How Much Does a Reverse Osmosis System Cost? Purchase, Installation and 5-Year Running Costs

An RO system's purchase price ranges from about $150 for a basic countertop unit to $8,000 for a whole-house system, depending on type, according to the two cost surveys this article relies on. That spread is wide enough that "how much does RO cost" genuinely depends on which type of system you're asking about, which is why the table below separates them rather than quoting one blended number.

Table 1. System Cost by Type, as Reported by Two Published Surveys

These are two separate sources, shown in their own columns, not blended into one number. A tank system and a tankless system fall into the same general under-sink price range in these surveys, even though they differ in footprint and wastewater efficiency.

What makes one system cost more than another

• Tank vs. tankless. A tankless system generally costs more upfront than a comparable tank system.

• Number of stages. More filtration stages before and after the membrane add cost.

• Daily production (GPD). Higher-capacity systems cost more.

• Pumps. Systems with a booster or permeate pump add cost over gravity-fed designs.

• Remineralization. An added remineralization stage increases the price.

• Certification. NSF/ANSI 58-certified systems can carry a premium over uncertified units.

Why published estimates disagree

HomeGuide and This Old House disagree sharply on whole-house RO, 4,800–8,000 versus 1,000–4,800, largely because they were published roughly eight months apart and likely use different survey methods and contractor samples. This Old House's and Angi's figures are close enough that they likely draw on a shared data source, so this article treats them as one source rather than two independent confirmations. Treat any single number in either range as an estimate, not a quote for your specific home.

Installation Cost: DIY or a Plumber?

DIY installation costs only the parts, while professional installation adds $150 to $700 in labor depending on what your kitchen already has in place. Which route makes sense largely comes down to whether your sink already has a compatible faucet hole and a nearby drain connection, since that single factor determines whether installation is a quick parts-only job or a more involved one worth paying a plumber for.

Installing it yourself

A DIY under-sink install involves connecting a drain line and saddle valve, adding an air gap, drilling a faucet hole if one doesn't exist, and finding space for the tank. If your sink already has a compatible faucet hole and a nearby drain, the job is mostly connecting fittings. If it doesn't, drilling and fitting take more time but still cost only the parts, not labor.

Professional installation

Table 2. Professional Installation Costs

A lab water test isn't required to install an RO system, but it's a reasonable add-on if you want a baseline reading of what's actually in your water before and after filtration.

Ongoing Costs: Filters, Membrane, Water and Power

Ongoing RO costs come from four sources: pre- and post-filters, the membrane, the water sent to the drain, and electricity for any pumps, and all four are the part most cost guides leave out. A purchase price alone tells you almost nothing about what an RO system actually costs to live with over several years, which is exactly why the worked 5-year example later in this article adds all four together rather than stopping at the sticker price.

Filters and membrane

Pre-filters typically need replacing every 6 to 12 months, and the membrane every 2 to 5 years, according to the two surveys this article relies on. HomeGuide (Jul 2025) puts membrane replacement at 2 to 5 years; This Old House (Mar 2026) narrows that to 3 to 5 years, pricing a replacement membrane at $50 to $100. EPA's own figure for replacement membranes is $20 to $100. For the specific signs a membrane needs replacing now rather than on a fixed schedule, see our guide on when your RO membrane needs replacing. Shop replacement RO filters when it's time.

The water RO sends to the drain

A typical point-of-use RO system is only 10 to 20% efficient, meaning it sends 4 to 9 gallons to the drain for every gallon of treated water produced, according to EPA. Less efficient units can send up to 10 gallons to the drain per treated gallon. The formula: gallons to the drain per treated gallon = (1 ÷ efficiency) − 1.

Table 3. Water and Sewer Cost per Treated Gallon by Efficiency (at EPA's $15.21 per 1,000 gallons)

The math for the 20% row: 1 ÷ 0.20 = 5 gallons drawn per gallon treated; 5 × $15.21 ÷ 1,000 = $0.076, rounded to $0.08. A WaterSense-labeled system sends no more than 2.3 gallons to the drain per gallon treated, which works out to roughly 30% efficiency and the lowest water cost per gallon in this table.

Electricity for pumps and UV

Only tankless RO systems and systems with a booster pump or UV stage draw electricity; gravity-fed tank systems with no pump use none. The formula: cost = watts × hours used ÷ 1,000 × rate per kWh. At the US residential average of 18.31¢/kWh (EIA, July 2026), a system's electricity cost depends entirely on its pump's wattage and how many hours a day it actually runs, which varies by household water use. This article doesn't assign a wattage figure unless it's named from a specific system's own spec sheet, since an invented number would be more misleading than no number at all.

The 5-Year Cost of Owning an RO System

A worked example for one tankless system DFS sells comes to roughly $928 over 5 years, or about $0.20 per treated gallon, once filters, membrane and water cost are included. This is one example, not an average across all systems, and the point of walking through it in full is to show exactly how the pieces from the sections above (system price, filter cost, and the reject-water math from Table 3) combine into a single real number rather than leaving readers to do that math themselves.

