---
product_id: 38866492
title: "Rheem 18kW 240V Tankless Electric Water Heater, Gray"
brand: "rheem"
price: "C$62970"
currency: NIO
in_stock: true
reviews_count: 8
category: "Rheem"
url: https://www.desertcart.ni/products/38866492-rheem-18kw-240v-tankless-electric-water-heater-gray
store_origin: NI
region: Nicaragua
---

# 18 kW power output 4.4 GPM max flow rate ±1°F digital LED thermostat Rheem 18kW 240V Tankless Electric Water Heater, Gray

**Brand:** rheem
**Price:** C$62970
**Availability:** ✅ In Stock

## Summary

> 🔥 RTEX-18: Hot water that keeps up with your hustle!

## Quick Answers

- **What is this?** Rheem 18kW 240V Tankless Electric Water Heater, Gray by rheem
- **How much does it cost?** C$62970 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.ni](https://www.desertcart.ni/products/38866492-rheem-18kw-240v-tankless-electric-water-heater-gray)

## Best For

- rheem enthusiasts

## Why This Product

- Trusted rheem brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Space-Saving Design:** Compact wall-mounted unit is 90% smaller than traditional tanks—perfect for modern minimalist homes.
- • **Endless Hot Water Flow:** Self-modulating tech adapts power dynamically, delivering continuous hot water on demand without waste.
- • **DIY-Friendly Installation:** Threaded 3/4 inch NPT water connections simplify setup and future servicing—upgrade hassle-free.
- • **Energy Efficiency Champion:** Consumes power only when water flows, slashing heating bills by up to 50% with smart modulation.
- • **Precision Temperature Control:** External digital thermostat with LED display ensures exact hot water temps to the degree.

## Overview

The Rheem RTEX-18 is a professional-grade tankless electric water heater delivering 18 kW of power with up to 4.4 gallons per minute flow. Featuring a precise external digital thermostat with ±1°F accuracy and advanced self-modulating technology, it provides endless hot water while optimizing energy use. Its compact, wall-mounted design saves space and installs easily with threaded 3/4 inch NPT connections. Ideal for single to mid-range whole-home applications, this unit offers up to 50% savings on water heating bills and a sleek, modern upgrade for energy-conscious professionals.

## 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.

Review: Rheem tankless water heater - Love this tankless heater, it works great! Never run out of hot water while showering! There's only 2 of us in our home so not sure how it would work with a family but I'm sure a bigger size or maybe another mounted where hot water is needed most?? Would definitely buy again!!
Review: If you know what you're getting, you'll love it! - There are many factors to consider before buying an electric tankless heater. By far the most important -- at least for me -- is whether the ground water temperature in your area is consistently warm enough to give the water heater a chance to succeed. I live in North Central Florida where the groundwater temperature is a rock-solid 72F (~22C) year-round. This is the ideal setup for tankless electrics; if you are far north this heater will likely fall short at the exact worst time, i.e. when it's winter and you could really use a nice, hot shower. I recommend looking closely at the map provided on Rheem's website and product pages to determine if this product is right for you. Second caveat, if you have a natural gas hookup, it is worth researching whether a gas-powered unit would be more efficient and/or less costly. There are considerations beyond this, of course, but those are the key ones that will determine whether you will be a happy camper or have cold water poured on those dreams of long, hot showers. If you're still considering after reading the above, then the short of it is (drumroll) ... I'm very satisfied and fully recommend making the jump to tankless! Here's the long-winded version: There is about 25- to 30-feet of pipe to travel between the water heater and the showerhead in my bathroom, and it takes about 25 seconds (well, 22.93 ... yes, I used a stopwatch) for the shower water to reach max temp. I did not use a stopwatch on my tank heater, but I'd guestimate it takes about 10 seconds longer for the tankless to deliver hot water than the tank unit it replaced. The main benefit, again, is that the tankless will continue to deliver hot water indefinitely while the tank is finite -- so, no more playing beat the clock and if you get in the water and realize you forgot your razor or something. The temperature coming out of the showerhead lines up with the temperature on the digital display for the main shower. There is a slight, but noticeable (I'd say 2F-4F/1C-2C) drop from the maximum temperature for the shower furthest away from the water heater. There is enough overhead that you can crank it a few degrees higher -- just be sure your shower handle can settle on something that won't scald you if you go above the recommended! I can also verify that the throughput on the model I bought (24 kW) is enough to handle two showers running at the same as well as start a load of laundry on hot -- I'm sure it could handle more, but there's not a scenario I can imagine where I would need it to. All in all, the flow is as good or better than the water heater it replaced. The dimensions listed on the product page are accurate. As far as your monthly bill, this hasn't made a significant impact although it may in the future. Here's some data from my most recent utility bill compared to the same month last year. Keep in mind the following figures are the daily averages listed on my bill for the whole home, not just the heater, although it is the only major appliance we have replaced over the past 12 months. April 2025 = 33.90 kWh electric and 0.06 KGA water (whole-home daily average) April 2024 = 31.34 kWh electric and 0.03 KGA water (whole-home daily average) Based on the above info (and the prior two months), it's essentially a wash -- we're using more power but only because we're taking longer showers because we can actually enjoy the heat now rather than worrying whether we're leaving enough water for everyone else! I'm sure that our water usage will level out once the novelty wears off, but that might be a while :) Now for the elephant in the room: Installation. If you can't say right now, with confidence and without any further research, whether you could get away with a DIY install, I'll answer the question for you: No, you can't. The plumbing end of the equation is easy -- the only hard part was ditching the tank unit. Beyond that, all you will need is a few fittings and a little pipe to hook it all up, plus the proper hardware to secure it to the wall. Any homeowner who would be comfortable ripping out a vanity sink/faucet and installing a new one should be able to do this portion themselves. The electrical hookup is another story. First, you will need 200-amp service to make this viable; if you don't, save yourself the headache. Second, depending on the distance between your electrical box and your water heater, you may need to have an auxiliary breaker box installed, as we did. Just as water temperatures vary regionally, so do electrician's rates. In our area we paid $850 to have a licensed electrician and his journeyman knock it out -- it took them about three hours and that includes the cost of the pictured auxiliary box. I would expect that rate to be higher in major metros but hopefully it gives a ballpark for what you can expect to pay beyond the sticker price.

