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I've recently purchased a home that has two hot water heaters - one at each end of the house. One in the garage, one in a closet. They're both showing their age, and both cost quite a bit to operate. My goal of this change is to make sure I have equipment that's not on the verge of failure, while also making sure that my energy usage is as efficient as is practical.

What comes to mind as an option is to replace the one in the garage with a heat pump/hybrid water heater (something like this), and run a recirculation pump to the other end of the house, removing the existing second hot water heater entirely.

Does this seem practical, or should I consider something else?

I'm in Florida; do not have a gas hookup; I have grid-tied solar @ 12KwH.

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    It's practical for sure, but it may be less efficient unless your recirculation loop is very well insulated. Very likely the reason they went with two heaters instead of a recirculation loop in the original design is that it provides hot water quickly at either end of the house, without the heat loss that typical recirculation loops cause. But since you're changing from resistance heat to a heat pump, you'll probably still come out ahead on efficiency, but possibly not as much as you would have by replacing both current heaters with heat pumps of the same size.
    – Nate S.
    Feb 4, 2021 at 18:51
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    How large is your house? I'm in Florida too and have worked/replaced water heaters in homes that have two, very similar to your layout. One in the kitchen/garage/utility area and one at the other end where the bathrooms and bedrooms are located. Wasteful to send the hot water to the other end of the house... This way, the heaters are set at different levels: kitchen one really hot and bathroom one not so hot.
    – JACK
    Feb 4, 2021 at 18:56
  • I thought your concern was efficiency. A recirc system is laughably inefficient, greatly increasing the surface area (and downgrading the insulation value) of the hot water tank. New hot water heaters are insanely insulated, to the point where they warn you that new heaters will not fit where old ones were. Seems like you'll have the worst of both worlds, a bunch of extra piping (you WILL run a new return loop for the recirc, right? Right?), an expensive, complex water heater, and all those insulation losses from the recirc loop, which you can't possibly insulate as well as heaters are.
    – Harper - Reinstate Monica
    Feb 4, 2021 at 21:48
  • @Harper-ReinstateMonica, yes, re-circ does waste some energy, both from heat loss in the plumbing and electricity running the pump. There are extremely efficient pumps so electricity usage is probably not a consideration. On the flip side, there is water consumption...having to leave the hot water tap running for a long time waiting for it to get hot wastes a lot water, depending upon the bill rates for water, that should be considered. Besides, it's not always about saving money/energy, sometimes you just want thing "nice". I have hot water within 3 seconds of every sink in my house....NICE.
    – George Anderson
    Feb 4, 2021 at 23:01
  • @Harper-ReinstateMonica And what do you mean about a "expensive complex water heater"? Recirc doesn't require that. You just run the recirc line from the point furthest from the WH and pipe it in with the cold inlet pipe. It works best if the plumbing was originally designed for recirc, but it still helps out in conventional tree layouts. The OP would want to run the recirc line to the place that's most important to him/her, probably the master bathroom. And it saves water.
    – George Anderson
    Feb 4, 2021 at 23:07

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Not quite sure what you mean by "showing their age": electric water heaters either leak or don't leak and work or don't work (mostly). Predicting time of failure is difficult. I have a rental house that has an 80 gallon electric water heater that's probably about 40 years old and working fine. Others I've had to replace after 15 years.

But getting to your question, yes, consolidating 2 water heaters into one is a good idea and presumably you'd put the new one in the garage, freeing up closet space in the house.

Bear in mind that a heat-pump style water heater will COOL the space it's installed bc it pulls heat from the air. In FL that may be a good thing! Not so much in the north.

You'll have to do some additional plumbing to install the re-circ pump, depending upon your exact plumbing layout.

You might also want to consider a timer on the re-circ pump. I have re-circ and a timer in my house and set it so it doesn't run between 11:00 PM and 6:00 AM.

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  • The only maintenance item is the sacrificial anti-corrosion anode. Its rate of consumption will vary with water quality.
    – Harper - Reinstate Monica
    Feb 4, 2021 at 21:45
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Given you are in a "primary cooling" climate, you might want the HPWH inside the building for additional "free" cooling. You could set up an exhaust vent for the non-cooling-season to dump the cold air outside when you don't want it. If you choose the garage and the garage location allows, dump the cold air on your a/c condensor in cooling season (but redirect that in heating season if it's a heat pump)

A long recirculation loop can be a big heat waster - insulate it very, very well, and consider using either a timed or motion-sensor activated pump rather than continuous or thermostat only recirculation.

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