--- product_id: 38866492 title: "Rheem 18kW 240V Tankless Electric Water Heater, Gray" brand: "rheem" price: "€ 1099.71" currency: EUR in_stock: true reviews_count: 13 category: "Rheem" url: https://www.desertcart.hr/products/38866492-rheem-18kw-240v-tankless-electric-water-heater-gray store_origin: HR region: Croatia --- # 18 KW power output 4.4 GPM flow rate ±1° LED digital thermostat Rheem 18kW 240V Tankless Electric Water Heater, Gray **Brand:** rheem **Price:** € 1099.71 **Availability:** ✅ In Stock ## Summary > 🔥 RTEX-18: Hot water on demand, savings on command! ## Quick Answers - **What is this?** Rheem 18kW 240V Tankless Electric Water Heater, Gray by rheem - **How much does it cost?** € 1099.71 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.hr](https://www.desertcart.hr/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—maximize your living area. - • **Effortless Installation:** Threaded 3/4 inch NPT water connections simplify setup, making DIY upgrades a breeze for savvy homeowners. - • **Durable Dual Copper Elements:** Field-serviceable copper immersion heaters guarantee long-lasting performance and easy maintenance. - • **Energy-Smart Self-Modulation:** Advanced self-modulating tech adjusts power dynamically, slashing your water heating bill by up to 50%. - • **Precision Temperature Control:** External digital thermostat with LED display ensures ±1° accuracy for perfect hot water every time. ## Overview The Rheem RTEX-18 is a high-efficiency, tankless electric water heater delivering 18 KW of power and up to 4.4 gallons per minute flow. Featuring a precise LED digital thermostat with ±1° accuracy and advanced self-modulating technology, it optimizes energy use to cut heating costs by up to 50%. Its compact design is 90% smaller than traditional tanks, perfect for space-conscious homes. Durable copper immersion heating elements are field-serviceable, and simple threaded water connections enable straightforward installation. Ideal for single or multiple point-of-use applications, the RTEX-18 offers endless hot water with modern convenience and cost savings. ## 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: 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) Review: Thermistor Breaks and Reinstall Might Trash the Unit - Update: Rheem agreed to warranty the unit and send a new one. Although it was a bit of work to get done, I am thankful to not have to go out and buy a new one. Worked well for a while, but then the thermistor stopped working. It was a pain to get the replacement part I needed, and warranty didn't cover it. When installing the new one, the small partition inside the hole that the thermistor presses against broke, completely bricking the unit. The thermistor then was stuck with water leaking where the wire comes out, and I had to break it to remove it. Poor design. I don't have experience with other tankless heaters, but I would caution against this one for long term usage. ## 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 | | Best Sellers Rank | #8,295 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #1 in Water Heaters | | Brand | Rheem | | Brand Name | Rheem | | Capacity | 18 gallons | | Color | Gray | | Customer Reviews | 4.2 out of 5 stars 2,180 Reviews | | Efficiency | 99.8% | | Flow Rate | 4.4 gpm | | Global Trade Identification Number | 00020352685335 | | Heat Output | 18 KW | | Included Components | Fittings, Aerators | | Item Depth | 18.25 inches | | Item Dimensions W x H | 14.5"W x 18.25"H | | Item Type Name | Water Heater | | Item Weight | 14.8 pounds | | Manufacturer | Rheem | | Manufacturer Part Number | RTEX-18 | | Material Type | Stainless Steel | | Maximum Pressure | 150 | | Maximum Temperature | 140 °F | | Model Number | RTEX-18 | | Mount Type | Wall | | Number of Items | 1 | | Power Source | AC Power | | Product Dimensions | 14.5"W x 18.25"H | | Special Feature | LED Display | | Special Features | LED Display | | Style Name | Whole Home, 18 kw | | UPC | 020352685335 | | Unit Count | 1 Count | | 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 ### ⭐⭐⭐⭐⭐ Cost savings in a small box! *by X***R on August 7, 2023* 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) ### ⭐⭐⭐⭐⭐ Thermistor Breaks and Reinstall Might Trash the Unit *by A***Y on June 5, 2026* Update: Rheem agreed to warranty the unit and send a new one. Although it was a bit of work to get done, I am thankful to not have to go out and buy a new one. Worked well for a while, but then the thermistor stopped working. It was a pain to get the replacement part I needed, and warranty didn't cover it. When installing the new one, the small partition inside the hole that the thermistor presses against broke, completely bricking the unit. The thermistor then was stuck with water leaking where the wire comes out, and I had to break it to remove it. Poor design. I don't have experience with other tankless heaters, but I would caution against this one for long term usage. ### ⭐⭐⭐⭐⭐ Great water heater *by A***R on March 6, 2023* 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. ## 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.hr/products/38866492-rheem-18kw-240v-tankless-electric-water-heater-gray](https://www.desertcart.hr/products/38866492-rheem-18kw-240v-tankless-electric-water-heater-gray) --- *Product available on Desertcart Croatia* *Store origin: HR* *Last updated: 2026-08-14*