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Rheem RTG 8.4 GPM Propane Outdoor Review

Name: Rheem RTG 8.4 GPM Propane Outdoor
Brand: Rheem
SKU: B0C828BV45

7.5Very good · out of 10Rated from the listing's specs, no buyer reviews yet

Written from the listing's specs, not from our own use · How we rate

An 8.4 GPM maximum flow, a ±1 °F temperature hold and freeze protection: the Rheem RTG 8.4 GPM Propane Outdoor covers what matters most in a gas tankless heater. It makes most sense for one shower plus the kitchen in a typical family morning; we rate it 7.5/10 from its listing.

Price$953Price on Sep 30, 2026 · may have changed

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

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Specifications

Brand	Rheem
Category	Gas tankless water heaters
Fuel	Propane
Stated maximum flow	8.4 GPM
Stated gas input	180,000 BTU/h
Flow at a stated rise	8.4 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
ASIN	B0C828BV45

Full listing title: Rheem RTG Series 8.4 GPM Liquid Propane Tankless Water Heater Oudoor | 180,000 BTUs High Efficiency On Demand, Continuous Hot Water | Non-Condensing

Listing evidence

Fuel	Liquid Propane Full listing title
Stated maximum flow	8.4 GPM Full listing title
Stated gas input	180,000 BTUs Full listing title

Updated October 2026

Exact listing, ASIN B0C828BV45

Rating from a published formula

Compared with its closest rivals

Two gas tankless heaters close to it on our rating, each with a dated price.

Compare side by side ↗

Rheem RTG 8.4 GPM Propane Outdoor

7.5Very good · out of 10$953 Price on Sep 30, 2026 · may have changed

Stated: 8.4 GPM · 180,000 BTU/h
Gas tankless water heaters

This product ↑

MIZUDO 120,000 BTU Natural Gas

7.6Very good · out of 10$539.99 Price on Sep 30, 2026 · may have changed

Stated: 5.1 GPM · 120,000 BTU/h
Gas tankless water heaters

See the review ↗

ThermoMate Condensing Propane

7.6Very good · out of 10$559.99 Price on Sep 30, 2026 · may have changed

Stated: 5.28 GPM · 114,000 BTU/h · 120 V
Gas tankless water heaters

See the review ↗

Up to 8.4 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 two showers and a kitchen tap, less when the water comes in cold.

What it has going for it

What changes in the morning shower rush

±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.

Freeze protection. Stated in the listing. Useful in a garage, a crawl space or a cabin that sits empty in winter, as long as the unit keeps power.

Natural gas or propane?

Propane: that's what the listing names. A propane unit runs off a tank outside, so the tank size and the regulator are part of the plan.

Natural gas: it's a different set of gas jets and pressures. Only the maker's conversion kit, if there is one, and a licensed gas fitter can switch it; ask before you order.

Great for you if…

You run one shower and the kitchen tap at once, rarely more
A shower that suddenly runs cold drives you mad
It will live in a garage, a cabin or another cold spot

Skip it if…

You'd rather wait for buyer reviews: none are captured for this listing yet
You want the high-efficiency kind: the listing doesn't call it condensing
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 RTG 8.4 GPM Propane Outdoor listing names:

Up to 8.4 GPM
8.4 GPM at a 35 °F rise
180,000 BTU/h input
Propane
±1 °F temperature hold claimed
Freeze protection named
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 RTG 8.4 GPM Propane Outdoor if the maker asks, and read the install conditions: many tankless warranties need a licensed install and regular flushing.

For the Rheem RTG 8.4 GPM Propane Outdoor, the installation manual settles the venting, the gas line and the clearances.

Rheem RTG 8.4 GPM Propane Outdoor, view 3

Price and cost per GPM of stated flow

$953 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 $113.45 (price ÷ stated GPM, our arithmetic). That puts it in the pricier third of the 10 gas tankless heaters we have a price and a stated flow for.

Count the install in the budget: vent pipe, possibly a 3/4" gas line, and a licensed plumber or gas fitter.

The button opens the exact listing (ASIN B0C828BV45), where today's price, stock and seller apply.

Rheem RTG 8.4 GPM Propane Outdoor, view 4

A better fit for your house?

Want the high-efficiency kind? The Rheem RTGH 9.5 GPM Propane Indoor (7.8/10) is a condensing unit, per its listing.

Only one bathroom? The ThermoMate Condensing Natural Gas (7.7/10) states up to 5.28 GPM.

Our take

The verdict

What we'd buy the Rheem RTG 8.4 GPM Propane Outdoor for is an 8.4 GPM maximum flow, with a ±1 °F temperature hold as a bonus. No buyer reviews yet, so this Rheem gas tankless heater has to win you over on paper. The catch with the Rheem: the headline GPM is a mild-weather figure, so leave yourself margin for January. We'd pick it if you run one shower and the kitchen tap at once, rarely more; otherwise, put it next to the MIZUDO 120,000 BTU Natural Gas 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 8.4 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), and clean the inlet filter. Our flushing and descaling guide has the checklist.

The one thing we'd check first

Before the Rheem RTG 8.4 GPM Propane Outdoor goes in your cart, check your winter rise: it is rated 8.4 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 warranty terms

15 years are stated on the heat exchanger. Read what it requires: a licensed install, the gas type and regular flushing are the usual conditions.

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 RTG 8.4 GPM Propane Outdoor stacks up against the closest alternative, the MIZUDO 120,000 BTU Natural Gas.

Criterion	Rheem RTG 8.4 GPM Propane Outdoor	MIZUDO 120,000 BTU Natural Gas
Our rating	7.5/10	7.6/10
Max flow	8.4 GPM	5.1 GPM
Gas input	180,000 BTU/h	120,000 BTU/h
Temperature hold	±1 °F stated	Not stated
Warranty	15 years (heat exchanger)	2 years

Pick the MIZUDO 120,000 BTU Natural Gas if you want our higher-rated option (7.6/10); stay with the Rheem RTG 8.4 GPM Propane Outdoor for more flow (8.4 GPM) and a bigger burner (180,000 BTU/h).

Compare side by side ↗See the MIZUDO 120,000 BTU Natural Gas review →

The score in detail

How we rated it

Spec-based rating on a 4.5–8.5 scale: 4.5 + average of the 4 criteria × 0.4. Capped at 8.5 because no customer evidence is included.

Key specifications

8 / 10

Build, warranty & certifications

8 / 10

Listing documentation

7 / 10

Fit & compatibility

7 / 10

This product has no captured buyer-review record yet, so its rating comes from the documented listing alone: four criteria scored out of 10 (key specifications; build, warranty and certifications; listing documentation; fit and compatibility), placed on a 4.5–8.5 scale. Read the full methodology.

Read the methodology →

Frequently asked questions

Is the Rheem RTG 8.4 GPM Propane Outdoor any good?

We rate it 7.5/10 (very good). The rating comes from its documented listing alone, as no customer-review record is captured yet.

How much hot water can the Rheem RTG 8.4 GPM Propane Outdoor deliver?

The listing states a maximum flow of 8.4 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.

What do you get with the Rheem RTG 8.4 GPM Propane Outdoor?

Its listing states up to 8.4 GPM, 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 RTG 8.4 GPM Propane Outdoor?

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 warranty terms: 15 years are stated on the heat exchanger. Read what it requires: a licensed install, the gas type and regular flushing are the usual conditions. 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 RTG 8.4 GPM Propane Outdoor?

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 RTG 8.4 GPM Propane Outdoor yourselves?

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

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