What filtered water actually costs per gallon

The short answer

For a three-person household over five years, filtered drinking water costs roughly 28 to 42 cents per gallon, depending on the system. Bottled water at typical US jug prices costs about $1.50 per gallon. The municipal water itself costs about half a cent.

The surprise is not that filters beat bottled water — that is obvious. The surprise is that a $35 pitcher and a $449 countertop system land within four cents of each other, because replacement filters, not hardware, dominate the total. Over ten years the more expensive machine becomes the cheaper water.

How the number is calculated

No hidden model. Four inputs, one division:

The 0.6 gallons per person per day covers drinking and cooking — not showering, laundry or the garden. For three people that is 657 gallons a year, or 3,285 gallons over five years. If your household differs, the calculator takes your own numbers.

Cost per gallon — 3 people, 5 years

The tap-water line is an order-of-magnitude figure: most US utilities charge somewhere between $2 and $8 per thousand gallons, so drinking water costs a household a few dollars a year. Whatever you spend beyond that is the price of treatment, not of water.

Filters are the cost. The machine is a rounding error.

Split each five-year total into hardware and consumables and the picture inverts:

The pitcher is the clearest case. Its certified filter life is 15 gallons. A three-person household drinks through roughly 44 filters a year. The $35 sticker buys you the jug; the water is on a subscription you did not sign.

Stretch the horizon and the ranking flips

In year one the pitcher wins by a factor of three. By year ten the countertop system is the cheapest water on the page. If you are renting for a year, buy the cheap thing. If this is your home, the arithmetic points the other way — provided the machine lasts, which is the assumption doing the most work in that last column.

Cost is the second question. Certification is the first.

A cheap gallon of the wrong treatment is not a bargain. What each option is independently certified to reduce — not what the box says:

• ZeroWater pitcher — IAPMO R&T, to NSF/ANSI 42 and 53: chlorine taste and odour (99.4%), lead (98.8%), hexavalent chromium (99.4%), mercury (94.2%), PFOA/PFOS (99.8%). Not certified for TDS — despite the meter the brand is known for — nor for fluoride, arsenic, cysts or bacteria.
• Waterdrop G3P800 — IAPMO R&T, to NSF/ANSI 58, and that certified performance table contains a single line: TDS. NSF/ANSI 372 is also held, but that governs the lead content of the unit's own parts, not lead removal from your water. The PFAS, arsenic and lead figures shown at retail come from SGS laboratory tests, which Waterdrop reports separately from the certification. The model does not appear in NSF International's own certified-products database.
• AquaTru — the manufacturer states NSF certification for a range of contaminants. Confirm the exact model against your exact contaminant in the certifier's database before buying.

What this page does not include

• Reverse-osmosis reject water. The Waterdrop sends about one gallon to the drain for every three it produces — roughly 217 gallons a year here. At municipal rates that is under two dollars a year, so it barely moves the cost; as an environmental cost it is real, and we would rather name it than bury it.
• Installation labour. The under-sink unit assumes a DIY fit. A plumber typically adds $150–$300, which on a five-year horizon is another 5–9 cents a gallon.
• Whole-house systems. They treat every tap, so dividing their cost by drinking gallons flatters or damns them arbitrarily. They belong to a different question, and the calculator handles them there.
• Your actual prices. These are list prices. Filters are frequently discounted in multipacks, which is the single easiest way to move the numbers above in your favour.

Method and sources

Consumption of 0.6 gallons per person per day for drinking and cooking is a planning assumption, at the higher end of typical guidance, chosen so the running costs are not understated. Hardware and filter prices are US list prices checked in August 2026 and will drift. Electricity is estimated at $10–15 a year for units with a pump; it is the least certain figure here and also the smallest.

Certification data comes from the certifiers, not from retailers: NSF certified drinking-water treatment units, IAPMO R&T listings, and the WQA. General guidance from the CDC and the EPA.

Some links on this site are affiliate links; options shown without a link earn us nothing. We do not rank by commission, and on this page the cheapest water is not the option that pays us most.