Navien vs Rinnai Tankless Water Heater (2026)

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Quick answer from a licensed plumber: Flow does not separate these two. At a 35°F rise Navien lists 11.2 GPM for the NPE-240A2 and Rinnai lists 11.1 GPM for the RX199iN (its spec sheet says 11.0). The differences are recirculation, weight and how you buy. Every Navien NPE-A2 has a pump and a 0.5-gallon buffer tank built in; the Rinnai RXP has a pump and the RX has none. Navien says its warranty is void on a unit bought through the internet, so it comes from a Navien dealer. Rinnai publishes a list of authorized online sellers, and we link one Amazon listing whose seller name matches that list.

Our take: want the pump and buffer tank built in and will buy from a dealer? The Navien NPE-240A2 (no Amazon link; Navien’s warranty is void on internet purchases). Want the lighter unit from a seller whose name matches Rinnai’s authorized list? The Rinnai RX199iN: Check the Rinnai RX199iN on Amazon. Want Rinnai with a built-in pump? The smaller RXP160iN (9.0 GPM at most, and 6.9 GPM at a 45°F rise per Rinnai, against 8.7 for the Navien) (not linked: on 10/3/2026 its listing did not meet our seller rules).

Navien and Rinnai both sell condensing gas tankless heaters in the whole-house size. We compare the top of each range: the Navien NPE-240A2 and the Rinnai SENSEI RX199iN, with the RXP pump version. Both are 199,000-class whole-house units that vent with plastic pipe. The maker documents show the flow figures are nearly the same. What differs is how each handles recirculation, what each asks of your gas line and water, and how the warranty treats where you bought it. We also note the smaller sizes: Navien makes the NPE-180A2 and NPE-210A2, and Rinnai the RX130iN, RX160iN and RX180iN. We do not cover Rinnai’s non-condensing RE and REP series, Navien’s NPE-S2 series, or Rheem; our best gas tankless water heater guide covers Rheem.

Navien vs Rinnai Side by Side

Spec	Navien NPE-240A2	Rinnai RX199iN / RXP199iN
Input (min–max BTU/h)	13,300–199,900	15,000–199,000
Flow at 35°F rise	11.2 GPM	11.1 GPM (brochure); 11.0 GPM (spec sheet)
Flow at 45°F rise	8.7 GPM	8.6 GPM
Flow at 60°F rise	6.5 GPM	6.5 GPM
Flow at 70°F rise	5.6 GPM	5.5 GPM
UEF	0.95	0.98
Recirculation	Pump and 0.5-gallon buffer tank built in (A2)	Pump built in on RXP; none on RX (add-on kit available)
Vent (2-inch / 3-inch)	75 ft / 150 ft; PVC, CPVC, approved polypropylene, stainless	75 ft / 150 ft; PVC, CPVC, polypropylene; ABS exhaust: Rinnai’s manual conflicts (see Before You Buy)
Allowance per 90° elbow (2-inch / 3-inch)	8 ft / 5 ft	6 ft / 5 ft
Gas and water connections	3/4-inch NPT gas, cold and hot	3/4-inch NPT gas, cold and hot
Natural gas supply pressure	3.5–10.5 in. WC	3.5–10.5 in. WC
Propane	Kit included, installed by a qualified gas servicer	Set in the controller menu with a propane label; kit is labels and a manual (Rinnai)
Weight	77 lb	55 lb (RX199iN); 58 lb (RXP199iN)
Residential warranty	15 yr heat exchanger, 5 yr parts, 1 yr labor	15 yr heat exchanger (or 12,000 hours), 5 yr parts, labor 5 yr if registered within 90 days, otherwise 1 yr
Where the warranty stands	Void if bought through the internet or e-commerce channels, or via an unauthorized supplier; licensed installer required	Not valid if bought from an unauthorized PRO or online dealer (Rinnai’s site); trained pro recommended by the warranty
Amazon link on this page	None (no Navien heater found)	Yes: RX199iN, third-party seller (eFaucets)

