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Rheem RTGH 9.0 GPM Natural Gas Indoor Review

Name: Rheem RTGH 9.0 GPM Natural Gas Indoor
Brand: Rheem
SKU: B0C826LQ24

5.5Fair · out of 10Not in our top-5 rankings

Written from the listing and 30 buyer reviews, not from our own use · How we rate

On paper, the Rheem RTGH 9.0 GPM Natural Gas Indoor gets the important things right: a 9 GPM maximum flow, condensing efficiency and a ±1 °F temperature hold. It suits a family that showers back to back before school, and its sibling listing, the Rheem RTGH 8.4 GPM Natural Gas Indoor, holds #4 in our indoor natural gas tankless water heater ranking.

Variants of this model

These are sold as variants of one listing family. Each variant has its own page.

Rheem RTGH 8.4 GPM Natural Gas Indoor · 8.4 GPM (No WiFi) · 7.3/10
Rheem RTGH-95DVLN-3 Natural Gas Indoor · 9.5 GPM (No WiFi) · 7.1/10

Price$1,219.99Price on Sep 30, 2026 · may have changed

Check the price on Amazon ↗Affiliate link · price and stock on Amazon

Compare side by side ↗

Specifications

Brand	Rheem
Category	Gas tankless water heaters
Fuel	Natural gas
Stated mounting location	Indoor
Stated maximum flow	9 GPM
Stated gas input	180,000 BTU/h
Condensing design	Stated in the listing title
Flow at a stated rise	9 GPM at a 35 °F rise
Temperature hold	±1 °F, per the listing
Freeze protection	Stated in the listing
Stated warranty	15 years on the heat exchanger
Buyer reviews	30 · 4.2/5
ASIN	B0C826LQ24

Full listing title: Rheem RTGH Series 9.0 GPM Natural Gas Tankless Water Heater Indoor | 180,000 BTUs Super High Efficiency On Demand, Continuous Hot Water | Condensing Ultra-Low Nox

Listing evidence

Fuel	Natural Gas Full listing title
Stated mounting location	Indoor Full listing title
Stated maximum flow	9.0 GPM Full listing title
Stated gas input	180,000 BTUs Full listing title
Condensing design	Condensing Full listing title

Updated October 2026

Exact listing, ASIN B0C826LQ24

Rating from a published formula

Compared with its closest rivals

Two gas tankless heaters on natural gas too, with about the same flow, closest to it on our rating, each with a dated price.

Compare side by side ↗

Rheem RTGH 9.0 GPM Natural Gas Indoor

5.5Fair · out of 10$1,219.99 Price on Sep 30, 2026 · may have changed

Stated: 9 GPM · 180,000 BTU/h
30 buyer reviews
Gas tankless water heaters

This product ↑

Rinnai RXP160iN Condensing Smart Sense

5.4Fair · out of 10$1,685.60 Price on Sep 30, 2026 · may have changed

Stated: 9 GPM
34 buyer reviews
Gas tankless water heaters

See the review ↗

Noritz NR98SVNG Natural Gas

6.5Good · out of 10$1,815.58 Price on Sep 30, 2026 · may have changed

Stated: 7.5 GPM
12 buyer reviews
Gas tankless water heaters

See the review ↗

Up to 9 GPM from a 180,000 BTU burner

That's the maximum flow the listing states, at a 35 °F rise. Up north in winter, 42 °F water has to climb 63 °F to reach a 105 °F shower, and the flow drops with it. Ask for the flow chart and read that line. Our calculator counts a shower at 2 GPM, so on paper that's room for three showers at once, fewer when January water comes in cold.

What it has going for it

What changes in the morning shower rush

Condensing. A second heat exchanger pulls heat out of the exhaust before it leaves, so more of the gas you pay for ends up in the water. The exhaust runs cool enough for plastic vent pipe, and the condensate needs a drain.

±1 °F hold. The burner adjusts as the flow changes, so the shower stays where you set it when somebody opens the kitchen tap. On paper, at least: that is the seller's claim.

One shower at a time, or two?

Two at once: up to 9 GPM, and our calculator counts a shower at 2 GPM, so that's two showers and a tap on paper. The listing gives 9 GPM at a 35 °F rise and the seller says it serves up to 3 showers. How much of it is left in January is on the maker's flow chart, at a 63 °F rise.

One at a time: a smaller unit covers that for less money.

