RTEX-18

Works great and easy to install

Easy to install and keeps our water hot!! After a bad experience with our last one (different brand) we are so impressed with this one and hope it last us a long time! We have a 3bd 2ba and it keeps up with our water!

I’ve installed three of these, and all have worked flawlessly. One of them provides adequate hot water for a small home (2 adults) having a shower, lavatory, kitchen sink, dishwasher, and clothes washer. Although it can draw up to 46 amps, the 100 amp main breaker has never tripped in spite of having an electric stove, air conditioner, clothes dryer, and refrigerator/freezer. The customers are delighted even after three years of constant use. A central location is important, as is minimizing piping bends. Be sure not to overtighten the compression fittings at the entrance and exit of the device. A clog in the shower head caused the heater not to work (as designed) due to low flow. My guess is that anyone having problems usually has an upstream or downstream issue not related to the proper performance of the heater.

I'll leave the original review below. It's been a little over 2+ years and have had to replace every single part and then finally replace the entire unit. Then the new one brand new out of the box did not work properly then finally fail 1yr and 2 months after purchase. This unit should be removed from sale and recalled that is how dangerous they are. If you have this unit installed I would highly recommend take it out and replacing with something else. It almost burned my house down! Just take a look at the pictures in this review and see for yourself. Okay full detail review below. 1st I'd like to say Rheem makes good products but this is not one of them. Here's why: 1st unit failed only less than 1 year of use. The elements exploded inside and needed to be replaced. Fine no problem, kill breaker, shut water off, unscrew 4 wires, take out element replace, re-screw wires, done in 30 minutes. Far beats dealing with a leaking water heater tank with 2 inches of water in your basement. Or lugging a 50lb broken tank up your stairs to replace at the Lowes or Home depot. Ok so I put the new elements in and it's heating again. Not more than a few months later the wire harness started arcing and fused together melting off and almost catching fire. I happened to see the arcing when the unit was on and didn't realize this was not part of how it operates. Thought it was just how it is. It tripped the breaker thankfully. I contacted the company and they sent me a new wire harness. I replaced it, still the unit wouldn't heat. So they sold me new inlet and outlet water sensors and a new flow sensor. That didn't fix it. So they said the motherboard must have fried. So I replaced the motherboard. That didn't fix it. So I purchased a completely new one. I mount the new one hooked it up and the water heater would stop heating randomly during a shower. So I set it to bypass mode 125 degrees and said "heck with the temp controls just give me heat" So a brand new unit I cannot even set the temperature. But I figured 125 is hot enough. Okay moving on. Fast forward to a few days ago, Sept 2nd 2023 brown colored water shot out of my shower head and I knew right away the heater blew. It made 1 year. I open the element rods and sure enough the 1st one exploded worse than any before. Okay no problem, let me swap it with a spare. So I did but.. I had to remove the entire unit from the wall and shake and empty out all the guts that exploded sitting inside the element housing. Still not that hard. So I did it see picture of sink.. EZPZ right? Nope, after repressurizing, a weld must have cracked and a slow drip came down the 1st pipe element housing. I thought maybe its not tight enough. So I tightened it more and the crack go worse and went from a small drip to a full stream. I confirmed it was coming from a welded joint not the threads on the element rod. Okay now the entire unit is trash and needs to be junked all because as I was tightening the element rod it put stress on the joints and cracked them. This is horrible quality in the build and should not happen. So I put the old one back in and swap every part. Wire harnesses, motherboard, elements and finally the sensors. Oh but the sensor's I tightened too much and they broke through the housing which also makes the entire unit useless as that cannot be repaired. So I threaded bolts into their holes and set it to bypass. I ordered a Mizudo instead which does not have copper housings, instead cast aluminum and does not have it's heating rods mixed with the water like this and many unit's have. So far it's been excellent. I highly recommend not purchasing these Rheem electric water heaters for 2 reasons. Fire hazard and quality. They constantly break. Amazon should remove this from their store before someone's house burns down and someone gets hurt or killed. Original Review Below I love this water heater. I really don’t have any complaints. Super easy to install. Takes up like no space. No more water tank to explode damaging my basement. It takes longer to get hot water at the furthest end of the house but it’s so worth it. Once it’s hot it stays hot and I can run a shower plus 2 faucets before I start losing heat. This one took 2 dbl 40amp breakers and it’s powerful enough to heat multiple faucets simultaneously. We never take more than 1 shower at a time anyway with a family of 4. Hasn’t been a problem keeping up with our hot water needs at all. And for the price? This is a great purchase. Ditch the tank! You’ll thank yourself later.

