Navien vs Rheem Tankless Water Heaters

Both are condensing, both are fed by roughly 199,000 BTU/h of gas, and both will run two showers in most of the country. The difference is what each manufacturer chose to put inside the box, and what each chose to publish about it.

Side by side on published figures

The row that matters most for sizing is the third one. Rheem publishes flow at a 70°F rise, which is close to a real winter in the northern half of the country. Navien and Rinnai publish a maximum, which is measured at a rise so small it never happens in January. You can size honestly from the Rheem figure; for the other two you have to do the arithmetic yourself from the tankless GPM chart.

Quick picks

Tap any row to read the full assessment below, or go straight to Amazon from the right-hand column. We earn a commission on qualifying purchases at no extra cost to you.

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	Rheem Prestige RTGH-95DVLNThe condensing gas tankless most houses should start with: 5.5 GPM at a 70°F rise covers two showers in a cold-inlet climate, and the 12-year residential heat exchanger warranty is the longest on this list.	Most whole-house gas jobs	Check price on Amazon No live price feed on this site, so we show none. #ad
2	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
3	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

The three units in full

Pick 1 — Most whole-house gas jobs

Rheem Prestige RTGH-95DVLN

The condensing gas tankless most houses should start with: 5.5 GPM at a 70°F rise covers two showers in a cold-inlet climate, and the 12-year residential heat exchanger warranty is the longest on this list.

Published specifications for the Rheem Prestige RTGH-95DVLN

Fuel	Natural gas (LP variant sold separately)
Gas input	Up to 199,900 BTU/h
Flow at a 70°F rise	5.5 GPM
Maximum flow	9.5 GPM at a 35°F rise
Efficiency	Up to 0.93 UEF, stainless condensing heat exchanger
Minimum activation flow	0.4 GPM
Venting	Up to 150 ft of 3-inch PVC; 60 ft of 2-inch PVC
Dimensions	18-1/2 in W x 9-3/4 in D x 27-1/2 in H
Warranty	12-year heat exchanger (residential), 5-year parts, 1-year labor

What is good

• +The 70°F-rise figure is published, so you can size it honestly instead of guessing from the headline number
• +Condensing design vents in PVC, which is far cheaper to run than stainless category III pipe
• +0.4 GPM activation means a trickle at a bathroom faucet still fires the burner
• +Long PVC vent runs let you put it where the gas line already is

What is not

• −Needs a gas line sized for nearly 200,000 BTU/h — many existing 1/2-inch runs are not
• −Condensate has to go somewhere, which means a drain or a condensate pump
• −Annual descaling is not optional on hard water

Skip it if: Skip it if your gas meter and line cannot carry 199,900 BTU/h. Upsizing the gas line is often the single largest cost in a tankless conversion, and no amount of unit quality fixes a starved burner.

Check price on Amazon

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

Specifications above from Rheem RTGH series specification sheet (PDF); Pace Supply listing, RTGH-95DVLN, 199 kBtu/hr. We have not tested this unit ourselves.

Pick 2 — 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

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

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

Pick 3 — 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

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

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

What the Navien buffer tank actually fixes

The cold-water sandwich is the slug of cool water that arrives when you turn a tap off and back on quickly: the burner has stopped, the pipe between the unit and the fixture still holds the last hot water, and behind it is water that was heated by nothing. Navien's answer is a small internal buffer tank plus a pump, so there is always a reservoir of hot water to cover the restart. If your household takes a lot of short draws — a kitchen at dinner time, a family cycling through one bathroom — that is the feature you are buying.

• 13,300 BTU/h minimum fire lets it modulate very low for a single faucet, where a less flexible unit short-cycles.
• NaviCirc recirculates through existing supply lines, so you do not have to add a dedicated return.
• 2-inch PVC venting and a 1/2-inch gas connection make retrofits easier than a 199,900 BTU headline suggests.
• More parts. A pump and a buffer tank are two more things that can need service in year eight.

What the Rheem gives you instead

• A published 70°F-rise flow, so the unit you size is the unit you get in February.
• 12 years on the heat exchanger in residential service, which is the part that fails and the part that costs money.
• 0.4 GPM activation, low enough that a trickle at a bathroom faucet still fires the burner.
• Up to 150 feet of 3-inch PVC venting, which lets you put the unit where the gas line already is rather than where the wall is.

What to buy

If you are still deciding between the technologies rather than the brands, tankless vs tank water heaters is the page to read first, and Rinnai vs Rheem tankless covers the other half of this three-way.