---
product_id: 38866492
title: "18kW 240V Tankless Electric Water Heater, Gray"
brand: "rheem"
price: "133084 kr"
currency: ISK
in_stock: true
reviews_count: 9
category: "Rheem"
url: https://www.desertcart.is/products/38866492-18kw-240v-tankless-electric-water-heater-gray
store_origin: IS
region: Iceland
---

# 18kW powerful heating 4.4 GPM flow rate ±1°F digital thermostat 18kW 240V Tankless Electric Water Heater, Gray

**Brand:** rheem
**Price:** 133084 kr
**Availability:** ✅ In Stock

## Summary

> 🔥 Endless hot water, zero wasted energy ⚡

## Quick Answers

- **What is this?** 18kW 240V Tankless Electric Water Heater, Gray by rheem
- **How much does it cost?** 133084 kr with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.is](https://www.desertcart.is/products/38866492-18kw-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

- • **Compact Space-Saver:** 90% smaller than traditional tanks, fits discreetly under sinks or tight spaces for modern living.
- • **Durable Dual Copper Elements:** Field-serviceable copper immersion heating elements built for longevity and easy maintenance.
- • **Energy-Smart Self-Modulation:** Automatically adjusts power output to match your hot water demand, saving up to 50% on energy bills.
- • **Precision Temperature Control:** External digital thermostat with LED display ensures exact hot water temps to the degree.
- • **Simple, Threaded Installation:** Bottom 3/4 inch NPT water connections with threaded design for quick, hassle-free replacement.

## Overview

The Rheem 18kW 240V Tankless Electric Water Heater delivers continuous hot water on demand with precise digital temperature control and advanced self-modulating technology. Its compact design saves space by being 90% smaller than traditional tanks, while durable copper heating elements ensure long-lasting performance. With a flow rate up to 4.4 GPM and easy installation via threaded water connections, this unit is perfect for single shower or mid-range whole-home applications, offering up to 50% energy savings and a sleek, modern upgrade for your home.

## 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: Tankless Hot Water install - 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.
Review: Great product! - Easy to install and keeps our water hot!! After a bad experience with our last one (different brand) we are so impressed with this one and hope it last us a long time! We have a 3bd 2ba and it keeps up with our water!

## 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 | #5,588 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 (3,883) |
| 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

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

## 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

### ⭐⭐⭐⭐⭐ 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.

### ⭐⭐⭐⭐⭐ Great product!
*by H***G on December 7, 2025*

Easy to install and keeps our water hot!! After a bad experience with our last one (different brand) we are so impressed with this one and hope it last us a long time! We have a 3bd 2ba and it keeps up with our water!

### ⭐⭐⭐⭐⭐ Flawless performance for years in a small home
*by R***S on October 31, 2025*

I’ve installed three of these, and all have worked flawlessly. One of them provides adequate hot water for a small home (2 adults) having a shower, lavatory, kitchen sink, dishwasher, and clothes washer. Although it can draw up to 46 amps, the 100 amp main breaker has never tripped in spite of having an electric stove, air conditioner, clothes dryer, and refrigerator/freezer. The customers are delighted even after three years of constant use. A central location is important, as is minimizing piping bends. Be sure not to overtighten the compression fittings at the entrance and exit of the device. A clog in the shower head caused the heater not to work (as designed) due to low flow. My guess is that anyone having problems usually has an upstream or downstream issue not related to the proper performance of the heater.

## Frequently Bought Together

- Rheem 18kW 240V Tankless Electric Water Heater, Gray
- HYDRO MASTER Tankless Water Heater Service Valve Kit with Pressure Relief Valve 3/4-Inch IPS Isolator Clean Brass
- 3/4 Inch IPS Isolator Tankless Water Heater Service Valve Kit with Pressure Relief Valve, Clean Brass, 3/4 Inch Service Installation Valve for rheem,rinai,ecosmart,navien,noritz,takagi,bosch

---

## Why Shop on Desertcart?

- 🛒 **Trusted by 1.3+ Million Shoppers** — Serving international shoppers since 2016
- 🌍 **Shop Globally** — Access 737+ million products across 21 categories
- 💰 **No Hidden Fees** — All customs, duties, and taxes included in the price
- 🔄 **15-Day Free Returns** — Hassle-free returns (30 days for PRO members)
- 🔒 **Secure Payments** — Trusted payment options with buyer protection
- ⭐ **TrustPilot Rated 4.5/5** — Based on 8,000+ happy customer reviews

**Shop now:** [https://www.desertcart.is/products/38866492-18kw-240v-tankless-electric-water-heater-gray](https://www.desertcart.is/products/38866492-18kw-240v-tankless-electric-water-heater-gray)

---

*Product available on Desertcart Iceland*
*Store origin: IS*
*Last updated: 2026-01-25*