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Community and Q&A

Rheem Hybrid Water Heater Changing Modes

stk | Posted in Energy Efficiency and Durability on

I recently had a 50-gal Rheem Hybrid water heater installed.  This is the model currently sold at the orange big box store.  I also have a PV system with an eGauge, so I can see real time energy use.  I run the water heater in “heat pump” mode for maximum efficiency.  The water heater occasionally goes into a “pre-warm” mode, which kicks in about 5KW of resistance heat, even though the water heater is supposedly in “heat pump” mode.  Does anyone know why it does this?

On the Status screen, it says “pre-warm” status.  The “pre-warm” 5KW kicks in for about 15-20 minutes then it turns off.  Sometimes it does it after a shower, but I have also seen it happen in the middle of a steady state operation with no hot water being used.

I’d like to understand what is going on and to not have it do this, as I am OK with longer recovery times in order to save energy.  Thanks for any insights!

Water heater installed in garage.  Located in Seattle, WA.

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  1. user-2310254 | | #1


    If the HPWH is in heat pump mode, the electric resistance element should be off. If it is in energy-saver mode, the heat pump and electric element are active. Can you double-check your settings?

    Can you also check your alarm history? If there is a sensor issue (A101, A102, A105, A106, for example), the HPWH with switch to the electric element.


  2. stk | | #2


    It's in Heat Pump mode, not Energy Saver mode. I checked the alarm history and there is just an alarm for not connecting the water leak sensor (which I elected not to use in my install).

    To be clear, it does this only sporadically, not in any obvious pattern.

    I forgot to add in my initial post the response I got from Rheem Tech Support: "In pre-warm mode, the unit does use the electrical elements. If the water temperature drops below a certain temperature, the elements will turn on in any mode to attempt to help the heat pump recover. Also, the incoming water temperature plays a big part in determining if the elements have to come on to assist the heat pump with heating the water."

    It sure sounds like this person is really talking about the Energy Saver mode.

    Thanks. --Sid

  3. user-2310254 | | #3


    What climate zone on you in? Are you on municipal or well water?

    I ask because it could be that you incoming water is cold enough to trigger an "add-heat function" in the HPWH programming. That may be what the tech was suggesting.

  4. Jon_R | | #4

    Possibly too cold water temperatures risk slugging of the compressor. Maybe you could find another way to pre-warm water before it gets to the HPWH (like a passive buffer tank or drain water heat recovery).

  5. stk | | #5

    I think Seattle is Climate Zone 4. I get municipal water from Seattle Public Utilities. Thanks.

  6. Green_Rick | | #6

    Just noticed the prewarm mode with my Rheem HPWH after starting from being off and drained due to plumbing work. I was surprised and disapointed to see this and would much prefer it stay purely on heart pump mode.
    Has anyone figured out exactly what conditions trigger this pre-warm mode?

  7. walta100 | | #7

    My guess is in the mode you have selected should the tank temp fall to far below the set point the heating element will be energized.

    My Rheem central heat pump default control settings seem to be selected to maximize comfort at any cost.


  8. user-2310254 | | #8


    This patent application may explain what's going on ( It may be that the two lock out modes are designed to safeguard the heat pump. If the heat pump cannot raise the temperature to the preset temperature within either of the lockout periods, the controller turns on the heater element. I suspect the control works this way to minimize complaints about slow recovery times.

    Do you have your tank set to 120 degrees or something higher? (Note that some sources say the tank should be at 140 degrees to avoid Legionnaire's, but then you have to worry about scald risk.) How many users in your household, and do they tend to all put demand on the HPWH at the same time? If you really want to operate off the HP 100% of the time, you may have to lower the temperature setting or change user behavior.

  9. onslow | | #9


    You might find reading the whole 77 pages as tedious as I did, but ultimately there are explanations for basic energy management approaches used by various manufacturers.
    Done by NREL - Laboratory Performance Evaluation of Integrated Residential Heat Pump Water Heaters (another poster provided a link I have lost)
    The link I found is:

    The tests are from 2011, which means new products may have adjusted their methods in response to consumer preferences. The notes for the Rheem tested in this group of five would seem consistent with what you are experiencing. Rheem (unit C) chose to ensure hot water delivery over ultimate efficiency. (see the charts on pg 51 and pg 56)

    The Stiebel Eltron (unit D) behaved more like what you are desiring with very little (if any) resistive operation, which helps system efficiency in certain contexts. The AO Smith blended resistive with different set points for activation with the HP and resolved draw down demand with an 80 gal. tank.

    There is much to be learned about how things were in this report, only problem is finding out how each company is programming now. A fairly current Rheem manual is pretty silent on the specifics, but it will talk to your phone. I am actually surprised that you obtained as much info as you did from the Rheem techs. When I was trying to find out the CFM and W.C. of the fan in their units, they had no clue. Nor a resource to find out.

  10. walta100 | | #10

    The fact that you are getting a “pre warm” message means your tank has cooled below the unknown pre warm temp.