Figures come from the Navien and Rinnai documents listed under Sources. Rinnai’s brochure and spec sheet differ on the maximum flow (11.1 vs 11.0 GPM), so we show both. Navien’s pump and buffer tank are listed for the A2 models; its NPE-S2 series is not covered here. When we checked on September 29, 2026, our Amazon searches turned up no Navien water heater, only parts, so the Navien side has no link. On October 3, 2026 the Rinnai RX199iN was listed In Stock on Amazon from eFaucets, a third-party seller, not Rinnai or Amazon. Its name matches an entry on Rinnai’s authorized e-tailer list (efaucets.com), but Amazon does not confirm that the storefront is the same company. The RXP160iN is no longer linked: on 10/3/2026 its listing did not meet our seller rules. See our tank vs tankless comparison if you are still deciding between a tank and a tankless, and our best tankless water heater guide for the wider field.

Built-In Buffer Tank and Pump

Navien NPE-240A2 Condensing Tankless Water Heater

13,300–199,900 BTU/h · 11.2 GPM at a 35°F rise · UEF 0.95 · 120 V · 3/4-inch NPT gas, hot and cold · 2- or 3-inch PVC, CPVC, polypropylene or stainless vent · built-in recirculation pump and 0.5-gallon buffer tank · 77 lb

The NPE-A2 is the Navien with ComfortFlow, which Navien describes as a buffer tank and a recirculation pump built into the heater. Navien’s FAQ says the buffer tank reduces the “cold water sandwich” and the pump cuts the wait for hot water. Its installation manual gives two modes. Internal recirculation pre-heats inside the unit, and the recirculation inlet stays capped with no return line connected. External recirculation uses a return line, up to 500 feet of equivalent length in 3/4-inch copper or 100 feet in 1/2-inch copper before you need an external pump. Navien lists a minimum flow of 0.5 GPM, or under 0.01 GPM when the optional ComfortFlow recirculation is on, and says recirculation raises energy use.

The buying rules matter more than the spec sheet. Navien’s warranty says it is void on a product purchased through the internet or other e-commerce channels, or through an installer who got it from a supplier Navien has not authorized, and on an installation by a non-licensed installer. For a single-family home on standard or controlled recirculation, it lists 15 years on the heat exchanger, 5 on parts and 1 on labor. If the heater has ever run with an external pump circulating continuously, parts drop to 3 years and the heat exchanger to 5. Navien’s FAQ says technical support cannot send parts for an unregistered product. On September 29, 2026 our Amazon searches returned Navien parts but no Navien tankless water heater, so nothing is linked on this side.

Buffer tank (0.5 gallon) and recirculation pump built in, per Navien’s spec sheet
Lists 11.2 GPM at a 35°F rise and 6.5 GPM at 60°F
Navien lists 1/2-inch gas pipe for runs up to 24 feet, subject to local codes
Propane conversion kit included, per Navien’s spec sheet

Heaviest of the two here: 77 lb, against 55 lb for the Rinnai RX199iN
Navien says its warranty is void on units bought through the internet or other e-commerce channels, so buy from a Navien dealer
We found no Navien water heater on Amazon on the check date, so there is no link
Continuous external-pump loops cut the parts and heat exchanger coverage to 3 and 5 years

Verdict: The pick if you want the buffer tank and pump built in, will buy from a Navien dealer, and will have a licensed installer set it up.

