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Product Guide

Choosing an Energy-Efficient Water Heater

From an energy standpoint, heat-pump water heaters are the best but they still struggle for a toehold in the market

It's been a challenge to interest builders and consumers in heat-pump water heaters but factors such as utility rebates and bans on new gas hookups are making them more attractive and more affordable. Photo courtesy of Scott Gibson.

A long-running ad campaign for Maytag featured an affable but underworked repairman who spent his days snoozing in an office chair because the appliances he sold rarely needed any attention. “I’m the loneliest guy in town,” he complained with a sigh.

The story line may ring a bell with John Miles, who heads Eco Systems, Sanden International’s heat-pump water heater operation in the U.S. Although the products he represents are among the most efficient residential water heaters on the market, Miles is still waiting for that breakthrough year when consumers and HVAC specialists finally wake up to the unique advantages that heat-pump water heaters offer.

They are head and shoulders above anything else that’s available, but command just a little over 1% of the market—of the more than 8 million residential water heaters sold in the U.S. last year, roughly 100,000 of them were heat-pump appliances, Miles said in a telephone call, and Sanden accounted for only a small percentage of that.

“It’s been a hard nut to crack,” Miles said.

Heat-pump water heaters are unfamiliar to many U.S. consumers despite widespread success in Japan and Europe. Like other types of air-source heat pumps, including appliances used for space heating, they extract residual heat from the air without burning any fuel directly. Sanden’s product is unique in the U.S.—it’s a split system with the storage tank inside the house and a separate compressor outside. But a growing number of manufacturers offer heat-pump technology in integrated units that combine the compressor and the storage tank.

Heat-pump water heaters are but one option among many for residential water heating. Water heaters with integral storage tanks powered by either gas or electricity are the industry’s old standbys. Manufacturers have increased the energy efficiency of…

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  1. Expert Member
    Deleted | | #1


  2. user-1110970367 | | #2

    I like the second to last paragraph about plumbers. I waited for a Rheem HP Water Heater to go on sale. Picked it up. However, when I called my normal plumber to install it, the receptionist of the plumber was pretty confused. Once the owner came out, they agreed to install it, but I still left that conversation feeling like I was putting some untested NASA technology in my house.

  3. McAfee | | #3

    With a UEF of 3.3, the electric HPWH's sound very impressive. What about the situation where you've got it in an electric baseboard heated basement though? (East coast of Canada)

    If the compressor is inside it's getting that 3.3 UEF at the expense of some your electric baseboard heating and cooling the space as well. So your water is cheaper but your space heating costs are going to rise in the winter. At 3.3 it's probably still advantageous but that number isn't the "whole home" picture right?

    I'd see it as great for a Canadian summer (cheap hot water with dehumidification and cooling as added benefits) but in the winter it's a more complex picture than the UEF presents.

    It could be run in standard mode in the winter and HP in the summer I suppose but then your payback period extends out so far that you'd have to replace the tank before you hit payback I'd guess.

    1. Expert Member
      Dana Dorsett | | #10

      >"What about the situation where you've got it in an electric baseboard heated basement though? (East coast of Canada)"
      >"It could be run in standard mode in the winter and HP in the summer I suppose but then your payback period extends out so far that you'd have to replace the tank before you hit payback I'd guess."

      There's no point to ever switching it over to standard mode. If it's cooling the basement in winter the baseboard pick up the slack only on an as-needed basement at the same efficiency as a resistance heating element in a heat pump water heater. Forcing it into resistance heating mode except in summer foregoes any potential marginal efficiency gains during the winter and shoulder seasons. Solar gains and heat entering the basement via the floor above can be bigger than you might think during the shoulder seasons.

      If the rest of the house is heated with something less expensive (like a wood stove), or more efficient (like a heat pump), ducting a basement heat pump water heater to take it's air & heat from some other part of the house is a viable option. The Rheem Performance Platinum series shown in the top picture of the article come set up for ducting, but several others are too.

      1. McAfee | | #30

        Good points. Ducting to extract heat from an area where you're producing cheaper heat (maybe a MSHP zone) is a good idea. Certainly would add to the cost but make it more appealing longer term.

