How fast does an under-sink RO pay for itself?

Against ZeroWater pitcher filters, for 7 people at average use: $849 ÷ ($425 − $178) ≈ 3.4 years. For heavy users (0.78 gal per person per day): about 0.75 years. Against Brita Elite or a PUR faucet filter, RO costs more every year at average and heavy use and does not pay back on money.

The Water Math

Do Your Own Math › The Water Math › Reverse osmosis worth it

Is reverse osmosis worth it?

Q: Is reverse osmosis worth it?

For money alone, rarely. At average US drinking and cooking volumes (about 0.23 gallons per person per day, EPA Exposure Factors Handbook), a lead-certified PUR faucet filter costs about $82 a year and a Brita Elite pitcher about $86 for 7 people, against about $178 a year for a Waterdrop G3P800 under-sink RO. RO pays back against ZeroWater pitcher filters in about 3.4 years at average use and under a year for heavy users. The real reason for RO is a contaminant on your water report that the exact model is certified to reduce.

Corrected 30 October 2026. Earlier versions of this page assumed 0.6 gallons of drinking and cooking water per person per day. The EPA's own data put the average at about 0.23 gallons. The answer changed, and so did this page. What changed →

For money alone: rarely. At average use, a lead-certified faucet filter (about $82 a year for 7 people) or a Brita Elite pitcher (about $86) costs far less than an under-sink RO's filters (about $178 a year).
Against ZeroWater pitcher filters: RO pays back in about 3.4 years for 7 average users, and in under a year for heavy users.
The real reason for RO is what it removes, when your water report shows something that the exact model is certified to reduce. A clean report means "buy nothing" is a valid answer.

Do your own math →

Evidence behind this site: 201 studies and official sources · 47 certification listings read · 26 documented incidents · last checked 30 October 2026 · corrections

How much water we count, and why

Filter costs scale with the gallons you drink and cook with, so this number decides the answer. We use the EPA Exposure Factors Handbook (chapter 3, table 3-1, national survey data). Its figures include water added to food and drinks.

Average, all ages: 869 mL a day, about 0.23 gal per person per day. That is 587 gal a year for 7 people and 168 gal for 2. This is our default.
Heavy users: the 95th percentile for adults, 2,958 mL, about 0.78 gal a day. That is 1,997 gal a year for 7 people.
The EPA's RO labeling work assumes 1 gal a day. That is an assumption, not a measurement. You can pick it in the calculator.

Yearly running cost, 7 people

Filters per year = gallons ÷ listed capacity, or the maker's time limit if that comes first. Prices as read on the dates below.
Option	Average use (587 gal)	Heavy use (1,997 gal)
PUR faucet filter (RF-9999, 100 gal, $14.00)	$82	$279
Brita Elite pitcher (OB06, 120 gal, $17.50, 6-month limit)	$86	$291
Waterdrop G3P800 under-sink RO: filters + electricity (estimate) + drain water	$178	$315
Culligan ZeroWater pitcher (ZEROFXX1, 20 gal, $14.50)	$425	$1,447

How the RO figure is built: CF $29.99 (550 gal or 6 months), CB $29.99 (1,100 gal or 12 months) and RO membrane $139.99 (2,200 gal or 24 months). At average use the time limits come first, so that is about $160 a year in filters. Add about $15 of electricity (our estimate; the maker publishes no wattage) and the drain water: 1 gallon to drain per 3 made, at $15.21 per 1,000 gal (US average water and sewer rate, AWWA 2023 via EPA).

Payback against a pitcher

Against ZeroWater, average use, 7 people: $425 − $178 = $247 saved a year. The $849 unit takes $849 ÷ $247 ≈ 3.4 years to pay back. Over 5 years: RO $849 + 5 × $178 = $1,739, against ZeroWater 5 × $425 = $2,126.
Against ZeroWater, heavy use, 7 people: $1,447 − $315 = $1,132 saved a year. Payback ≈ 0.75 years.
Against Brita Elite or a PUR faucet filter: RO costs more every year, at average and at heavy use, so it never pays back on money.
Two people, average use: ZeroWater filters cost about $121 a year, less than RO filters alone. RO never pays back.

Price of the Waterdrop G3P800 unit: $849 (list $999), read on waterdropfilter.com on 27 and 30 October 2026. Installation by a plumber adds roughly $150–300 (This Old House, March 2026).

So when is RO worth it?

When your water report shows something that a specific RO model is certified to reduce, and a cheaper certified filter is not certified for it. Reverse osmosis is certified under NSF/ANSI 58. The Waterdrop G3P800 is listed for lead (IAPMO R&T WC-13976) and for PFOA/PFOS (WC-14805). Check the exact model's listing against your report.

For lead alone, a certified faucet filter or pitcher does the job for far less. That is what the EPA's Flint field study tested. Faucet filters certified for lead →

Read your water report first

If you are on city water, your utility sends a free Consumer Confidence Report every year. If it is clean, and your home has no lead service line or old lead plumbing, spend $0. How to read your water report →

Is reverse osmosis worth it?

How much water we count, and why

Yearly running cost, 7 people

Payback against a pitcher

So when is RO worth it?

Read your water report first

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