    Looking at the flow chart from the patent it is clear this water heater only operate if the resistance element is working. The computer will not turn on the heat pump until the resistance element has warmed the tank above the unknown pre warm temp. Also the patent makes it clear regardless of the mode selected the resistance element will come on after some unknown time period if the heat pump fails to reach the set temp before the timer runs out.


  11. willymo | | #11

    Anyone have a clue as to the difference between "heat pump only" mode and "energy saving" mode? My Econet app is constanly urging me to swithc to Energy Saving mode. Seems like "het pump only" should use the least energy, ya?

    Love the water heater, and the rebates, HATE the opaqueness of the app and instructions!


    1. samjose | | #17

      I'm wondering the same thing because my daily usage increased about 0.5 kWh by changing from "energy saving" to "heat pump only". I didn't have any issues w/recovery in heat pump mode vs. energy saving.

      Here in California, with solar, I thought it would be beneficial to set the schedule to shift usage to 3 a.m. to prevent usage during TOU peaks and A/C during evenings.

  12. user-2310254 | | #12


    Heat pump only mode is the most efficient mode but offers lower recovery time. Energy saving mode runs the heat pump but will also turn on the electric element if recovery is taking too long. At least that is how I understand the "modes." Here is a link that might be helpful:

  13. walta100 | | #13

    According to this patent you have 3 options.

    1“Energy Saver” that only turns on the heatpump after the element as somewhat warmed the tank and will turn on the element is the heat pump takes too long to warm the water.

    2 “Normal” is the same as energy saver but gives the heat pumps less time to its job.

    3 “Electric Only” this turns off the heat pump.

    If your unit has a fault the app maybe trying to get you to enable the element to hide the fault until the warranty expires.

    You could have a refrigeration leak it dirty filter or coils.


  14. irene3 | | #14

    Can I ask who installed the water heater? I am also in Seattle, and when I was looking into getting a hybrid a few years ago, plumbers wouldn't handle replacing a gas water heater with an electric one because it involved electrical work, and electricians wouldn't take out a gas heater, and I couldn't find a place with both on staff who could give me a quote for the whole job. (I may have mangled the details, but it was something like that.) You'd think Big Box Store would have both available (though ordinarily I wouldn't go through them for install), but they just said they didn't do installs on hybrids at all. Eventually, not wanting to go the whole general contractor route with coordinating two sets of folks at once, I bailed and got another gas water heater.

    1. user-2310254 | | #15

      Hi Irene3,

      When I replaced my gas water heater with a HPWH, it was a three-step process. I hired an electrician to add a subpanel and run a 220 VAC/30 Amp circuit from it to where the HPWH would be located. I then hired a plumber to install the HPWH. The plumber purchased the HPWH from a local supply house along with the fittings and lines he needed to rerun the cold and hot water lines. After he finished up, I made the final connection between the HPWH and the 220 VAC/30 Amp connector. It's important to determine whether or not your electrical service can support the HPWH. My home is fairly new, so adding the subpanel and circuit was a fairly simple process.

      Also... This isn't part of your post, but I want to mention that it is important to consider location when installing a HPWH. You need a big enough space and may or may not want to include inlet and outlet ducts.

  15. irene3 | | #16

    Thank you very much. I was afraid it might still be the case that it took multiple different folks. I did check our electrical capacity at the time and there was plenty for a HPWH, but since then we've put in a heat pump furnace, so I don't know offhand how much is left. The space is fine -- we have a good-sized unfinished basement. Now, of course, putting in an electric water heater would mean decommissioning the gas line as well, as that's our last gas appliance. On the other hand, we would then save the base charge on gas, which is around $140 a year, so that would make the increase in electricity usage more palatable.

  16. stk | | #18

    I randomly stumbled back on this question from 2019. Happy to see all the additional information posted. FWIW, my hybrid was (and still is) set to 140 degrees, which may increase the need for "prewarm?" I noticed that the big box is now selling a newer generation of Rheem Hybrid which may further refinement of the "heat pump mode" operating parameters.

  17. raywu1688 | | #19

    I have the Rheem 80-gallen hybrid heat pump water heater. Any idea whether Rheem auto-push firmware updates into the heater?

    Is High Demand mode = all electric element use, no heat pump?

    Energy Save mode, what criteria push it into electric element mode instead of heat pump?

    Thanks much.

  18. ph_aficionado | | #20

    We have an 80 gal. unit set to Heat Pump Only at 110F. ~4 showers per week. Have never seen it kick in the pre-heating mode using the electrical elements.

    Another note on the Energy Saver Mode from Rheem: “Energy saver mode is not recommended for water systems utilizing recirculating.”

    1. raywu1688 | | #21

      I look at consumption chart in the app and did not notice any outliners when using Energy Saver mode with recirculatory pump though. The charts seems to have same pattern as Heat Pump mode and my setting is 135-138F usually because it is a vacation rental on weekends.

      If set to High Demand, usage spike from normal daily of 2kwh to 20-30 kwh daily. I usually have 10-16 guests on weekends and they have complaint of cold water when in Heat Pump mode, so I set it to High Demand. Does High Demand ever use heat pump?

      1. willymo | | #23

        Ray (I guess ^), I assume you have wifi; you can set the temp to 110, then put it up to 140 a day or 2 before they arrive. You might also want to add a mixing valve set to 120 so nobody gets scalded.