        The UEF is undeniably good but because it's at the expense of the space heating equipment you already have (and its efficiency level) there's some uncertainty as to the level of savings you might achieve because it's dependent on your home.

        In the right situation it might be great (like a basement where you've got lots of excess heat and maybe some summer dampness). But you can't just look at the UEF in isolation. That complexity and challenge in determining payback is what makes it a tougher decision than it appears at first glance. I suspect that's what makes it a more challenging sell, particularly when it's an emergency situation where a heater is needed pronto.

        In a pretty good house, or Passive House it's a much easier decision but those are still unfortunately more niche build homes.

  4. user-723121 | | #4

    What is the life expectancy of a heat pump water heater? This must be part of the equation. I am only using 10 therms per month (5) therms per person for hot water. With natural gas at 60 cents per therm my annual water heating cost is $72.00. The heat pump water heater is likely a better fit for large families.

    1. user-626934 | | #5

      TBD...Mine at home is currently 9 years old. The technology is pretty well established....should be in the ~15year range that is already typical for water heaters.

      1. Expert Member
        KOHTA UENO | | #12

        Hey John! In case you [or other readers] don't already know, replacing the anode can extend the life of water heaters until other parts (e.g burner, compressor) wear out. The anode is the magnesium/aluminum rod that corrodes preferentially to protect the glass-coated steel tank. I have been doing this to multiple atmospheric gas tank water heaters--the one in my parents' basement has been going strong since the early 1990s (Long Island NY water quality).

        The anode type will depend on the model of the water heater--some of them have a powered anode that don't need replacement. And of course, stainless steel or polybutylene tanks don't need this protection.

        More on anodes here (and see pics below):

        I also put in a full-port ball valve flush setup and try to flush out sediment every 6 months or so: More important for gas burners (heat source is bottom of tank) versus electric or HP.

        Last but not least: mad props to Larry Weingarten for spreading this information! ( Thanks Larry!

        1. Expert Member
          MALCOLM TAYLOR | | #15

          It helps extend the life a lot but good luck getting it out of most heaters once it's time. The anode head is usually foamed in and buried quite deep. You need a 1 1/6'"socket and an extension bar for leverage. You need a helper too, as the empty tank will want to move. About one if four will simply not be removable without damage. A horrible task.

          1. Expert Member
            KOHTA UENO | | #17

            My personal experience for the half-dozen anode replacements that I've done: it's sometimes not bad, it's sometimes a total bear. And I am all-for-all in terms of removal. And I'm not some type of goliath--I'm a 5'3" short fat dude.

            The hex head anode heads are typically below the surface level, but they don't seem to actually bury them in foam. The annoying ones are when the use a "combination anode," where you have to unplumb the water heater to get it out (

            Agree that you need a 1-1/16" socket, breaker bar, and cheater pipe. I've done them with helpers, and I've done them without. The worst one required unthreading the T&P, threading in a piece of pipe for leverage into the socket, and levering between my body and the breaker bar.

          2. Expert Member
            MALCOLM TAYLOR | | #18


            The last two I did, made by GSW, had a small plastic cap on the top, which when removed had a smooth layer of foam you had to dig down through to get to the nut. OCD owners would do well to loosen and tighten that nut every year to make replacement a sure thing. I'm only 1 for 2 on those GSW ones.

          3. Jeremy_G | | #36

            I've replaced about 20 anodes in water heaters in a Michigan condo development that were about 10 years old. About half I could remove with an 18V impact driver. Another third needed a breaker bar and a couple needed a pneumatic impact wrench. There could be factors, like water chemistry, that are site specific. I've done a couple more in Maryland (15 and 5 year old tanks) and they were relatively easy.

  5. GBA Editor
    Sean Conta | | #6

    The most salient point here that I don't often consider is that 75-80% of people replace their hot water source in an emergency. Makes sense ... how do we get HPWHs in front of people at this moment?