A worked example

Table 4. 5-Year Cost Example: USWF Tankless RO System (DiscountFilterStore.com, priced September 2026)

5-year total: 308.38+(154.79 × 4) = $927.54 Cost per treated gallon over 5 years: $927.54 ÷ (938 gal/yr × 5) = $0.198, or about $0.20/gal

This example assumes the filter set is replaced once a year, a reasonable interval for pre- and post-filters but not a figure confirmed on this specific product's own page, and it doesn't include a membrane replacement, which this system's manufacturer doesn't specify on a fixed schedule within the first 5 years. Your actual cost will differ based on your household's water use, your local water rate, and your specific system.

RO vs. bottled water

At $0.20 per gallon in this worked example, RO costs a fraction of bottled water's $1.44 per gallon average wholesale price (IBWA, 2023). Retail bottled water, what you'd actually pay at a store, runs higher than that wholesale figure. For a full breakdown of bottled water costs by format, see our guide on filtered water vs. bottled water cost.

How to Lower the Cost of Reverse Osmosis

Choosing a WaterSense-labeled system and maintaining it yourself are the two most direct ways to reduce RO's ongoing cost. Neither requires a more expensive system overall; both are about getting the efficiency and maintenance habits right on whatever system you already own or are about to buy.

Choose a WaterSense-labeled system

A WaterSense-labeled RO system sends no more than 2.3 gallons to the drain per gallon of treated water, compared with 4 to 10 gallons for a typical conventional system. EPA estimates this saves more than 3,100 gallons of water a year per system and nearly $50 a year in water costs.

Maintain it yourself

• Change filters on the schedule your system specifies, not only when flow noticeably drops.

• Buy complete filter sets rather than individual cartridges when it's cheaper per unit.

• Consider a permeate pump, a non-electric accessory that EPA notes can improve a system's efficiency without adding to your electric bill.

Shop RO filters and check what an inline RO filter actually does before assuming every stage in your system needs the most expensive replacement available.

What to Check Before You Buy

NSF/ANSI 58 certification, a stated efficiency or recovery rating, and daily production capacity (GPD) are the three specs worth checking before you buy an RO system.

Certifications that matter

NSF/ANSI 58 requires at least 75% reduction in total dissolved solids, and model plumbing codes (the IPC and UPC) require point-of-use RO systems to meet it. ASSE 1086 separately sets a 40% minimum efficiency standard. No federal or state law actually requires an RO system to carry any certification at all, according to EPA, so checking for it yourself is the only way to confirm a system meets these standards.

Capacity and efficiency

Table 5. Buyer's Checklist

Frequently Asked Questions

How much does it cost to install a reverse osmosis system?

Professional installation labor runs $150 to $500 (HomeGuide, Jul 2025), or $300 to $700 for installation overall (This Old House, Mar 2026). DIY installation costs only the parts, since the labor is your own time.

How much does a whole-house reverse osmosis system cost?

Published estimates disagree significantly: This Old House (Mar 2026) puts point-of-entry systems at $1,000 to $4,800, while HomeGuide (Jul 2025) puts them at $4,800 to $8,000. The gap likely reflects different survey dates and contractor samples, so treat both as estimates rather than a single reliable figure.

How much does it cost to maintain an RO system each year?

Ongoing costs include pre-filters (replaced every 6–12 months), a membrane (every 2–5 years, 20–100 per EPA), and the water sent to the drain, which varies by system efficiency. This Old House estimates roughly $400 a year in operating costs, though your actual figure depends on your specific system and local water rate.

How much water does reverse osmosis waste?

A typical point-of-use system sends 4 to 9 gallons to the drain for every gallon of treated water, and less efficient units can send up to 10 gallons, according to EPA. A WaterSense-labeled system caps that at 2.3 gallons per treated gallon.

Is reverse osmosis cheaper than bottled water?

Generally, yes. This article's worked example puts RO at about $0.20 per treated gallon over 5 years, compared with bottled water's $1.44 per gallon average wholesale price (IBWA, 2023); retail bottled water costs more than that wholesale figure.

How long does an RO membrane last?

Published estimates range from 2 to 5 years (HomeGuide) or 3 to 5 years (This Old House). EPA requires membranes to pass a test demonstrating at least 1 year of service life under the ASSE 1086 challenge test, with real-world life typically longer than that minimum.

Sources

• EPA WaterSense: Point-of-Use Reverse Osmosis Systems (updated August 2026)

• EPA WaterSense Supporting Statement for Point-of-Use Reverse Osmosis Systems (November 2024)

• EPA WaterSense Performance Summary for Point-of-Use Reverse Osmosis Systems (December 2024)

• EPA WaterSense Performance Overview (December 2024)

• EIA Electric Power Monthly (data released September 24, 2026)

• IBWA: bottledwater.org (2023 pricing data)

• HomeGuide: Reverse Osmosis System Cost (byline July 14, 2025)

• This Old House: Reverse Osmosis System Cost (March 30, 2026)

• Angi, reverse osmosis system cost estimates (2026)

• DiscountFilterStore.com product pages: USWF Tankless RO Water Filter System and its replacement filter set (priced September 2026)