Rinnai Tankless Water Heaters
The longest stated heat exchanger warranty here, and recirculation that does not need new pipe.
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Rinnai's SENSEI RX199iN publishes 0.98 UEF and 11.1 GPM, runs on natural gas or propane, and installs indoors or outdoors. The SE+ RSC199iN carries ThermaCirc360, which recirculates with or without a dedicated return line — the feature that turns a re-pipe into a straightforward install. Both state 15 years on the heat exchanger.
Rinnai is a tankless specialist with a Japanese parent and the longest track record in the American residential tankless market. Two things define its current range: the efficiency figures, and a recirculation system that is genuinely retrofit-friendly.
The two ranges
| Model | Input | Flow | UEF | Install | Fuel | Warranty |
|---|---|---|---|---|---|---|
| SENSEI RX199iN | 199,000 BTU/h | 11.1 GPM max | 0.98 | Indoor or outdoor | Natural gas or propane | 15 years per retailer listings |
| SE+ RSC199iN | 199,000 BTU/h | 11 GPM max | 0.95 | Indoor only | Natural gas | 15 years heat exchanger, 5 years parts, 1 year labor |
A 0.98 UEF is the highest figure in our registry for any gas appliance, and it is worth understanding what that buys: slightly lower gas consumption, and easier qualification for utility efficiency rebates that set a UEF threshold.
Quick picks
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| # | Product | Best for | Price |
|---|---|---|---|
| 1 |  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 |
| 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 — 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.
| 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.
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.
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.
ThermaCirc360, and why it matters more than the UEF
The number one complaint from new tankless owners is that the wait for hot water at a distant fixture got longer, because the unit only starts heating when flow begins. The fix is recirculation, and recirculation normally needs a dedicated return line back to the heater — which in an existing house usually means opening walls.
ThermaCirc360 can recirculate through the existing cold supply instead, using it as the return path. That changes the project from a re-pipe into a straightforward install, and it is the single most practically valuable feature on either of these units.
Indoor or outdoor
The RX199iN is rated for indoor or outdoor installation, which removes the venting cost entirely in a mild climate. That is a real saving: a long stainless or PVC vent route is frequently a four-figure line item.
The honest caution is freeze risk. Outdoor tankless units rely on an internal freeze protection heater and mains power. In a climate where winter design temperatures sit well below freezing for days, a multi-day power outage during a hard freeze is how an outdoor unit splits. In the southern half of the country it is an easy win; in the upper Midwest it is a calculated risk.
Where Rinnai is weaker
- No rise-qualified flow figure published prominently. 11.1 GPM is a maximum. Rheem's published 5.5 GPM at a 70°F rise is the figure that lets you size against your own inlet temperature.
- The RSC199iN is natural gas and indoor only, so the model with the best recirculation is the less flexible one on fuel and siting.
- No buffer tank on these models, so the cold-water sandwich on very short repeated draws is less well addressed than on the Navien NPE-A2.
- Warranty figures vary between the manufacturer page and retailer listings on the RX199iN; read the current warranty document for the exact model.
Our verdict
Buy the RSC199iN if you want recirculation and have no dedicated return line, which describes most existing houses. Buy the RX199iN if you want the highest published efficiency, the flexibility of propane, or an outdoor install in a mild climate.
If your priority is sizing the unit honestly from published data, the Rheem Prestige RTGH's rise-qualified figure makes it the easier purchase. Best gas tankless water heaters.
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.