## 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

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B01MR7Z39V |
| Amperage | 75 Amps |
| Best Sellers Rank | #4,486 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #1 in Water Heaters |
| Brand | Rheem |
| Color | Gray |
| Customer Reviews | 4.2 4.2 out of 5 stars (3,924) |
| Date First Available | January 19, 2017 |
| Efficiency | 99.8% |
| Global Trade Identification Number | 00020352685335 |
| Heat Output | 18 Kilowatts |
| Is Discontinued By Manufacturer | No |
| Is Electric | Yes |
| Item Depth | 18.25 inches |
| Item Weight | 14.78 pounds |
| Item model number | RTEX-18 |
| Manufacturer | Rheem |
| Manufacturer Part Number | RTEX-18 |
| Maximum Flow Rate | 4.4 Gallons Per Minute |
| Maximum Operating Pressure | 150 |
| Maximum Temperature | 140 Degrees Fahrenheit |
| Model | Professional Classic Tankless Electric RTEX-18 |
| Mounting Type | Wall |
| Product Dimensions | 14.5"W x 18.25"H |
| Special Feature | LED Display |
| Special Features | LED Display |
| Style | Whole Home, 18 kw |
| UPC | 020352685335 |
| Voltage | 240 Volts |
| Wattage | 18000 watts |

## Product Details

- **Brand:** Rheem
- **Capacity:** 18 Gallons
- **Power Source:** AC Power
- **Product Dimensions:** 14.5"W x 18.25"H
- **Special Feature:** LED Display

## Images

![Rheem 18kW 240V Tankless Electric Water Heater, Gray - Image 1](https://m.media-amazon.com/images/I/91J18WlAKqL.jpg)

## Available Options

This product comes in different **Style** options.

## Questions & Answers

**Q: will this supply two showers, washer and dishwasher for two people? (1000 sf house)**
A: Hello-

Sizing an electric tankless is very difficult. I always recommend that you call Rheem at 800-432-8373 to get a suggestion. I want to say this will only keep up with ONLY 1 source of hot water at any one given time.

That being said, the RTEX-18 performance ( @240V )-
1.5GPM - 82degree rise
2.0GPM - 62degree rise
2.5GPM - 49degree rise
3.0GPM - 41degree rise

So.... what it can keep up with all depends on:
-the temp of water coming into the house
-the flow rate of each faucet/shower head/washing machine/source of hot water
-outlet temp desired

I hope this helped :)
Ben

**Q: How many amps**
A: Paperwork says it requires four 40 amp breakers or two DP 40 amp breakers. Max draw of 75 amps.

**Q: Rheem rtex-18  be big enough to heat water in my shop to wash my hands and perhaps take a shower in kansas city, mo?**
A: Yes you could even go with the unit rtex-15 one smaller if that's it. Good luck

**Q: how many breakers and what amp.**
A: The RTEX-18 (240 Volt) requires (2) 40 amp breakers and 8 AWG wire.

## Customer Reviews

### ⭐⭐⭐⭐⭐ Rheem tankless water heater
*by J***X on January 31, 2026*

Love this tankless heater, it works great! Never run out of hot water while showering! There's only 2 of us in our home so not sure how it would work with a family but I'm sure a bigger size or maybe another mounted where hot water is needed most?? Would definitely buy again!!

