Navien vs Rheem Tankless Water Heater 2026: NPE-240A2 and NPE-240S2 vs IKONIC Compared

Quick Answer: Navien and Rheem’s 199,000 BTU condensing flagships are closer than most comparisons suggest. ENERGY STAR rates the Navien NPE-240S2 and the Rheem IKONIC ECOHS200iN identically: 0.96 UEF, 5.8 GPM at a 67°F rise and 176 therms a year, and both makers give 15 years on the heat exchanger, 5 on parts and 1 on labor. Both now offer a pump version (Navien NPE-240A2, Rheem IKONIC SR). Choose Rheem for built-in Wi-Fi and full-unit replacement under the heat-exchanger warranty; choose Navien for 1/2-inch gas pipe up to 24 feet and a larger cascade. Navien’s warranty is void if you buy the heater online, so price it through a licensed installer.

Last updated November 4, 2026: rebuilt against Navien’s NPE-240S2/NPE-240A2 product pages and NPE-S2 warranty page, Rheem’s IKONIC S and SR Series product pages, ENERGY STAR’s certified water heater database and SupplyStop prices. Corrected from the August version: Rheem’s heat-exchanger warranty is 15 years (not 12), the IKONIC does not have LeakGuard, Rheem now sells a built-in-pump IKONIC (SR Series), and Navien’s EZNav panel has no built-in Wi-Fi. We compare published specs, prices and terms; we don’t test heaters ourselves.

Navien and Rheem are two of the three condensing gas tankless brands homeowners cross-shop most, with Rinnai as the third. Each sells its flagship with and without a built-in recirculation pump, so the fair comparison is pump against pump and no-pump against no-pump.

Navien vs Rheem at a glance

Flow, UEF, input and gas use from ENERGY STAR's certified water heater database (checked November 4, 2026); sizes, venting and warranty from navieninc.com and rheem.com product pages. Rheem lists no prices on its site and Home Depot blocks automated price checks.

By the numbers

• 176 therms a year is ENERGY STAR’s estimate for the Navien NPE-240S2 and for every 199,000 BTU Rheem IKONIC, pump or no pump. Navien’s pump-equipped NPE-240A2 is listed at 178.
• 5.8 GPM at a 67°F rise for the NPE-240S2, ECOHS200iN and ECOHSR200iN, and 5.6 GPM for the NPE-240A2, per ENERGY STAR. The 11.2 GPM on both brands’ pages needs a 35°F rise.
• 15 years on the heat exchanger from both makers. Rheem’s product pages say its term “includes full unit replacement”; Navien’s drops to 5 years if an external pump runs continuously.
• $389 separates Navien’s no-pump and pump flagships at SupplyStop ($1,810.00 vs $2,199.00, November 4, 2026).
• 1 year of labor from both brands, compared with up to 5 years from Rinnai if you register its Sensei heaters within 90 days.

Flagship vs flagship: what actually differs

On output and efficiency, there is nothing to choose between the no-pump models: same burner size, same ENERGY STAR flow and the same gas-use estimate. The practical differences are elsewhere.

• Wi-Fi: Rheem builds EcoNet Wi-Fi into the IKONIC ECOHS and ECOHSR models. Navien needs a NaviLink Lite ($159.95 at SupplyStop) or NaviLink module ($219.90) for app control.
• Gas and venting on retrofits: both rate their heaters for 1/2-inch gas line subject to local code; Navien specifies runs up to 24 feet. Rheem’s page adds flex venting through an existing B-vent up to 50 feet and approval for manufactured homes, which can simplify replacing an old tank. Navien allows 75 feet of 2-inch PVC against Rheem’s 70.
• Size: the Navien is about an inch shorter and half an inch shallower, and the NPE-240S2 weighs 73 lb.
• Large systems: Navien’s NPE-S2 series page lists Ready-Link cascading up to 32 units and common venting up to 12, which matters for ADUs and light commercial jobs more than for a single house.

For the Navien side in depth, see our Navien NPE-240S2 review, with Navien’s full temperature-rise table and its warranty exclusions. Rheem’s full range, including its electric models, is in our best Rheem tankless water heater guide.

