RHEEM RTEX-18 18kw 240v Tankless, Instant Electric Water Heater – Wholesale Water Heater

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RHEEM RTEX-18 18kw 240v Tankless, Instant Electric Water Heater

  • Brand: Rheem
  • Availability: In Stock
  • SKU: RTEX-18
  • Description
  • Specifications

The Rheem RTEX-18 Electric Tankless Water Heater offers powerful and reliable hot water delivery for larger residential and commercial applications. With its compact yet durable design, it provides ample hot water while saving space and energy. Equipped with advanced heating technology and digital temperature control, the RTEX-18 ensures consistent performance, efficiency, and customizable comfort for any setting.

Model NumberRTEX-18Recommended Wire Size (CU)8 AWGHeight18-1/4"
Kilowatts18kWMin. Flow (GPM)0.3Width14-1/2"
Recommended Breaker Size(2x40)AMax. Flow (GPM)7Depth3-1/2"
Voltage240/208VAmps75AWater Conn.3/4" NPT


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Download Rheem documents for this water heater such as the Specifications and installation manual.

Specifications Manual

Professional Classic® tankless electric water heaters offer continuous hot water quick and on demand for single point-of-use or multiple applications

Performance Features

  • On-demand continuous hot water
  • Compact and stylish with digital temperature control in increments of 1° ranging from 80° to 140°
  • 99.8% Energy efficient
  • Robust copper immersion heating elements with brass top increases durability and are threaded for easy replacement
  • Simple Installation
  • Digital temperature display

Unique Features

  • External Digital Thermostatic Control with LED display (+/- 1 degree accuracy)
  • Most advanced self-modulation, adjust power to meet hot water demand
  • Two durable Copper Immersion heating elements, field serviceable
  • Simple Installation Bottom 1/2"NPT or 3/4"NPT water connections

Choosing a Model

First, it is important to determine the incoming groundwater temperature where you live. This is significant because it represents the temperature that the water heater needs to elevate to meet your preferred water temperature.

Second, you must determine what you need to heat water for. For instance, is it just for a single sink, or is it for a 2-bathroom home? You can determine how much hot water you'll need based on the table below showing the average water usage of standard home fixtures.

Lastly, you can use the chart below to find the unit you need based on the groundwater temperature and the flow rate needed. On the red left side column find the incoming ground water temperature you found earlier. Next, look at the top dark grey column showing the GPM (Gallons Per Minute). Once you line both the column and row up you should see a number such as "8" or "24". This number indicates the number of kilowatts you need as well as the model number. All of these models start with "RTEX-", and the next portion will be the amount of kilowatts you need. For instance, a "RTEX-08" or a "RTEX-24"

If all else fails you can check out this simple guide below and choose based on the number of bathrooms you'll be supplying.

Rheem RTEX-04 Rheem RTEX-06 Rheem RTEX-08 Rheem RTEX-11 Rheem RTEX-13 Rheem RTEX-18 Rheem RTEX-24 Rheem RTEX-27 Rheem RTEX-36

Shipping Guarantee

All of our freight shipments have a shipment guarantee! This means that if your water heater arrives later then the estimated delivery window shown on the product page we will credit you $100 upon delivery. 

How long does shipping take?

Shipping times can vary from water heater to water heater, however most in stock shipments will arrive in 2-5 business days depending on how close the warehouse is to the shipping address. On each product page we give an estimated delivery window which will show roughly when a product will arrive, if you need a better estimate please call into (313) 626-6800 and one of our customer support representatives can assist you. 

Expedited Shipping

A select number of our products are available for expedited shipping. If we offer expedited shipping on a product it will show the option at checkout. Cost and times will depend on your location and availability of the water heater. Most expedited shipments will arrive in 1-3 business days. All expedited shipments are shipped LTL and are only estimated delivery times. For any guaranteed expedited shipments/overnight shipments please contact our customer support team for a quote. 

Where do you ship from?

Our standard deliveries will ship from the closest warehouse to your shipping address. We have several warehouses in Michigan and can also ship out of any Rheem warehouses in the United States. Rheem has warehouses in Colorado, California, Florida, Texas, New Jersey, Alabama, and Illinois. Depending on availability and your location we will determine the best possible warehouse to ship from to ensure a timely delivery.

Do you deliver on weekends?

Deliveries, except for USPS, are not typically made on Saturdays or Sundays. This means any commercial water heater will not be shipped over the weekend.

Where do you ship?

We ship to the continental united states. Some products can be shipped to Alaska and Hawaii, but please contact us first to determine additional shipping cost and estimated delivery time.

Certain products are not available in Texas and California. If a product is excluded from certain states it will be noted in the product description. These products are not allowed in these states, so there are no exceptions to these exclusions.

Residential water heaters are not available for shipment. Please arrange for local pickup if needed.

Can I pick up my order?

Most orders are available for pickup at any of our warehouses in Detroit, Michigan. If you would like to pick up your order please select that option at checkout. Local pickups may be subject to a pickup fee. If your order is not being shipped from the manufacturer it is typically available the same day you place the order.

Can I track my shipment?

Once your order ships, you will receive a Ship Confirmation email, and have an option to receive email updates on the delivery status of your order. You will also receive a tracking number from the designated carrier for your shipment. If you do not receive this tracking number please contact us, and we will provide it to you.

If you're purchasing an item being dropshipped you will not receive tracking information until the product has been shipped from the manufacturer.

How will my shipment arrive?

Smaller parts and accessories will arrive to your porch or mailbox. Please note that tankless water heaters may require a signature upon delivery. 

For large items that cannot be shipped via standard UPS or FedEx services, we work with delivery companies to get your items to you. These partners deliver to your curb at the end of your driveway, and you are responsible for moving the items from there. Please note, if you live down a road or driveway that the delivery truck cannot access without causing damage to the truck we may need to make special arrangement for delivery, so please let us know. These carriers will call to schedule delivery so you can be home to inspect your items and accept delivery.

We recommend opening the boxes and inspecting the products for any signs of damage, such as broken parts or chips and cracks in the finish. While we do our best to make sure items are packaged safely and securely to prevent damage, we recognize that fragile products will occasionally break in transit to your doorstep. If you see any signs of damage, firmly refuse the damaged items and keep any that are in good condition. Do not let the driver leave without inspecting. If driver refuses to stay during inspection, sign "Subject to Inspection" on the delivery receipt and call us immediately to report damages.