Lighter Unit, Pump Optional (RXP)

Rinnai SENSEI RX199iN and RXP Condensing Tankless Water Heaters

15,000–199,000 BTU/h (RX199iN, RXP199iN) · 11.1 GPM at a 35°F rise per Rinnai’s brochure (its spec sheet says 11.0) · UEF 0.98 · 120 V · 3/4-inch NPT gas, hot and cold · 2- or 3-inch PVC, CPVC or polypropylene vent, or concentric · natural gas or propane set in the controller menu · 55 lb (RX199iN), 58 lb (RXP199iN)

The SENSEI RX series is Rinnai’s condensing line. The RX199iN has no pump. The RXP models add an internal pump and Smart-Circ, which Rinnai’s manual says starts learning your hot water use over the first 24 hours. Recirculation runs either on a dedicated return line (3/4-inch pipe up to 400 feet in total, 1/2-inch up to 100 feet) or in crossover mode, with a thermal bypass valve at the farthest fixture; Rinnai warns warm water may come out of the cold side of the faucet for a few seconds. The Rinnai documents we opened do not mention a buffer tank. Rinnai also lists an add-on kit, RX2RXPCK, that turns a no-pump RX into a pump model.

Rinnai’s flow table lands within 0.1 GPM of Navien’s at every rise we compared (our arithmetic): 11.1 GPM at 35°F, 8.6 at 45°F, 6.5 at 60°F and 5.5 at 70°F. The warranty is 15 years on the heat exchanger (or 12,000 operating hours, whichever comes first), 5 years on parts and 5 years of labor if you register within 90 days of installation; otherwise labor is 1 year. Rinnai’s site says products from unauthorized online dealers carry no Rinnai warranty, and it publishes a list of authorized e-tailers that may also sell through Amazon. The RX199iN listing was In Stock from eFaucets on October 3, 2026, a third-party seller whose name matches that list; Amazon does not verify the match, so check the seller name at checkout. This is our third-party exception: no Rinnai unit we checked was sold by Amazon or Rinnai. We no longer link the smaller RXP160iN (9.0 GPM at most); on 10/3/2026 its listing did not meet our seller rules. We do not link the RXP199iN: its Amazon offer showed Voomi Supply in one of our reads and Big Frog Supply in another, and Voomi Supply is not on Rinnai’s list.

Rinnai lists a UEF of 0.98 for the RX199iN and RXP199iN
Weighs 55 lb, about 22 lb less than the NPE-240A2 (our arithmetic)
Gas type is set in the controller menu with a label, not a parts swap, per Rinnai’s manuals
Choose a pump model (RXP) or add the RX2RXPCK kit later, per Rinnai

The linked listing is from a third-party seller, not Rinnai or Amazon
The RX199iN has no recirculation, and the RXP160iN tops out at 9.0 GPM
Crossover recirculation can put warm water in the cold line, per the manual
Rinnai’s own documents disagree on small points: 11.0 vs 11.1 GPM, and 30 vs 90 days to register for proof of purchase

Verdict: The pick if you want the lighter unit, will buy online from a seller whose name matches Rinnai’s authorized list (check it at checkout), and will pay a qualified pro to install it. Choose an RXP if you want the pump built in.

Check the Rinnai RX199iN on Amazon

Not linked: Rinnai RXP160iN (with pump) — on 10/3/2026 its Amazon listing did not meet our seller rules. We re-check listings every week.

I send an occasional note when a new guide goes up — repairs worth doing yourself, and the parts that actually last. No spam, no course funnel; written by a licensed Georgia plumber.

