Customer Reviews for Rheem Performance 13 kW Self-Modulating 2.54 GPM Tankless Electric Water Heater

Installation was not difficult. The electrician had to move breakers to install the 2 required 220 volt breakers. New wiring with heavier guage (8 guage is spec)wire was needed also. But this was all expected. The water from the sinks and shower are sufficiently hot. However if a larger volume of water is used, say for the washing machine or the bathtub faucet, it sets a code E5 which basically means that the water exiting the unit is too cold. To remedy this, a restrictor must be put in these devices to slow the flow. Which means that if it took say 5 minutes to fill your tub before, it now takes 10 to 12 minutes. Same goes for the washer. My guess is that folks in warmer climates don't have this problem as bad, or at all. But here in the Northeastern U.S., the winter temperature of our municipal water supply is a balmy 50 degrees Fahrenheit. I will say though, that we do enjoy the seemingly endless hot water for showers and such, but baths and washing clothes is now a pain in the butt.

This 27K Rheem is awesome!

Better than the Gas on demand If the install is in a new construction then the use of THERMO-REGULATED point of use faucets and fixtures is needed. Then add in a recirculation pump and you will have abundant near limitless hot water without delay. Make sure you can have 400 Amp electric service, at full load the unit pulled 160Amps. There are 5 errors and the last one is more of a condition than an error, and it automatically clears when the flow is too much that the unit can not heat to the desired temp. I originally tried to use the Rheem gas on demand unit but that did not work for me, see below: The performance of the gas on demand heater was unsatisfactory for install into an older house (1998 with copper pipes) The unit continuously cycles on and off and makes quite the racket if installed close to sleeping areas. The automatic program logic failed to learn lifestyle use. The unit would not enable the recirculation pump when the unit had just cycled and reached full heating capacity, quite the waste of energy and a wear on equipment. We would often finish using the sink to wash hands before warm water was received, this was only solved by leaving the pump on continuously which disrupted sleep. Even using title 24 program logic was difficult and if desired the use of the remote motion sensor unit would be about the only feasible way to work out the performance program logic oversights. Then there is the errors and the logic abort tree / flow chart of the old unit; there was a vast array of errors that can stop the unit from heating, most times the solution to to restart the unit! Well, Rheem, why not have it try that by itself and see if it can automatically recover. Hot water is not something that I want to have to continuously troubleshoot, the performance and reliability needs to be utility level at 99.999999% plus! Then when the unit flow sensor broke Rheem took their sweet time to ship the part needed, there were not local dealers who could fix it. 4 days without hot water was far too long; then they wanted me to change out the unit.

This product can be anywhere from a 2-5 star and here’s why for me. I bought this product in October of 2018, installed in December of 2018 and worked great for the first 8 months. After a while I noticed that the water wasn’t getting as hot as it did at first. I even turned the heat up to the max and it still was luke warm. I called a tech to come look at it and he couldn’t figure it out at first so he called tech support, they told him to check the heating elements but he didn’t want to break the water heater bc they were to tight for him to take off so I did it instead and then I found the problem. The first heating element where the cold water first comes into contact had a lot of scale deposits. About half the tube was filled and the second tube had about a quarter filled. Once I got the scales flushed out it started working like normal again. It was an easy fix but I would like to know what caused this excessive build up of scale. Has anyone else had this problem?

Easy to install! Works amazing! Even with multiple people and sources using it.

So far so great much better performer then the similar EEMAX model that got corroded by lime scale which is my fault. This unit we have is quieter more efficient and delivers more consistent hot water very happy.

works great using it in my shop

There seems to be a quality control issue and and a User manual issue. The instructions in the manual are not detailed enough on how to open the front cover of the unit. Also many units in the store are returned units and were missing part. I was lucky on the 3rd unit . The connecters inside the unit are not big enough for the thick wires that need to be used for this.It was a struggle to connect them. When all said and done, the unit works great .

Not happy. Barely heats water enough to over come the 60 Degree incoming water temp. It will Increase temp by 25 to 30 degrees but only for 3 to 5 minutes at a flow rate of 1.5 gpm as posted by the inboard diagnostic information from the unit itself. I Would NOT recommend this technology for daily use.

Everything came to our home as promised and on time. I like the size and the features which it has...no tank!! We just finished installing everything this last Sat. and have used it every day since then, takes about the same time to have hot shower water as our solar and electric tank. It meets our expectations and hope it lasts a very long time.

