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Green Building News

A New Generation of Heat-Pump Water Heaters is on the Way

Plug-in versions will run on standard household current, opening the door to wider market adoption

A.O. Smith is one of three companies planning to roll out plug-in heat-pump water heaters that do not require a 240-volt circuit. This illustration comes from a webinar earlier this month in which the manufacturers discussed the new products. Illustration courtesy A.O. Smith.

Three major water heater manufacturers say they are developing heat-pump water heaters (HPWHs) that will run on a 120-volt circuit, a development that could make the high-efficiency appliances a drop-in replacement for gas models and attractive to a much larger pool of consumers.

Rheem, A.O. Smith, and GE Appliances all are working on the plug-in models, with two of the companies saying they should be available this year. GE has not announced when its version might be on the market, and it’s not clear where the new models will be sold.

The disclosures came during an unusual webinar hosted by the New Buildings Institute and the Building Decarbonization Coalition on May 13 in which the manufacturing competitors talked about products still in development to an audience of several hundred listeners.

Heat-pump water heaters are far more efficient than conventional electric tank models. They rely on the same technology that makes air-source heat pumps so attractive, but until now they have been limited to models that run on 240-volt current. Homeowners who wanted to switch from a gas water heater to a HPWH will be forced to upgrade the electric panel if the panel doesn’t have the capacity for a new, dedicated 240-volt circuit. That can get expensive.

But the models under development, and in some cases now in field tests, are designed to run on either a dedicated 120-volt circuit or a shared circuit that also powers other devices. Consumers would not be forced to upgrade their panels.

Panama Bartholomy, director of the Building Decarbonization Coalition, said development of the plug-in HPWHs could be traced to a conference in San Francisco in 2019 in which industry and environmental interests met to discuss how to reduce the use of fossil fuels. The result was the Roadmap to Decarbonize California’s Buildings, which included plans to replace gas-burning appliances with electric versions.

As explained by Amruta Khanolkar, a project manager at the New Buildings Institute, the Advanced Water Heating Initiative included a number of goals for the new class of water heaters that would make them appealing to the retrofit market. That included the ability to run on a 120-volt, 15-amp circuit, and be plugged in rather than direct-wired to the panel. The target was the market for 7 million water heaters that have to be replaced annually.

“If consumers want to decarbonize and switch to an electric water heater, the only option they currently have is going for expensive and extensive panel upgrades,” she said. “This technology, if validated, will no longer require that.”

While better suited as a drop-in replacement for an existing water heater, the plug-in models have a couple of disadvantages when compared to their 240-volt cousins. Because of the reduced current, they take longer to heat water and have lower first-hour ratings, a measure of how much hot water they can produce in the first hour of operation. Manufacturers are trying to compensate in several ways. One approach is to store water at a relatively high temperature and mix it with cooler water as it leaves the tank. Another is to include auxiliary heating coils to boost water temperatures when the heat pumps can’t meet demand.

The company representatives indicated that the plug-in versions would make about the same amount of noise as the 240-volt models when operating, cost about the same, and would use the same type of refrigerant. Both noise levels and the development of refrigerants with lower global warming potentials seemed to be an area of interest for all three companies.

GE Appliances

GE’s place at the table was a little surprising. The company dropped out of the heat-pump water heater market in 2017, citing low demand for its GeoSpring model. The company sold its manufacturing line to Bradford White, which had been buying the GeoSpring and selling it under its own label, AeroTherm. The move allowed Bradford White to continue selling a HPWH.

As recently as March, a spokeswoman for GE Appliances confirmed the company was out of the business and made no mention of the development of what appears to be a retooled GeoSpring HPWH. The issue came up with the publication of a consumer guide to electrification, which mentioned plug-in models that were not commercially available, including the GeoSpring.

Tom Zimmer, who leads the water heater division at GE Appliances, said on the webinar that it was developing both a 120-volt and a 240-volt GeoSpring model, although he did not say when they might be back on the market. The new model would come with tank sizes of 40, 50, 65, and 80 gallons and have a built-in WiFi module.

Zimmer acknowledged some of the difficulties in selling HPWHs, including higher costs when compared to gas models, higher installation costs if panel upgrades are required, and marginal energy savings. A model that runs on a 120-volt circuit has added disadvantages.

