 0.0003 kg/L tap CO2
Example 2 — A Light Drinker With Small Bottles
1 L/day, 0.33 L bottles at $0.75, tap at $2.00/m³, 10 g plastic, 0.2 kg/L bottled CO2, 0.0003 kg/L tap CO2
Example 3 — A Heavy Drinker Buying Larger Bottles
3 L/day, 1 L bottles at $1.20, tap at $3.00/m³, 20 g plastic, 0.22 kg/L bottled CO2, 0.0004 kg/L tap CO2
❓ Frequently Asked Questions
🔗 Related Calculators
How much does drinking bottled water cost per year?
At 2 litres a day in 0.5 litre bottles costing $1 each, that is 1,460 bottles a year, or $1,460 annually, against about $1.83 a year for the same volume of tap water at $2.50 per cubic metre, a saving of roughly $1,458 a year switching to tap.
How much plastic does bottled water use per year?
At 1,460 bottles a year and 12 grams of PET plastic per bottle, that works out to about 17.5 kilograms of plastic a year for one person's drinking water habit alone, all of it avoided by drinking tap water instead.
Is bottled water really that much worse for CO2 than tap water?
Yes, by a wide margin. Bottled water's CO2 footprint, roughly 0.2 kg CO2e per litre from bottle production, filling and transport, is typically hundreds of times higher than tap water's, around 0.0003 kg CO2e per litre for treatment and pumping.
Why is tap water so much cheaper than bottled water?
Because tap water is delivered in bulk through fixed infrastructure with minimal packaging, while bottled water pays for the bottle itself, the cap, the label, filling, refrigeration and transport, all costs that scale with every single unit sold rather than being spread across a whole pipe network.
How is the number of bottles calculated?
Annual litres consumed divided by the bottle size, rounded up to the next whole bottle since you cannot buy a fraction of one. Two litres a day for a year is 730 litres, which needs 1,460 bottles at 0.5 litres each.
Does a bigger bottle size change the plastic footprint per litre?
Generally yes, larger bottles use somewhat less plastic per litre of water delivered than very small single-serve bottles, because bottle material scales roughly with surface area rather than volume, so switching to larger bottles reduces but does not eliminate the plastic gap against tap water.
What is a realistic CO2 factor for bottled water?
Published life cycle assessments commonly cite figures around 0.15 to 0.25 kg CO2e per litre for bottled water delivered locally, rising higher for water shipped long distances internationally, so adjust the default if you know your brand's typical distribution distance.
Does tap water have any CO2 footprint at all?
Yes, a small one, from pumping, treatment chemicals and energy at the treatment plant, typically a fraction of a gram of CO2e per litre, several hundred times smaller than bottled water's footprint per litre.
How much does switching to tap water save over ten years?
Multiply the annual savings figure by ten. At the default 2 litres a day habit saving about $1,458 a year, that is close to $14,580 over a decade, before accounting for any price inflation in bottled water.
Is filtered tap water still cheaper than bottled water?
Almost always, even after adding the cost of a pitcher filter or under-sink system and its replacement cartridges, because those costs are typically far lower per litre than buying individual bottles day after day.
Does the scenario table account for different bottle sizes too?
The table varies daily intake at a fixed bottle size so the cost and plastic scale is easy to see across habits from half a litre to three litres a day; changing the bottle size input above updates every row in the table to match.
Why does the plastic figure matter beyond the cost savings?
Because plastic bottles that are not recycled persist in the environment for years and contribute to the broader plastic pollution problem beyond their purchase price, so the plastic figure captures an environmental cost the dollar savings figure does not.