Great for you if…

Two showers and the dishwasher run at the same time in your house
You care about the gas bill as much as the hot water
A shower that suddenly runs cold drives you mad

Skip it if…

You want a long review record: only 30 buyer reviews so far
The far bathroom already waits a minute for hot water: no built-in recirculation is named

Gas, venting and what's in the box

What the Rheem RTGH 9.0 GPM Natural Gas Indoor listing names:

Up to 9 GPM
9 GPM at a 35 °F rise
180,000 BTU/h input
Natural gas
Indoor mounting
Condensing
±1 °F temperature hold claimed
Freeze protection named
Low NOx
CSA, ETL or UL mark named

Warranty & support: 15-year warranty on the heat exchanger, as stated in the listing · CSA, ETL or UL certification named in the listing.

That is the maker's promise, not ours. Keep the invoice, register the Rheem RTGH 9.0 GPM Natural Gas Indoor if the maker asks, and read the install conditions: many tankless warranties need a licensed install and regular flushing.

Read the installation manual for the vent, the gas line size and the clearances before you order; it overrides anything above.

Rheem RTGH 9.0 GPM Natural Gas Indoor, view 3

Price and cost per GPM of stated flow

$1,219.99 Price on Sep 30, 2026 · may have changed

At the price on Sep 30, 2026, each GPM of stated maximum flow works out at about $135.55 (price ÷ stated GPM, our arithmetic). That puts it in the pricier third of the 45 indoor gas tankless heaters we have a price and a stated flow for.

The online price is the heater alone. Venting, a bigger gas line where needed and the installer's day are a separate bill, often as big as this one.

The button opens the exact listing (ASIN B0C826LQ24), where today's price, stock and seller apply. Sizes and variants of the same family often sit at different prices.

Rheem RTGH 9.0 GPM Natural Gas Indoor, view 4

A better fit for your house?

No easy route for a vent pipe? The A. O. Smith 10 GPM Natural Gas Outdoor (8.0/10) mounts on an outside wall, per its listing.

On propane, not natural gas? The Rheem RTGH 9.5 GPM Propane Indoor (7.8/10) runs on propane.

The far bathroom takes ages to run hot? The Rinnai REP199eN Smart-Circ (7.3/10) has built-in recirculation, per its listing.

Our take

The verdict

What we'd buy the Rheem RTGH 9.0 GPM Natural Gas Indoor for is a 9 GPM maximum flow, with condensing efficiency as a bonus. Only 30 buyers have rated it so far (4.2/5), so treat the score as an early read. The catch with this Rheem indoor gas tankless heater: the headline GPM is a mild-weather figure, so leave yourself margin for January. We'd pick it if two showers and the dishwasher run at the same time in your house; otherwise, put it next to the Novieex 100,000 BTU Natural Gas Indoor first.

Check the price on Amazon ↗Affiliate link · price and stock on AmazonAll gas tankless water heaters →

Living with it

Install day

Old tank out, unit on the wall, vent through the wall or the roof. Plan the gas line for 180,000 BTU/h; a licensed pro handles it, and often a permit.

The first shower

Hot water arrives after the cold already in the pipes, then stays (within ±1 °F, per the listing). A trickle from a bathroom tap may not light the burner; open it a bit more.

The first winter

January water comes in colder, so the same unit gives fewer GPM. The listing's 9 GPM is at a 35 °F rise; a northern winter asks for about 63 °F. Stagger the showers if you sized it tight.

Once a year

Flush the heat exchanger with a pump and a descaler (the service valves make it an hour's job), check the condensate drain and the neutralizer, and clean the inlet filter. Our flushing and descaling guide has the checklist.

What buyers say

Buyers give it 4.2/5, a solid record, slightly below our ranked picks' 4.3 average. Only 30 reviews so far, and our formula damps averages built on fewer than 50.

The numbers

Buyer rating: 4.2/5
Reviews: 30
Ranked picks' average: 4.3/5

The one thing we'd check first

Before you order the Rheem RTGH 9.0 GPM Natural Gas Indoor, check your winter rise: it is rated 9 GPM at a 35 °F rise, and a northern winter asks for nearer 63 °F.

Before you buy

Your winter flow

Find your winter inlet temperature (your water utility or a thermometer at the cold tap in January), subtract it from 105 °F, and read the maker's flow chart at that rise. Our sizing guide shows how.

Vent and gas line

A licensed plumber or gas fitter confirms the vent route, the combustion air and a gas line that can deliver 180,000 BTU/h. Get that quote before you order; our installation guide lists what they will ask.

The condensate

A condensing unit drips acidic water that needs a drain, often through a neutralizer. Our condensing guide explains the extra parts.