“When you move from the 240-volt to the 120-volt configuration you are giving up energy use on the input side, so it takes longer for tanks to recover, especially those that are operating on pure heat-pump operation, and there is a tendency to get lower first-hour ratings because of that difference,” he told the webinar audience.

“In round numbers, you nearly have to double the tank capacity to get comparable first-hour delivery,” he added. “That’s something we have to factor in as we think about these conversions.”

The company didn’t discuss its reasons for jumping back into HPWHs except to note that the industry is evolving. Through a spokeswoman, Zimmer said, “GE Appliances will be a full-line manufacturer to meet the needs of the industry. This need is evolving, and as it starts to include HPWHs (120V or 240V), GE will bring great products to serve those needs. The 120-V HPWH product is still under development, and we do not have a launch date to communicate at this time.”

A.O. Smith

Arthur Smith, a product manager for specialty residential products, would say only that the company’s 120-volt plug-in model would be available sometime this year. “That’s about as specific as I’ll get,” he said. The plug-ins will be available in a variety of capacities and will include backup electric resistance elements. Smith, however, said he expected the heat-pump would be in heating mode almost all of the time.


Kevin Clark, a regional manager for the company, said Rheem models had been in test homes for more than a year. A total of 13 units have been installed in Connecticut, Georgia, and California, with another six are planned by June. Clark said a total of six new HPWHs would be available sometime this summer. It would be a California-centric product, at least to start. Unlike the other two companies, Rheem is not including an auxiliary electric element in its models.

Scott Gibson is a contributing writer at Green Building Advisor and Fine Homebuilding magazine.


  1. this_page_left_blank | | #1

    I find this somewhat puzzling. I'm not sure who they think this is going to appeal to. Any existing home already has the wiring for a 240V water heater, either in place or available very nearby in the same room as the water heater. Any new homes will continue to have the same setup. I guess if you wanted to install the water heater in your bathroom or kitchen, this might interest you. Given the lower performance, no one in their right mind is going to install this in a utility room just to save the $100 it might cost to have an electrician run a wire 10-20 feet from the service panel.

    I'd rather they just make the current models more accessible and affordable. In Canada right now, you can't buy one anywhere. You can hire a plumber to install one, and it will cost you about the same as a ductless minisplit (in the ballpark of $4000).

    1. cody_fischer | | #3

      It appeals to me! I have a fossil gas water heater and a panel with no available space for an additional 240v circuit. Going to cost me $1500 to put in a sub panel and dedicated circuit. I might just wait until these come on the market now.

      1. Flytrappist | | #22

        For the new house I am building, I decided to skip a HPWH due to the noise level. I don't want a 45-55 decibel hot water tank within the house envelope. I could relocate it to the garage, which would delay the hot water to most of the house, and it would only be efficient for about 6 months of the year.

    2. charlie_sullivan | | #4

      1. Locations for panels and water heaters include at least garages, utility rooms and basements and having both in the same location is not a given.

      2. There are panels that are full, and a replacement or a sub-panel is needed.

      On the other hand, if you are worried about overloading the panel, 8 A at 240 V has less risk of overloading either phase than 16 A at 120 V. If someone accidentally has a heat pump dryer, and heat pump water heater, two window A/C units, a dehumidifier, a microwave, and a toaster all on the same phase, that's more likely to create an overload than if more of those were 240 and thus inherently balanced between phases.

      1. this_page_left_blank | | #11

        It seems like the concern is panel space, not actual load. Since this thing plugs into a standard outlet, it has to have a max draw of 12A.

        Most heat pump dryers are 240V, I think.

    3. RedDenver | | #6

      Not sure why you think existing homes already have 240V wiring for a water heater. I've lived in 3 homes and none of them had that. I'm interested in the 120V HPWH because I do have 120V outlets in my utility room but not enough space for two breakers for 240V in my main panel.

      1. user-7560403 | | #54

        Exactly, especially any home that has all gas for heating, stove, water heater and dryer. Most of them aren't gonna have 220v circuits run to allow for electric appliances. It's gonna cost the builder extra to add these circuits for something they deemed unnecessary at the time of construction. My guess also is it's assumed people would not want to convert from gas to electric. Plugging one of these 15a 120v heaters into an existing 15 amp or even 20 amp circuit could also be an issue if the circuit is serving other receptacles, appliances or lighting, likely overloading the circuit.

