Bottled or Filtered Water: How to Calculate What You Really Spend Each Month
A pack of bottles at the supermarket. A big water jug that needs replacing. A single-serve bottle when you head out without your thermos.
They're small purchases that, spread out over the month, can go unnoticed. Until you ask yourself: how much are we really spending on water?
Comparing that spending with a filter means looking at the initial purchase, the replacements, and how much it will be used at home. With your own numbers, you can find out whether there are any savings and how much they would be.
Start with what you buy in a month
Go through your receipts, orders, and payments from the last four weeks. Include the water you buy for home and the single-serve bottles you could replace by filling a water bottle.
Write down three things for each purchase:
- How many containers you bought.
- How many liters each one holds.
- How much you paid, including delivery when applicable.
For example, a pack of twelve half-liter bottles contains six liters. A large container and a single-serve bottle have different prices, so it's best to calculate them separately.
Cost per liter = price paid ÷ liters purchased.
If you buy large jugs, check the volume shown on the label. Also keep refundable deposits separate from the cost of the water: a deposit you'll get back isn't a recurring expense.
Compare the same amount of water
For the comparison to be useful, both options need to cover the same amount of water.
If you buy 120 liters a month, calculate how much it would cost to filter those same 120 liters with a suitable system. If you would only replace half of your purchases, use that half.
Also think about what would actually change. Maybe you'll keep buying water when you travel or when you want to keep a backup supply at home. That expense should stay in the budget.
Your savings depend on the purchases you actually stop making.
What to include in the cost of filtering
In addition to the price of the system, consider:
Replacement cartridges. Calculate how many you would need over the period you're comparing. Check whether the system comes with the first one so you don't count it twice.
Installation and accessories. Add adapters, fittings, or installation service if your model requires them.
Incoming water and operation. Consider the additional cost of your water supply and, when applicable, electricity or water the system discards.
Maintenance and deliveries. Include the costs you'll actually have for cleaning, service, or shipping of replacements.
PFC has different replacement guidelines depending on the product: for example, approximately 2–3 months for the faucet filter and the pitcher, and 6–8 months for the dispenser. Always confirm your model's instructions and capacity before you calculate.
An example to understand the calculation
Let's imagine a household that buys 120 liters a month at an average cost of $0.25 per liter, delivery included.
Its spending would be:
120 liters × $0.25 = $30 a month.
$30 × 12 months = $360 a year.
Now let's assume that household can replace all of that volume with a suitable filter and has these costs:
| Item | Example assumption |
|---|---|
| System with first cartridge included | $25 |
| Five replacements during the first year, at $14 each | $70 |
| Other additional costs for the year | $12 |
| First-year total | $107 |
In this example, the cartridge is changed every two months: the one included at the start and five replacements at months 2, 4, 6, 8, and 10. We assume the volume used stays within the allowed capacity.
The result would be:
$107 ÷ 12 = $8.92 average monthly cost.
$360 − $107 = $253 difference over the first year.
These figures are hypothetical: they illustrate the method and do not represent a PFC quote or guaranteed savings. The $12 in additional costs is also an assumption that you should replace with your actual expenses.
Also, the monthly average doesn't mean you'll pay exactly $8.92 every month. At the start, you buy the system; after that, costs are spread out according to maintenance.
What if you keep buying some bottles?
Let's say that, in the same example, you keep buying $10 a month worth of bottled water.
That adds $120 a year:
$107 for filtration + $120 in remaining purchases = $227.
Compared with the original spending of $360, the difference would be $133 a year, keeping the other assumptions the same.
This second calculation may look more like your routine. Using a filter at home and buying water on certain outings can go hand in hand; what matters is including both expenses.
The second year deserves its own calculation
If the system is still working, you don't need to include its purchase again. However, the replacements and other costs continue.
In our example, the second year would require six cartridges, because there would no longer be a new one included with the initial purchase. If each one still cost $14 and the other expenses were $12:
6 × $14 + $12 = $96 for the second year.
Check prices and maintenance needs when you update your budget. What you spend in the first year and in the years after isn't always the same.
Before deciding, make sure the option is right for you
The price per liter is just one part of the choice. You also need a system suited to your incoming water, enough capacity, and a maintenance routine you can keep up with.
Don't budget for a filter meant to improve taste as if it solved any contamination problem. And don't stretch the cartridge's life to make the savings look bigger.
Other details count at home too: the space the containers take up, who carries the groceries, and where you fill your water bottles. You can weigh them separately, without assigning them a dollar savings you haven't measured.
Run your numbers with these five figures
To get started, gather:
- Liters you buy per month: ___
- Total monthly spending on those purchases: ___
- Purchases you'd keep making after installing the filter: ___
- Cost of the system and its installation: ___
- Replacements and other first-year expenses: ___
With that information, you'll be able to compare your current situation with a concrete alternative.
At PFC, we want to help you choose a product that fits your home and your budget. Tell us how many people will use it, how you get your water now, and how much water you want to filter.
Browse PFC filters and replacements and build your comparison with current prices.
Free your water with PFC.
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