### ⭐⭐⭐⭐⭐ If you know what you're getting, you'll love it!
*by 2***W on May 27, 2025*

There are many factors to consider before buying an electric tankless heater. By far the most important -- at least for me -- is whether the ground water temperature in your area is consistently warm enough to give the water heater a chance to succeed. I live in North Central Florida where the groundwater temperature is a rock-solid 72F (~22C) year-round. This is the ideal setup for tankless electrics; if you are far north this heater will likely fall short at the exact worst time, i.e. when it's winter and you could really use a nice, hot shower. I recommend looking closely at the map provided on Rheem's website and product pages to determine if this product is right for you. Second caveat, if you have a natural gas hookup, it is worth researching whether a gas-powered unit would be more efficient and/or less costly. There are considerations beyond this, of course, but those are the key ones that will determine whether you will be a happy camper or have cold water poured on those dreams of long, hot showers. If you're still considering after reading the above, then the short of it is (drumroll) ... I'm very satisfied and fully recommend making the jump to tankless! Here's the long-winded version: There is about 25- to 30-feet of pipe to travel between the water heater and the showerhead in my bathroom, and it takes about 25 seconds (well, 22.93 ... yes, I used a stopwatch) for the shower water to reach max temp. I did not use a stopwatch on my tank heater, but I'd guestimate it takes about 10 seconds longer for the tankless to deliver hot water than the tank unit it replaced. The main benefit, again, is that the tankless will continue to deliver hot water indefinitely while the tank is finite -- so, no more playing beat the clock and if you get in the water and realize you forgot your razor or something. The temperature coming out of the showerhead lines up with the temperature on the digital display for the main shower. There is a slight, but noticeable (I'd say 2F-4F/1C-2C) drop from the maximum temperature for the shower furthest away from the water heater. There is enough overhead that you can crank it a few degrees higher -- just be sure your shower handle can settle on something that won't scald you if you go above the recommended! I can also verify that the throughput on the model I bought (24 kW) is enough to handle two showers running at the same as well as start a load of laundry on hot -- I'm sure it could handle more, but there's not a scenario I can imagine where I would need it to. All in all, the flow is as good or better than the water heater it replaced. The dimensions listed on the product page are accurate. As far as your monthly bill, this hasn't made a significant impact although it may in the future. Here's some data from my most recent utility bill compared to the same month last year. Keep in mind the following figures are the daily averages listed on my bill for the whole home, not just the heater, although it is the only major appliance we have replaced over the past 12 months. April 2025 = 33.90 kWh electric and 0.06 KGA water (whole-home daily average) April 2024 = 31.34 kWh electric and 0.03 KGA water (whole-home daily average) Based on the above info (and the prior two months), it's essentially a wash -- we're using more power but only because we're taking longer showers because we can actually enjoy the heat now rather than worrying whether we're leaving enough water for everyone else! I'm sure that our water usage will level out once the novelty wears off, but that might be a while :) Now for the elephant in the room: Installation. If you can't say right now, with confidence and without any further research, whether you could get away with a DIY install, I'll answer the question for you: No, you can't. The plumbing end of the equation is easy -- the only hard part was ditching the tank unit. Beyond that, all you will need is a few fittings and a little pipe to hook it all up, plus the proper hardware to secure it to the wall. Any homeowner who would be comfortable ripping out a vanity sink/faucet and installing a new one should be able to do this portion themselves. The electrical hookup is another story. First, you will need 200-amp service to make this viable; if you don't, save yourself the headache. Second, depending on the distance between your electrical box and your water heater, you may need to have an auxiliary breaker box installed, as we did. Just as water temperatures vary regionally, so do electrician's rates. In our area we paid $850 to have a licensed electrician and his journeyman knock it out -- it took them about three hours and that includes the cost of the pictured auxiliary box. I would expect that rate to be higher in major metros but hopefully it gives a ballpark for what you can expect to pay beyond the sticker price.

### ⭐⭐⭐⭐⭐ Tankless Hot Water install
*by A***R on May 6, 2025*

I replaced a 55 gallon hot water tank with this unit, I bought a little larger unit than what the ratings said I needed to be safe. Make sure you check your electrical panel to make sure you have room for 3 x 40 double pole 40 amp circuit breakers. I didn’t have enough room, had to add a sub panel plus had to run 9 x 8 gauge wires the unit requires. I’m pretty handy, but asked a certified electrician to help me with the pre wiring. To be honest, I would have been afraid to try and do this myself even with all my experience. Installation was pretty simple after you have the wiring installed. Use 1 inch piping from your electrical panel to the tankless electrical unit or you won’t be able to pull the nine 8 gauge wires through the pipe. I also suggest having an electrical panel with a main breaker so you don’t have to shut the whole house down for the final install. Additionally i installed a surge protector to hopefully protect the unit from power surges which appears to have delicate electronics inside. We’ve only had this unit in operation for 4 days so far, but the water is really hot, have had no issues at this point and I love the added space gained without having the tank. Time will tell if we save 50% on energy, but from all my research it makes sense even with us living in a warm climate. There are several tankless unit manufacturers with great ratings, I went with Rheem because if I have an issue, they are based in the USA and hopefully that means English speaking in my time zone….. Hope my review is helpful to you. Update: it’s been 7 months, still works great, very happy with this decision even though I can say I’ve seen significant energy savings

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*Product available on Desertcart Nicaragua*
*Store origin: NI*
*Last updated: 2026-03-04*