The 10-Year Cost of a Water Filter
Last updated: September 17, 2026
The price on the box is the down payment. For most systems, replacement filters cost more over a decade than the system itself — which is why this site treats 10-year cost as a ranking factor. Below is the worksheet we use. We deliberately publish no prices here: filter prices change, and we'd rather give you the formula than a number that goes stale.
The formula
10-year total cost
Purchase price + (replacement filter price × replacements per year × 10) + installation cost (plumber or DIY parts, if any)
Cost per gallon
10-year total cost ÷ (gallons per year your household drinks/cooks with × 10)
Where to find each number
| Input | Where to find it | Watch out for |
|---|---|---|
| Purchase price | The manufacturer's current product page | Sale prices come and go; use the regular price for planning |
| Replacement filter price | The manufacturer's replacement-filter page | Multi-packs and subscriptions change the unit price |
| Replacements per year | Filter life in the specs — use the gallon rating, not the month rating | "6 months" assumes average use; heavy users replace sooner |
| Installation | Your plumber's quote, or $0 for DIY/countertop | Under-sink RO often needs a drain connection and possibly a plumber visit |
| Gallons per year | Your household's actual drinking + cooking water | A common planning figure is ~1 gallon per person per day for drinking and cooking |
Worked structure: what the math usually reveals
- Pitchers look cheap, then don't. A low purchase price with a 100-gallon cartridge replaced 3–4 times a year adds up fast. The cartridge schedule — not the pitcher — is the product you're buying.
- RO looks expensive, then doesn't. Higher upfront cost, but membranes last 12 months and pre/post filters 6 months. Over 10 years the per-gallon cost often beats pitchers for high-use households.
- Capacity ratings are the honest metric. Always divide the gallon rating by your real usage. A "6-month" filter in a 4-person household that cooks daily is a 3-month filter.
- Subscriptions cut the unit price. Most brands discount replacement filters 10–15% on subscription. Factor it in if you'll actually keep it.
Three traps to avoid
- Comparing purchase prices only. A $40 pitcher with $25 quarterly cartridges costs more over 10 years than many under-sink systems. Run the full formula.
- Ignoring the install. If an under-sink system needs a plumber, that's part of year-one cost. Get the quote before you compare.
- Forgetting wastewater on RO. Reverse osmosis rejects a portion of feed water. Check the system's efficiency rating — on metered water, it shows up on the bill.
Use it on our picks
Run the worksheet on the systems we review: the Aquasana OptimH2O RO (365-gallon carbon/Claryum sets every 6 months, 12-month membrane) and the Epic Nano pitcher (100-gallon filters, ~3–4 months). Pull the current prices from the manufacturer pages, plug them into the formula, and you'll know your real number — which is more than most review sites will ever tell you.