Before You Buy

Size by temperature rise, not by BTU. Rise is the hot water setting minus your incoming water temperature. A 120°F setting with 60°F incoming water is a 60°F rise (our arithmetic), and both makers list 6.5 GPM at that rise. Add up the fixtures that run at the same time, then compare with the flow table. Our tankless water heater size calculator does the adding.
Check the gas line. Both heaters need about 200 cubic feet of natural gas per hour at full fire (our arithmetic from 199,900 BTU/h at 1,000 BTU per cubic foot), on top of any other gas appliance. Both manuals print NFPA 54 natural gas pipe tables with matching figures. On the low-pressure table (0.5 in. WC drop), 3/4-inch pipe carries 199 cubic feet per hour at 30 feet, and 1/2-inch carries 95 (Rinnai’s table; Navien’s starts at 3/4-inch), so a long run on low pressure can call for larger pipe (our reading of the tables). The higher-pressure table (3.0 in. WC drop, meant for 6 in. WC supply or more per Navien and 8 in. or more per Rinnai) lets 1/2-inch carry 250 at 30 feet. Ask your gas utility what pressure your meter delivers. Navien’s manual recommends making the heater the first appliance after the meter; its FAQ says that is not required if the line is sized right.
Plan the vent and drain. Both list 2-inch vent to 75 feet and 3-inch to 150 feet, less an allowance for each elbow, and both need a condensate drain. Rinnai’s manual conflicts on ABS: its materials table marks ABS “not permitted (for exhaust)”, while its room-air venting section says ABS is acceptable exhaust in the U.S. and intake only in Canada, so have the installer confirm the vent material for your install. Navien says the heater limits exhaust to 149°F so Schedule 40 PVC can be used, but in high-temperature applications where the exhaust can run hotter, the vent must be CPVC, approved polypropylene or stainless, and with 2-inch vent the first 3 feet must be CPVC. For an outdoor install, Navien sells an outdoor vent kit and Rinnai an outdoor vent cap, and Navien’s FAQ recommends outdoor mounting only in mild climates.
Test your water. Both makers give the same core limits: total hardness up to 200 mg/L, pH 6.5 to 8.5, total dissolved solids up to 500 mg/L, iron up to 0.3 mg/L and manganese up to 0.05 mg/L. Navien also lists sulfate and chlorine limits, and Rinnai lists dissolved carbon dioxide. Over 200 mg/L, both require a softener or their scale product. Scale build-up is what the flush removes; our guide to descaling a tankless water heater walks through the flush.
Decide on recirculation now. A built-in pump saves adding one later. Both retrofit pumps in our hot water recirculating pump guide, from Watts and APCOM, are not for tankless heaters, per those makers, so on a tankless you rely on the heater’s own pump or the maker’s accessories. Both makers say to insulate hot and return lines.

Warranty, Registration and Where You Buy

Read this before you click any buy button. Navien’s residential warranty runs from the date of installation, requires a properly licensed plumber or contractor, and is void if the product was bought through the internet or other e-commerce channels or from a supplier Navien has not authorized. Navien wants proof of the installation date, and its FAQ says technical support cannot send parts without a registered product (serial number, installation date, homeowner and installer details). Rinnai’s warranty runs from the date of purchase and needs proof of purchase; its warranty document says a dated receipt or registration within 30 days works, while the manual says 90 days, so keep the dated receipt and register as soon as the heater is installed; registering within 30 days of purchase meets both documents. Registering within 90 days also extends labor coverage from 1 year to 5 (the warranty counts from installation, Rinnai’s website from purchase). Rinnai cuts the heat exchanger period to 8 years or 12,000 hours if temperature settings exceed 160°F. It adds that in California and Quebec, and other places that bar warranty benefits conditioned on registration, registration is not required to get the longer periods. Neither warranty covers water-quality or scale damage, and neither covers a space-heating-only use.

Who Should Install It

A gas tankless is licensed work. If you ever smell gas, Navien’s manual says not to light any appliance or touch any electrical switch, and to call your gas supplier from a neighbor’s phone, or the fire department if you cannot reach the supplier. Rinnai recommends a carbon monoxide alarm in the hallway near the bedrooms in each sleeping area. Navien’s manual says only a licensed professional should connect the gas supply or measure the inlet gas pressure, and its warranty requires a licensed installer. Rinnai’s manual says a trained and qualified professional must install the appliance, connect the gas and adjust the parameter settings; its warranty wording recommends an installer who has attended a Rinnai training class, and Rinnai’s site says the older wording required one. Propane conversion on a Navien is for a qualified service agency. Ask your building department whether a permit is needed. Once it is running, keep the Navien NPE-A2 error codes and Rinnai tankless error codes pages handy, and read our tankless installation cost guide for what changes the scope of the job.