Recirculation: both brands now build the pump in

The August version of this page said Rheem only offered built-in recirculation on a pro-channel model. That is no longer the full picture: Rheem’s IKONIC SR Series, including the ECOHSR200iN, puts a recirculation pump in the same cabinet as the S Series, and ENERGY STAR rates it at the same 0.96 UEF and 176 therms. Navien’s NPE-240A2 uses ComfortFlow, which Navien describes as a pump plus a small buffer tank aimed at the “cold water sandwich”, and it lists the A2 at 0.95 UEF and 178 therms, slightly behind its own no-pump S2.

If you already have a return line and an external pump, the no-pump models are the cheaper route. Keep the pump controlled: Navien treats a continuously running external pump as “uncontrolled recirculation” and cuts the heat-exchanger warranty to 5 years and parts to 3. Navien names an aquastat as the minimum control. Our recirculating pump guide covers the options.

Warranty and where you buy

Navien terms from its NPE-S2 warranty page; Rheem terms from the warranty note on its IKONIC S and SR Series product pages ("5-year parts, 1-year labor. Coverage varies by model. Exclusions apply."). Read the full warranty document for either brand before you buy.

Rheem’s full warranty certificate (AP21265 Rev 04) fills in the gaps the product page leaves: every term ends after 12,000 hours of operation, a continuously running recirculation pump drops the IKONIC to 3 years on the heat exchanger and parts, commercial use gets 5/5/1, and an online purchase is not listed as a void condition. Our Rheem IKONIC review walks through the certificate, the S vs SR models and Rheem’s winter flow table.

The biggest practical difference is Navien’s purchase rule. Buying an NPE-240S2 or NPE-240A2 online and hiring a plumber to fit it leaves you without Navien’s warranty, so Navien really is an installer-supplied product. Both brands also exclude damage from scale, so hard-water homes should plan for descaling. Our tankless warranty guide compares all the major brands’ terms.

The deciding factor: do you need electric?

If gas isn’t an option, such as a house with no gas line or an ADU, Navien drops out. Navien’s water heater range is gas tankless plus heat pump tanks, with no electric tankless model, while Rheem also makes a full electric tankless lineup, from the point-of-use RTEX-13 up to the whole-home RTEX-36.

Which should you buy?

• Want app control without extra hardware, or are replacing a tank through an existing B-vent: buy the Rheem IKONIC ECOHS200iN, or the ECOHSR200iN if you want a built-in pump (model-by-model details in our Rheem IKONIC review).
• Have a licensed Navien installer and want the lowest verified price on a 0.96 UEF flagship: buy the Navien NPE-240S2 ($1,810.00 at SupplyStop on November 4, 2026).
• Want Navien’s buffer-tank recirculation: buy the NPE-240A2, or size down to the NPE-210A2 or NPE-180A2.
• Want longer labor coverage than either: look at the Rinnai RX199iN, which gets 5 years of labor if registered within 90 days. Our Rinnai vs Navien and Rinnai vs Rheem comparisons cover the third brand.
• Still deciding between tankless and a storage tank? See tankless vs tank.

The bottom line

On efficiency and flow, Navien’s NPE-240S2 and Rheem’s IKONIC ECOHS200iN are a tie, and both brands now sell a version with the pump built in. Rheem’s edges are built-in Wi-Fi, B-vent retrofit flexibility and full-unit replacement under its 15-year term. Navien’s are its gas-pipe and venting allowances and a verifiable dealer price, offset by the strictest purchase rule of the big three. Size either one to your winter groundwater temperature first with our sizing guide, check venting in our venting guide, and get quotes from installers who service the brand.

Sources: Navien NPE-240S2 and NPE-240A2 product pages, NPE-S2 series and warranty pages (navieninc.com, November 4, 2026); Rheem Performance Platinum IKONIC S Series (ECOHS200iN) and SR Series (ECOHSR200iN) product pages (rheem.com, November 4, 2026); ENERGY STAR certified water heaters database (data.energystar.gov, November 4, 2026); SupplyStop prices (November 4, 2026).