Rinnai vs Rheem Tankless

Both brands sit at the 199,000 BTU class, both are condensing, and the flow difference between them is under two gallons a minute at full fire. The real difference is what each company is willing to put in print, and the two companies choose opposite things to be transparent about.

Side by side on published figures

Note what the second and third rows do to each other. Rinnai's 11.1 GPM and Rheem's 9.5 GPM are not comparable numbers: Rheem states the 35°F rise its maximum was measured at and then publishes the 70°F figure as well. Rinnai publishes the maximum alone. A maximum GPM with no rise attached is a ceiling, not a capacity, and it is the most misread specification in the category. Tankless sizing chart by rise.

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.

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	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	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

The three units 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.

Published specifications for the Rinnai SENSEI RX199iN

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.

Check price on Amazon

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 — 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.

Where Rinnai wins

• 0.98 UEF on the SENSEI RX199iN, the highest gas figure in our registry and a real operating-cost difference over a twenty-year life.
• A stated 15-year heat exchanger warranty on both Rinnai units here, against Rheem's 12 years residential.
• Indoor or outdoor installation on the RX199iN. In a mild climate that can remove the venting cost from the job entirely, which is often a large share of the install.
• Natural gas or propane on the RX199iN, where the Rheem RTGH sells its LP variant as a separate model.
• ThermaCirc360 on the RSC199iN, which recirculates with or without a dedicated return line — the retrofit feature that fixes the long wait at a far bathroom.

Where Rheem wins

• The rise-qualified flow figure. 5.5 GPM at a 70°F rise is the number you can check against your own winter inlet temperature. It is the reason the RTGH leads our tankless roundup despite a lower headline maximum.
• A published 0.4 GPM minimum activation flow, which tells you whether a low-flow bathroom faucet will fire the burner at all.
• Published vent runs — up to 150 feet of 3-inch PVC, 60 feet of 2-inch. On a retrofit where the vent has to reach an awkward wall, that number decides whether the job is possible.
• Retail availability and local parts. Rheem parts sit on supply-house shelves in most of the country.
• A documented residential warranty structure of 12 years on the heat exchanger, 5 on parts and 1 on labor, all stated together.

The condition that flips it

The gas line decides more than the badge

Every unit on this page wants up to around 199,900 BTU/h. If your meter and your gas line cannot carry that, no amount of brand quality fixes a starved burner, and upsizing the line is frequently the largest single cost in a tankless conversion. Check that before you choose between these three, not after. Best gas tankless water heaters covers what the supply side actually has to deliver.

The second thing to settle before the badge is condensing versus non-condensing, because it determines whether you need a condensate drain and what the vent can be made of. All three units here are condensing. Condensing vs non-condensing tankless.

Pick Rinnai if...

• You want the longest stated heat exchanger warranty.
• You want the highest published efficiency on this list.
• The unit can go outside, or you need propane.
• You need recirculation and have no dedicated return line.

Pick Rheem if...

• Your inlet water is cold and you want to size from published data rather than hope.
• The vent route is the hard part of the job.
• You want parts and service available locally.
• A 12-year heat exchanger warranty with stated parts and labor terms is enough.