FAQ

Is Navien or Rinnai better?

Not on flow. At a 35°F rise Navien lists 11.2 GPM for the NPE-240A2 and Rinnai lists 11.1 GPM for the RX199iN (its spec sheet says 11.0), and the two tables stay within 0.1 GPM at 45, 60 and 70°F (our arithmetic). The differences are recirculation (Navien A2 models have a pump and 0.5-gallon buffer tank built in; the Rinnai RXP has a pump and the RX has none), listed UEF (0.95 vs 0.98), weight (77 lb vs 55 lb) and warranty terms. Pick on those, on which one a local installer will service, and on where you can buy it under warranty.

Which one has built-in recirculation?

Every Navien NPE-A2 model, according to Navien’s spec sheet, which lists a built-in pump and a 0.5-gallon buffer tank. Rinnai builds a pump into the RXP models only; the RX199iN has none, though Rinnai sells an add-on kit for it. The Rinnai documents we opened do not mention a buffer tank. Both makers give return-line limits: Navien 500 feet of equivalent length in 3/4-inch copper, Rinnai 400 feet of 3/4-inch pipe in total.

Can I use 1/2-inch gas pipe for either?

Both have a 3/4-inch gas inlet. Navien says 1/2-inch pipe can be used up to 24 feet subject to local codes, and Rinnai lists the RX as 1/2-inch gas line compatible, with sizing left to the gas code tables. Whether it works depends on your supply pressure and total gas load. A 199,900 BTU/h heater needs about 200 cubic feet of gas per hour at 1,000 BTU per cubic foot (our arithmetic). The makers’ low-pressure table lists 1/2-inch pipe at 95 cubic feet per hour at 30 feet, and Navien’s low-pressure table starts at 3/4-inch. Have a licensed gas installer size the line.

Can I buy a Navien or Rinnai tankless online and keep the warranty?

Navien: no, according to its warranty, which is void on a product purchased through the internet or other e-commerce channels. Rinnai: only from an authorized dealer. Its warranty page says products from unauthorized online dealers carry no Rinnai warranty, and it lists authorized e-tailers that may also sell through Amazon. Check that the seller name matches that list, keep the receipt, and register the heater.

Do I need a water softener for either one?

Both makers list up to 200 mg/L (12 grains per gallon) of total hardness as the limit, pH 6.5 to 8.5 and up to 500 mg/L total dissolved solids. Above 200 mg/L both say a softener or their scale product (Navien PeakFlow, Rinnai ScaleCutter) is required, and both say damage from poor water quality is not covered by the warranty. Test your water first. Between 61 and 200 mg/L, both recommend a softener or their scale product, more strongly as hardness rises, and both list a flush once a year for a home in the middle hardness bands.

Why Trust Plumbing Picks

Plumbing Picks is written by a licensed Georgia journeyman plumber. Every size, rating and spec on this page comes from the manufacturer documents listed below, which we opened and read, or from the Amazon listing we link; nothing here comes from hands-on testing. The linked Rinnai RX199iN was listed In Stock on Amazon on October 3, 2026 from eFaucets, a third-party seller, not Rinnai or Amazon. We normally link only units sold or shipped by Amazon or the maker. None of the Rinnai heaters we checked was, so we link a genuine-model listing from a seller whose name matches Rinnai’s authorized list. We found no Navien water heater on Amazon that day, so Navien has no link. Where a link goes to Amazon we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.

Sources

Bottom Line

Size the heater by flow at your temperature rise, then decide on recirculation, gas line, vent and water before you pick a brand. The Navien NPE-240A2 has the pump and buffer tank built in but comes through a Navien dealer, because Navien voids its warranty on internet purchases. The Rinnai RX199iN is the lighter unit, the RXP adds a pump, and Rinnai names the online sellers it authorizes. Have a licensed installer do the gas, vent and setup, register the heater, and keep the receipt.