        1. raywu1688 | | #24

          Already doing that (manually, don't want to constantly override auto-schedulings, heat pump mode), but set to weekdays at 134F because winter well water in Hemet won't do with just 120F. I then set it to High Demand 138F on weekends when guests arrive, so they can mix with cold water to make hot water tank last longer if they do multiple water jet tubs simultaneouly.

          Still unsure whether Hight Demand is auto-all-electric or heat pump might kicks in though? could ask Rheem, but not sure will get straight/correct answer.

    2. walta100 | | #22

      ph_aficionado I just want to make sure you understand the risk you are taking with such a low temperature setting on a water heater. There are many harmful bacteria that can survive and multiply at 110 °F

      120° is generally considered the minimum safe temp. In order to kill legionnaires bacteria it is recommended to get the tank to 140°f for 32 minutes several times each year.

      Yes I am sure the lower temp does save some energy but it is not enough to risk people’s lives for.


      1. ph_aficionado | | #25

        Yes, thank you. I agree that running the tank at 140F+ a few times a year is a good practice to kill any possible legionnaires bacteria. I was just saying that day-to-day we keep it at 110F.

    3. cussnu2 | | #26

      4 showers PER WEEK???

      1. ph_aficionado | | #27

        There are several aspects to this. One I encourage everyone to consider is having a bidet. We've had a cheap Luxe one for two years (, and about a year ago upgraded to a fancier model ( I discovered bidets after traveling to Japan and Southeast Asia, and never looked back. They greatly reduce the need for frequent showering (not to mention reducing toilet paper use to a minimum). Highly recommended.

        1. luislarrea | | #60

          Preach. People with bidets don't walk around with stinky butts.

          1. willymo | | #62

            HA! One of several (many?) ways that Americans are behind the rest of the world. One potential issue is, in winter, if only using cold water, it can be painful. You can get a portable handheld ( and fill it with warm water. Nice!

            Or you can go more involved and get one with hot water connection, or electric, for more $$.

  19. Hein_Nashua_NH | | #28

    Generic reply about the Rheem because Rheem/HomeDepot sensors comments and questions.

    I self installed the 80 gallon model using pex and sharkbite and a self installed sub-panel.
    We are just 2, but frequently get 3 daughters and husbands visiting and showering at which point we need the 80 gallons.

    In general I am very happy with the low energy. consumption. Our gas bill is nicely down.
    For the 2 of us we run 40Kwh/month in heatpump only mode which is less than a good day from our 7Kwh solar system. This jumps frightingly when the Element come on.

    I am NOT happy with the Econet application for its lack of displaying the live temperature sensor data and it's lack of browser support - why the heck does everything need to be an app?!

    I am NOT happy with the temperature control hysteresis, it allows too wide a drop before restarting the heatpump. This is possibly done to avoid shortcycling the compressor, but as it is it runs too late too long.
    Knowing what I know now (nobody told me!) I should have installed a temperature controlled mixing valve, and I may still retrofit that.

    As it is, with temp set to 124, it frequently drops to 120 or below and my wife likes her showers hotter than that (30 ft pipe run?).
    Once I install a regulator I'll set that to 122 or so, and set the heater to 130.
    Main goal would be to l allow the heater temperature to drop a long way say down to 125 and kick in the compressor already before the drop it becomes noticeable at the shower.
    And it would allow for safer (bacteria) core temps yet avoiding scalding.
    Side goal would be even more relative capacity.

    Finally, I think the algorithm in the heater should keep upper and lower temp closer, maybe to the point of running an artificial circulator occasionally?

    As for the install, please be sure to indeed add a heat-trap as recommended in the manuals.
    The attached picture shows mine during installation, before further support, insulation and condensate line.

    It really 'traps' the heat in the short 12" upward strech.
    When not in use for hours the rest of the piping stays nicely cool, not losing heat.
    Of course the price is a slightly longer time before hot water reaches the faucet.
    In my case that's no issue as the hybrid system allowed me to install in the 'core' of the house near main consumption points instead of the 50+ ft run of 3/4 copper piping we had to get to the vented gas heater.

    note: During the summer I disconnect one of the hvac air outlets in the top the picture and hooked it up to the cold air outlet on the heater. This heater has a nice flange to connect to an elbow.

    Hope this helps,

  20. oaklandcavictorian | | #29

    Hein, thanks for your detailed system description.

    I have an idea I want to request someone on this forum to try out on their Rheem unit... Please read on!

    I'm deciding between this Rheem unit and a Sanden Eco2 (formerly SanCO2) because I want to be able to schedule them to go to max temperature just before peak electricity rates kick in (in Oakland, CA on PG&E this is at either 3pm or 4pm depending on standard or EV rate schedule). Then I want to schedule their temperature setting to be so low that the heater won't turn on unless we have a full house of guests visiting for a rare holiday or similar, and then turn back on after 9pm when the electricity rate schedule gets cheap again.

