Heat pump water heaters–an interesting choice, but not a one-size-fits-all solution

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An evolving water-heater technology has been moving more mainstream over the past couple of years.  This technology uses a heat pump (think air-conditioner working in reverse), to heat the water.  I’ll focus on GE’s GeoSpring Hybrid water heater for discussion purposes.

GE's "hybrid" water heater

The good news is that this technology is ready to roll.  Heat Pump Water Heaters (HPWH) can be twice as efficient as a standard electric resistance water heater, and that increased efficiency can add up to big savings over time.  This can be a great choice for many homeowners.

It’s not for everyone, however.  In most cases, if you heat you water with natural gas, it won’t make sense to switch to the heat pump.  This does depend on things like the gas and electric utility rates, usage patterns, and climate.

The GE model is only available in a 50-gal tank, and it won’t provide either the capacity nor the efficiency benefits for high-usage situations.  The heat pump is more efficient, but it takes long to recover—that is it takes longer to make the water hot.  To compensate for this there is a standard heating element that you can use to speed things up in “high demand” situations.  In fact, you can set it to standard mode and it will function just like a regular electric resistance heater.  However, the more you heat water using the electric element instead of the heat pump, the less you save.

Because of the compressor and fan, a heat pump water heat does make some noise while it’s running—about the same as a full-size microwave.  Since water heaters are often in basements, garages, or otherwise isolated from the living space, this may not be an issue.  But it’s something to be aware of.

In simple terms, the heat pump uses heat from the air and transfers it to the water.  A secondary effect is that it cools the air around it.  This is actually a nice side benefit in cooling climates.  However, in colder climates where you’re paying to heat your home for much of the year, in some sense you’re robbing Peter to pay Paul, and I don’t think this technology makes sense in the northern U.S., snow country.  In the north, where inlet water temps (the temperature of the water is it hits your home from the city lines or your well) can be quite cold, you’ll also be in the “high demand” mode much of the time, again, reducing your savings.

Height can also be issue, and this won’t fit in some shorter crawlspace where a “low-boy” water heater is needed.

Bottom line:  A HPWH can be good choice in cooling climates where you heat your water with electricity—especially where electric rates are high.  Not the best choice if you already heat with gas or see snow for half the year.

Thanks,
Mike

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3 Responses to “Heat pump water heaters–an interesting choice, but not a one-size-fits-all solution”

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