Navien Water Heaters
A buffer tank and a pump inside the cabinet. That is the whole product thesis, and it solves a real problem.
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Navien's NPE-A2 range puts a buffer tank and a recirculation pump inside the heater cabinet — its ComfortFlow system. That is specifically aimed at the cold-water sandwich on short repeated draws. The NPE-240A2 delivers 11.2 GPM maximum, modulates from 13,300 to 199,900 BTU/h, and vents in 2-inch PVC with a 1/2-inch gas connection.
Navien is a tankless and combi specialist with a Korean parent, and it has built its North American position on one idea executed consistently: put the things people bolt onto a tankless install inside the unit.
The problem ComfortFlow solves
A tankless heater has no reservoir, so it reacts to flow. Turn a draw on and off quickly — somebody washing hands while a shower runs, or a dishwasher cycling — and the heat exchanger cools between firings, producing a slug of cool water. That is the cold-water sandwich, and it is the complaint that distinguishes a merely adequate tankless install from a good one.
A buffer tank gives the unit a small reservoir to draw from while the burner catches up. It is a genuinely sound engineering answer rather than a marketing feature, and it is most valuable in exactly the households that buy tankless: multi-bathroom houses with overlapping short draws.
Quick picks
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| # | 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 | 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 |
The picks 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.
| 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.
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 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.
| 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.
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.
Pick 3 — 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.
| 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.
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.
The published specifications
| Specification | Value |
|---|---|
| Heat input range | 13,300 to 199,900 BTU/h |
| Maximum flow | 11.2 GPM |
| Efficiency | 0.95 UEF |
| Heat exchangers | Dual stainless steel |
| Recirculation | ComfortFlow built-in buffer tank and pump; NaviCirc for no-return-line operation |
| Venting | 2-inch PVC |
| Gas connection | 1/2 inch |
| Warranty | Not stated in the quick-facts document; check the current warranty document |
The install advantages people miss
- 13,300 BTU/h minimum fire. The widest modulation range here, which means a single bathroom faucet does not force the burner to run far above the draw.
- 2-inch PVC venting. Smaller than the 3-inch many condensing units want, which makes an awkward retrofit route feasible.
- A 1/2-inch gas connection. Easier to make up than larger fittings, though the gas SUPPLY still has to carry nearly 200,000 BTU/h — the connection size is not the constraint.
- NaviCirc, which recirculates through existing supply lines with no dedicated return and no external pump or controls.
Where it is weaker
- More internal components. A pump and a buffer tank are two more serviceable items inside the cabinet. The counter-argument to integration is always serviceability.
- No rise-qualified flow figure published prominently — 11.2 GPM is a maximum, like most of this category. Rheem's 5.5 GPM at a 70°F rise is the kind of figure that lets you size honestly.
- Warranty terms not stated in the summary documentation, as above.
- Overkill for a small home. In a one-bathroom house the buffer tank is solving a problem you do not have, and you are paying for it.
Our verdict
Buy a Navien NPE-A2 for a multi-bathroom house with long pipe runs and overlapping short draws, which is the usage pattern that exposes every other tankless unit. The buffer tank genuinely earns its place there, and NaviCirc can save a re-pipe.
For a simpler install — one or two bathrooms, a short vent route, no recirculation needed — a plain condensing unit with a published rise-qualified flow figure and clearly stated warranty terms is the easier purchase. Navien vs Rinnai.
What goes in with it
A water heater is a system, not a box. These are the parts that go in with it, and the ones people discover they need halfway through the job.
- Flush kit
The annual descale is not optional on a tankless unit, and you need a pump, hoses and a bucket.
- Descaler solution
What actually dissolves the scale once the kit is hooked up.
- Recirculation pump
Fixes the cold-water delay that makes new tankless owners call a plumber.