    Could @S_K or someone maybe try out my idea of how to trick the system to never enter pre-warm with a simple stair step scheduling approach? Here is an example of the idea (assuming 3pm - 9pm as peak rate hours):

    7am = 130 F
    8am = 135 F
    9am = 140 F
    10am = 145 F (or max)
    2:30pm = 145 F (or max)
    2:55pm = 110 F
    9pm = 110 F
    9:10pm = 115 F
    10pm = 120 F
    11pm = 125 F

    So, basically, using the Rheem's max temperature of 145 F as thermal energy storage and coupling the output to an anti-scald tempering valve that regulates the output temperature to, say, 125 F. The Sanden unit would be even better at this because it has a 120 gallon tank option and claims to go as high as 175 F due to the CO2 refrigerant supercritical thermodynamic cycle, however it looks to be $2K more expensive with fewer systems installed which makes me worry about service when something inevitably goes wrong. Thus, I would lean toward this Rheem unit, but I want to be sure that I would be able to run entirely with the heat pump and I could figure out a way for the "pre-warm" resistive heat elements to never kick in other than for rare maintenance cycles.

    Aside... I am also considering the Chiltrix CX34 which is a "split" system like the Sanden, however it only has a max temperature of 131 F due to the thermodynamic cycle of its refrigerant choice of R410a, so it wouldn't be as useful at storing thermal energy during the 3-9 pm off time. The Rheem unit uses R134a refrigerant like the modern USA automotive industry, so it cannot get as high as the Sanden CO2 solution but they claim to be able to reach 145 F on their datasheet. I like the anti-legionella benefit of routinely hitting 140+ F as well. Has anyone in the SF Bay Area or a similar climate zone been able to achieve 145 F with the Rheem in heat pump only mode?

    1. Hein_Nashua_NH | | #32

      Like William Morse, I suspect you are over thinking it.
      Here in NH we have flat rate electricity, but I do have Solar.
      Therefor I like to heat from 10am onwards admittedly only saving pennies, but it feels right.
      [I did the math. Due to distribution cost going both ways - is it better to use when producing with solar but it is minimal. In the month of May for our 7KW tops solar I would earn $5 more if all usage is while producing versus no usage while producing. Neither situation being practical/realistic, but I can still nudge usage towards production ours with pool pump timers and the Hot Water heater]

      "however it looks to be $2K more expensive "
      There is no way to recover this saving a dollar here and there

      My Rheem 80G was $1600 + 75 delivery to my back door, and I had $600 rebate.
      I'm about to install temperature valve (factory set to 120, hard to go above) to allow me to safely heat extra to say 130 and when the sun shines.
      Even at just $120 for the valve plus some couplings self installed it will be hard to recover that little money but I do this mostly for COMFORT as I find the temperature is often way lower than requested. This will give me a bigger, better, buffer.

  21. willymo | | #30

    I think you are over-thinking this. I routinely change the Rheem from 110 to 140, after being at 110 for hours or days. Set on Heat-pump only, it never uses the rods. It also can be set via timer, not sure how many timers/day, but you basically only need 2, 110, and 140. The only time it uses the rods is when I have turned it off, and drops even further. So I don't do that anymore!

    HTH's, Bill

  22. Green_Rick | | #31

    I agree with William. Not sure what the cutoff temp would be that causes heating elements to kick in though. An odd thing I noticed with setting the schedule on the app was it sometimes would switch into energy saver mode from heat pump only. Don't know if this was due to app updates or some other reason. I stop using the scheduling app after the second time this happened, and just leave it at set temp with heat pump only.

  23. oaklandcavictorian | | #33

    Thanks for all your replies. I was only overthinking it because of SK's original post for this thread that the resistive rods kick on unexpectedly and the diagnosis was due to low temperature. Since I haven't bought the unit yet, I don't have you guys' experience with the heat pump having no issue in raising from 110 to 140 with no resistive rod activation. Does anyone have a sense of when the heat pump would struggle and trigger the resistive rods to kick on? I assume it is dependent on ambient temperature (i.e. cold ambients reduce heat pump capacity and COP) and also the current temperature of the water in the tank. This is just for my interest.

    I would of course much rather not have to schedule the stair step, especially based on seeing the Apple iOS app store reviews of their very buggy app not communicating with the unit itself. Thus, it seems like the best way to schedule it is to push the buttons on the unit's touchpad... and I'd rather be pushing buttons for two schedule set points as William describes.

    One note for Hein... up in NH it sounds like you have a straightforward rate structure. But here in Oakland, California with my electric car I am on an EV rate structure that is drastically higher during peak hours. See attachment for the current rate plan. 49 cents vs. 17 cents. I may switch to a simple time-of-use plan where the delta between peak and off peak is more like 37 cents vs. 27 cents.

    1. derekisastro | | #34

      Lol, also being a Californian on PG&E, I must reinforce your point about electricity costs in different parts of the country ... I think a significant section of the USA population, even on this website (which I thought meant people would approach issues with a broader understanding of the nuances involved in the regional green building) often forgets how much regional electricity prices vary ... they sometimes think their "9c/kWh" electricty prices are country wide. When you're paying up to, virtually 50c/kWh, it's amazing how much you can save with off-peak usages and heat-pump only modes.