These systems are amazing. The future is in your hand when you hold one. I fully recommend. Please, however read on to understand them better. Customer support is awesome and available. This 18kw unit did NOT worked in my home, and I went thru two of the 18kw units before I determined the problem thinking the first one was not working and the problem . Please read on. You will want one and never look back if you read on.. I guarantee You WILL want this one of these water heaters, however, please read on. These WH’s are complicated. They work awesome in the lab environment they were created in. If your home does not match that lab setting or you can’t recreate it. It will not work. I went thru three of them to solve my problem. YOU WILL NEED. Flow restrictions, preasesure regulators, water softener, volt/amp meter filters(?), and a lot of patience tuning it to work. Once tuned however, they are flawlessly perfected at heating water instantly. Wow! the future is in these devices. Why was mine so difficult? I’m the last house from the power company. Literally at the end of the line. And I put in the 18kw unit. They are all super easy to install in both wiring and plumbing, but, what appeared to be my problem was there wasn’t enough physical energy to run it properly. Duel 40 amp req. So it wouldn’t work unless the flow restriction was almost closed. I tweeted and tweeted every possible measure to get it to work. I’m on well water too, so that incoming cold temperature affects the system and set up on a 40/60 pressure switch. The water rate It was moving was to fast and I never could get both sides(heating chambers) of the water heater to come on. It just would NOT work. It would come on for a sink at half open but when you tried to shower. It would turn off and say E5. Oh how I grew to hate that display. A simple to read display and simple to adjust temperature dial. I literally went from Flintstones to The Jetsons in appearance. About the 13kw unit. I had to get instead; WHICH SOLVED MY PROBLEM. It’s a little more than half the power necessary to function. Single 50 amp It is doing its job beautifully now. I have almost full water pressure again and it seems sold at 130 deg. But again, several hours spent tuning so it did work. If the flow rate is to high and water temperature to low it will not work. You have to tune them with additional devices to stabilize them so that units performance in the lab environment it was created in and it needs in your home. I have replaced two tanks now. One electric in a home and one propane in a camper. Worth it! Worth IT! WORTH IT! As for durability; install a water softener or they probably won’t last long without regular maintenance descaling it. I believe fully in this new technology and as well this 18kw unit but if you don’t understand advanced plumbing and advanced electrical troubleshooting if you’re a do-it-yourselfer, hirer someone who is because the electrical power supply will Kill you if you don’t understand it. Let this advice be not a discouraging experience, let it be that your knowledge now of some of the possibilities YOU might encounter moving in the direction of The Jetsons.

There are many factors to consider before buying an electric tankless heater. By far the most important -- at least for me -- is whether the ground water temperature in your area is consistently warm enough to give the water heater a chance to succeed. I live in North Central Florida where the groundwater temperature is a rock-solid 72F (~22C) year-round. This is the ideal setup for tankless electrics; if you are far north this heater will likely fall short at the exact worst time, i.e. when it's winter and you could really use a nice, hot shower. I recommend looking closely at the map provided on Rheem's website and product pages to determine if this product is right for you. Second caveat, if you have a natural gas hookup, it is worth researching whether a gas-powered unit would be more efficient and/or less costly. There are considerations beyond this, of course, but those are the key ones that will determine whether you will be a happy camper or have cold water poured on those dreams of long, hot showers. If you're still considering after reading the above, then the short of it is (drumroll) ... I'm very satisfied and fully recommend making the jump to tankless! Here's the long-winded version: There is about 25- to 30-feet of pipe to travel between the water heater and the showerhead in my bathroom, and it takes about 25 seconds (well, 22.93 ... yes, I used a stopwatch) for the shower water to reach max temp. I did not use a stopwatch on my tank heater, but I'd guestimate it takes about 10 seconds longer for the tankless to deliver hot water than the tank unit it replaced. The main benefit, again, is that the tankless will continue to deliver hot water indefinitely while the tank is finite -- so, no more playing beat the clock and if you get in the water and realize you forgot your razor or something. The temperature coming out of the showerhead lines up with the temperature on the digital display for the main shower. There is a slight, but noticeable (I'd say 2F-4F/1C-2C) drop from the maximum temperature for the shower furthest away from the water heater. There is enough overhead that you can crank it a few degrees higher -- just be sure your shower handle can settle on something that won't scald you if you go above the recommended! I can also verify that the throughput on the model I bought (24 kW) is enough to handle two showers running at the same as well as start a load of laundry on hot -- I'm sure it could handle more, but there's not a scenario I can imagine where I would need it to. All in all, the flow is as good or better than the water heater it replaced. The dimensions listed on the product page are accurate. As far as your monthly bill, this hasn't made a significant impact although it may in the future. Here's some data from my most recent utility bill compared to the same month last year. Keep in mind the following figures are the daily averages listed on my bill for the whole home, not just the heater, although it is the only major appliance we have replaced over the past 12 months. April 2025 = 33.90 kWh electric and 0.06 KGA water (whole-home daily average) April 2024 = 31.34 kWh electric and 0.03 KGA water (whole-home daily average) Based on the above info (and the prior two months), it's essentially a wash -- we're using more power but only because we're taking longer showers because we can actually enjoy the heat now rather than worrying whether we're leaving enough water for everyone else! I'm sure that our water usage will level out once the novelty wears off, but that might be a while :) Now for the elephant in the room: Installation. If you can't say right now, with confidence and without any further research, whether you could get away with a DIY install, I'll answer the question for you: No, you can't. The plumbing end of the equation is easy -- the only hard part was ditching the tank unit. Beyond that, all you will need is a few fittings and a little pipe to hook it all up, plus the proper hardware to secure it to the wall. Any homeowner who would be comfortable ripping out a vanity sink/faucet and installing a new one should be able to do this portion themselves. The electrical hookup is another story. First, you will need 200-amp service to make this viable; if you don't, save yourself the headache. Second, depending on the distance between your electrical box and your water heater, you may need to have an auxiliary breaker box installed, as we did. Just as water temperatures vary regionally, so do electrician's rates. In our area we paid $850 to have a licensed electrician and his journeyman knock it out -- it took them about three hours and that includes the cost of the pictured auxiliary box. I would expect that rate to be higher in major metros but hopefully it gives a ballpark for what you can expect to pay beyond the sticker price.

Super cheaper than in store!!! Save money and buy here!! Works amazing

Great heater! Fast but don't expect high flow or multi faucet use at same time with really hot water. You will need a dedicated 240v, 30 amp circuit to run this. Manual does not tell you how to remove the cover which you need to do to wire it - take the 3 screws out of the bottom of the cover, pry it open from there and pivot it back towards the top of the unit