Product images: Amazon listings

Rheem RTEX-24, 24 kW 240V Review

Name: Rheem RTEX-24, 24 kW 240V
Brand: Rheem
SKU: B01MS9DVEE

8.3Very good · out of 10Variant of the Rheem 18 kW Electric, 240V, #1 in our Whole-House Electric Tankless Heaters ranking

Written from the listing and 893 buyer reviews, not from our own use · How we rate

On paper, the Rheem RTEX-24 (24 kW 240V) gets the important things right: a 5.9 GPM maximum flow, 24 kW at 240 V and a 5-year warranty. It suits a southern house with warm tap water and no gas line, and its sibling listing, the Rheem 18 kW Electric (240V), holds #1 in our whole-house electric tankless water heater ranking.

Variants of this model

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

Rheem 18 kW Electric, 240V · Whole Home, 18 kw · 9.3/10
Rheem 11 kW Multi Fixture, 240V · Point-of-Use, 11 kw · 7.2/10
Rheem 8 kW Multi Fixture, 240V · Point-of-Use, 8 kw · 7.2/10
Rheem 3.5 kW Point-of-Use, 120V · Point-of-Use, 3.5 kw · 7.0/10
Rheem RTEX-06T, 6.5 kW 240V · Point-of-Use, 6.5 kw · 6.0/10

Price$549Price 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	Electric tankless water heaters
Fuel	Electric
Stated maximum flow	5.9 GPM
Stated heating power	24 kW
Stated voltage	240 V
Temperature range	80 to 140 °F
Wire gauge	8 AWG
Stated warranty	5 years
Buyer reviews	893 · 4.3/5
ASIN	B01MS9DVEE

Full listing title: Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray

Listing evidence

Fuel	24kW Full listing title
Stated maximum flow	up to 5.9 GPM Listing text
Stated heating power	24kW Full listing title
Stated voltage	240V Full listing title

Updated October 2026

Exact listing, ASIN B01MS9DVEE

Rating from a published formula

Compared with its closest rivals

Two electric tankless heaters of about the same power, closest to it on our rating, each with a dated price.

Compare side by side ↗

Rheem RTEX-24, 24 kW 240V

8.3Very good · out of 10$549 Price on Sep 30, 2026 · may have changed

Stated: 5.9 GPM · 24 kW · 240 V
893 buyer reviews
Electric tankless water heaters

This product ↑

Stiebel Eltron Tempra 29 Plus

7.9Very good · out of 10$798.99 Price on Sep 30, 2026 · may have changed

Stated: 28.8 kW · 240 V
451 buyer reviews
Electric tankless water heaters

See the review ↗

SIVUATEK 18 kW Electric, 240V

7.7Very good · out of 10$245.99 Price on Sep 30, 2026 · may have changed

Stated: 4.3 GPM · 18 kW · 240 V
266 buyer reviews
Electric tankless water heaters

See the review ↗

24 kW at 240 V

The heating power the listing states. At 240 V it draws about 100 A, on 8 AWG wire per the listing. That's the line to show your electrician before anything else: the panel decides whether this fits, not the shower.

What it has going for it

What changes in the morning shower rush

5.9 GPM max. That is the headline figure, usually at a modest temperature rise. Our calculator counts a shower at 2 GPM, so think one shower and a sink at a time, maybe two showers where the water comes in warm.

80 to 140 °F. The setpoint range per the listing. Above 120 °F at the tap is scalding territory for kids, so most homes set it lower.

Warm tap water or a cold January?

Warm tap water: where it comes in around 62 °F (much of the South), 24 kW gives about 3.8 GPM of 105 °F water on our calculator's maths. That's one 2 GPM shower at a time.

A cold January: where it comes in at 42 °F, it's about 2.6 GPM, one 2 GPM shower at a time. Up north, that's the figure to size against, and it's why the honest answer is sometimes a second unit or gas.

Great for you if…

You live somewhere the tap water never gets icy
You want a long warranty: 5 years are stated
You trust a long track record: 893 buyer reviews

Skip it if…

You want self-modulating power: the listing doesn't say it modulates
Your panel is already close to full: 24 kW is about 100 A at 240 V

Power, wiring and what's in the box

What the Rheem RTEX-24 (24 kW 240V) listing names:

24 kW
240 V
8 AWG wire
Up to 5.9 GPM
80 to 140 °F setpoint

Warranty & support: 5-year warranty, as stated in the listing.

That is the maker's promise, not ours. Keep the invoice, register the Rheem RTEX-24 (24 kW 240V) if the maker asks, and read the install conditions: many tankless warranties need a licensed install and regular flushing.

Breakers and wire gauge are in the installation manual, and it overrides anything above; your electrician reads it first.

Price and cost per kW

$549 Price on Sep 30, 2026 · may have changed

At the price on Sep 30, 2026, each kW of stated heating power works out at about $22.88 (price ÷ stated kW, our arithmetic). That puts it in the pricier third of the 27 whole-house electric tankless heaters we have a price and a stated power for.

Budget for the electrician as well: new double-pole breakers, thick wire from the panel and, if the panel is full, an upgrade.

