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Rheem

Rheem RETEX-36 Performance 36 kw Self-Modulating 6 GPM Electric Tankless Water Heater

Based on 18 reviews
Condition: New
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$624.99
Holiday Deal · 5% off was $660.00

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Availability: Only 2 left in stock, order soon!
Fulfilled by MPAD USA
Arrives Friday, Nov 20
Order within 15 hours and 7 minutes

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At a glance

Condition
New
Model
RTEX-36
Capacity
6 gal
Dimensions
21.62"W x 18.25"H
Weight
19 lb
Color
Gray
Power Source
AC
In the box
683089 8 GPM ELEC TNKLSS

Features 1

  • This refurbished product is tested and certified to look and work like new. The refurbishing process includes functionality testing, basic cleaning, inspection, and repackaging. The product ships with all relevant accessories, and may arrive in a generic box

Specs 24

Brand Rheem
Capacity 6 gallons
Power Source AC
Product Dimensions 21.62"W x 18.25"H
Special Feature Digital Thermostatic Temperature Controls, UEF up to .94
Special Features Digital Thermostatic Temperature Controls, UEF up to .94
Wattage 36 KW
Flow Rate 8.8 gpm

Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Friday, Nov 20

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

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View our full returns policy here.

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Top Amazon Reviews

Really happy with it it’s been a few months
It has worked great does take a minute for one shower to get hot water
Reviewed in the United States on May 2, 2025 by john
Takes too much power to run
Takes way too much power to run
Reviewed in the United States on June 15, 2026 by john buettner
REtex -36 water hearter
⸻ Review of the Rheem RETEX-36 Performance Tankless Electric Water Heater This water heater is awesome—compact, powerful, and heats water instantly. Super easy to control the temperature and great for saving space and energy. Just make sure your electrical setup can handle it, and it may struggle if multiple things run at once. Overall, a solid and reliable choice. ... show more
Reviewed in the United States on April 12, 2026 by Leidys Carmenate
So far so good
We recently changed to tankless, for the price it's worth it. Energy efficient so far, it is lounder than what I'm used to if I'm in the other room I can hear it but nothing that bothers me. Easy to assemble and very good size
Reviewed in the United States on July 10, 2024 by Meg Leverington
Used
We received a used one, had to send back.
Reviewed in the United States on November 21, 2025 by Reva
I’m so impressed
Review Image by Eric
Lots to share here but stick with me and hopefully you’ll find this helpful: Install was straight forward if you have some plumbing experience and are familiar with how to solder and braze. It’s also good to know how to work with electrical too. The hardest part was running the 8 gauge, 3 conductor wire needed for each main (4 in total) element. You will need qty 4 240v double pole breakers (the ones that look like they are two connected standard breakers connected to the same lever). Also make sure your panel has enough room for 4 of these breakers. The double pole breakers in particular that I bought were Siemens (model Q240 for about $15.00 each). I highly encourage anyone to have a 200 amp service if you live in a typical single family home under 2000 sq feet. Inconveniently, My breaker is in the opposite side of the mechanical room where this is mounted so a spool of this type of wiring cost almost twice as much as the actual heater itself but still worth it. The inlets and outlet of the water heater are 3/4” pipe so i elected to use 3/4” pipe for the rest of the install, all the way to the existing pipe that feeds the rest of the house which was 1/2”. Between Amazon, Home Depot, Lowe’s, and Ace Hardware stores you should have no problem fighting any fittings or unions as everything should be standard plumbing (so nothing special is needed to install this). Make sure you get the flushing bypass valves to be able to do annual maintenance and also make sure to get a descaling filter as recommended with the purchase (as a bundle)of this by Amazon. The Amazon recommended bundle included the filter, the flushing bypass valves and the 36kw unit. Absolutely under no circumstances should you solder any copper piping while connected to the inlet and outlet, the high temps that travel up the copper could hurt the electronic elements and/or possible seals of the water heater. I used standard PTFE (Teflon) on the threads and covered with pipe dope and had no leaks the first time on(Luck was on my side haha). A few months prior I had to get a new water expansion tank for the tank water heater that just died so I repurposed it here as you can see in the picture I uploaded. This could prevent any knocking caused by such things as appliances that have fast acting valves. I mounted the unit on studs with a 1 inch extension for extra support and space like suggested in the manual(I wouldn’t recommend mounting with just drywall screws and screw anchors). The manual is helpful in giving you quick guidance and pointers if you have experience but non-experienced DIY’ers will find it incredibly vague, unhelpful, and stressful. If you understood less than 85% of what I have been saying here then I’d recommend hiring a plumber and electrician to install it for you. I am having the town inspectors come and validate my work on the electrical and plumbing side so make sure you are also abiding by state/local code. Actual performance: After about a month of chilly Massachusetts fall, I can say this water heater works and works really darn well! I find that it heats water a faster than the old tank heater this unit replaced. In terms of temperature settings, the manual recommends 105F which worked great even for Southern New England in the early fall when temperatures only went down to 50F… but as it has gotten colder and closer to freezing a few nights with the average temp in the low 50’s I’ve found to to work a little better at 107. You notice a difference Quickly as you increment the heat up 1 degree at a time. I theorize that by January (coldest month in MA usually) that I can raise it to 109/110 and be golden. I can have a person in the shower, dishwasher running with hot water, and the washing machine running a cycle with warm/hot water and this thing handles the demand like a boss. Though due to electrical current draw I’d suggest just running 2 of the 3 aforementioned things. Electric bill also has not gone up that much either since installation which was my main concern. It’s on demand so you aren’t wasting money anymore heating up something for hours on end when no one is even home. Overall I’d highly recommend this and hope more people switch to on-demand water heaters. ... show more
Reviewed in the United States on October 3, 2022 by Eric
Great digital control!
Went in easy, handles 2 showers, sink and laundry all at once! Absolutely satisfied.
Reviewed in the United States on November 22, 2021 by T. and G. M.
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