Search  for anything...

Rheem 18kW 240V Tankless Electric Water Heater, Gray

  • Based on 1,881 reviews
Condition: New
Checking for product changes
$422.33 Why this price?
New Year Deal · 6% off was $449.00

Buy Now, Pay Later


As low as / mo
  • – Up to 36-month term if approved
  • – No impact on credit
  • – Instant approval decision
  • – Secure and straightforward checkout

Ready to go? Add this product to your cart and select a plan during checkout. Payment plans are offered through our trusted finance partners Klarna, PayTomorrow, Affirm, Afterpay, Apple Pay, and PayPal. No-credit-needed leasing options through Acima may also be available at checkout.

Learn more about financing & leasing here.

Selected Option

Free shipping on this product

30-day refund/replacement

To qualify for a full refund, items must be returned in their original, unused condition. If an item is returned in a used, damaged, or materially different state, you may be granted a partial refund.

To initiate a return, please visit our Returns Center.

View our full returns policy here.


Availability: In Stock.
Fulfilled by Amazon

Arrives Saturday, Jan 25
Order within 16 hours and 22 minutes
Available payment plans shown during checkout

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
Style: Heater
Great product, installed it in a tiny house and works wonderfully
Reviewed in the United States on December 26, 2024 by Mirian

  • Tankless water heater
Style: Heater
It was easily installed by my contractor and is working well. Unlimited use of hot water. It saves a lot on electrical bill compared to a traditional water heater that is constantly being heated to keep optimum temperature.
Reviewed in the United States on November 15, 2024 by JM

  • Works very well
Style: Heater
Was cheaper than Home Depot. Pulls about 8kw upon use. You may feel the need to set the temp to 145 if you are converting from water heater tank. You don't unless you have multiple hot water using devices going at the same time. Biggest acclimatization is that it'll get warmer before it gets hot in the shower. You'll need to either let it run longer to get to the final temp or go into the shower and know that you need to adjust as you're showering. ... show more
Reviewed in the United States on September 25, 2024 by Amazon Customer

  • Pre-purchase research didn't reveal a couple issues.
Style: Heater
I wanted to have more space in my garage where my old water tank was at, it was too tight of a fit in front of my car. The wife and I are empty nesters and from what we read before purchase, this tank would be suitable for the two of us. This tank did resolve the space issue, and I now have room in front of my car in the garage that I didn't have before. I am happy about that. What I hadn't read was that with a tank the water at the faucet goes from inside the wall temperature up to tank temperature when the tank water reaches the faucet. With this tankless water heater the temp goes from wall temp down to underground Inlet temp for a few seconds before you actually get hot water. I did install a water circulating pump to resolve this issue since my farthest sink was taking too long for hot water even when I had a tank. A bigger concern was that this tank can not support two simultaneous showers. So if we want to shower at the same time it needs to be in the same shower. That does have its advantages, but when we have overnight guests we need to know when they are showering so we can avoid showering at that time. The tank was easily able to support two simultaneous showers. The biggest issue is taking a bath. I never take them, but my wife does. Our showers have single handle valves that point down when off, then rotate counter clockwise through the cold, up into the warm, then left into the hot. The issue is that this unit cannot make enough hot water to fill the tank. If I had a valve that allowed me to slow the flow while still being set to warm or hot she could get a tub of hot water. I suppose she could fill the tub through the shower head which slows the water flow where the heater could keep up, but that would take a long time to fill. She also likes to rinse her hair bent over the tub at certain times separate from a shower using the tub spout. This is also now not possible since at that flow the heater can't keep up. If I had to do it again I would go with a larger model. This size appealed to me because it required two lines of 8/2 wire on 40 amp double pole breakers where the next size up required three. I hope someone finds this information useful. Good luck. Edit: After about 8 months, I am liking this water heater more and more. Initially it seemed to struggle with the flow, and I had increased the temp to the maximum of 140°, thinking if it was hotter, I could add more cold water to increase the volume of hot water. About a month ago I turned it down to 120° and not only do I have plenty of hot water for the two simultaneous showers, my wife no longer has a problem filling the tub when needed. It seems to make more water at 120° than it did at 140°. If this changes in the winter when the inlet water temp is lower, I'll update this review again. ... show more
Reviewed in the United States on March 3, 2023 by Lee S.

  • Cost savings in a small box!
Style: Heater
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

Can't find a product?

Find it on Amazon first, then paste the link below.