Water Heater System GuideNavien and Rheem both appear in this source set through tankless water-heater facts, but this page is not a controlled head-to-head, and an apples-to-apples spec match was not verified. Navien's figures come from Navien pages, and Rheem's figures come from Rheem pages. This page does not declare a winner. Use it as a quote-review checklist, not as a lab-style ranking.
A note on how to read this comparison
The cited record does not test Navien and Rheem units under the same installation, water temperature, fuel, venting, recirculation, or household demand assumptions. Navien's facts come from its residential tankless page and NPE-240A2 product page. Rheem's facts come from its residential tankless page and an IKONIC article. Those are useful published records, but they are not a neutral test bench.
A fair quote review should keep each claim attached to the source that makes it. Navien's cited model facts are tied to NPE-240A2. Rheem's cited facts include several tankless lines and IKONIC savings statements. A homeowner comparing bids should ask each installer to identify the exact model and to connect every performance, efficiency, or savings claim to the product record for that model.
Navien published specs
Navien's own residential tankless page positions the company as the #1 manufacturer of all gas tankless water heaters, condensing and non-condensing, in North America. That is brand-position context, not a purchase decision by itself. The more useful comparison work happens at the cited NPE-240A2 product record.
On the NPE-240A2 page, Navien describes ComfortFlow as its exclusive built-in recirculation pump and buffer tank system. Navien also says it was the first to combine a buffer tank, recirculation pump and fine-tuned controls in a tankless water heater. The same NPE-240A2 record lists a Uniform Energy Factor of 0.95. For flow, Navien gives 11.2 GPM (42.4 l/m) at 35F rise, 8.7 GPM at 45F rise, and 5.6 GPM at 67F rise. The product page also lists an input range of 13,300 - 199,900 BTU/h and says the unit is field convertible between Natural Gas and Propane.
Navien also publishes a residential warranty for the NPE-240A2: 15 years heat exchanger, 5 years parts, 1 year labor. Those facts should stay attached to the cited model unless a separate source supports another Navien unit.
Rheem published specs
Rheem's own tankless page markets a full line of tankless water heaters positioned around family fit. The same page lists tankless lines that include IKONIC, RTG-R Series, ThermaForce, RTGH Series, and Professional Classic electric. That makes the line name an important part of quote review because the cited Rheem facts are not one universal tankless specification.
For IKONIC, Rheem lists .96 UEF, ENERGY STAR rated, and savings up to 33% per year in energy costs. Rheem also states IKONIC saves about $1,650 over 15 years compared with a standard 50-gallon tank model. Those are Rheem's cited savings claims, and they should not be turned into a household-specific estimate without the local assumptions supplied in the quote.
The cited Rheem tankless page also lists RTGH Series tankless at .93 UEF and RTG-R Series tankless at 0.82 UEF. Those figures show why a Rheem comparison should identify the quoted line and exact model before treating any efficiency claim as relevant.
How to actually choose
Use this comparison as a documentation filter. Navien's cited record is centered on NPE-240A2, ComfortFlow, temperature-rise flow figures, fuel convertibility, input range, and residential warranty. Rheem's cited record is centered on tankless line names, line-level UEF claims, and IKONIC savings statements. Those are different source sets, so the page should not be used to rank the brands by name alone.
Ask each installer to state the exact model, product line, fuel setup, venting or placement approach, hot-water demand assumption, water-temperature assumptions, warranty handling, and any savings basis. The better proposal is the one that documents the quoted equipment and explains the local installation assumptions. If a bid borrows a claim from a different line or model, keep that claim out of the decision until it is sourced.
Frequently asked questions
Is this a verified Navien and Rheem head-to-head?
No. This is not a controlled head-to-head, and an apples-to-apples spec match was not verified. It compares each brand's own cited published facts.
What Navien model facts are cited here?
The cited Navien product record is NPE-240A2, including ComfortFlow, UEF, flow by temperature rise, input range, fuel convertibility, and residential warranty.
What Rheem facts are cited here?
The cited Rheem facts include tankless line names, IKONIC UEF and savings statements, RTGH Series UEF, and RTG-R Series UEF.
Does this page declare a winner?
No. It is a source-backed checklist for comparing quotes, not a brand ranking.
What should decide the final choice?
Use exact model documentation, line or product-family match, installation assumptions, fuel setup, warranty handling, and household hot-water demand.