    I recently went through this at my house - my old gas tankless died and I knew I wanted to replace it with a Sanden. The Sanden arrived in 1 day (I'm in Seattle, thank you Small Planet Supply) but I had to have electrician and plumber help to run a new electric circuit and piping to/from the outdoor unit. In the end it was about 6 days without hot water - not too bad really. Yes cold showers are very unpleasant, but 15 years from now when that Sanden is still quietly cranking out 150 degree water I've long forgotten those 6 days. And it's even possible my wife will have too!! :D

    1. GBA Editor
      Brian Pontolilo | | #7

      Hi Sean.

      That was a forehead slapper for me too. But it makes perfect sense.

      1. McAfee | | #8

        Mid-stream incentives can help with uptake. Many jurisdictions provide incentives to put in efficient equipment. Knowing that 75-80% of people buy them in an emergency, they need to be stocked so they're available to contractors and retail customers when that emergency strikes.

        A distributor who sells wholesale and retail can serve the contractor market and the keen retail consumer. Being able to sell it with the incentive built in so there's minimal paperwork and delays lowers some barriers. Make it easy!

        1. albertrooks | | #19

          Dan, I like the idea of being able to sell with the incentive built in. Small Planet Supply serves plenty of contractors and homeowners. Being able to process the local utility rebate would be really helpful for all in the process. I'm making a mental note to discuss this with NEEA.

          1. McAfee | | #29

            Good luck!

  6. Expert Member
    RICHARD EVANS | | #9

    I have a Rheem heat pump hot water and really like it. It can be controlled remotely using an app on your phone. The app also shows you how many kWh the water heater is using.

    Not sure what the national (US) average kWH usage is for a family of 2... But so far, we are averaging about 42 kwH per month. at $.19 per kWh, that is less that $100 per year. We have a large Drain Water Heat Recovery Device as well that 'warms up' the cold well water some.

    The de-humidification aspect has been nice as our new home drys out from its construction phase. The heat pump hot water generates about 4-5 gallons a week. (I'm on bucket duty)

  7. kyeser | | #11

    How noisy are the heat pump water heaters? If I install one in my basement, am I going to hear it upstairs? If we end up finishing the basement and decide to stick this in an appropriate sized area, will I hear it in the rest of the basement?

    1. user-2310254 | | #13


      I have a Rheem HPWH installed in the garage. It is not particularly noisy (and only runs for a short time once or twice a day in our two-person household). If you put it in an appropriately size closed off room with insulated walls, you may notice a low hum when it is on.

    2. GBA Editor
      Deleted | | #14


    3. ERIC WHETZEL | | #16

      Our Rheem HPWH is in our mostly unfinished basement. Although open to most of the basement, the noise has never been bothersome. I'd say it's comparable to the noises coming from your fridge.

      At first you notice every time it cycles on, but after a few days, or a couple of weeks, it just becomes background noise you tend to ignore (at least for us).

      I was worried about the noise, prior to installation, based on some online reviews that suggested the noise was really annoying. I think it comes down to individual tolerance and your expectations. If you know someone who has one, it's definitely worth checking out. You won't know for sure if the noise will annoy you until you hear it in person.

    4. GBA Editor
      Sean Conta | | #20

      I just installed a new Rheem Prestige for a client build and it's really very quiet. Just a soft compressor hum. This is a 700 sq ft backyard cottage and it's in a closet off one of the bedrooms. It's hardly noticeable in that bedroom with the closet door closed and if you're in the main space you can't hear it at all. It is ducted in & out which probably helps a bit with noise i would think.

  8. john_heckendorn | | #21

    @Scott Gibson, nice overview of the current state of water heating options. I did have to chuckle at this, though:

    "'It’s been a hard nut to crack,' Miles said."

    No duh. That $3500 price quoted for the smallest Sanden solution grossly underestimates the total cost of purchase and installation, which can run to $10,000, at least in my part of California, based on anecdotal evidence and quotes that I've received. This pushes any ROI out to eternity, pretty much, compared with saner alternatives. And the pool of technical experts capable of troubleshooting and/or fixing the thing is probably miniscule, which adds risk to the equation.

    I'd love to have a Sanden -- or one of its Eco Cute competitors, of which there are none in the United States. Maybe that's why it's so extremely uncompetitive in our market.