The button opens the exact listing (ASIN B01MS9DVEE), where today's price, stock and seller apply. Sizes and variants of the same family often sit at different prices.

A better fit for your house and panel?

Colder tap water where you live? The WINTEMP WN-36kW Electric, 240V (8.1/10) is rated 36 kW.

Panel short on spare amps? The SIVUATEK 18 kW Electric, 240V (7.7/10) is rated 18 kW, about 75 A at 240 V.

Only one sink far from the heater? The ThermoMate 14 kW Electric, 240V (7.9/10) is a 14 kW point-of-use unit.

Our take

The verdict

What we'd buy the Rheem RTEX-24 (24 kW 240V) for is a 5.9 GPM maximum flow, with 24 kW at 240 V as a bonus. 893 buyers give it 4.3/5, which is a solid sign. Where it falls short: no stated self-modulation, while most picks here have it. We'd pick it if you live somewhere the tap water never gets icy; otherwise, put it next to the WINTEMP WN-36kW Electric (240V) first.

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

Living with it

Install day

New breakers, 8 AWG wire, the unit on the wall next to the old tank's spot, water in and out. An electrician does the panel side.

The first shower

Hot in a few seconds once the water in the pipes has passed. Set it between 80 and 140 °F.

The first winter

With 42 °F water coming in, 24 kW gives about 2.6 GPM at 105 °F on our calculator's maths. Low-flow shower heads stretch that further.

Upkeep

Clean the inlet screen and flush out scale on hard water. Our flushing and descaling guide has the routine.

What buyers say

Buyers give it 4.3/5, a solid record, right on our ranked picks' 4.3 average. And with 893 reviews behind it, that number is hard to argue with.

The numbers

Buyer rating: 4.3/5
Reviews: 893
Ranked picks' average: 4.3/5

The one thing we'd check first

Before the Rheem RTEX-24 (24 kW 240V) ships, check your panel: 24 kW at 240 V is roughly 100 A, so an electrician should look at the panel first.

Before you buy

Your panel

Take a photo of the panel label (main breaker size and free slots) and send it to the electrician with the listing. Our electrical requirements guide explains what they will look for.

Your winter flow

On our calculator's maths, 24 kW gives about 2.6 GPM with 42 °F winter water and 3.8 GPM with 62 °F water. Our flow-rate calculator does it for your region.

The install

Hardwired 240 V work needs a licensed electrician and often a permit. Our install cost guide shows what usually ends up on the quote.

Scale

Hard water still builds up on the elements and the inlet screen. Our flushing and descaling guide covers the routine.

How it compares

How the Rheem RTEX-24 (24 kW 240V) stacks up against the closest alternative, the WINTEMP WN-36kW Electric (240V).

Criterion	Rheem RTEX-24, 24 kW 240V	WINTEMP WN-36kW Electric, 240V
Our rating	8.3/10	8.1/10
Heating power	24 kW	36 kW
Max flow	5.9 GPM	8.7 GPM
Breakers	Not stated	1 × 50 A
Self-modulating	Not stated	Stated
Buyer reviews	893 · 4.3/5	203 · 4.4/5

Pick the WINTEMP WN-36kW Electric (240V) if more power (36 kW) and more stated flow (8.7 GPM) matter more to you; on our rating, the Rheem RTEX-24 (24 kW 240V) comes out ahead.

Compare side by side ↗See the WINTEMP WN-36kW Electric, 240V review →

The score in detail

How we rated it

Our score: 8.3/10

Buyer rating (45%)

38.7 / 45

4.3/5 average

Review volume (35%)

27.9 / 35

893 buyer reviews

Documented specifications (20%)

16.4 / 20

82/100 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 RTEX-24 (24 kW 240V) any good?

We rate it 8.3/10 (very good). It is based on 893 buyer reviews averaging 4.3/5 and the specifications stated in the listing.

How much hot water can the Rheem RTEX-24, 24 kW 240V deliver?

The listing states a maximum flow of 5.9 GPM and a heating power of 24 kW on 240 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.

What electrical service does the Rheem RTEX-24, 24 kW 240V need?

The listing states 240 V and 24 kW. At 240 V, that is roughly 100 A. A licensed electrician checks the panel, the breakers and the wiring before it goes on the wall.

What do you get with the Rheem RTEX-24 (24 kW 240V)?

Its listing states up to 5.9 GPM, 24 kW of heating power and a 5-year 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 RTEX-24 (24 kW 240V)?

Your panel: take a photo of the panel label (main breaker size and free slots) and send it to the electrician with the listing. Our electrical requirements guide explains what they will look for. Your winter flow: on our calculator's maths, 24 kW gives about 2.6 GPM with 42 °F winter water and 3.8 GPM with 62 °F water. Our flow-rate calculator does it for your region. The install: hardwired 240 V work needs a licensed electrician and often a permit. Our install cost guide shows what usually ends up on the quote. Scale: hard water still builds up on the elements and the inlet screen. Our flushing and descaling guide covers the routine.

Where can I buy the Rheem RTEX-24 (24 kW 240V)?

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 RTEX-24 (24 kW 240V) yourselves?

No, we haven't used it ourselves. Everything on this page comes from its listing and 893 buyer reviews, read line by line and weighed with our published formula.

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