Janine is considering buying a water filter and a reusable water bottle rather than buying bottled water. Will doing so save her money? The cheapest option saves her __$ over a year.

Question

1. How much water does Janine drink in a day? She normally drinks 6 bottles a day, each 16.9 ounces.
2. How much does a bottle of water cost? She buys 24-packs of 16.9 ounce bottles for $3.79.
3. How much does a reusable water bottle cost? About $10.
4. How long does a reusable water bottle last? Basically forever (or until you lose it).
5. How much does a water filter cost? How much water will they filter?
6. A faucet-mounted filter costs about $28 and includes one filter cartridge. Refill filters cost about $33 for a 3-pack. The box says each filter will filter up to 100 gallons (378 liters)

Answer 1

Calculate the amount of water in gallons consumed in 1 year:

6 bottles/day * 365 days/1 year * 16.9 oz/1 bottle * 1 gallon/128 oz = 289.15 gallons

Calculate the annual cost of plastic bottle water:

289.14 gallons/year * 128 oz/1 gallon * $3.79/24 bottles * 1 bottle/16.9 oz = $345.84

Calculate number of filters needed in 1 year:

289.15 gallons * 1 filter/100 gallons = 2.89 filters/year

Annual cost of filters (at the refill price)

2.89 filters * $33/3 filters = $31.79

The annual savings in terms of consumables is $345.84-$31.79=$314.05

However, you should note that the first year expenses of using a reusable water bottle mean that the actual capital investment (cost) is higher, so the savings are less.

In year 1, Janine will need to buy a water bottle ($10), the initial filter equipment ($28), and a 3-pack of replacement filters ($33, only 2.89-1=1.89 refill filters will be used in the first year).

Year 1 costs for Janine will be $10 water bottle+$28/initial filter+$33/3 filters*1.89 refill filters= $58.79

In year 1, Janine saves $345.84-$58.79= $287.05