      2. this_page_left_blank | | #55

        You're right, upon reflection it's probably uncommon in older homes where natural gas or propane was the fuel of choice for heating. Panel space is also a real problem, but a more general problem for older homes, and not brought on solely by the water heater issue. Our use of electricity has steadily increased over time. Provided you do have space in the panel, converting a 120V electrical run to a 240V is often very simple.

    4. FrozenCanuck | | #31

      THIS! Never mind the plug when they cost as much as a used car! It's like they don't want to sell many of them.

  2. Jon_R | | #2

    > One approach is to store water at a relatively high temperature

    Bad for efficiency, but better for the electric water heater Legionella problem.

    Perhaps direct PV solar panel input would be a useful option to boost efficiency.

    > JA13 and CTA-2045 Capable

    Would be interesting to hear more about these standards. When energy is used is going to be increasingly important and tank water heaters are the low hanging fruit for this.

  3. charlie_sullivan | | #5

    CTA-2045 is a standard plug-in port for demand response on appliances that solves the problem of future compatibility by not implementing any fancy communications standards or wireless links. It's just a spot to plug in a third-party cart to implement that stuff, so it can work with whatever different current or future communications and controls are used by a particular utility, home automation system, microgrid, or whatever.

    JA13 is a California standard for demand response. I don't know the details but one of the advantages of CTA-2045 is that you can take a water heater that wasn't initially design for JA13 compliance, and make it JA13 compliant by plugging in a low-cost module.

  4. user-5946022 | | #7

    This is appealing. An existing 25 year old slab on grade home with gas WH on L1 and elec panel on L2 would be almost impossible to add 240 for WH, so this would be very appealing.
    I can think of several new construction homes in the last 2-3 years with gas WH that do not have 240 run to the WH area - maybe it is or should be required, but it is not enforced or done. Another issue is space on panels - to the extent there is any extra space on a house originally set up for gas WH, the space for the 240 may be going to an EV charger, impacting the feasibility of converting from Gas WH to Electric

    Storing the water at higher temps to avoid Legionella is appealing. Given the current insulating technologies, it seems maintaining temp on stored water can be much more successful than it used to be. The higher temp impacts both tank size and first hour recovery - conceivably you could deliver the same service with a smaller tank size, using less space.

    The electric resistance heat is also appealing. I wonder if it could work much like an inline instant WH. The need for recovery is usually associated with showers taking place concurrently or consecutively. Wonder if the lower flow shower heads facilitate making a temp boost from an inline instant WH connected to these WH a feasible solution to deliver sufficient hot water.

    1. chiefsilverback | | #25

      I have a 66 gallon AO Smith HPWH with the temp set to 150 and then mix it down to 120 with a tempering valve. Works like a dream and we've yet to run out of hot water...

  5. Expert Member
    PETER G ENGLE PE | | #8

    My favorite inexpensive, plug-in, 120V inline water heater.

    1. charles3 | | #33

      Seriously? What makes it your favorite?

  6. tjanson | | #9

    Someone, please, make a "lowboy" HPWH.

    1. Chris_in_NC | | #17

      The 43-gallon Sanden still appears to be the only game in town for a lowboy HPWH.

      I feel your pain, as I also need a lowboy solution....

    2. user-5946022 | | #20


  7. RossTM | | #10

    Will the 120V heaters have lower performance when running in heat pump only mode? Or is the lower performance only relevant when they are running in hybrid/electric mode? If it's only when they are using the electric backup, it seems the lower performance is not an issue for those of us who would try to set it up to never use the electric backup.

    The thermostatic mixing valve is an attractive option since then you could heat the water up hotter when there is plentiful solar/wind power and let it cool some when electricity is expensive while still maintaining constant temperatures. Of course you could just add a mixing valve to any of these.

  8. Expert Member
    PETER G ENGLE PE | | #12

    We need to be careful defining "lower performance." From what I gather, the 120V water heaters will have similar COP to the 240V water heaters, so similar performance. Where they will suffer is in recovery speed, because they only have half the power input to the heat pump. This means that in the end, it will cost the same amount to heat a tankful of water. It's just that the 120V HPWH will take twice as long to do it.

