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Rheem 18kW 240V Tankless Electric Water Heater, Gray

  • Based on 1,907 reviews
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Availability: In Stock.
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Arrives Sunday, Feb 23
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Style: Heater


Features

  • External digital thermostatic control with LED display (+/1 degree accuracy)
  • Most advanced self-modulation, adjust power to meet hot water demand
  • Durable Copper immersion two heating elements, field Serviceable. Flow Rate- up to 4.4 GPM
  • Simple installation bottom 3/4 inch NPT water connections
  • Threaded for easy replacement, simple installation, digital temperature display

Description

This tankless electric water heater is ideal for mid-range whole-home applications. This unit is ideal for single shower applications in the Midwest. The Rheem Performance tankless electric water heaters offer a continuous, endless supply of hot water. A lower kilowatt unit can provide hot water on demand for single or multiple point-of-use applications while a higher kilowatt unit could provide hot water for a whole house depending on the inlet ground water temperature. Tankless electric water heaters save space, save energy, save money, and require no venting. The sleek, compact size, 90 percent smaller than a tank, allows you to save space and place the unit wherever you want, including under a sink. Tankless units only draw energy when hot water is flowing, while traditional tanks are constantly drawing energy to keep the water in the tank at the desired temperature. Rheem's self-modulating technology can save Up to 50 percent on your water heating bill.

Brand: Rheem


Product Dimensions: 14.5"W x 18.25"H


Special Feature: LED Display


Color: Gray


Wattage: 18000 watts


Brand: ‎Rheem


Product Dimensions: ‎14.5"W x 18.25"H


Special Feature: ‎LED Display


Color: ‎Gray


Wattage: ‎18000 watts


Voltage: ‎240 Volts


Maximum Flow Rate: ‎4.4 Gallons Per Minute


Heat Output: ‎18 Kilowatts


Efficiency: ‎99.8%


Style: ‎Heater


Maximum Operating Pressure: ‎150


Mounting Type: ‎Wall


Is Electric: ‎Yes


Manufacturer: ‎Rheem


Item Depth: ‎18.25 inches


UPC: ‎020352685335


Global Trade Identification Number: ‎35


Part Number: ‎RTEX-18


Item Weight: ‎14.78 pounds


Country of Origin: ‎China


Item model number: ‎RTEX-18


Is Discontinued By Manufacturer: ‎No


Size: ‎Small


Finish: ‎Stainless Steel


Shape: ‎Rectangle


Installation Method: ‎Wall Mount


Item Package Quantity: ‎1


Water Consumption: ‎7 Gallons


Special Features: ‎LED Display


Usage: ‎Inside; Professional


Included Components: ‎Fittings, Aerators


Batteries Included?: ‎No


Batteries Required?: ‎No


Date First Available: January 19, 2017


Frequently asked questions

The Rheem 18kW 240V tankless electric water heater can provide a maximum flow rate of up to 4.4 gallons per minute at a 35°F temperature rise. The flow rate may vary depending on your home's incoming water temperature.

This tankless water heater requires 240V electrical connection, and it's recommended to be installed by a professional. It's designed for easy replacement of your existing water heater and it comes with a digital temperature control in 1-degree increments for complete control of hot water.

Yes, the Rheem 18kW tankless water heater is highly energy efficient. It's designed to heat water only when it's needed, eliminating the need for a storage tank and reducing energy consumption.

Yes, this product comes with a 5-year warranty for heating chamber and 1-year warranty for parts. Please register the product to activate the warranty.

Top Amazon Reviews

🚀 Abunda's Overview

This is our summary and key points to consider based on customer reviews.


The Rheem Tankless Water Heater was generally well received, with users particularly praising its compact design and nearly instant hot water supply. Noteworthy also were its energy-saving qualities and the fact that it never runs out of hot water. Some users, however, expressed concerns about installation difficulties and sufficient hot water supply for simultaneous multiple use (such as two showers at once). A few users also mentioned some confusion regarding the unit's wiring, and one cautioned that the unit might not work as effectively for filling bathtubs. As a whole though, most reviewers found the product to be well worth the purchase.

Pros

  • 👍 Compact design frees up space
  • 💰 Significant energy saver
  • 🔥 Provides nearly instant hot water
  • 💧 Unlimited hot water supply

Cons

  • 👎 Difficulty with self-installation; may require a professional
  • 🛠 Some confusion around the wiring
  • 🚿 May not provide sufficient hot water for multiple simultaneous uses
  • 🛁 Might not supply enough hot water for filling bathtubs

Should I Buy It?

