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Community and Q&A

Heat Pump Versus Electric Water Heater

dvogel1 | Posted in Energy Efficiency and Durability on

I am designing a 2 story house for Asheville, NC. There will be a large, sealed, insulated and conditioned crawl space.

Because the plumbing fixtures are far apart I am considering 2 small hot water heaters. One adjacent to two showers and a second adjacent to the kitchen sink and dishwasher. I have selected 50 gal Rheem Marathon electric units.

An alternative is to install heat pump water heaters in the crawl space. They cannot be placed in the living space, however they can be placed directly below the fixtures. They would require much longer piping. In either case the piping would be well insulated.

I am wondering if the heat pumps have a significant enough efficiency advantage to overcome the additional pluming.

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  1. paul_wiedefeld | | #1

    The heat pump water heaters will use about 1/4 as much energy, so 75% less. You can also mix and match based on projected fixture usage.

  2. johngfc | | #2

    You might also consider an on-demand or automated (e.g. movement-sensing) circulation pump. If you don't need the capacity of both HWHs, this could be less expensive and perhaps more energy-efficient solution.

  3. ericpanderson | | #3

    Be careful with the existing Gen 5 Rheem HPWH. There are some extensive posts there about them being very noisy. I have the Gen 4, which I love and is very quiet, but the next gen after mine are very noisy evidently.

  4. walta100 | | #4

    Remember the heater serving the kitchen only needs to be a few gallons as the flow rate for modern faucets is very small and dishwashers are also low volumes users especially if the large heater is feeding the small one hot water.


  5. Expert Member
    Dana Dorsett | | #5

    If the crawl space is tall enough to accommodate a heat pump water heater, that it the clear winner. Most are pretty tall. Not only will an HPWH use dramatically less energy to heat the water, it will also substantially help dehumidify the crawl space. (Does anybody make a lowboy HPWH, other than the shorter-fatter tank options on a $anden $plit $ystem water heater?)

    From an energy use point of view, a demand-actuated hot water circulation system would in most cases be a better (and probably cheaper up front) solution than multiple local small water heaters. With a pump driving the initial flow to the active tap hot water arrives very quickly.

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