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ThermoMate CZ422LP Propane Indoor

Product images: Amazon listings

ThermoMate CZ422LP Propane Indoor Review

7.8Very 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

On paper, the ThermoMate CZ422LP Propane Indoor gets the important things right: a 5 GPM maximum flow, a 0.81 UEF rating and a ±1 °F temperature hold. With freeze protection as well, it suits one shower at a time and not much more.

Price$399.99Price on Sep 30, 2026 · may have changed
Check the price on Amazon ↗ ThermoMate CZ422LP Propane Indoor (opens in a new tab)Affiliate link · price and stock on Amazon
Compare side by side ↗
Specifications
BrandThermoMate
CategoryGas tankless water heaters
FuelPropane
Stated mounting locationIndoor
Stated maximum flow5 GPM
Stated gas input113,000 BTU/h
Stated voltage120 V
Stated efficiency0.81 UEF
Temperature hold±1 °F, per the listing
Vent size3"
Freeze protectionStated in the listing
ASINB0DRDCD8MN

Full listing title: ThermoMate CZ422LP, Propane Tankless Water Heater Indoor, Up to 5 GPM

Listing evidence
FuelPropane Full listing title
Stated mounting locationIndoor Full listing title
Stated maximum flow5 GPM Full listing title
Stated gas input113,000 BTU Listing text
Stated voltage120V Listing text
Updated October 2026
Exact listing, ASIN B0DRDCD8MN
Rating from a published formula

Compared with its closest rivals

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

Compare side by side ↗

ThermoMate CZ422LP Propane Indoor

ThermoMate CZ422LP Propane Indoor

7.8Very good · out of 10$399.99 Price on Sep 30, 2026 · may have changed
  • Stated: 5 GPM · 113,000 BTU/h · 120 V
  • Gas tankless water heaters
This product ↑
APUS 95,000 BTU Propane Indoor

APUS 95,000 BTU Propane Indoor

7.4Good · out of 10$299.99 Price on Sep 30, 2026 · may have changed
  • Stated: 4.42 GPM · 95,000 BTU/h · 120 V
  • Gas tankless water heaters
See the review ↗
Novieex 100,000 BTU Propane Indoor

Novieex 100,000 BTU Propane Indoor

7.2Good · out of 10$269.98 Price on Sep 30, 2026 · may have changed
  • Stated: 4.3 GPM · 100,000 BTU/h · 110 V
  • Gas tankless water heaters
See the review ↗

Up to 5 GPM from a 113,000 BTU burner

That's the maximum flow the listing states, and headline flows are usually quoted at a mild temperature rise. With January water coming in at 42 °F and a 105 °F shower, the rise is 63 °F and the real flow is lower; the maker's flow chart has that number. Counting 2 GPM per shower, as our calculator does, that's one shower and a sink at a time, maybe two showers where the water comes in warm.

What it has going for it

What changes in the morning shower rush

0.81 UEF. Uniform Energy Factor is the federal efficiency label: the higher it is, the less gas or power goes up the vent instead of into your shower.

±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?

One at a time, plus the kitchen tap: 5 GPM covers that on paper.

Two at once: fine on a warm day in the South. In January up north, the second shower is where it runs out, so check the flow chart at a 63 °F rise.

Great for you if…

  • 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

What ThermoMate promises

The seller states, word for word, in the ThermoMate CZ422LP Propane Indoor listing:

  • The ThermoMate instant water heater delivers hot water on-demand for two showers at the same time, maintaining a stable 105°F (based on 65°F inlet temperature).
  • Equipped with 4 ceramic heating cores, it auto-activates frost protection when temperatures hit 41°F (5°C).
  • Easily adjust water temperature (90–140°F) and keep track of flow, fan, and flame status on the 3.5-inch LED display.

The seller's claims, quoted as written; we haven't measured any of it. The flow at your winter rise is in the maker's chart, not in the bullet points.

ThermoMate CZ422LP Propane Indoor, view 3

Gas, venting and what's in the box

What the ThermoMate CZ422LP Propane Indoor listing names:

  • Up to 5 GPM
  • 113,000 BTU/h input
  • Propane
  • Indoor mounting
  • 0.81 UEF
  • 3" vent
  • 120 V plug for the controls
  • ±1 °F temperature hold claimed
  • Freeze protection named
  • CSA, ETL or UL mark named

The installation manual has the last word on venting, gas line and clearances; your installer reads it before you order.