Easy to install and very good efficiency

I purchased this to replace a seisco ra18 and so far so good. It can handle two showers at the same time. Hopefully it will be more reliable that the seisco.

I replaced a faulty Ecosmart tankless (lasted 4 years) with the Rheem and they are the exact same. I was originally hoping the Rheem would be more reliable but apparently they are manufactured by same company. Other than that I am pleased with the tankless. The 36K does draw a ton of electricity under full load, 150amps, but the four elements kick on in series as needed so most of the time Im only using one or two at the same time (40amps-80amps). Im a master electrician by trade and I actually put my amp meter on it

Quality product works great

Flawless as I would expect from rheem. Replaced a Titan water heater that worked when it felt like it with this unit and have had not one single problem since. Plenty of hot water endlessly if needed...

So far so good. Time will tell the ultimate story but so far it is unlimited hot water.

For myself, easy to install, though i knew what i was getting into. I purchased this to replace (2) 50 gallon tanks. I knew that i was going to need the (4) 40 Amp breakes and 4 lines of 8/2 wiring. Please make sure you have enough room in your power panels or hire an electrician to ensure this would be a good fit. Fortunately, i do have 2 separate 200 Amp breaker panels. I put 2 breakers in each panel so when we turn on pool pump on later in early May, it shouldn't cause any issues. Enough hot water for the house -- 2 full bathrooms and washer and many sinks---no problems with enough hot water. It's been in for a week now and all is well. Looking forward to start saving on the monthly electric bill. Great product.

This water heater is so pretty and doesn’t take up much space. It works great. I would recommend it!

I purchased this product on March 27th 2019 after my hot water tank kicked the bucket. I own a 2 bedroom 1 bath condo thinking this would be the perfect fit and save energy. I was wrong! I kept getting an E5 error code from the tankless water heater and called customer service in CT. They informed me that my water pressure was to high and that I need to turn down the pressure at the angle stops. So I did so with a terrible result of slow water pressure. I uninstalled the unit, returned it to the store and purchased another Reheem tank water heater.

Water heater works great ! Hot water right of way install was a breeze

Easy to install. Gives great got water but I can not give 5 stars as my electric bill doubled so not worth the higher electric bill.

I installed this in my single family home. This installation was fairly easy for the do-it-yourselfer. I did have to replace one shower head with a low flow unit. The water it hot and endless.

Key points: 1. More than sufficient capacity for a family of four in Roanoke, VA, even in Winter. 2. Handles 2 simultaneous showers with ease (probably more). 3. Self-installation was straightforward. 4. Accessories, in addition to the WH, for a typical install run over $250.00. 5. Needs 4 Double Pole 40 amp breakers and 4 runs of 8 gage wire (about $150.00 in parts). 6. I added Rheem Brass Service Valves Model# RTG20220AB ($90.09). 7. Works fine on our 200 amp service. 8. Even, predictable heating during showers/tub fills. 9. Takes 15 - 20 seconds to heat up to target temperature at faucets near the unit. Then, it will give you endless hot water. 10. Goes up to 140F. We keep it set at 115F with good results. 11. I selected the Rheem RETEX-36 over Rinnai and EcoSmart because Rheem was the only brand whose warranty applied to homeowner installations. 12. I chose electric over gas because 1) I wanted it located under the bathrooms, which happen to be far from exterior walls, making ventilation needed for a gas unit a challenge. 2) Electric on-demand is much less expensive to install than gas. 13. Tankless electric heaters are generally more efficient than gas water heaters; efficiency here means more of the input power ends up as hot water. However, gas is usually less expensive for the same BTU. I’ll update following the first bill to share how operating cost compares to the old 40 gallon gas unit. The nitty-gritty: I installed a Rheem 36Kw Electric Tankless water heater to replace an underperforming, worn-out 40 gallon gas unit that wasn’t able to keep up with the demands of our teenagers and two working parents. As other reviews state, when it is on, it uses a lot of power, to be expected with any larger capacity tankless water heater. This is a well-known trade-off. It is only on when hot water is running. It has an onboard computer that uses thermistors and flow sensors to modulate its power to its four heating elements. So, it draws more power if you are using more hot water. For example, one shower running at 2.5 GPM draws fewer amps than filling a tub at 6 GPM. Set at 115F (it can go up to 140F) it will full our garden tub at 5 GPM with no problems. The install was straightforward, but I am comfortable with plumbing and electrical. I had an electrician come by and verify before I installed since Rheem’s website suggests at least a 300amp panel. The electrician said he thought the unit would be fine, even with my electric heat pump and electric range. He was right, it works fine and after a month of use in Winter, we have yet to trip any breakers. As other reviews note, when it is heating, some lights in the house flicker a little. This is to be expected of any high-draw appliance. It is the same as when your heat pump/air conditioner first comes on, for example. It sustains with a tankless electric WH because the WH is drawing a lot of power while, and only while, hot water is running. I have found only my budget LED light fixtures are sensitive to flickering. My more expensive LED bulbs aren’t affected by flickering. BTW the flickering is subtle and not enough to bother us. A side-note: with the Rheem units, you can run them on any number of their four 40 amp breakers. If you run the RETEX-36 on three, instead of four breakers, it becomes equivalent to the RETEX-27 in power usage and in heating capacity/performance, and so on. Just make sure the first breaker is always on, it powers the unit’s brain. The RETEX-27 would have had plenty of capacity for my modest home, though I sprung for the 36 based on reassurance from the electrician and because I like the idea of filling the tub quickly when I want to. So, had the 36 tripped my main breaker, I’d have been able to either run it on three of the four breakers, OR return the RETEX-36 for a RETEX-27. Fortunately, it works fine. I added Rheem Brass Service Valves Model# RTG20220AB. It is an excellent, well-made product. The package includes the code-required relief valve. This add-on was well worth the added cost and serves a triple purpose. 1) Regular flushing is a must for longevity and reliability. 2) In VA, code requires hot and cold shutoff valves for water heaters. This unit has quality ball valves on the hot and cold side. 3) this unit has union joints that will make swapping out the water heater in the future a breeze. I hope the WH lasts a long time. But, let’s face it, like any high-power appliance, WH’s eventually wear out.