  24. bgix | | #35

    Wow. So much good stuff here... Answers to questions that I never knew I had. I am getting the 80 gallon "Performance Platinum Rheem" within the next month or two from the Orange Big Box here in Seattle. My original plan was to install in my basement garage, with an intake duct of just a few inches to suck air from my basement utility room that houses my gas furnace and electric cloths dryer, and set it to 110 or so on Heat-Pump-Only mode. Ductless exhaust of cold air to the garage where my beer fridge lives.

    Based on the comments here, I am re-thinking it... Probably set the internal temp somewhat higher for Legionaires prevention (125? 140?) with a mixing valve perhaps installed right at the tank set to 110-120? Do we not care about the 30 feet of hot water pipe to the shower head?

    Or is there a way to automatically once a week or once a month to heat to 140 just to kill the bad germs?

    My use case is 4 adults full time (3 shower heads) with an occasional extra 2 adults. Showers themselves are generally distributed over a couple hours, but occasionally back-to-back.

    1. jonathanb | | #45

      A question: did you get your Performance Platinum? How'd it work out?

      Reason for asking: I got the Ruud version, and there seems to have been a manufacturing quality issue with the 5th gen units. They're crazy loud. I did a warranty replacement, and the replacement had the same problem. It's louder than our 4 ton heat pump outdoor unit was, and it's located inside the house.

      If anyone has had luck, and the 5th Gen Rheem/Ruud is performing according to the noise spec of 49 dB, I'd love to hear about it. What was your manufacture date?

  25. user-2310254 | | #36

    Rheem says the utility room has to be at least 700 cubic feet and ducts have to be between 5 and 8 inches. But I didn't see anything in the use guide about colocating a HPWH with other appliances. Do you know if your furnace uses sealed or atmospheric combustion.

    Even if the furnace has its own air source, I'd be concerned that cloths dryer will cause the HPWH intake filter (which is pretty basic) to clog more quickly or even allow fine particles to build up on the heat pump. I guess you could check it religiously or install an inline filter.

    OSHA says 140 degree water kills legionella after 32 minutes. If this bacteria is a concern in your area, you can mitigate your risk by maintaining the tank at that temperature. Will that step make your showers 100 percent safe against a respiratory infection? I have no idea but maybe one of the experts will offer an opinion.

    1. bgix | | #37

      The utility room is 840 cubic feet (just measured). The garage 1125 cubic feet. The intake duct for the heat pump will be full sized (8")... But no more than 6-12" long, through a single layer piece of sheet-rock. The cloths dryer's hot-moist output is to the outside. The furnace combustion intake and output are both external... It is 28.5 years old and is a standard forced-air with cold return through house-wide ductwork.

      I am wondering if I will need to add a register between the garage and the rest of the house if there is an air-pressure differential between the room acting as input, and the garage... But I am hoping that it will not be needed, since the intake utility room has an effective cubic footage of "the whole house" blowing air into the 1125 cubic foot garage. Also, it is a 1924 vintage house with single pane windows, and a fair amount of opportunities for drafts... it is *not* a modern airtight living space. Thanks for the pointers.

  26. user-2310254 | | #38

    You don’t want air exchange between the garage and the living space. It’s a safety and health issue. Being able to scavage heat from the dryer might work out, but both appliances have to be running at the same time. Maybe you can manage that, but I’d still keep an eye on the HPWH’s filter (at least initially).

    1. bgix | | #39

      Oh, again, that is a great point on air exchange with garage... It is a small garage that hasn't had a car parked in it for decades, but I can't rule it out for the future... I may add a vent from the garage to the outside if I think an air pressure differential develops. In any case, I have CO detectors. I'm not planning on scavenging heat *directly* from the dryer. I just note that the utility room tends to get pretty warm when either the furnace or dryer is on, but this is mostly ambient heat exchange... we aren't deliberately trying to warm the room by directing dryer exhaust air internally.

      That said, it might be interesting to try to synchronize the furnace (which is scheduled to turn on an hour before we get out of bed) with a water heater heating cycle. Like our peak hot water usage, the furnace is part of our morning routine, our house dropping to < 60 while we sleep in the winter.

  27. David_Gregory_CZ3_CA | | #40

    Continuing the thread - my install details below the questions; I also would love to know which mode is most efficient, given my particular usage patterns:

    1. @ C Z - by 'status screen' do you mean the screen on the water heater itself? Or the app? I would love to know if this is happening but not easy to keep an eye on the heater itself...
    2. Is there an affordable/recommended 240V equivalent to the Kill-A-Watt meter (plug-based) or would I need an Ammeter (clamp) or even hard-wired-in data logger? (will also ask PEC tool library in SF)
    3. Just noticed (after daylight savings time shift?) that app times seem to be off, and overall not trustworthy: showing no usage every other hour (only 2 hour granularity?!? then why show a '0' data point?!?); showing some usage after 3pm when it should be off and only slowly coasting down from 140F (see below); also, usage seems to ramp up from 6am to 2pm, whereas I'd expect usage to pop up ~10am (120F>140F shift) and then taper (maybe granularity problem).
    4. Is it worth it financially, and/or environmentally (total energy use) (2 sep.?s), to bump up to 140F and have more standby losses, vs. just leaving at 120 and letting it run if it needs to (given only 40gal)?
    5. Thoughts on +/- of stratification vs. mixing (transfer efficiency from HP coil w/larger deltaT, but more cycling? vs. more storage if better mixing)? If mixing is advantageous for any reason (e.g., legionella growth during 19hr coasting), how best to? I recall the Sandens recommend 80gal if used for hydronic heat to maintain stratification, I believe for efficiency reasons...
    6. Worth installing heat-recovery on shower to keep HP off until morning on 2 shower evenings? usage is low, materials modest, labor unpaid...;)

