Bottled water feels cheap because you pay a few dollars at a time. Reverse osmosis feels expensive because you pay most of it on one day. Spread both over five years, at real drinking volumes, and the order flips — by thousands of dollars for a family, though not for everyone, and not against every bottled route. This article shows every line of the arithmetic, including the one bottled route that stays competitive for years.
We have not hands-on tested any of these systems, and we will not pretend otherwise. The bottled prices below come from retailer and delivery-service listings we checked in November 2026, and the reverse osmosis prices come from the same verified figures used across our reverse osmosis hub: manufacturer-store system and filter prices, checked November 2026. Prices move; the method does not.
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The four ways to buy a gallon, priced
Single-serve cases. Walmart’s Great Value 40-pack of 16.9 oz bottles was listed at $5.47 in checked November 2026 listings — about $0.14 a bottle. A case holds 40 × 16.9 oz = 676 oz, and 676 ÷ 128 = 5.28 gallons, so $5.47 ÷ 5.28 = $1.04 per gallon. Premium brands cost far more per gallon; this is close to the cheapest case water in America, which is the fair comparison.
Refill stations. Self-serve kiosks — Primo and similar machines in grocery and big-box stores, where you fill your own jug — typically charge $0.30–$0.50 per gallon in 2026 pricing roundups. We use $0.40 per gallon, the middle of that range: about $2.00 to fill a five-gallon jug, plus the jug itself (roughly $10–$15 once, excluded below).
Five-gallon delivery. Primo’s catalog showed $9.49 for a five-gallon purified bottle in a November 2026 price check, and Culligan dealers publish $6.50–$9.99 per five-gallon bottle by franchise — $7.75 at the Lansing, Michigan dealer, for example. We use Primo’s $9.49, which is $1.90 per gallon, bottle-only. Delivery fees (one published Primo example is $14.99 per delivery), cooler rental (roughly $10–$25 a month at Culligan dealers) and deposits all sit on top, and all are excluded below, which flatters delivery.
Home reverse osmosis. Our tank model uses our own calculator’s defaults: a $250 system (the class of our best reverse osmosis systems guide’s tank picks — iSpring RCC7AK at $239.99, APEC ROES-50 at around $231), $90 a year in filters, tap water at $10 per 1,000 gallons, and a traditional tank drain ratio of about 3 gallons per gallon purified, so each drinking gallon pulls 4 gallons from the tap. Filters are time-based, not volume-based — that fact drives everything below. The calculator’s own worked example ($250 system, $90 filters, a lower 2:1 waste ratio, 3 gallons a day) lands at $774 over five years; our family scenario lands at $756. Different assumptions, same neighbourhood.
Cost per gallon, side by side
| Route | Price basis | Cost per gallon |
|---|---|---|
| Single-serve cases (Great Value 40-pack) | $5.47 ÷ 5.28 gal per case | $1.04 |
| Refill station (own jug) | Midpoint of $0.30–$0.50/gal range | $0.40 |
| 5-gallon delivery (Primo) | $9.49 ÷ 5 gal, fees and cooler excluded | $1.90 |
| Tank RO, family of four (2 gal/day) | $756 ÷ 3,650 gal over 5 years | $0.21 |
| Tank RO, couple (1 gal/day) | $683 ÷ 1,825 gal over 5 years | $0.37 |
| Tank RO, heavy use (4 gal/day) | $902 ÷ 7,300 gal over 5 years | $0.12 |
| Tankless RO (Waterdrop G3P800, sale price) | $1,608 ÷ 3,650 gal over 5 years | $0.44 |
Two lessons hide in that table. First, RO’s per-gallon cost is fixed cost divided by volume: the same $610 of system and filters costs $0.37 a gallon over a couple’s 1,825 gallons and $0.12 over a heavy user’s 7,300. Bottled routes charge the same per gallon however much you drink. Second, the premium tankless system — $759 on sale plus around $800 of filters over five years, from our systems guide, plus about $49 of water at its 3:1 pure-to-drain ratio — lands at $0.44 a gallon for a family: cheaper than cases or delivery, but more than a $0.40 refill station at this volume. Hardware bragging rights do not repeal arithmetic.
Three households, five years, all the math
Each scenario counts drinking and cooking water only, over 5 × 365 = 1,825 days. RO totals are built the same way every time: $250 system + 4 filter years inside the 60 months at $90 ($360) + water at $10 per 1,000 gallons on 4 gallons of tap water per gallon purified. Run your own version — your prices, your volume, your waste ratio — in our true cost calculator.
| Scenario (5-year volume) | Cases at $1.04/gal | Refill at $0.40/gal | Delivery at $1.90/gal | Tank RO (all-in) |
|---|---|---|---|---|
| Couple, 1 gal/day (1,825 gal) | $1,891 | $730 | $3,464 | $683 |
| Family of four, 2 gal/day (3,650 gal) | $3,781 | $1,460 | $6,928 | $756 |
| Heavy user, 4 gal/day (7,300 gal) | $7,563 | $2,920 | $13,855 | $902 |
Worked once, in full, for the family: cases are 3,650 gal × $1.04 = $3,781 (and 3,650 × 128 oz ÷ 16.9 oz = about 27,600 bottles). Refill is 3,650 × $0.40 = $1,460. Delivery is 3,650 × $1.90 = $6,928 before any delivery fee. RO is $250 + $360 of filters + (3,650 × 4 gal tap × $0.01) = $756. The couple’s RO water line is $73, for $683; the heavy user’s is $292, for $902. Bottled totals scale exactly with thirst; the RO total moves only $219 across a fourfold difference in drinking.