    Keeping the water hotter in the tank helps to offset the slow recovery by making it seem like the tank is bigger. It also reduces growth of Legionella as discussed above. However, the COP of the heat pump drops with increasing output temperature, the water gets more expensive.

    1. RossTM | | #13

      Will the recovery time be slower when it is just using the heat pump? My guess is no... why would a heat pump need 240V power anyway? I'd bet it is just that the backup electric element will be much less powerful in the 120V version.

  9. CollieGuy | | #14

    We have an older home, and our domestic hot water was originally supplied by a stand alone oil-fired tank. Upon taking possession, we installed a new oil-fired boiler, Tekmar Control system, and indirect water heater.

    Our 100-amp service is pretty much maxed-out. In addition, our basement level is fully finished with the electrical panel located at one end and utility room at the other; even if we had sufficient capacity for a 240-volt tank, running a new dedicated circuit is not in the cards.

    Thankfully, our Nyle Geyser RO HPWH plugs into a standard wall outlet. It's controlled by a Kasa KP115 smart plug that allows it to recharge our indirect tank once a day between 02h30 and 05h30. At the start of each cycle, it draws in the order of 350 to 400-watts, and you'll see that slowly climb to roughly 700-watts by the time it finishes its job.

    Today's energy use was 1.75 kWh.

  10. walta100 | | #15

    If California does force/ convince customers off gas most every house will pushing the limits of their electric service. Finding space in the panel for new circuits for a stove water heater and EV charger is going to have lots of people upgrading their panels or accepting reduced performance from a water heater.

    To get a HPWH to share a 120v 15a circuit with other loads it seems likely they will need to lower the BTU output below 4200 that Rheem’s current units produce and all but eliminate the resistive elements so reduced performance seems likely.


    1. Jon_R | | #16

      Full HP performance at up to 700W is < 6A @ 120V. Which seems reasonable to be on a 15A shared circuit. Also fine without 240V. But agreed, resistance heat assist would need more watts.

  11. AndyKosick | | #18

    I think these heaters will be a great asset for retrofits. The issue (as always) will be making sure good system design is taking place. Understanding the hot water usage of the home, helping homeowners choose good low flow shower heads that meet their needs, then choosing the right heater for the job. The prevalence of emergency replacements throw all that out the window. Dealing with the emergency replacement problem and helping home owners get plans in place for appliance replacement will be key to these 120v HPWHs making a difference.

    1. paul_wiedefeld | | #19

      To that emergency replacement point - water heaters are probably in the conversation for worst product experience imaginable. Why would a company be content with their product failing randomly? Seems like there’d be a market for a sensible, forward thinking installer/manufacturer, but alas.

      1. john_m1 | | #35

        Hardly seems the stuff of the most technologically advanced country on earth. I completely agree. The industry is ripe for a superior product.

  12. jimcrook | | #21

    Seems fine. I'm already stuck with a Rheem hybrid water heater that stopped working in heat-pump mode after a couple of years. No one in my (highly populated) area is willing or able to repair it. Saved on electricity for a couple of years, but was also irritatingly loud (about 45-50 decibels) even though it's located in my garage. All that said, I'd be willing to try again with another unit to reduce the energy use.

    1. rondeaunotrondo | | #32

      My understanding is that Rheem is reasonable with warranties. Have you pursued this avenue?

      1. jimcrook | | #46

        I did call Rheem early on, and they referred me to a plumber who was more than 100 miles away. As I remember it, the warranty wouldn't have covered labor at that point (just parts). I spoke to the plumber and he basically put me off getting it fixed. Since then I've occasionally called local plumbers and 95% of them have said, "We don't work on hybrid water heaters." One offered to come out, and said it would be a couple hundred bucks to look at it. I decided just to live with "electric only" mode. This all occurred circa 2016-2018 though, so maybe things have changed and plumbers are learning how to repair these things. Once this one goes out permanently, I'm going to seriously look at getting another one. I'd probably look at getting a better one (i.e., not straight from the orange store), and installed by a better plumber (mine was kind of a bonehead) in a slightly different location.