ThermoMate CZ422LP Propane Indoor, view 4

Price and cost per GPM of stated flow

$399.99 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 $80.00 (price ÷ stated GPM, our arithmetic). That puts it in the cheaper third of the 45 indoor 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 B0DRDCD8MN), where today's price, stock and seller apply.

ThermoMate CZ422LP Propane Indoor, view 5

A better fit for your house?

Two showers and the dishwasher at once? The Ranein 190,000 BTU Natural Gas Indoor (7.9/10) states up to 8.5 GPM.

No easy route for a vent pipe? The Westinghouse 120,000 BTU Propane Outdoor (7.6/10) mounts on an outside wall, per its listing.

Want the high-efficiency kind? The ThermoMate Condensing Propane (7.6/10) is a condensing unit rated 0.86 UEF, per its listing.

Our take

The verdict

Our favourite thing about the ThermoMate CZ422LP Propane Indoor is a 5 GPM maximum flow, closely followed by a 0.81 UEF rating. No buyer reviews yet, so the ThermoMate CZ422LP Propane Indoor has to win you over on paper. Honestly, the catch: no word on the warranty. We'd pick it if a shower that suddenly runs cold drives you mad; otherwise, put it next to the Rheem RTGH 9.5 GPM Propane Indoor first.

Check the price on Amazon ↗ ThermoMate CZ422LP Propane Indoor (opens in a new tab)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 (3" pipe, per the listing). Plan the gas line for 113,000 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. 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 ThermoMate CZ422LP Propane Indoor goes in your cart, check your gas line: 113,000 BTU/h is a lot of gas at once, so ask your plumber whether the existing line can feed it.

Before you buy

Your winter flow

5 GPM is the headline. In a northern January the water comes in near 42 °F, so a 105 °F shower needs a 63 °F rise and the real flow drops. Our flow-rate calculator runs the numbers for your house.

Vent and gas line

Ask the plumber to check the gas line size and the meter against the heater's input, and to quote the vent route at the same visit. Our install cost guide shows what that usually adds.

Power at the wall

It plugs into a 120 V outlet for its fan and controls, so plan one within reach of where it hangs.

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 ThermoMate CZ422LP Propane Indoor stacks up against the closest alternative, the Rheem RTGH 9.5 GPM Propane Indoor.

CriterionThermoMate CZ422LP Propane IndoorRheem RTGH 9.5 GPM Propane Indoor
Our rating7.8/107.8/10
Max flow5 GPM9.5 GPM
Gas input113,000 BTU/h199,900 BTU/h
Efficiency0.81 UEFCondensing
WarrantyNot stated15 years (heat exchanger)

Both score 7.8/10. The Rheem RTGH 9.5 GPM Propane Indoor adds more flow (9.5 GPM) and a bigger burner (199,900 BTU/h).

Compare side by side ↗See the Rheem RTGH 9.5 GPM Propane Indoor 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

9 / 10

Build, warranty & certifications

7 / 10

Listing documentation

9 / 10

Fit & compatibility

8 / 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 ThermoMate CZ422LP Propane Indoor any good?

We rate it 7.8/10 (very good). The rating comes from its documented listing alone, as no customer-review record is captured yet.

How much hot water can the ThermoMate CZ422LP Propane Indoor deliver?

The listing states a maximum flow of 5 GPM and a gas input of 113,000 BTU/h on 120 V. 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 ThermoMate CZ422LP Propane 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 ThermoMate CZ422LP Propane Indoor?

Its listing states up to 5 GPM, a 0.81 UEF rating, temperature held within ±1 °F and freeze protection. 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 ThermoMate CZ422LP Propane Indoor?

Your winter flow: 5 GPM is the headline. In a northern January the water comes in near 42 °F, so a 105 °F shower needs a 63 °F rise and the real flow drops. Our flow-rate calculator runs the numbers for your house. Vent and gas line: ask the plumber to check the gas line size and the meter against the heater's input, and to quote the vent route at the same visit. Our install cost guide shows what that usually adds. Power at the wall: it plugs into a 120 V outlet for its fan and controls, so plan one within reach of where it hangs. 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 ThermoMate CZ422LP Propane 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 ThermoMate CZ422LP Propane Indoor 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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