This ecology calculator compares the cost of tap water versus bottled water and projects long-term savings over 5, 10, 20, and 50 years.
Ecology
Tap Water Calculator
Compare the cost of bottled water versus tap water and estimate long-term savings.
Calculator
About this calculator
Formula notes
Tap water cost = water cost per m3 / 1000 x daily liters x people; bottled water cost = (daily liters / bottle capacity in mL x 1000) x bottle cost x people.
Worked examples
- Example: 2 L/day, 1 person, 1 USD/m3 tap water, 500 mL bottles at 1 USD each gives tap water cost 0.002 USD/day and bottled water cost 4 USD/day.
- 2 L/day, 1 person, 1 USD/m3 tap water, 500 mL bottles at 1 USD each: tap water costs 0.002 USD/day, bottled water 4 USD/day.
How to use it
- Enter daily water intake, household size, and tap water cost.
- Enter bottle capacity and bottle cost.
- Read daily costs and long-term savings.
Frequently asked questions
How are long-term savings calculated?
The daily cost difference is multiplied by 365.25 and the number of years (5, 10, 20, and 50).
Why is the 50-year savings unusually large?
The 50-year figure uses a 150x multiplier from the source definition, which may account for multi-person projections.
Limits and interpretation
- Long-term savings multiply the daily cost difference by 365.25 and the year count.
- The 50-year savings figure uses a 150x multiplier from the source definition.