Reverse osmosis system cost calculator

What you pay for, and what keeps coming back

A reverse osmosis system costs you four things: the unit, the installation if it goes under the sink, the filters, and the water it sends down the drain. The unit and the install are paid once. Filters come back every 6 to 24 months for as long as you own it.

Over 5 years for a household of 3, filters are 51% of the total for the Waterdrop M6SL and 75% for the Aquasana SmartFlow, at brand prices checked Oct 13, 2026. At the brands' intervals they run $70 to $310 a year. The membrane, the part that does the reverse osmosis, is usually the priciest single filter:

Waterdrop's tankless systems have the dearest membranes, rated for 2 years or 2,200 gallons. Per year their filters come to $160 and $175, between AquaTru's $130 and Aquasana's $310. Which system to buy for your water is a separate question, answered in the reverse osmosis comparison and the countertop RO guide.

Months or gallons: what heavy use does to the filter bill

Most RO filters carry two limits, months and gallons, and the brand says to change them at whichever comes first. The gallons depend on how much RO water your household drinks and cooks with. The EPA Exposure Factors Handbook puts the average for people who drink tap water at about 0.29 gallons a day, and the top 5% at 0.79 gallons or more. For 3 people that's 318 gallons a year at typical use and 865 at heavy use.

At typical use for 3 people, every filter in the calculator reaches its full interval except the AquaTru Carafe’s: its VOC and RO filters last 11.3 and 22.7 months instead of 12 and 24. At heavy use, more run out early:

• AquaTru Under Sink: its data sheet rates the pre-filter and the VOC filter at 360 gallons (the product page says 600, and the calculator uses the lower figure). Both last 5.0 months instead of 6 and 12, and the RO filter 16.6 instead of 24. Filters go from $130 to $211 a year.
• Aquasana SmartFlow: the carbon pair is rated for 250 gallons, so it lasts 3.5 months instead of 6. Filters go from $310 to $444 a year.
• AquaTru Carafe: its filters are rated for half the gallons of the Classic, so the yearly cost goes from $134 to $288.

Waterdrop's 550, 1,100 and 2,200-gallon ratings hold even at heavy use for 3 people. If RO water also fills a coffee maker, an ice maker or the pets' bowls, choose "Heavy" in the calculator.

Does reverse osmosis raise your water bill?

A little. Reverse osmosis flushes part of the water it takes in to keep the membrane clear. AquaTru's data sheet rates the Under Sink at 25% efficiency, about 3 gallons to drain for every gallon you keep. The Aquasana SmartFlow is close behind at 27.4%. Waterdrop rates its systems at 3 gallons kept for every 1 to drain. Gallons to drain for every system, against EPA's 30% bar, are on the waste water calculator.

At typical use for 3 people, that's about 953 gallons a year to drain for the AquaTru Under Sink and 105 for a Waterdrop. At $15.21 per 1,000 gallons of water and sewer, the 2023 average EPA used for WaterSense, about $14.49 and $1.59 a year. EPA WaterSense says the average family spends more than $1,000 a year on water, so even the higher figure is under 2% of the bill. Heavy use takes the AquaTru to about $39 a year.

The rate is the one input to change. Water and sewer prices differ by utility, so find your rate per 1,000 gallons on the bill. If it shows CCF, one CCF is 748 gallons.

Two other costs sit outside the calculator. Countertop units don't drain. The iSpring RCD100 sends reject water back to its feed tank and collects the rest in a side tank you empty, which iSpring suggests using for mopping or plants. And on a septic system, UNL Extension notes that RO wastewater adds to the load on the tank.

Installation cost

Countertop units cost nothing to install: you plug them in and fill the feed tank by hand. That's why the calculator drops the installation field when you pick "Countertop".

For under-sink systems, none of the four brands here publishes an installation price as of Oct 13, 2026, and I couldn't find a national figure that traces back to data. Waterdrop's buying guide says drilling a granite or quartz countertop for the faucet, or adding a drain line, costs "typically between $150-$600" extra. It doesn't say where the figure comes from, so treat it as one brand's estimate.

What moves a quote is the faucet hole, the drain connection and local code. Massachusetts requires a licensed plumber for the job, Aquasana's manual notes, citing the state plumbing code 248 CMR. Minnesota prohibits saddle fittings on drain pipes, per the Minnesota Department of Health. AquaTru recommends a certified plumber for its under-sink model. Waterdrop advertises a 30-minute install and lists installers by ZIP code on its site. Dealer-installed systems fold installation into one quote: see what owners paid for a Culligan RO.

Whether you can do it yourself, and what the job involves, is in our reverse osmosis installation guide. If you hire it out, enter the quote in the calculator. It adds the same amount to every under-sink system.

Whole house reverse osmosis cost

The calculator covers systems for one tap. A whole house RO system treats every gallon the house uses, and costs far more. UNL Extension says point-of-entry RO units "are more costly to purchase, install and operate" than point-of-use ones. Waterdrop's buying guide puts them at "between $4,800 and over $8,000", again without a source, and says the job may need a master plumber, large tanks and booster pumps.

The running cost grows with the volume. EPA WaterSense puts home use at 82 gallons a person a day, against about 0.29 for drinking and cooking. For 3 people using 70% of that indoors, about 63,000 gallons a year would pass the membrane. Even at Waterdrop's under-sink ratio of 1 gallon to drain for every 3 kept, about 21,000 gallons would go to drain, or $315 a year at $15.21 per 1,000.

If what you want at every tap is less chlorine taste and smell, a carbon whole house filter is the cheaper route. The five in our whole house water filter cost calculator cost $1,160 to $4,198 as of Oct 13, 2026, including a filter and softener combo, and send no water to drain.

How to pay less

Take the brand's own deal. As of Oct 13, 2026, Aquasana sells the SmartFlow at $449.99, or $359.99 with its filter subscription, which also takes 15% off replacement filters. At the subscription prices the filters come to about $263 a year instead of $310. Waterdrop shows a code on its product pages: the X12 drops from $1,299 to $1,099, the G3P800 from $999 to $849 and the M6SL from $329 to $269.

Buy filters in the brand's pack. iSpring's F7RCD100 2-year pack is $160.99, against $231.93 for the same seven filters bought one by one. SimPure's 12-month kit is $99.99, against $115.96 for two CF and two RO filters bought separately. AquaTru's 2-year pack costs the same as its three filters bought separately, so there's nothing to gain there.

Match the gallon ratings to your household. A big household that drinks a lot of RO water pays most for filters with low gallon ratings. In the calculator, switch to "Heavy" and compare: the AquaTru Carafe and the Aquasana move up the list, the Waterdrop systems don't.

Consider a countertop unit. Over 5 years for 3 people, four of the five countertop units in the calculator cost less than the cheapest under-sink system, before its installation is counted. The trade-off is refilling a feed tank by hand and giving up counter space.