    Appreciate any thoughts!

    my install:

    Rheem Performance Platinum XE40T10H45U0 - 30A 240V w/2 elec. resistance elements (for price/availability reasons; hope to not ever use them), in vented crawlspace, w/mixing valve, Berkeley CA. 2 months in operation but only 1 month of app data. Scheduled setback to 120F during peak rates (3pm-12pm) and continuing into late morning (until 10am), then 140F off-peak 10am-3pm. 3 people HH, ~ 4 showers/week, typ. evening; other HW uses mostly off-peak mornings. If only one shower (~8-9pm), HPWH seems to stay off; if two, kicks on and cycles. May try narrowing 140F window to reach temp closer to 3pm to reduce standby losses (at potential loss of capacity? wish there was user-accessible data on top-middle-bottom tank temps!)

  28. RunSilent | | #41

    Something that bit me when installing a Professional Prestige ProTerra 80 gal is the noise it generates. This was installed last year during construction of a new house where, unfortunately, it was installed against an interior wall. It generates a pretty loud tone that you can easily hear in the house. The architect, builder and I didn't have experience with them so we didn't catch it before construction. Also, I ran across a comment where somebody said the new models seem louder than the older ones. We're looking at how to tie it down without strapping it to the wall (Calif) since that really increases the sound levels in the house. Also going to add some dampening material to the wall. If anybody has experience quieting this things I'm all ears...

    1. David_Gregory_CZ3_CA | | #43

      @Eric Earnst - not an expert but FWIW:
      - ducting
      - strap to walls with BR isolators (or dep. on inspections schedule, non-contact / padded blocking restraints)
      - extra drywall
      - damping in wall (be careful about how dense/contact w/both sides)

      The noise is across a range of frequencies so may need a range of solutions…both “light” and “heavy” materials…

      Final tip: I have mine set to run up to 140degF by 3pm when I (in normal times) am not home, then coast until the next day (mix down to 120 w/valve)

      Hope that’s at least a little useful…good luck and let us know how it turns out!

      1. jonathanb | | #46

        I can confirm there's a quality issue with the 5th Gen hybrid water heaters. They are way louder than spec. I've done a warranty replacement twice (paid for fully by Rheem) and both replacement units had the same problem. Instead of the rated 49 dB that the 4th Gen units got, it's more like 62-65 dB. That's way too loud for inside the house.

        I may try putting insulated flex duct on the exhaust and intake and see if that reduces the noise.

        Another idea I'm trying: heat to 135 in the early morning before we wake up, and then drop the temperature to 120 all day. I'm not sure if that will prevent it from turning on, which is the goal. It's so bad we might put it in electric mode during the daytime, if it doesn't need to run very often.

        Until I hear confirmation that Rheem has fixed the quality issues, I can't recommend the 5th Gen Rheem/Ruud hybrids.

        The AO Smith is rated at 51 dB. That's what I would buy if I had to do it over.

        1. walta100 | | #49

          Jonathan you may want to consider filing a complaint form with federal Trade Commission FTC.

          Maybe if you are lucky will read it and light a fire under Rheem to fix the problem or change the advertising.


        2. RunSilent | | #54

          I've not done anything about my loud unit, the local expert came out to install the new "sound reduction kit" Ruud sent us but he said it wouldn't make any difference so we passed (a ball bearing fan and a cheesy piece of foam). I implemented a schedule to heat to 140 after midnight and we've been able to coast during the day. I would still like a better resolution so anybody with this issue please speak up if you have a breakthrough! Any feedback on whether the 2022 model is quieter (or at least acceptable) would be very helpful as well.

          I brought home a sound pressure meter from work to get sound levels and used a spectrum analyzer app to get the sound spectrum. I've attached the data I sent them.

  29. westshorenc | | #42

    Anyone doing upstream preheat, from a geothermal desuperheater as an example? I have such a setup and with the Proterra hybrid water heater in the recommended ES mode it appears to be delayed in energizing the compressor ( the hot water availability drops to 1/3 or less per the app indication). Preheated incoming water may be confusing the sensors and algorithms.

  30. Deleted | | #44


  31. MichDoug | | #47

    Any update on the 5th Gen Rheem noise issue. Planning to buy a 50 gal one soon.

    Also, anyone have a max current draw in heat pump only mode? The spec sheet gives max amps, but I assume that is for when the coils are running at max

    1. kkrugler | | #50

      I believe the heat pump uses 360 watts at steady state, though typically startup has a higher load. At 240V, that's about 1.5A.