If you are looking for a compact, energy-efficient solution for your hot water needs, and do not mind possibly hiring professionals for installation, then yes, the Rheem Tankless Water Heater is a sound purchase. However, if you have a larger household or often require multiple simultaneous uses of hot water, you might want to consider a larger model.


  • Tankless water heater
Great product, installed it in a tiny house and works wonderfully
Reviewed in the United States on December 26, 2024 by Mirian

  • Easy install but may need electrician for the wiring from the breaker box to the hot water heater.
Works great. Plumbing install was pretty easy but had to hire an electrician for the wiring from the breaker box to the hot water heater. Unit easily keeps up with primary bathroom that includes shower, bathtub and two sinks.
Reviewed in the United States on February 5, 2025 by Duane

  • Great water heater
Great electric water heater with user friendly install. Make sure to read the manual. I purchased the 18kw system. Depending on the state you live in, depends on if it will run up to two showers at the same time. We're only able to run one, as our outlet temperature is too cold and I have to run an on-line flow regulator at 2.0 gallons per minute. Not an issue for the most part, it'll end up saving on water I'm the end. Things to note: The temperature and pressure of your cold water (inlet) determines how it works out of the box. Read the manual because you will likely need an inlet flow regulator. This will fix the issue if the heater displays and "E5" error code. The error code means the water is leaving the heater too fast for it to heat, leaving you with like warm water. Because it's electric, you may notice light fixtures blinking when running hot water. This is due in part because of the power draw of the heater, but also because the fixtures or outdated/old. I have led recessed lighting and led light bulbs in some rooms. They have no issues, but my other light fixtures that are not led, will blink when running hot water. A system like this will "expose" older hardware. Make sure you have the water shut off valve before the water filter. The water filter helps delay the build up of water deposits in the water heater, which extends the life and make maintenance of the heater easy. ... show more
Reviewed in the United States on March 6, 2023 by Amazon Customer Amazon Customer

  • Easy to install, works well.
This item arrived slightly damaged, although the packaging was not. I'm not sure if it was a manufacturing or handling issue, but some of the sheet metal frame was bent. I straightened it up with some pliers, as (although not visible once fully installed) it did effect mounting of the cover. Otherwise, the install was fast and straightforward. It does need a ton of amperage to operate (2x dual pole 40 amp breakers), so make sure there's room for them in your panel. The ground is a little "hidden", just a lug on the structure to the left of the opening. Also, I opened up that opening for 1 inch conduit. God help the man that tries to pull 5 #8 wires through 3/4 inch conduit. Get a step drill bit for that, if you're so inclined. After the necessary plumbing and wiring, install took less than an hour. It makes cold water hot, and saves a bunch of space. ... show more
Reviewed in the United States on August 14, 2022 by J. Theren

  • Cost savings in a small box!
a 10+ year old rheem tank needed to be replaced. it wasn't broken but end of service life. and so much so if you drain it. after a lot of research I decided to go with tankless. fearful at first because hey is this truly better? the idea of having on demand seemed appealing. cost savings, of course. but then what type to get?! In the end I settled for a 18k rheem. ecosmart is also well reviewed, but supposedly this is just a rebranded rheem? (like dewalt and black/decker). It is super easy to install. it is small, frees up space, another bonus. costing half of a tank heater. if you can do it yourself... the installation cost is high, as you will have to run new electric and change some plumbing, but that is no biggy. you'll spend about $60 for a valve kit, $50 sharkbites and pex and some for the 8 gauge wire (that can add up if it is a long run btw). for this model you need 2x40amp breakers the water is instantly hot, it easily serves 2 showers, one shower+dishwasher and laundry (tested!) I am very very impressed. also it feels cleaner as there is no water sitting in the tank (you should have seen the drain I had to do from the old tank to get it out of the way). highly recommend a tankless heater and this model works for our household. note: read about technical issues, so far all good, but will update if experienced. installation cost will add up if you can't do it yourself and requires logistics (between plumber and electrician). another installation note: when you get a valve kit with pressure relief (required by most code), it is effectively a gender changer. so when you get flexible hose (female), you need a M/M nipple to attach it to the valve kit... (that is another $20 for 2 nipples to take into consideration). That nipple needs to be taped on the valve attach side, the flex hose side has a o-ring and doesnt need tape (and don't add it either as it will leak) ... show more
Reviewed in the United States on August 7, 2023 by xander

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