    1. albertrooks | | #22

      @John Heckendorn, That might be a heavy brush to paint the situation in California. There are utility rebates I think (I'm in Vancouver BC), or coming soon. The instal depends on a few factors such as power etc. I've not heard of any $10k DHW instals yet, but plenty of $1500 if power is near. It can be admittedly problematic since it's still very new to installers. There is no troubleshooting to do on the service end. The compressor is factory sealed and the repair is to swap a new unit. I'm around most of the oldest systems in North America from the NEEA trials. The early problems came from when we heated homes with it as a combi. Those have been worked out and its a mostly maytag repairman experience (sleepy).

      Nowdays we are ganging 3-6 of the heat pumps together to make a central plant feeding 400-800 gallons of storage serving anywhere from 24 to 100 living units (with 2 or more baths). The measured annual COP in the northwest has been well above 3. Just in time for electrification.

      The thing I like about them in California is that they will produce and store a full days DHW on 4-6 hours of production. If you've got 1200 watts from PV, then its free site energy turned into DHW at a COP of 3.5 to 4.5ish depending on daytime ambients. An uphill climb for sure, but the view from the top is pretty good.

      1. john_heckendorn | | #23

        Without going into excruciating detail, there's an order of magnitude difference between the fully loaded cost of a Sanden vs. a Rheem HPWH (at least here in California), and relatively little difference between the two in energy efficiency or savings. In principle, I'd much prefer a CO2 split system, but as a practical matter, it just doesn't make sense.

        Oh, and monetary incentives for HPWHs -- at least in my part of the state -- are almost not worth the time it takes to do the paperwork. Laughably low. I exaggerate a bit, but I do believe the administrative overhead costs a lot more than the rebate.

        1. Expert Member
          Michael Maines | | #24

          We have a Sanden unit on a project I designed here in Maine. I'm not privy to the installed cost but the entire job was on a super tight budget and the owner said installation "wasn't bad," and that he'd do it again. I'm sure it was nowhere near $10K. This would be a good thread in which to go into excruciating detail. Aside from having to dig and insulate a trench to the outdoor unit, I don't see where the additional cost would be, beyond the initial unit cost. I believe the COP on Sanden units is about 5, which is significantly better than the 3 or so of other heat pump water heaters. They still don't pencil out well on ROI but I don't see how the cost could possibly be $10K unless it's all taxes and fees.

          1. john_heckendorn | | #25

            I'll see if I can provide a breakdown on an estimate I received recently. BTW, this included the 83 gal. tank, which pushes the price up a little over their smallest unit.

            If memory serves, Rheem's COP tops out at 3.77. Interestingly, I saw some literature suggesting that Sanden and Rheem (or their parent) have a working partnership of some kind in Oceania, which makes me wonder if there's a global deal in the works.

          2. albertrooks | | #26

            Yes, I hear that it can range from simple to more complicated. The additional cost is replacing a on demand gas unit since Power has to be run. SMUD (Sacramento utility) has been trying to give away $2500 as a rebate with few takers. Rebates are still a clunky delivery to incentivize consumers. We can get $1000 to $2000 here in Vancouver, but the average consumer has a hard time understanding how to work it through. There are none in the southern California at the moment I think. The California Utility Commission is planning to release something pretty significant soon. The drumbeat has been steady. It's the high COP that's attractive to them certainly, but it's also the ability to load shift that will drive it. A simple method to store energy from daytime PV production through evening peaks is a big step in flattening that duck curve. Depending on where you are in California, you do get some winter ambients which can take the high 5 COPs down a bit. I like to look at an annualized COP which is location based.

            The cost delta between a unitary and a slit Co2 system is certainly real. It's one of those cases where the benefits are split over both the consumer and society. the unit cost delta between the two is roughly $1500 to $2000, and then a bit more in labour. However the global benefit (consumer + society) is really significant: The additional first cost investment yields a significantly higher annualized COP, the high unit capacity yields better renewable use, High storage temperature (150f) offers ability to 24 hour load shift, refrigerant GWP of 1 instead of > 2000, longer installed life, no use on internal conditioned energy. No need for electric resistance (hybrid) in high use or cold ambients. Its a pretty cool tool.

