--- product_id: 322325986 title: "18kW 240V Tankless Electric Water Heater, Gray" brand: "rheem" price: "¥163824" currency: JPY in_stock: true reviews_count: 5 category: "Rheem" url: https://www.desertcart.jp/products/322325986-18kw-240v-tankless-electric-water-heater-gray store_origin: JP region: Japan --- # 18kW powerful heating 4.4 GPM flow rate ±1° LED digital thermostat 18kW 240V Tankless Electric Water Heater, Gray **Brand:** rheem **Price:** ¥163824 **Availability:** ✅ In Stock ## Summary > 🔥 Hot water on demand, savings on repeat! ## Quick Answers - **What is this?** 18kW 240V Tankless Electric Water Heater, Gray by rheem - **How much does it cost?** ¥163824 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.jp](https://www.desertcart.jp/products/322325986-18kw-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 - • **DIY-Friendly Installation:** Threaded ¾ inch NPT connections and field-serviceable copper elements make upgrades hassle-free. - • **Space-Saving Sleek Design:** 90% smaller than traditional tanks—fits discreetly under sinks or tight spaces. - • **Endless Hot Water, Zero Wait:** Experience continuous, on-demand warmth without the bulk of a tank. - • **Energy-Smart Self-Modulation:** Automatically adjusts power to your exact hot water needs, saving up to 50% on bills. - • **Precision Temperature Control:** Digital thermostatic control with ±1° accuracy for perfect comfort every time. ## Overview The Rheem 18kW 240V Tankless Electric Water Heater delivers instant, endless hot water with advanced self-modulating technology that optimizes energy use. Featuring a precise LED digital thermostat, durable copper heating elements, and a compact design 90% smaller than traditional tanks, it’s perfect for mid-range whole-home or single shower applications. Save space, cut energy costs by up to 50%, and enjoy easy installation with threaded water connections and field-serviceable parts. ## 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: Hot water on demand - Great product, have been using ours for 2 years and it works great. 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) ## 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 | #93,045 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #95 in Water Heaters | | Brand | Rheem | | Brand Name | Rheem | | Capacity | 18 gallons | | Color | Gray | | Colour | Gray | | Customer Reviews | 4.2 out of 5 stars 2,099 Reviews | | Efficiency | 99.8% | | Flow Rate | 4.4 Gallons Per Minute | | Global Trade Identification Number | 00020352685335 | | Heat Output | 18 Kilowatts | | Included Components | Fittings, Aerators | | Is Electric | Yes | | Item Depth | 18.25 inches | | Item Dimensions W x H | 36.8W x 46.4H centimeters | | Item Type Name | Water Heater | | Item Weight | 14.78 Pounds | | Manufacturer | Rheem | | Manufacturer Part Number | RTEX-18 | | Material Type | Stainless Steel | | Maximum Pressure | 150 | | Maximum Temperature | 140 Degrees Fahrenheit | | Model Number | RTEX-18 | | Mount Type | Wall | | Number of Items | 1 | | Number of Packs | 1 | | Power Source | AC Power | | Power source | AC Power | | Product dimensions | 36.8W x 46.4H centimeters | | Special Features | LED Display | | Special features | LED Display | | Style Name | Heater | | 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:** 36.8W x 46.4H centimeters - **Special features:** 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 ### ⭐⭐⭐⭐⭐ Hot water on demand *by B***K on 10 August 2025* Great product, have been using ours for 2 years and it works great. ### ⭐⭐⭐⭐⭐ Cost savings in a small box! *by X***R on 7 August 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) ### ⭐⭐⭐⭐⭐ Buen producto *by J***V on 8 December 2023* Bastante cumplidor aun para lo que yo esperaba ya que solo requiero una cantidad relativamente baja de agua caliente y da bastante mas de lo esperado, totalmente recomendable ## 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.jp/products/322325986-18kw-240v-tankless-electric-water-heater-gray](https://www.desertcart.jp/products/322325986-18kw-240v-tankless-electric-water-heater-gray) --- *Product available on Desertcart Japan* *Store origin: JP* *Last updated: 2026-10-07*