      1. MichDoug | | #52

        Thanks, very helpful

    2. rpertusio | | #55

      Hi. Just installed the Rheem 80gal.
      NO major noise issues. I can hear the compressor, but it's not deafening as I've heard in some YouTube videos. Slightly less noise than the GE GeoSpring it replaced.

      I have an Emporia Vue 2 to monitor my household energy usage.
      The WH heater in heat pump mode varies. It dips as low as 275W and peaks about 403W. It averages around 330W.

      See attachment for about a random 40 minute span of measurements.

  32. user-2310254 | | #48

    My plumber's distributor says I'll probably have to wait until June if I want a 2022 unit, which I do.

    Note that Rheem makes a 15 amp and a 30 amp HPWH. Both are 240 VAC, but the 15 amp unit has a smaller heating element for homes with less capacity in the panel. Of course, you may never use the heating element if the unit stay in heat pump mode.

    1. MichDoug | | #53

      Is a 2022 unit with a noise fix? Is there a date code or other indication to know which ones to avoid?

      1. rpertusio | | #56

        I have the XE80T10HS45U0 purchased online from the 'Orange' big box store on 3/28/2022 and received a unit with a production date of "08MAR2022". (It was picked up in Ohio.) I don't believe I have the 'noise problem'. Fan is very low noise, and while I can hear the compressor, I wouldn't consider it bothersome. Slightly less noise than the GE GeoSpring 50 that I replaced.

      2. ejg24 | | #57

        After following 3 different forums, people are reporting that Rheem has solved the noise issue on the units manufactured after Jan 2022.

        I spoke to one installer and was told the supply houses receive batches of HW heaters all having the same manufacturer date. If you have a noisy unit that came from a supply house, replacing it from the same place will likely not solve your problem until the supply house has depleted their supply stock and they get more recent units. So this installer told me that he could solve my AFTER Jan 2022 requirement by going to the Orange box store instead. The turnover at that store is higher than the supply houses and the manu date can be validated before purchase. So this is how my installer purchased my unit.

        I am installed and only using HP mode, I take 4 showers a week, plus 1 load of laundry.

        I read these heaters loose 1 degree per hour and I doubt this loss is linear. My gut tells me the loss is notably higher at the higher end hold temps compared to the lower end. So those storing energy at higher temps are probably loosing efficiency and not gaining as much as they are think doing that. I’d like to see data to confirm this and without it any debate either way is probably not constructive.

        Yes, the app is underwhelming. It does time schedule the modes fine. It stinks that the current water temp, the most obvious metric to provide, is not given. Might be that concealing it possibly shields Rheem/Rudd from issues reported by the consumer.

        The biggest annoyance is that the energy used bar chart graphic that shows one bar for every 1 hour timeslot is in disarray. Every other time slot is always empty. That is, if my HP runs from 1-4am, only slots, 2 and 4am have kWh data. At the same time, every 6 hrs, the info shows I burn 140wh of energy and this includes days where the Rheem is “OFF” for days on end. (All odd number hours are always zero)

        Rheem phone support has no answers. They told me the support staff has not been given any documentation to help customers. They told me to wait for the next App update which they were told would be released “next” week and that was 3 weeks ago. Still nothing.

  33. kkrugler | | #51

    Just from my own personal experience, I believe there's been a change from 2019 to 2021 Rheem Performance Platinum water heaters in how they handle "Heat Pump" mode.

    In the 2019 model that I installed in my guest house, even in Heat Pump mode it would use the heating element if needed.

    In the 2021 model that I have in my main house, it went into serious alarm mode (loud beeping) when the tank temperature dropped too low during a prolonged period of high demand, and I didn't see any sign that the heating element kicked in.

  34. guybarth | | #58

    Does the app tell you the temp of water in the tank, not just the set temp? I plan on purchasing the 80 gallon professional unit for my new construction in Guatemala and I will be on off grid solar. I was planning on setting the temp high during peak solar hours and lower for the rest of the day, it would be nice to see the temp in the tank to inform my settings.

    1. ejg24 | | #59

      Lots of buyers feel let down that Rheems heat pump water heaters do not provide the current temp of the water. It is one of the most obvious pieces of information you would think that Rheem would provide, but they don’t. The closest they come is a tiny icon of a cylinder that is colored green when there is water available at the temp you set it to heat to. Then when you use some of that water, the green fill level of the cylinder might show half way instead of full. Then as the water cools more in the tank the cylinder can change to the color blue or red at lowering fill levels depending on that heated water availability. Rheem does not define this icon behavior anywhere.

      The app and its remote connectivity is nice but it does not provide as much information as you would imagine.

      The app can be used to plan for when you want the unit to heat the water via a time-window scheduling schema based on the day of the week. So if you want to only heat water at 4-5am on TH, you can do that for any temp you select. For me 120 deg serves my needs.

