Best Tankless Water Heaters for 2026
Ranked on the figures that matter in February, not the ones on the front of the box.
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For most houses the Rheem Prestige RTGH-95DVLN is the tankless unit to start with: 5.5 GPM at a 70°F rise, up to 0.93 UEF, and a 12-year residential heat exchanger warranty. If you want the highest published efficiency, the Rinnai SENSEI RX199iN at 0.98 UEF. For electric, the Stiebel Eltron Tempra 24 Plus, because it publishes its full rise-versus-flow curve.
Every unit below is ranked on a rise-qualified flow figure wherever the manufacturer publishes one, and we say so when they do not. That matters more in this category than anywhere else in water heating, because the headline GPM on a tankless box is almost always measured at a temperature rise that does not exist in winter.
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 |  Stiebel Eltron Tempra 24 PlusThe electric tankless to buy if you are going to buy one at all: it publishes its full rise-versus-flow curve, and the Advanced Flow Control throttles flow instead of letting the temperature sag. | Whole-house electric, warm inlet | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 6 |  EcoSmart ECO 27The biggest electric unit most homes can actually feed: 27 kW across three 40 A breakers, 6.6 GPM maximum, and a lifetime limited warranty on the unit. | Maximum electric output | Check price on Amazon No live price feed on this site, so we show none. #ad |
How we ranked these
In order: whether the unit's published figures let you size it honestly; its output at a realistic rise; warranty terms from manufacturer documentation rather than retailer listings; and how much install burden it adds beyond the appliance itself. We have not tested these units — our method says exactly what we did instead.
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 — Whole-house electric, warm inlet
Stiebel Eltron Tempra 24 Plus
The electric tankless to buy if you are going to buy one at all: it publishes its full rise-versus-flow curve, and the Advanced Flow Control throttles flow instead of letting the temperature sag.
| Output at 240 V | 24 kW |
|---|---|
| Output at 208 V | 18 kW |
| Breakers | 2 x 50 A double-pole |
| Wire | 2 x 6 AWG copper |
| Current draw | 100 A |
| Minimum electrical service | 150 A |
| Rise at 240 V | 54°F at 3.0 GPM; 73°F at 2.25 GPM; 37°F at 4.5 GPM |
| Rise at 208 V | 41°F at 3.0 GPM; 54°F at 2.25 GPM; 27°F at 4.5 GPM |
| Maximum flow | 8 GPM |
What is good
- Publishes rise at four flow rates on both voltages, which is the only honest way to size an electric tankless
- Advanced Flow Control cuts flow to hold the set temperature rather than delivering lukewarm water
- No venting, no gas line, no condensate
- Small enough to go in the cabinet it replaced
What is not
- 100 A of draw and a 150 A minimum service rules out a lot of older houses
- At 208 V it loses a quarter of its output, and plenty of homes are nearer 208 than 240
- Running cost follows the electric rate, which is usually worse than gas per BTU
Skip it if: Skip it if your inlet water drops to 45°F in winter and you want two showers at once. At a 73°F rise it delivers 2.25 GPM — one shower, nothing else. Cold-inlet climates are where electric tankless disappoints people.
No live price feed on this site, so we show none. #ad
Specifications above from Stiebel Eltron Tempra Plus technical specifications (PDF); Stiebel Eltron Tempra Plus submittal sheet (PDF). We have not tested this unit ourselves.
Pick 6 — Maximum electric output
EcoSmart ECO 27
The biggest electric unit most homes can actually feed: 27 kW across three 40 A breakers, 6.6 GPM maximum, and a lifetime limited warranty on the unit.
| Output | 27 kW at 240 V, single phase |
|---|---|
| Current draw | 113 A |
| Breakers | 3 x 40 A |
| Wire | 3 x 8 AWG |
| Maximum flow | 6.6 GPM |
| Minimum activation flow | 0.3 GPM |
| Dimensions | 17 in x 17 in x 3-5/8 in |
| Weight | 14.7 lb |
| Connections | 3/4 in NPT |
| Warranty | Lifetime limited |
What is good
- Highest output of any single electric unit here, so it holds temperature at higher flow
- Lifetime limited warranty on the unit is unusual at any price
- 3-5/8 inches deep — it genuinely disappears on a wall
- 0.3 GPM activation flow is the lowest on this page
What is not
- 113 A of draw needs three circuits and, in practice, a 200 A service
- The published flow is a maximum, not a rise-qualified figure — you have to do the rise math yourself
- No buffer, so a sudden flow change is felt at the shower head
Skip it if: Skip it if your panel is 100 A or 125 A. Three 40 A circuits and 113 A of draw is a service upgrade, and a service upgrade usually costs more than the entire water heater.
No live price feed on this site, so we show none. #ad
Specifications above from EcoSmart ECO 27 technical data (BIMobject). We have not tested this unit ourselves.
Sizing these units for your house
Pick the GPM you need from your simultaneous fixture count, then check it against the unit's output at your temperature rise. Two showers plus a sink is about 4.6 GPM. In a cold-inlet climate that means the 199,000 BTU class — the first four units on this page. In a warm-inlet climate a 24 kW electric unit can cover it, if your service can carry 100 A.
| Unit | Published flow | At what rise | Covers |
|---|---|---|---|
| Rheem RTGH-95DVLN | 5.5 GPM | 70°F | 2 showers + a sink, any climate |
| Rinnai RX199iN | 11.1 GPM max | Not stated at 70°F | 3 showers in a warm climate; 2 in a cold one |
| Navien NPE-240A2 | 11.2 GPM max | Not stated at 70°F | As above, with a buffer tank for short draws |
| Rinnai RSC199iN | 11 GPM max | Not stated at 70°F | As above, with built-in recirculation |
| Stiebel Eltron Tempra 24 Plus | 3.00 GPM | 54°F at 240 V | 1 shower + a sink in a moderate climate |
| EcoSmart ECO 27 | 6.6 GPM max | Not stated | 1 to 2 showers depending on inlet temperature |
Condensing or not
Every gas unit on this page is condensing, which is now the mainstream choice for a reason: condensing units vent in PVC rather than stainless category III pipe, and on a long vent run that difference can exceed the price gap between the units. The Rheem RTGH can vent up to 150 feet in 3-inch PVC. Condensing vs non-condensing covers the trade-off properly.
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.
What we would not buy
- An electric whole-house unit in a northern climate. At a 73°F rise the Tempra 24 Plus delivers 2.25 GPM. That is one shower. It is not a defect; it is physics and a kilowatt limit.
- Any gas unit without first having the gas supply sized. This is the single most common way a tankless project goes wrong, and it goes wrong after the unit is already bought.
- A tankless unit with no isolation valves fitted. Without them you cannot flush it, and an unflushed tankless unit in hard water does not reach its lifespan.
- An outdoor unit where winter design temperatures sit well below freezing for days. Outdoor tankless units rely on an internal freeze heater and mains power; a multi-day outage in a hard freeze is how they split.
How we chose
We compared published specifications against manufacturer documentation, preferred units that publish rise-qualified flow figures, checked warranty terms against the manufacturer rather than the retailer listing, and read owner reviews for complaints that repeat. We have no test bench and make no testing claims. How we pick.