  13. earthling | | #23

    Ok, I'm so confused - Why are Induction water heaters -not- the next greatest thing invented for reduced energy consumption! I've been looking forward to them stealing the market for 10 years. They have very few moving parts, very low energy consumption, very quick heating capability, would not need a 240... I think they already sell them in China. It seems like a no-brainer to me. What am I missing?

    1. charlie_sullivan | | #28

      An induction water heater is no more efficient than a regular electric water heater. There might be advantages like avoiding deposition of scale on the heating element, but they use 2-3X more electricity than a heat pump water heater.

    2. CollieGuy | | #30

      Electric resistance would be, for all intents and purposes, 100 per cent efficient. Induction would be no more than 85 to 90 per cent efficient due to the related electronics/power supplies (that waste heat ends up in the ambient air and not the water).

  14. DavidfromPNW | | #24

    LOL. you think 240 is onerous. Try installing an electric tankless. That's a moonshot in a retrofit. "you want how many places on my panel...?"

  15. n7ws | | #26

    My 50 gallon, resistance heated tank is in a utility closet within the electric heat-pump conditioned envelope of my home. It's on a dedicated 30A 240VAC circuit.

    Coincidentally, I'm currently looking at replacing it. A few years ago it would be a DIY project but at nearly 80, I'm not about to manhandle the tank in and out of a confined space. So, I'll need an installer. Naturally, the subject of heat-pumps leaps to mind and I'm trying to imagine a case where one of these makes sense. I can't, but I'm open to convincing.

    1. charlie_sullivan | | #27

      I think the case for it is pretty straightforward. You'd use less electricity. How much less depends on how much hot water you use, and what temperature it comes into you house at (depends on climate). And how much money and carbon emissions you'd save depends on regional electricity price and the emissions profile and your regional grid.

      1. n7ws | | #38

        Well, let's see if it's straightforward. I just put a thermocouple on the inlet and outlet pipes of my existing WH. Inlet T was ~80F and outlet is ~122F. I'm in Tucson and room temp right now is ~80F. My only hot water use is for showering (est 2 gal/min * 20 min) and dish washing (5 gal in machine, 5 gal misc), clothes washing is all cold, except for rare occasions. So for a back-of-the-envelope calculation let's say hot water consumption is 50 gal/day.

        So I have to heat 50 gal of water 42 deg/day. Converting gals to pounds, to BTU to kWH times degrees, and factoring in 93% efficiency, etc, if I did the math correctly (always questionable) I need to buy 5.14 kWH. I pay ~$0.13/kWH so in round numbers that's $0.72/day.

        If I use a HPWH, for example a Rheem that claims 375% efficiency that number is $0.18/day. At a cost differential of about $700 including tax credit, the payback is about 3.5 years. (Ignoring the time value of money)

        But what about wintertime? I have no idea what the inlet T is but the water is piped at least 3 ft underground and it is AZ. Suppose it's 50 deg F. The numbers go to $1.23/day for conventional and $0.31/day for the HPWH. But... the HP is pulling heat out of room air which has been heated by another heat pump. I'm not about to walk into those weeds, I'll leave it for someone else.

        Considering noise and reliability issues, I'm sticking with conventional. BTW, carbon is a non-issue with me. Plants love CO2, I'm not going to deprive them.

        1. paul_wiedefeld | | #39

          Noise and reliability aside, you'd also get supplemental cooling. Looks like Tucson averages 1500 HDD and 4000 CDD, so the contribution would be large, but probably difficult to quantify since it might not directly offset AC use unlike integrated systems.

          1. n7ws | | #40

            As a general rule that's likely the case. But that's not the way this particular house works. Heating and cooling energy usage is quite similar between winter and summer. A roof-mounted HP isn't the greatest. I have supplemental evaporative cooling, although I've pretty much abandoned it because of maintenance and water consumption issues.

          2. charlie_sullivan | | #41

            Wes, if your heating and cooling energy use is similar, then the summer advantage and the winter loss offset each other nicely, so your calculated 3.5 year payback will come true. That's pretty good--better than an investment in the stock market.

