Best Tankless Water Heater for 2 Bathrooms

The useful question is never "how many bathrooms" but "how many fixtures at the same instant". A two-bathroom house where the showers are 30 minutes apart has the demand of a one-bathroom house. A two-bathroom house with teenagers and one school bus has the demand of a small hotel.

The arithmetic

Quick picks

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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	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	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
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
4	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

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.

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 2 — 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 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.

Pick 4 — 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.

Published specifications for the Stiebel Eltron Tempra 24 Plus

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.

Check price on Amazon

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.

Why the Navien leads here specifically

Because two-bathroom households produce exactly the usage pattern that exposes a tankless unit's weakness: short, repeated, overlapping draws. Somebody turns a sink on while a shower runs, the unit modulates, somebody turns it off again, and the shower temperature wobbles.

The NPE-240A2's ComfortFlow system puts a buffer tank and a recirculation pump inside the cabinet, which smooths exactly that. It also modulates down to 13,300 BTU/h, so a single faucet does not force the burner to run far above what the draw needs.

The second-bathroom distance problem

In most two-bathroom houses one bathroom is close to the heater and one is not. The far one is where the complaints come from, and the complaint is a wait rather than a temperature.

• Built-in recirculation — the Navien and the Rinnai RSC199iN both have it. The Rinnai's ThermaCirc360 works without a dedicated return line, which matters in a retrofit.
• A separate comfort pump at the far fixture, on a timer. Recirculation pumps, and specifically recirculation without a return line.
• A point-of-use heater at the far sink, which is cheaper than either and solves the sink but not the shower. Point-of-use water heaters.

How we chose

We prioritized behavior under overlapping short draws, which is the two-bathroom failure mode, then rise-qualified flow, then whether recirculation is integrated. We have not tested these units. How we pick.