Flushing

Hard water scales the heat exchanger. Service valves on the water lines turn the yearly flush into an hour with a bucket and a pump; our flushing and descaling guide shows the routine.

How it compares

How the Rheem RTGH 9.0 GPM Natural Gas Indoor stacks up against the closest alternative, the Novieex 100,000 BTU Natural Gas Indoor.

Criterion	Rheem RTGH 9.0 GPM Natural Gas Indoor	Novieex 100,000 BTU Natural Gas Indoor
Our rating	5.5/10	5.7/10
Max flow	9 GPM	4.3 GPM
Gas input	180,000 BTU/h	100,000 BTU/h
Efficiency	Condensing	Not stated
Warranty	15 years (heat exchanger)	1 years
Buyer reviews	30 · 4.2/5	45 · 4.0/5

Pick the Novieex 100,000 BTU Natural Gas Indoor if you want our higher-rated option (5.7/10); stay with the Rheem RTGH 9.0 GPM Natural Gas Indoor for more flow (9 GPM) and a bigger burner (180,000 BTU/h).

Compare side by side ↗See the Novieex 100,000 BTU Natural Gas Indoor review →

The score in detail

How we rated it

Our score: 5.5/10

Buyer rating (45%)

22.7 / 45

4.2/5 average, confidence-damped (30 reviews < 50)

Review volume (35%)

14.1 / 35

30 buyer reviews

Documented specifications (20%)

17.8 / 20

89/100 listing documentation score

Our rating is an evidence index on a 0–10 scale. It is not a buyer star rating, and we have not used the product ourselves.

Buyer rating (45%): the captured average shown on this variant's own listing page (not shared with the other Rheem variants), damped when there are fewer than 50 reviews.
Review volume (35%): more reviews mean more reliable evidence, on a logarithmic scale up to 5,000 reviews.
Documented specifications (20%): how completely the exact listing documents the attributes that matter.

Our editors then look at how it compares with the other heaters we rate. A commission is never an input to the rating. Read the full methodology.

Read the methodology →

Frequently asked questions

Is the Rheem RTGH 9.0 GPM Natural Gas Indoor any good?

We rate it 5.5/10 (fair). It is based on 30 buyer reviews averaging 4.2/5 and the specifications stated in the listing.

How much hot water can the Rheem RTGH 9.0 GPM Natural Gas Indoor deliver?

The listing states a maximum flow of 9 GPM and a gas input of 180,000 BTU/h. The headline flow is a mild-weather number: with cold winter water coming in, the same unit gives you less. Read the maker's flow chart at your winter rise, or let our flow-rate calculator do the sums.

Can the Rheem RTGH 9.0 GPM Natural Gas Indoor be installed indoors?

Yes, the listing says indoor mounting. That means a vent route to the outside, combustion air and a gas line sized for the unit, all as the maker and your local code require. A licensed plumber or gas fitter sorts that out.

What do you get with the Rheem RTGH 9.0 GPM Natural Gas Indoor?

Its listing states up to 9 GPM, a condensing heat exchanger, temperature held within ±1 °F, freeze protection and a 15-year heat exchanger warranty. These are the seller's figures, not our measurements: how steady the temperature is in your shower and how it copes with your winter water can't be read from a listing.

What should I check before ordering the Rheem RTGH 9.0 GPM Natural Gas Indoor?

Your winter flow: find your winter inlet temperature (your water utility or a thermometer at the cold tap in January), subtract it from 105 °F, and read the maker's flow chart at that rise. Our sizing guide shows how. Vent and gas line: a licensed plumber or gas fitter confirms the vent route, the combustion air and a gas line that can deliver 180,000 BTU/h. Get that quote before you order; our installation guide lists what they will ask. The condensate: a condensing unit drips acidic water that needs a drain, often through a neutralizer. Our condensing guide explains the extra parts. Flushing: hard water scales the heat exchanger. Service valves on the water lines turn the yearly flush into an hour with a bucket and a pump; our flushing and descaling guide shows the routine.

Where can I buy the Rheem RTGH 9.0 GPM Natural Gas Indoor?

We link to the exact listing on Amazon, where today's price, stock and seller apply. It is an affiliate link, and it has no effect on the rating.

Have you used the Rheem RTGH 9.0 GPM Natural Gas Indoor yourselves?

No, we haven't used it ourselves. Everything on this page comes from its listing and 30 buyer reviews, read line by line and weighed with our published formula.

Gas tankless water heaters ↗All Rheem products Comparison tool All product reviews