During winter, in Washington DC, unit delivers only about 1.5 GPM (shower only) of hot water, which is 1/3 what is listed on product headline - 3.5 GPM. I did read the selection guide for my geography and we are averaging outside air temp of 40 degrees F but the fact that the best this unit can do is heat one faucet OR a shower kinda hot (even when set to 140 degrees) is ridiculous. At inlet temp of 37-47 degrees it should power a shower and faucet. I get a shower kinda hot and if I turn on the hand faucet a trickle of COLD water it turns the shower 100% cold. So no use of other water in the house while someone is taking a shower. Not realistic. I’m sure it will be better in summer but hey winter does come for 25% of year. I talked with Rheem tech support, we troubleshooted all aspects but the unit just can not deliver 2.1 GPM of hot water (my shower is 1.6 GPM and faucet is .6 GPM). I believe the total output of hot water is really like 1.5 GPM since my shower is warm enough - ish. If the product can’t deliver the basics why bother manufacturing? The 27 kW should be as low as Rheem goes. I am swapping the 18 kw for a 27 kw from another brand and hope I can get my elusive shower and faucet hot at same time.

Easy to install and very quickly delivers continues hot water. Easy to adjust.

So far so good. Fairly easy to install if you have basic plumbing & electrical knowledge. My advice is to find your shower comfort zone and set the temp to that and run your shower at full hot. Will update in a few months.

I am very pleased with this tankless water heater. It was easy to install due to the excellent instructions. It works great. Instant hot water only when you need it. The Black Friday price was an added bonus. Just be prepared to spend the additional money for the appropriate fittings, wiring and breakers. Still worth every penny. Couldn't be happier!

Great Product.....Getting the #8 wires from the Box to the Tankless HWH will take you longer than the plumbing it.

I never run out of hot water no matter where in the house I want to use it. Truly not running out of hot water in the shower is a dream. The only thing I would recommend is making sure you are getting the right size for what you want it to do. I have a small house so the 13 was a good size for me but if your house is larger size up appropriately. I have been telling anyone who will listen that they will love it if they get one. And in one month my electric bill went down $45. I can safely say that it absolutely surpassed my expectations. One warning..when filling up your tub with regular hot water heaters people are used to turning on only the hot water until it runs out and then adding cold. With this heater you don’t run out of hot water so don’t scald yourself. Well worth every penny!

Easy install if you can do electric and plumbing. Single family ranch approx 900 sq ft. Hot showers, keeps up with washer, and dishwasher. Well worth the money!!!