RTEX-24

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.

This is the fourth tankless we've owned. The first was destroyed in a fire and we still have the other two working at family cabins. First I want to point out some fundamental pros. It is small, the size of a suitcase while a tankked heater needs a lot of space. Secondly as long as you have power you never run out of hot water. With three boys in the house we'd run out of hot water with the tank heater, not so with the tankless. The third pro takes a while to notice,, Less electricity use = smaller bill. My average monthly bill was $120. it was $90 after the tankless was installed. The cons would be that if you lose power you have no hot water, but how often does that happen? Also are you needing hot water at the time IF it happens? Second con is the 24& 27KW units need Three double throw 40 amp breakers. and needs feeding with 8 gauge wire. They are whole house units. No you cannot just wire it on your tank heater line. A tank heater doesn't require "INSTANT" power as it uses lower power most ALL of the time. A tankles uses a lot of power ONLY when you need hot water. Most of the time it is off. I've read the low star ratings and it is fairly obvious that these persons did not do their research or read the manual. One complaint was the water only became warm. The person was using a 6kw unit for his full house. Those units are for low flow point of use. Use the correct sie for the intended usage and need! The last con observation is you will notice that it takes the same amount of time to get hot water out to the faucet as it does with a tank heater. The law of physicials and all.... The bottom line here is DO YOUR DUE DILIGENCE/RESEARCH so there are no surprises. The manufacturers tell you what it does and what you need to make it work. My conclusion is I Recommend this unit. When you get it PROPERLY installed it will work so well you will forget about it.

UPUPDATE: 6/4/2025. Still all goo. Zero issues after 6 years. Nothing replaced. Electrical bill still the same as with the old tank version. UPDATE: 8/4/2021. All is great. No problems. Small change in lowering electric bill. Only bad is when power goes out no reserve hot water but a rare circumstance. Overall I feel like it was a good choice. Ok. Real world. This is for a Rheem RTEX-24 tankless water heater. Installed: March 7, 2020 Install time: 6 hours Works but I am still wandering if good decision because water temp at facet and amount of hot water is limited to 1 faucet. I am waiting on a new thermostat from Rheems great tech support. Pros: Small compared to water heater. Tech support is actually amazing. Will send parts at no cost and no proof of purchase. Cons: Intallation requires knowledge of installing breakers and running wire(I used AWG 6/2). Out put temp from unit says 140F but temp at faucets is 120F. It takes so much water and time to reach facets, over 1 minute compared to 28 seconds, on normal 50gal water tank at same distance. Called Rheem about water temp difference they are sending a new thermostat. Really good tech support. I am not an electrician or a plumber but have pretty extensive knowledge of both. Installation: I am replacing a 17 year old 50 Gallon standard Rheem tank. The tankless will be in the same location so distance and pipe can be compared after same location. I choose to run wire called AWG 6/2(50ft $94 at lowes) instead of the reccomend 8/2. I did this because most other tankless companies called for 6/2. This way if I needed to switch companies for $30 difference I was ready. Also you have to install 3 40Amp double-pole breakers in your breaker panel. These are similar to the breaker already on your current water heater or oven just the amp number on those is usually 50 amp. It takes up some good room in your panel, like 6 normal spots. After Install: So it works kinda. All voltage tests on elements are good. If you push the temp dial and hold it for 10 seconds a menu comes up. You can click the dial to 3 different numbers now (Flow amount, Outgoing Temp, incoming temp). I set the temp to 140F but can not get water at faucet above 122F. Also my incoming temp is 62F. So I should be able to get 3 faucets or 2 shower heads with a 54 degree rise with no problems. Rheem said this is very rare and is sending new thermostat free.

I was so excited to get this product - I had read nothing but good reviews, heard great things about the company and was thrilled to get it as a gift for the house for the Holidays. Unfortunately - it is one of the worst products I have ever purchased and I hope I save at least one other human from making the same horrible mistake that my family did. It does not heat water consistently, so while using it there are constant bursts of hot and cold water. Worst of all, it does not heat enough the water for us to be able to take baths anymore, which was the entire reason we got this product in the first place. Customer support was a joke. Because we installed it after Christmas, we missed the return window via Amazon, and the solution from Rheem involves hiring another plumber AGAIN to install something else, which isn't even guaranteed to work. I have never regretted upgrading an appliance more in my life, or buying something. I would give anything to be able to take a bath in my home right now. They should be ashamed to sell this product.

works great!

It calls for 3/220 electrical wire. It’s an over kill for my little house. I didn’t know it when I bought it just to much power as the ole people say over kill. To BIG. I didn’t know what o was buying

Good Equipment, installed almost a year ago and my electric bill dropped about 90.00 dollars per month.

I replaced a 55 gallon hot water tank with this unit, I bought a little larger unit than what the ratings said I needed to be safe. Make sure you check your electrical panel to make sure you have room for 3 x 40 double pole 40 amp circuit breakers. I didn’t have enough room, had to add a sub panel plus had to run 9 x 8 gauge wires the unit requires. I’m pretty handy, but asked a certified electrician to help me with the pre wiring. To be honest, I would have been afraid to try and do this myself even with all my experience. Installation was pretty simple after you have the wiring installed. Use 1 inch piping from your electrical panel to the tankless electrical unit or you won’t be able to pull the nine 8 gauge wires through the pipe. I also suggest having an electrical panel with a main breaker so you don’t have to shut the whole house down for the final install. Additionally i installed a surge protector to hopefully protect the unit from power surges which appears to have delicate electronics inside. We’ve only had this unit in operation for 4 days so far, but the water is really hot, have had no issues at this point and I love the added space gained without having the tank. Time will tell if we save 50% on energy, but from all my research it makes sense even with us living in a warm climate. There are several tankless unit manufacturers with great ratings, I went with Rheem because if I have an issue, they are based in the USA and hopefully that means English speaking in my time zone….. Hope my review is helpful to you. Update: it’s been 7 months, still works great, very happy with this decision even though I can say I’ve seen significant energy savings

Great unit, services kitchen, bathroom and laundry room no problem.

ES IMPORTANTE CONOCER LAS ESPECIFICACIONES Y TENER UN ASESORAMIENTO DE COSTOS ANTES DE COMPRAR MI EXPERIENCIA FUE MUY TRISTE PORQUE COMPRE EL PRODUCTO CON MUCHA ILUSION Y RESULTA QUE LA INSTALACION ME IBA A COSTAR 3 VECES QUE EL COSTO DEL CALENTADOR. LO TUVE QUE REGRESAR ESPECIFICAMENTE EL PROBLEMA FUE LA ESPECIFICACION DEL CABLE EN RELACION AL AMPERAJE DEL PRODUCTO

Awful product didn’t even last a year and started clogging up all my pipes with sediment

Très beau et bon produit. Par contre le 24 kw manque un peu de puissance. L’hiver n’est pas encore arrivé et il m’est impossible de faire remplir mon bain à plein débit d’eau chaude car l’eau est trop froide. Je dois remplir le bain avec la moitié du débit du robinet si je veux qu’il soit assez chaud. Avoir à acheter de nouveau, j’aurais choisi 32 ou 37 kw.

I am going to have to return it ,it is a very good unit but my power is not good enough