    2. john_m1 | | #34

      The only case I can make is not from a dollars standpoint or even climate but to get the NG combustion products out of my house. My HEPA filter goes red every time I turn my stove on. Directionally it is the right idea, but I think will fail as a consumer product. People want hot water to come out when they want it and not think too much about it.

      1. n7ws | | #37

        I realize the article mostly speaks of gas-fired retrofits but my situation refers to resistance-heated.

        1. john_m1 | | #43

          Understood, I really like these things. Efficiency in and of itself is cool. My fear is not understanding people who don't buy these things, and then creating a bad, hard to overcome, image of them. To the average consumer they should just be water heaters.
          Second, I can't for the life of me see why we don't push, much harder, SDHW. Even in the north its a total no brainer.

          1. n7ws | | #52

            First. After doing the calcs I could be tempted. I have 30A 240VAC so don't need to worry about a 120VAC machine. But it's inside the living space and I'm deeply concerned about noise. I'll have to study that.

            Second. I've owned two houses, the one I'm in and the previous one, that both had SDHW systems installed by prior owners. It's too much to detail here but with the maintenance/freeze-up issues (even in sunny AZ) they made no sense to me and I removed them both.

  16. john_m1 | | #29

    This is another one for early adopters. Unless there are strict measures to encourage adoption these will have to be for true believers.
    To the average homeowner hot water is a given.
    Has anyone proposed a triple system? Solar, heat pump, resistance and throw in gas back up.
    Anyone buying one of these already has.a heat pump and/or is willing to accept the lower performance in the form of longer recovery times.
    What would be interesting is if they have a heat pump can this use the outdoor unit.
    The realtors will kill this one. I live in a green town and people complain all the time about the on demand water heaters.
    Look at low flow faucets and shower heads many of the diverters get taken out. Where is Chris Benedict when you need here. IF you want wide adoption propose products that achieve this result for people who don't care. I didn't need another wifi app to control something I have never had to think about.
    Just saying!

  17. charles3 | | #36

    Does anybody have any insight into the reliability of the available 240V models?

  18. stephen_pate | | #42

    Rheem already has 120V versions of their heat pump water heaters. They are listed on the ProTerra as 15 amp versions. They don't come with a cord and plug, so I guess that's the innovation. The 120v model is the highest rated in the NEAA study test. The only comment I can make on that is the 120v will be the slowest to recover. I'm from Canada where you'll need the patience to get a Rheem. The plumbing wholesaler was pushing AO Smith and didn't care. I expedited directly with Rheem and told the plumber when there was stock. With 4 people, I use 70 kWh per month, except in May spring when my solar water heater helps to cut the consumption to 35 kWh. We like the water when we need it so don't use heat pump only mode. The EcoNet WiFi app is very convenient to monitor hot water levels, energy consumption, etc.

    1. john_m1 | | #44

      What are the incentives north of the border for SDHW? In my mind its a total no brainer. They can be mfg locally provides work of different skill levels and will still crank out hot water when everything else fails. There is a local installer down here, that had a customer who owned a small apt building, the gas was shut off and no one said anything because the how water kept coming.

      1. stephen_pate | | #48

        It depends on which province you live in. On PEI it is also dependent on your income varying between $1,200 and $1,800. They are announcing a new Federal $5,000 grant which would apply to the whole purchase if that's all you upgraded. Lots of paperwork on that one. All grants require an EnerGuide audit.

    2. CollieGuy | | #45

      Hi Stephen,

      These 15-amp models are 240-volts (note that the wattage of resistance elements exceed what a 15-amp/120-volt supply would support).

      1. stephen_pate | | #49

        I asked Rheem that question and they said it was possible to use 120V on a 15 amp breaker.

        1. this_page_left_blank | | #51

          2750W is 23A at 120V. So either they misunderstood your question or you misunderstood their answer, or their data sheet is wrong.

    3. this_page_left_blank | | #50

      Pretty sure the 15A versions of the ProTerra line are still 240V. What makes you think otherwise? The doc you linked states 208-240V under the image, and nowhere does it say 120V.

  19. paul_wiedefeld | | #47

    Is there a reason why manufacturers put such small output compressors on these tanks? For example, Rheem has 4,200 Btu/h compressors on their 240V versions, for both the 15 and 30 amp versions. Is it just size considerations? Worries about overcooling?

