Navien vs Rinnai Tankless

Both brands make genuinely good tankless water heaters at the 199,000 BTU class, both are condensing, and both offer recirculation without a dedicated return line. The differences are narrower than brand loyalty suggests, and they come down to two specific features.

Side by side on published figures

Quick picks

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Ranked picks with what each one is best for, our score and a link to check the current price on Amazon.

#	Product	Best for	Price
1	Navien NPE-240A2The high-flow pick: 11.2 GPM and a built-in buffer tank plus recirculation pump, which is what stops the cold-water sandwich on short, repeated draws.	Big draws and long pipe runs	Check price on Amazon No live price feed on this site, so we show none. #ad
2	Rinnai SE+ RSC199iNThe pick when you want hot water fast at a far bathroom and have no dedicated return line: ThermaCirc360 recirculates through the cold line instead, and the 15-year heat exchanger warranty is the longest here.	Recirculation without a return line	Check price on Amazon No live price feed on this site, so we show none. #ad
3	Rinnai SENSEI RX199iNThe efficiency pick, and the one to buy if the unit has to hang outside: 0.98 UEF, 11.1 GPM at full fire, and it runs on either natural gas or propane indoors or out.	Highest published efficiency	Check price on Amazon No live price feed on this site, so we show none. #ad

The three units in full

Pick 1 — Big draws and long pipe runs

Navien NPE-240A2

The high-flow pick: 11.2 GPM and a built-in buffer tank plus recirculation pump, which is what stops the cold-water sandwich on short, repeated draws.

Published specifications for the Navien NPE-240A2

Fuel	Natural gas or propane
Heat input range	13,300 - 199,900 BTU/h
Maximum flow	11.2 GPM
Efficiency	0.95 UEF
Recirculation	ComfortFlow built-in buffer tank and recirculation pump
Heat exchanger	Dual stainless steel
Venting	2-inch PVC
Gas connection	1/2 inch

What is good

• +The buffer tank is the real feature — it smooths the short draws that make other tankless units run cold for a second
• +NaviCirc lets it recirculate through existing supply lines with no separate return
• +13,300 BTU/h minimum fire means it modulates very low for a single faucet
• +2-inch PVC venting and a 1/2-inch gas connection make retrofits easier than the headline BTU suggests

What is not

• −More internal parts than a plain condensing unit: a pump and a buffer tank are two more things to service
• −Warranty terms are not published on the quick-facts sheet — check the current warranty document before you buy
• −Condensate drain required

Skip it if: Skip it if you are replacing a single-bathroom apartment's heater. The buffer tank and pump are solving a problem a small home does not have, and you would be paying for both.

Check price on Amazon

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Specifications above from Navien NPE-2 series quick facts (PDF); Navien NPE-A2 series technical data. We have not tested this unit ourselves.

Pick 2 — Recirculation without a return line

Rinnai SE+ RSC199iN

The pick when you want hot water fast at a far bathroom and have no dedicated return line: ThermaCirc360 recirculates through the cold line instead, and the 15-year heat exchanger warranty is the longest here.

Published specifications for the Rinnai SE+ RSC199iN

Fuel	Natural gas
Gas input	199,000 BTU/h
Maximum flow	11 GPM
Efficiency	0.95 UEF
Installation	Indoor only
Recirculation	ThermaCirc360 — works with or without a dedicated return line
Warranty	15-year heat exchanger, 5-year parts, 1-year labor

What is good

• +Built-in recirculation means no separate pump, timer or control to buy and wire
• +ThermaCirc360 can use the cold supply as the return, which is the difference between a half-day job and a re-pipe
• +15-year heat exchanger warranty
• +0.95 UEF keeps it inside most utility rebate thresholds

What is not

• −Indoor installation only — no outdoor variant of this exact model
• −Natural gas only in this model number
• −Crossover recirculation through the cold line puts warm water in the cold tap for a few seconds

Skip it if: Skip it if you are plumbing a new build where a dedicated return line is going in anyway. You would be paying for the integrated pump twice over, and a plain condensing unit plus a separate pump is cheaper and easier to service.

Check price on Amazon

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Specifications above from Rinnai RSC199iN product page. We have not tested this unit ourselves.

Pick 3 — Highest published efficiency

Rinnai SENSEI RX199iN

The efficiency pick, and the one to buy if the unit has to hang outside: 0.98 UEF, 11.1 GPM at full fire, and it runs on either natural gas or propane indoors or out.

Published specifications for the Rinnai SENSEI RX199iN

Fuel	Natural gas or propane
Gas input	199,000 BTU/h
Maximum flow	11.1 GPM
Efficiency	0.98 UEF
Installation	Indoor or outdoor
Warranty	15-year heat exchanger (per retailer listings)

What is good

• +0.98 UEF is the highest published figure of any unit on this page
• +One model covers natural gas and propane, which matters if you may convert later
• +Outdoor installation removes the venting cost entirely in mild climates
• +11.1 GPM headroom means it throttles rather than straining in a three-fixture draw

What is not

• −Outdoor installation needs freeze protection and a power supply at the wall
• −Still a nearly-200,000 BTU/h gas load
• −No integrated recirculation pump in this model

Skip it if: Skip the outdoor install if your winter design temperature goes well below freezing for days at a time. Outdoor tankless units rely on an internal freeze protection heater and mains power — a multi-day outage in a hard freeze is how they split.

Check price on Amazon

No live price feed on this site, so we show none. #ad

Specifications above from Rinnai RX199iN product page. We have not tested this unit ourselves.

Where Navien wins

• The buffer tank. ComfortFlow puts a small reservoir and a pump inside the cabinet, which smooths the short repeated draws that make every other tankless unit wobble. This is the single best reason to choose Navien.
• The widest modulation range here — 13,300 to 199,900 BTU/h, so a single faucet does not force the burner far above the draw.
• 2-inch PVC venting, smaller than many condensing units want, which makes an awkward retrofit route feasible.
• Marginally the highest maximum flow at 11.2 GPM, though all three are within 0.2 GPM of each other.

Where Rinnai wins

• A stated 15-year heat exchanger warranty, with parts and labor periods also stated. Navien's quick-facts document refers you to its website rather than stating terms.
• 0.98 UEF on the RX199iN, the highest gas figure in our registry.
• Indoor or outdoor installation on the RX, which can remove the venting cost entirely in a mild climate.
• ThermaCirc360, which recirculates with or without a return line — the same retrofit advantage as NaviCirc, on a unit with a stated warranty.
• The longest track record in the American residential tankless market.

The feature that should decide it

Ask what your household's hot water pattern actually looks like.

The thing neither of them does

Publish a rise-qualified flow figure prominently. All three units quote a maximum GPM, which is measured at a low temperature rise and overstates what you get in a northern winter. Rheem publishes 5.5 GPM at a 70°F rise alongside its 9.5 GPM maximum for the same unit, and that transparency is why the RTGH leads our tankless roundup despite a lower maximum.

Pick Navien if...

• Your household produces overlapping short draws, which most multi-bathroom houses do.
• You want recirculation and a buffer in one cabinet with nothing external.
• The vent route is tight and 2-inch PVC helps.
• You are happy to request the warranty document rather than read terms on a spec sheet.

Pick Rinnai if...

• You want warranty terms stated before you buy.
• You want the highest published efficiency, or propane flexibility, or an outdoor install.
• You need recirculation with no return line and would rather have the stated warranty than the buffer tank.
• You value the longest track record in the US residential tankless market.