            The consumer only has visibility to the installed cost vs their local conditions (PV offsets, Electrical bill, available rebates). The additional global justifications are hard to see for the average person. Hopefully the "unleashing" of electrification will create the opportunity for utilities to balance out the benefits & investment with the consumer into a simple well communicated drive towards good clean "site based" energy efficiency choices in California and elsewhere.

          3. Expert Member
            Dana Dorsett | | #28

            >"I believe the COP on Sanden units is about 5, which is significantly better than the 3 or so of other heat pump water heaters. "

            The instantaneous COP at some fixed set of water temperature parameters isn't a good measure of it's average performance in-situ.

            The published UEF for the SAN-43SSAQA is 3.09...

            ...and 4.10 for the SAN-83SSAQA. See page 34:


            But even a UEF of 3.09 it can still outperform a higher-UEF Rheem on a whole house net energy use point of view in a heating dominated climate, since none of the heat is being drawn from condition space.

          4. john_heckendorn | | #33

            "But even a UEF of 3.09 it can still outperform a higher-UEF Rheem on a whole house net energy use point of view in a heating dominated climate, since none of the heat is being drawn from condition space."

            But the Rheem can be ducted so as not to use any heat from the house's conditioned space (or can be put in a garage). IMHO, that flexibility makes it stand out from the other single-unit HPWHs out there.

          5. john_heckendorn | | #42

            In round numbers, here's a breakdown of the fully loaded Sanden cost I was quoted (note: this is for the model with the 83 gal tank, which was recommended to mitigate recovery time):

            Compressor and storage tank: $4300 (believe this includes shipping from the distributor)
            Tax: $400
            Permit: $200
            Miscellaneous materials: $600
            Labor: $2400
            Company margin: $1800
            Gov/utility rebate for this unit: NONE AVAILABLE

            Why is margin broken out? Because the HVAC company is being transparent about needing to cover their overall high cost of doing business in California. Most companies here would have obscured this by jacking up labor to >$4000, which has been our experience with other building trades.

            The reason no rebate applies is because the storage tank is >55 gal. If it had been under that, there'd be a $300 rebate (big whoop) before EOY. Given that this is PG&E territory, we have to consider the chances of rebates/incentives for anything efficiency-related next year to be a long shot at best.

          6. albertrooks | | #48

            #28 - @Dana Dorset - >"I believe the COP on Sanden units is about 5, which is significantly better than the 3 or so of other heat pump water heaters. "

            The instantaneous COP at some fixed set of water temperature parameters isn't a good measure of it's average performance in-situ.

            The published UEF for the SAN-43SSAQA is 3.09...

            ...and 4.10 for the SAN-83SSAQA. See page 34:

            I Agree. While I love seeing that 5 COP, it can be misleading and climate variable. The UEF is a klunky measure too. While it will do a same condition side by side comparison, it leaves out how the unit can fit into the context of the project. We've got units in the north working in very cold ambients. Hybrids would have a hard time to operate in those conditions. See the single page from a utility study. It's not a published document,ent so I removed the utility and comparative unit info. Notice the dot diameter relates to flow. The higher the flow, the better the efficiency. UEF doesn't capture this or other site specific and occupancy variables. The flip side is the warm California conditions and what can be done with capacity and load shifting.

      2. user-723121 | | #27

        Greetings Albert,

        I appreciate your thoughtful information on HPWH. In the Mediterranean climate in which you live, could a very energy efficient home get domestic hot water and space heating form a HPWH? If so, the total cost of mechanical equipment might make the HPWH the way to go. With hydro electricity I would be interested in the numbers.

        1. albertrooks | | #47

          Hi Doug,
          Yes, I've got a home in Olympia WA that is heated entirely by a Sanden HPWH. The load on the house is 12kbtu/hr at 23f. According to Washington State University, the annual energy factor is above 3. The EF is an expression of annual COP that includes all pump energy. The system uses a Taco X Block to supply high temp radiators. This is a common system for us.

