Best Gas Tankless Water Heaters
In a cold-inlet climate, whole-house tankless means gas. Here are the four worth considering.
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The Rheem Prestige RTGH-95DVLN is the gas tankless unit most houses should start with: 5.5 GPM at a 70°F rise from up to 199,900 BTU/h, a 12-year residential heat exchanger warranty, and PVC venting up to 150 feet. All four whole-house units here need a gas supply sized for nearly 200,000 BTU/h.
Before the product comparison, the thing that decides whether any of this is feasible: gas supply. Your existing tank probably burns 36,000 to 50,000 BTU/h. Every whole-house unit on this page wants up to 199,900. That is four to five times the load through the same pipe.
Sometimes the existing line is fine, particularly in a house with a large furnace where the branch to the water heater comes off a generously sized trunk. Often it is not, and the fix is new pipe from the meter — occasionally a new meter. Have a licensed professional size the supply before you buy the unit, not after.
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.
| # | 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 |  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 |
| 3 | 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 |
| 4 |  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 |
| 5 |  Camplux Pro 10 (2.64 GPM propane)A 2.64 GPM propane unit that runs off a BBQ cylinder — the right answer for a cabin shower or an outdoor wash station, and the wrong answer for a house. | Outdoor and off-grid propane | Check price on Amazon No live price feed on this site, so we show none. #ad |
The picks 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.
| 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.
Pick 2 — 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 3 — 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 4 — 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 5 — Outdoor and off-grid propane
Camplux Pro 10 (2.64 GPM propane)
A 2.64 GPM propane unit that runs off a BBQ cylinder — the right answer for a cabin shower or an outdoor wash station, and the wrong answer for a house.
| Fuel | Propane (20 lb cylinder) |
|---|---|
| Output | 2.64 GPM |
| Gas input | 65,000 - 68,000 BTU/h depending on model variant |
| Temperature rise | Rated flow quoted at a 70°F rise |
| Temperature range | 50 - 140°F, adjustable |
| Minimum activation flow | 0.5 GPM |
| Installation | Outdoor / vented enclosure only |
What is good
- 0.5 GPM activation is low enough for an RV pump or a gravity-fed line
- Runs on a standard 20 lb propane cylinder with no gas line or permit
- 2.64 GPM is a genuine shower, not a trickle
- Temperature is set on a dial rather than by mixing at the fixture
What is not
- Outdoor use only — these are not indoor-rated appliances
- Battery or 12 V ignition means it stops working when the batteries die
- No freeze protection: it has to be drained for winter
Skip it if: Skip it for anything inside a house. These units are certified for outdoor use and venting an outdoor-rated propane heater indoors is a carbon monoxide risk, not a code technicality.
No live price feed on this site, so we show none. #ad
Specifications above from Tractor Supply listing, Camplux 2.64 GPM 68,000 BTU; Lowe's listing, Camplux Plus 10, 2.64 GPM 65,000 BTU. We have not tested this unit ourselves.
Comparing them on the numbers that matter
| Unit | Input | Flow | UEF | Indoor/outdoor | Heat exchanger warranty |
|---|---|---|---|---|---|
| Rheem RTGH-95DVLN | Up to 199,900 BTU/h | 5.5 GPM at a 70°F rise; 9.5 GPM max | Up to 0.93 | Indoor, direct vent | 12 years residential |
| Rinnai RX199iN | 199,000 BTU/h | 11.1 GPM max | 0.98 | Indoor or outdoor | 15 years per retailer listings |
| Rinnai RSC199iN | 199,000 BTU/h | 11 GPM max | 0.95 | Indoor only | 15 years |
| Navien NPE-240A2 | 13,300 to 199,900 BTU/h | 11.2 GPM max | 0.95 | Indoor | Check the current warranty document |
| Camplux Pro 10 | 65,000 to 68,000 BTU/h | 2.64 GPM | Not published | Outdoor only | Not published |
Two notes on that table, both of which are the point of this site. Rheem's 5.5 GPM figure looks worse than Rinnai's 11.1 — it is not, it is measured at a 70°F rise where Rinnai's is a maximum. And where a warranty term is not published in the manufacturer's quick-facts document, we have written that rather than repeating a retailer's number as if it were the manufacturer's.
Venting: the hidden half of the budget
Condensing units produce flue gas cool enough to vent in PVC. Non-condensing units need stainless category III pipe, which costs several times as much per foot. On a long run that difference can exceed the price gap between two units, which is why every whole-house unit here is condensing.
- The Rheem RTGH vents up to 150 feet in 3-inch PVC, or 60 feet in 2-inch.
- The Navien NPE-A2 series vents in 2-inch PVC with a 1/2-inch gas connection, which makes awkward retrofits easier than the BTU figure suggests.
- An outdoor unit like the Rinnai RX199iN removes the venting cost entirely — a real saving in a mild climate, and a real freeze risk in a cold one.
Condensing also means condensate: acidic water that has to reach a drain, which may mean a condensate pump and in some jurisdictions a neutralizer. Budget for it. Condensing vs non-condensing.
Propane
The Rinnai RX199iN runs on natural gas or propane, and the Navien NPE-A2 series is available for both, so a propane household has real whole-house options. Propane carries more energy per cubic foot than natural gas, so the supply sizing differs — but the regulator, the tank size and the vaporization rate become the constraints instead of the pipe.
For an off-grid cabin or an outdoor wash station the answer is different: a small outdoor unit like the Camplux Pro 10 at 2.64 GPM running off a 20 lb cylinder. That is a genuinely good product for that job and a dangerous one indoors.
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.
How we chose
Rise-qualified published flow first, then efficiency, then warranty terms from manufacturer documentation, then install burden — venting type, gas connection size and whether recirculation is built in. We read owner reviews for repeat complaints. We have not tested these units. Our method.