Break-even: when the family system pays for itself
For the family, RO’s running cost is $7.50 a month in filters ($90 ÷ 12) plus $2.43 in water ($29.20 ÷ 12) — $9.93 a month after the $250 purchase. Against cases at $63.02 a month ($3,781 ÷ 60), RO saves $53.09 a month, recovering the $250 in 4.7 months — during month 5. Against the refill station, the honest, hardest comparison, the family spends $24.33 a month ($1,460 ÷ 60), saves $14.40, and breaks even at $250 ÷ $14.40 = 17.4 months — during month 18. Against delivery the answer is month 3, earlier still once its excluded fees count. Drink less and break-even stretches: the couple saves only $2.24 a month against refill, which is why we do not push couples who already refill toward a purchase on cost alone.
The non-cost factors, honestly
- Convenience cuts both ways. RO is unlimited water at the tap, at 2 a.m., with no shelf to restock. Cases and jugs mean hauling: the family’s case habit is about 14 cases a month, and a full five-gallon jug weighs about 42 pounds.
- Plastic. The family’s five years of cases is roughly 27,600 bottles. U.S. PIRG’s analysis of 2021 data put Americans’ plastic water bottle use at 86 billion bottles, about 29% recycled. Refill and delivery jugs are reused — why refill is the bottled route we criticise least.
- Storage. Cases and spare jugs eat a pantry corner for five years; a tank system eats most of a sink cabinet. Pick your sacrifice.
- Renters and restrictions. Under-sink RO needs a drilled faucet hole and a drain tap, which many leases forbid. If that is you, skip to our guide to the best countertop RO for renters — no plumbing, five-year costs about $609–$1,024, still well under cases.
- Waste water. RO’s non-money cost: a traditional tank system sends about 3 gallons to the drain per gallon purified. We explain the ratios and fixes in RO waste water explained. In water-stressed regions that can legitimately decide it for refill.
- Taste and trust. Some people prefer a specific spring water’s taste, or distrust their tap after a local contamination story. That is a preference, not an error — just price it from the tables above.
Where bottled water still wins
Bottled wins outright in four situations. Short horizons: a one-year lease or dorm — refill’s $146 a year at couple volume never justifies a $250 install you will abandon. Very low volume: a single person drinking half a gallon a day spends about $190 over five years on refill water; no RO system touches that. Emergencies and travel: cases are shelf-stable, portable and power-free; a stored case is preparedness, not waste. No-install homes: if you cannot drill or tap a drain and do not want a countertop unit, delivery or refill is the rational choice. Our AquaTru vs Waterdrop vs Frizzlife comparison covers the countertop middle ground.
Frequently asked questions
Is reverse osmosis cheaper than bottled water?
Against cases and delivery, yes, at almost any household volume — a family’s five-year tank RO total here is $756 against $3,781 for the cheapest cases. Against refill-station water at $0.40 a gallon, RO is cheaper over five years for families and heavy users, roughly a wash for couples, and more expensive for a light-drinking single person. Volume decides.
How long until an RO system pays for itself?
For our family-of-four scenario, during month 5 against single-serve cases and during month 18 against refill-station water, using a $250 system, $90 a year in filters and $9.93 a month in total running costs. Your break-even moves with your bottled price and your daily gallons — the true cost calculator computes it from your own inputs.
What does RO water cost per gallon?
On the assumptions shown here, $0.12–$0.37 per gallon for a $250 tank system depending on how much you drink, because filters are bought by the calendar, not the gallon. A premium tankless system at a $759 sale price works out to about $0.44 a gallon at family volume. All figures include the system’s purchase price spread over five years.
Is refill-station water the same as RO water?
Often, yes in process: most refill machines purify with reverse osmosis (some add UV or remineralization), which is why refill is the strongest bottled competitor — RO water without owning the machine. The difference is maintenance you cannot see: your home filters change on your schedule; a kiosk’s service record is the operator’s responsibility.
Does bottled water avoid RO’s waste water?
At your house, yes; in total, not entirely. Commercial bottling and refill plants also purify water, including by RO, but at industrial scale, and the drain water is not on your home water bill. If household wastewater decides it for you, our waste-water explainer compares tank, tankless and permeate-pump ratios.
The verdict
If your household drinks a gallon or more a day and will stay put two years or longer, a basic tank RO system is one of the clearest money decisions in home water: about $756 over five years for a family, against $3,781 for the cheapest cases and $6,928 for delivered jugs. If you already refill at $0.40 a gallon, the saving shrinks to about $700 for a family and nearly vanishes for a couple — buy RO then for convenience, not math, and say so. A light drinker, renter, or anyone gone in a year should keep the jugs without guilt. Either way, run your own household through the true cost calculator first — your gallons should make this call.