  9. gary__b | | #31

    Over the next 2 years, I'm planning to do a fairly extensive remodel/addition on our house and make as many energy efficiency upgrades as reasonably practical. I'm in Portland, OR (Marine 4), with a currently leaky and cold unfinished basement. Part of the process will include air-sealing and insulating the basement, which will remain unfinished, and the living space will get mini-split heating/cooling in place of the current oil furnace.
    How should I factor an HPWH into my plans? This is similar to Dan's thread above, but I'm thinking bigger picture--I have a fairly clean slate to work with house-wide. I'd prefer it to stay in the basement. Obviously the "free" cooling in the warmer months is great, but I don't love the idea during the 6 warming months. Are there practical measures to make the most of the efficiency? E.g., Can it be switched between ducted outside versus unducted? Would insulating between the basement and main floor make sense (a frozen basement isn't really a problem here)? Would moving it into finished space make more sense? Thanks.

    1. Expert Member
      Dana Dorsett | | #32

      >"Are there practical measures to make the most of the efficiency? E.g., Can it be switched between ducted outside versus unducted? Would insulating between the basement and main floor make sense (a frozen basement isn't really a problem here)? Would moving it into finished space make more sense? "

      Leave it in the basement, air seal and insulate the basement walls, NOT at the basement ceiling (which would have almost no effect on heating use or comfort.) In most homes an un-ducted HPWH in the basement won't drop the basement temperature by more than a degree or so, winter or summer. Ducting it to the outdoors in winter would lower the efficiency of the HPWH.

      How big is the basement?

      How many occupants?

      Tub bathers, or showerers?

      1. gary__b | | #34

        1 degree? Very interesting, I appreciate that reality check. I was imagining a pretty big impact. Basement is about 1000 sf, 7 ft tall. 4 occupants (2+2), children tubbers, adults showerers.

        1. Expert Member
          Dana Dorsett | | #37

          >"1 degree? Very interesting, I appreciate that reality check. I was imagining a pretty big impact. Basement is about 1000 sf, 7 ft tall. 4 occupants (2+2), children tubbers, adults showerers."

          Most HPWHs don't need more than 750 cubic feet of room to work without ducting it- you have a full order of magnitude more than that.

          For yuks let's make a rough model of it:

          If the incoming water is 40F, and the tub fills are 35 gallons (290lbs) of 110F water each, that's a delta-T of 70F x 290lbs x 2= ~40,000 BTU for the tubbers.

          A pair of 8 minute (US average) 2 gpm showers is 32 gallons (267lbs) 0f 105F water, a 65F delta-T x 267lbs= 17,355 BTU for the showers.

          The other hot water uses will be swamped by those numbers (the error bars on the tub fill volume could be about as big.)

          Call it ~57,400 BTU total. Only 2/3 of that is coming from the basement air, or (x 0.67=) 38,500 BTU per day, or (/24=) 1604 BTU/hr of additional heat load (average) for the basement.

          Even if all the additional heat was being supplied by heat radiating from the 1000' of basement ceiling that's 1604 BTU/1000= 1.6 BTU/hr per square foot, which would be achieved with about a 1.5F drop in basement temperature.

          Of course that's the average temperature drop over the 24 hours- there could be a shorter term drop of a bit more than 2F right after a fully depleted tank had fully recovered, but that's the ballpark you're looking at. Adding complexity to the model, as the basement temperature drops a degree the basement heat losses to the outdoors & soil also drop, so the 1.5-2 degrees is more likely to be an overstatement. Should the basement air temp drop below the slab temperature (if that happens, probably won't) the slab itself will be sourcing some of the heat.

  10. kdelucas | | #35

    Hi @Scott Gibson,
    I was wondering in your research if you found a good option for a 400 SF cottage? I am working on a project of 22 cottages that will house formerly homeless individuals and families and looking for a cost effective and energy efficient option. The project will be all electric and located in Seattle.
    Thank you! This was a very informative article.

  11. chimewind | | #38

    One thing to note about the Sanden is that you have to keep the water lines connected to the heat pump from freezing. Since the heat pump is located outside there is risk of them freezing in cold climates.. This is why even in the Sanden manual it states you have to install electric heat tape to make sure the pipes don't freeze. I'm assuming that is not being taken into account with how efficient they are.

    1. john_heckendorn | | #45

      Yes, and therefore one has to think holistically about electrical power resiliency. A grid outage at the wrong time without an alternative source could mean you not only lose the capability to heat water, but might also critically damage the compressor feed lines.