  20. irene3 | | #53

    I've been wondering if it's even worth it to get a heat pump water heater when our usage is so low, or if we couldn't just get a small regular electric water heater (cheap, proven technology, and I think they are supposed to last longer than gas water heaters). Currently we use ~$20-$25 of gas per month (the water heater is the only gas appliance left), but around half of that is the base charge. So even if electricity cost three times as much (and I live in Seattle, so electricity is relatively cheap) we'd be paying only a little over a dollar a day, which is down at noise level in the budget.

    1. qofmiwok | | #57

      Same boat. Only 2 people in the house, so the heating bills are tiny anyway and it's hard to justify an ROI.

      1. Expert Member
        MALCOLM TAYLOR | | #58


        I feel much the same. You can get a Rheem Marathon that has a lifetime warranty and almost no standby losses and be done.

        1. kurtgranroth | | #59

          I struggle with "best electric water heater for 2 people" decision. On paper, it still looks like a Hybrid would easily beat out a Marathon over any notable amount of time, even accounting for a 10 year replacement.

          Again, ON PAPER, the 50 gallon Marathon vs Hybrid would have a roughly $300/yr cost difference. That pays off the initial cost difference in 2 years and completely pays for the Hybrid in 5. Even replacing the Hybrid every 10 years would result in thousands of dollars of overall savings, over a 10 year cycle.

          The problem is that ON PAPER isn't the same as IN REALITY. The DOE ratings for 50 gallon water heaters assumes an average 3 person household with over 60 gallons of usage per day. Presumably a 2 person household would use notably less. But how much does that impact the actual energy cost?

          That's where my struggle comes in -- where can I find the facts and figures needed to accurately compare a Marathon vs a Hybrid for a 2 person household in reality, since the published numbers show the Hybrid absolutely dominating.

          1. Chris_in_NC | | #60

            From a rough "back-of-the-napkin" analysis, the numbers for both types of units could be scaled per person. This isn't quite accurate, because hot water usage doesn't exactly scale per person based on normal household needs (as I understand it), but if a hybrid absolutely dominates a Marathon for energy use and ROI, it's likely that the same trend will hold if both units are scaled down by the same 30%.

            What I'm saying is that if the difference between the two types is significantly large (based on 3 people), small errors due to assumptions about scaling (for 2 people) are unlikely to significantly affect the conclusion.

            They're both similar insulated storage tanks, so standby losses would be similar, and it takes a certain amount of BTU to heat water to a given temperature delta. Sure, the more water you heat the more energy you use, therefore the shorter the ROI if the savings are based on energy usage.

            Feel free to pick apart my logic...

            I'm still making decisions like "what can I fit in a crawlspace", as none of the HPWH are short enough. So the Marathon-vs-hybrid decision becomes "Do I remodel my house to carve out space for a hybrid". There is a lowboy Marathon...

  21. edwardlouie | | #56

    I think it is as important or more important to make HPWHs able to be split so the compressor can come off the top and extended via quick connect line set outdoors. This would open up the feasible placement of HPWHs a lot. Electric water heaters are placed inside tight conditioned spaces often like a bedroom closets, kitchen closets, laundry rooms, under the staircase. Drilling big holes for air ducts is a crude solution, running line set is a more elegant solution. The compressor would need a mounting bracket kit for outdoors and be rated for the outdoors but the HVAC world knows how to do these things.

    1. charlie_sullivan | | #61

      The Sanden unit is similar to what you are wishing for. Expensive, but very high efficiency.

      1. Jon_R | | #62

        Maybe the $5K+ SANCO2 isn't so special. Reviewing Energy Star certifications, I see other HPWHs with higher efficiency. And LG has a split model (which I think is also more suitable for space heating).

  22. photon08 | | #63

    Has anybody been able to buy 15A/120V HPWH from any maker? If not, does any body have a pointer to Rheem/AO Smith/GE web site with 15A/120V HPWH models? I couldn't find any at Rheem and AO Smith web site.

  23. user-2701121 | | #64

    I just spoke with the same Rheem sales rep mentioned in the article - and he said it'll be at least another month before one can even order their 120v HPWHs - then a few months after that before they are delivered.

    1. photon08 | | #65

      Thanks a lot for finding that out.

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