      The app does track your electrical usage but there are quirks to it that make you doubt the information. For example, if you tell to heat water from 4-7am, you see the daily energy usage graph shoot up at 5am, then show no energy used at 6am, then at 7am again the graph shoots up again. The point is, no matter what, every other hour energy usage time slot is ALWAYS zero and this is when I validate that the compressor ran without stopping for 3hours straight. Then I also have days where I define to not heat water at all where I set the usage mode to be OFF. However no matter what, the unit shows energy usage. That is, every 6 hours, 140wh are used even in that OFF mode. I have no idea what the unit does. This is not documented anywhere and phone support is there but they don’t know either. Nobody wants to burn a 140 watt lightbulb for an hour, every 6 hours no matter what.

      Rheem phone support told me they are not Rheem employees and are a contracted out phone support center business. They have no technical documentation given to them and no product training and there is no information flow to provide answers to the questions I had. I was somewhat flabbergasted the person told me this.

      Now, what I described is the worst of things.

      The bottom line is I am happy with my heat pump water heater and can validate that it saves me significant money compared to natural gas. I only run in heat pump mode. In 60 deg basement air, with the cold output air vented to the outside, my first month usage of just about every other day of water heating, I used 37Kwh of energy which is slightly more that one day of solar generation for a month. So now I have no hot water expense now and no gasoline expense as drive an EV for transportation. Solar is good and my system will be paid for completely in 2 more years.

  35. luislarrea | | #61

    I don't know about anyone else but I've been disappointed with the 50 gal Rheem.

    First, it's actually 45 gal.
    Second, I moved from gas to electric and when I'd run out of cold water, it was usually subtle. Now, it's ice cold.
    Third, I have a recirculating pump and when I use it, hot water run out while 2nd person is showering. Needed to discontinue using it until I figure out something better.
    Fourth, the design makes it so you have to fully drain the tank if you need to service the pipes.
    Fifth, didn't realize this didn't come with heat traps--my $300 gas unit did. Will need to drain completely to properly install them.
    Sixth, app only lets you set temp for 4 different times per day.
    Seventh, and this is the kicker, I'm paying at least $60 a month for hot water now. I believe I was only paying about $20 for the gas unit. It was so low, I didn't think about it. My solution to water running out was adding a thermostatic valve. Works great but I need to overheat the water in order to get any use out of it.

    I'm currently in the middle of riddling with the settings to see if I can get this working more affordably. My initial solution was to raise the temp from 120º to 135º at 6PM in hopes that'll it'll be ready by 7PM when everyone is showering. That's when my energy usage skyrockets to 5x typical usage. From the looks of energy consumption, it starts heating the water at 5PM to have it at 135º by 6PM which is not what I want.

    With that said, instead of going from 120º to 135º, I'm going at 5º increments every hour. This is annoying because with scheduling limited to 4 times, I basically only get to do this once. Not a big deal for me but would be annoying if I wanted to target two different times. In any case, I don't even know if this gradual approach will even make a difference. I own a Sense so it's brutal to see the hourly usage spike for so long from 5-10PM.

    1. pnw_guy | | #63

      "I'm paying at least $60 a month for hot water now."

      If accurate, it sounds like there's a problem. I've seen many reports of hot water costs more in the $10-15/month range with heat pump water heaters, and I think some or many of those reports were for 60 or 80 gallon models.

      Maybe others will weigh in, but $60/mo sounds like something is way off.

    2. ejg24 | | #65

      Most all advertised HW heaters are less capacity than what is stated. All vendors do this and not just Rheem and I am not sure why. If you study all the written details describing your unit, you will eventually find this detail. I seem to remember that Orange store prints the actual number on their product description page for every capacity model. Also keep in mind your OLD unit was likely rated the same way. If you thought you were replacing a 50G unit you really weren’t. The old unit was likely around 45G as well.
      Transitioning from Gas to HP requires caution because you need to realize HP does not recover nearly as fast as Gas. So that is a planning issue on the lap of the buyer. Anyway, I think you either need to up the temperature of your water to get it to last longer or swap out the unit for a higher capacity.  The more people in your household the higher the chance you will need to go from 50G gas to 65G if you prefer using HP mode. The savings are there to justify it, for my Solar house they would be anyways.
      You may not have seen it, but there is a post in this thread from a guy telling people not to use HP if they have a Recirculating water system. Scroll back up and you will come across it.
      I heat my water just before the rates rise at 7am and you should do the same and then booster just before 7pm. You should not need more than 2 slots in the scheduler for that.
      In Pacifica I use 1.2Kwh heating a cold tank to 120deg and at 16cents/kwh = 19cents per heating. I do this 3x/week. Yes… I only shower 3x/week people so sue me ! This comes to 12 heatings/month or $2.28 of monetary value. Compared to gas, I seem to remember I was paying about 4x more.
      I made this transition because my old HWH was over 25 years old and starting to crap out on me.  So why not? Also, since I was not using all my generated Solar it was a no brainer as the company only wants me in the office 3 days a week.  I pretty much don’t need to charge my car at home anymore so im way overbudgeted now with free electricity.  My savings has got even better because the cost of gas has more than doubled this last year. That is just me and YMMV depending on your living situation.

  36. willymo | | #64

    Not sure why you are having those problems. I have a 50 gallon, and can get 2 showers at least before water temp goes down. Are you using heat pump only, or the electric resistance? Heat pump only will def use less electricity. It only uses ~350W on heat pump.

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