---
product_id: 38866492
title: "Rheem 18kW 240V Tankless Electric Water Heater, Gray"
brand: "rheem"
price: "$1566"
currency: NZD
in_stock: true
category: "Rheem"
url: https://www.desertcart.nz/products/38866492-rheem-18kw-240v-tankless-electric-water-heater-gray
store_origin: NZ
region: New Zealand
---

# 18kW high power output 4.4 GPM flow rate for steady hot water ±1°F precision digital thermostat Rheem 18kW 240V Tankless Electric Water Heater, Gray

**Brand:** rheem
**Price:** $1566
**Availability:** ✅ In Stock

## Summary

> 🔥 Endless hot water, zero wasted energy — upgrade your flow game!

## Quick Answers

- **What is this?** Rheem 18kW 240V Tankless Electric Water Heater, Gray by rheem
- **How much does it cost?** $1566 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.nz](https://www.desertcart.nz/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

- • **Compact Space-Saver:** 90% smaller than traditional tanks—fits discreetly under sinks or tight spaces.
- • **Smart Self-Modulation:** Automatically adjusts power to match your hot water demand, saving up to 50% energy.
- • **Effortless Installation:** Threaded 3/4 inch NPT water connections make setup and replacement a breeze.
- • **Precision Temperature Control:** External LED display with ±1°F accuracy keeps your comfort dialed in.
- • **Durable Copper Heating Elements:** Field-serviceable dual elements ensure long-lasting, reliable performance.

## Overview

The Rheem 18kW 240V Tankless Electric Water Heater delivers continuous hot water with precise digital temperature control and advanced self-modulating technology. Its compact design saves space while providing up to 4.4 gallons per minute flow rate, making it perfect for whole-home or single-shower use. Durable copper heating elements and easy installation ensure reliable, energy-efficient performance that can cut your water heating bills by up to 50%.

## 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.

## 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 | #6,531 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #1 in Water Heaters |
| Brand | Rheem |
| Color | Gray |
| 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)

## 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.

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*Product available on Desertcart New Zealand*
*Store origin: NZ*
*Last updated: 2026-02-16*