    2. hudson_valley_gregg | | #49

      Yes - pretty pathetic that the solution is not simply baked into the Sanden kit in the first place. I've got one in Beacon, NY. Had a few hiccups during installation, and the local plumber fought me tooth and nail on it - he was so firm that I just go with his "American Boiler" unit that he slots for all of his other customers. One note: The Sanden rep I got on the phone when I needed to replace a part was VERY helpful.

  12. DB_Seattle | | #39

    We recently had an energy audit performed (we live in Seattle), and even though we have natural gas servicing our current water heater, the energy consultant suggest we convert to an electric heat pump water heater since our electricity comes primarily from hydro electric (hence, less GHG emission). Do you or anyone else have any thoughts on this? My only hesitation about electric is the loss of water heat in case of power outage...

    1. bje11 | | #43

      The advice you got is the right advice, IMHO.

      It would have to be a multi-day outage for you to run out of hot water (and, of course, if you knew the outage was a likely to be that long, you would drastically reduce your hot water usage to avoid running out). After that, I'd be visiting a friend or local gym to use their showers.

    2. john_heckendorn | | #46

      If you will continue to have a reliable source of natural gas, you could consider installing a standby generator, which would help you during an extended outage, especially if you have other critical powered devices in your home. You'd have to run the numbers to size it properly, but it could replenish some of your hot water if necessary. These days -- unless your utility's rebates make 10-20 KWH of battery backup nearly free -- that will probably be the least expensive alternative. You'll need to think of the cost as insurance.

  13. lutro | | #40

    In this article, and many others, it's very hard to get a sense of relative costs, in part because of all the variables. Not mentioned here was a comparison of the cost of a heat pump water heater to a standard resistance electric water heater and additional solar PV panels to make up the difference in efficiency. Not everyone has room for additional solar panels, but if the additional panels cost less than the heat pump, then that might be a good choice for some people. If the numbers are favorable to this option, then the efficiency difference isn't the factor that it seems to be in this article. [Greetings and thanks to David Bainbridge, comment #38].

  14. lutro | | #41

    I question the bold section header, 'Condensing gas models are best, for now', in the context of a Green Building Advisor article. Cheapest, perhaps, but in support of Dan B's commnet # 39, the bold heading ought to be, 'Avoiding or limiting fossil fuel use is critical to our future, and should be considered ahead of modest cost savings.'

  15. nickdefabrizio | | #44

    Ha, I spent last night installing an AO Smith 50 gallon HPWH that I got for $600 at Lowes as a return (they swear it was fine but we will see). The $750 rebate from NJ will cover the cost and some of the piping materials. I plan to use it from April through October, and it will replace the dehumidifier I now run so that adds to the energy saving. In winter my Energy Kinetics boiler is hard to beat for hot water. Solar panels are going in this winter so this will dovetail nicely. Without the rebates and need for dehumidification I might have gone with a simple electric WH with two more PV panels. I have had multiple mini splits but I always worry that heat pumps are too fragile and finicky and there is something to be said about systems that have no or few moving parts.

    I love the quote above about old plumbers. Mine is 86 yrs old and still working. He is a friend who will be coming to Thanksgiving dinner today. Wait till I tell him I am installing the heat pump WH. He will first inspect my solder joints and tell me how sloppy they are. He will then remind me that my old boiler lasted 40 years and reliably produced heat and hot water with only one break down in that time period. And it was made in America. I will not disputed any of this and it is something to think about as we rely on complicated technology to solve a global crises. America owes a lot to guys like this who were able to make a good living with a high school education and hard work.

  16. ColbyForester | | #50

    I am currently building a house and it will have Propane gas installed in the house. Would a Tankless Condensing Propane water heater have a better payback than a Electric Heat Pump unit? I know price of propane and energy play a role but with just using average pricing for both. I live in Alabama so I guess you would consider a little energy savings with the area cooling and dehumidification as well.

    1. Expert Member
      Dana Dorsett | | #51

      Colby "...just using average pricing..." varies by quite a LOT from market to market, and with propane the prices can also vary based on how much you use, and whether you own the tank vs. the propane supplier owns the tank.

      In AL the latent-cooling benefits of the HPWH may make it almost a no-brainer from a comfort point of view and should be considered even if it costs a bit more, since it's humid enough in the shoulder seasons to have a latent load even when there is no sensible cooling load to speak of.

      The financial breakdown looks like this:

      Currently the EIA is pegging Alabama retail electricity at about 13 cents/kwh:

      With a UEF of 3.0 the HPWH puts 3 kwh or (x 3412 BTU/kwh =) 10, 236 BTU of heat into the water for every kwh used. Normalizing to million BTU (MMBTU) that takes (1,000,000/10,236=) ~98 kwh, which at 13 cents/kwh comes to $12.75/MMBTU.

      Residential retail propane is running about $2.35/gallon right now:

      A gallon of propane has 91,600 BTU source fuel, which at a UEF of 0.93 in a condensing propane tankless delivers ( 91,600 x 0.93=) ~85,200 BTU/gallon to the water. Normalizing to MMBTU that's (1,000,000 / 85,200= ) 11.74 gallons/MMBTU. At $2.35/gallon that's ~$27.60 /MMBTU, and that's not counting the electricity used by the tankless.

      So the fossil-burner would cost MORE THAN TWICE as much to heat the water than an HPWH at "...average pricing..." in Alabama.

      If you're using propane for space heating rather than a right sized heat pump the energy use numbers break down pretty much the same way- it's going to be WAY more expensive to heat the house with propane than with a heat pump. Unless you have some other application driving the decision to install propane, you're probably better off going all-electric and foregoing the cost of any propane plumbing, tanks, etc.

      1. DavidSilva | | #52

        Thanks Dana. I had a similar question for Massachusetts which I’d assume is more expensive than Alabama. Looks like $2.89 on average for propane vs 22 cents / kWh. If I’m following the formulas above correctly, this results in $33.93/mmbtu for propane vs $21.56/mmbtu for hpwh. Sounds like hpwh wins even if I don’t go solar. We’d also have to consider that 80 gallon hpwh is $2k vs 75 gallon propane is $1k. I’d have to do the math to see how long the payback for my family’s water habits would be at a $1000 premium.

  17. nickdefabrizio | | #53

    I have just installed a 50 gallon AO Smith HPHWH. So far it seems like it is doing the job....It is winter here so the air is dry. I haven’t seen the unit producing much in the way of condensation and it does not really reduce the temperature much. It will be interesting how this performs from an energy usage standpoint. It is also easy to switch to full electric mode if needed but I have not needed to do this yet. Of course there is only two of us and we conserve water by using a low flow shower head (something I recommend for everyone to save both water and energy).....

  18. user-7665154 | | #54

    I've been getting quotes on installing a HPWH by Rheem or Ruud. (That would get rid of my last fossil fuel system-a Buderus indirect with heating oil) since we're already on geothermal heating/cooling and solar PV. The quotes I've gotten are higher than expected -- around $4000-$4250.

    I see the Home Depot version of the 80 gal Rheem Prestige for $1699. I've done contracting/construction in the past, so I can do a little bit of many trades, and don't know why the labor for installation would be $2300 for a day's work. One factor could be that my quotes are for the trade version—the Professional model. So let's say then that brings it down to $2000 for installation.

    The electrical is nothing, and from what I can see, I just need to swap out the incoming and outlet lines, cap off the current line from the boiler and put in the condensate lines/drain. I'll change the expansion tank too. I'm happy to pay well for work done, but for $2K, I’m strongly considering doing the installation myself (with a helper).

    Two questions:

    1. Any reason why you would recommend against doing this installation myself (with a helper)? Very, very tempted.

    2. Any idea if the Professional (trade) model is better than the Home Depot version? (Interestingly, the HD model got 4.5 stars on the HD website, while Professional model got horrible reviews on the Rheem site:

    By the way, I really appreciate all the comments above and on this site. You guys are a very clear-thinking, helpful bunch. Impressive site. Thanks!

    1. rondeaunotrondo | | #55

      Also considering these questions. Hopefully someone answers!

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