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Innovative Water Heater: The Magic of Heat Pumps

By Clark Williams-Derry

This is promising:  Ecogeek reports on a new GE water heater that could cut energy consumption in half.  The trick:  it uses a heat pump to preheat the water coming into the tank.

I've waxed rhapsodic about the magic of heat pumps before. Start with a glass of lukewarm water, and a heat pump can turn it into a half glass of warm water, and a half glass of cold water, in a process that takes less energy than warming up a half cup of water on a stove top.  If done right, heating your home with a heat pump -- particularly one that draws heat from water that's circulated underground -- can be more climate-friendly than even the most efficient gas furnace.  So this new heater is really just an application of a tried-and-true technology, but in a slightly new way.

The heater isn't commercially available yet, but the announcement coincided with the release of new  Energy Star ratings for hot water heaters.  (Both press releases were dated April 1, but I don't think anyone's pulling my leg here...)  Obviously, it's a little premature to rave about a technology that's not even available in stores yet.  After all, nobody knows whether the technology will pan out, or whether any increased sales cost will be worth the energy savings. 

Still, the announcement is a useful reminder:  there are loads of efficiency opportunities left out there, and we don't have to wait for radically new technologies to capitalize on them.  Heat pumps, have been around since the days of Lord Kelvin; and household water heaters consume more electricity than home lighting. Still, it's taken over 150 years to put the two needs together. 

If I had to guess, there are plenty of similar opportunities out there -- energy-saving technologies that are perfectly obvious, and are just crying out for a little bit of capital and engineering muscle.  (For instance:  why doesn't my fridge connect to the outside world?  In wintertime, there's plenty of cold air for free, just outside my window.  In summertime, the hot air from the fridge's air pump gets recirculated into my already-overheated house.  Seems like a problem looking for a solution.  Any takers?)

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Or, why not connect the refrigerator to that hot water heater? Why do we send all the dryer exhaust outside in the winter when we could be heating and humidifying our house? Why isn't our oven/stove a heat pump so it doesn't heat up our house so much in the summer? Come to think of it, ditto for the dryer. I think the real trick to getting things like this to work is to come up for a standard for in-home heat exchange that works between appliances and the climate control system and ducts to the outside world and the water system, and making sure it's all insulated well enough to be efficient. Then changing the way we build houses to incorporate such systems.

Posted by: Eric L on 8 Apr 08

"I've waxed rhapsodic about the magic of heat pumps before."

The links in this sentence both return Not Found.

Posted by: Anne Onimos on 8 Apr 08

Real-world, on-the-ground assessments of ground-source heat pumps aren't showing performance as claimed. On the other hand, there are promising, high-efficiency, ductless, air-source heat pumps now in common use in Asia, Europe and Canada - but not the U.S. yet. If you push efficiency to levels it really ought to go - with Passivhaus ideas from Germany being one example (look it up) - then handling the micro-loads with these little ductless heat pumps makes a whole lot of sense. In my climate, (New England), really well-built houses could be carbon neutral with simple heat pumps and about 3 kilowatts of photovoltaics.

Posted by: David Foley on 9 Apr 08

I'm with Eric L. - like a great Greywater system that re-purposes water all over the house, it seems like there are still many advancements to make in leveraging temperature differentials for various purposes. That's why I love solar water heaters so's tough to argue with the logic of trying to capture this energy that's pounding down on your roof (and will continue to do so for the very foreseeable future) and make it useful. We'll be keeping track of this and other water heater advancements here:

Posted by: Dan Gill on 10 Apr 08

The Enviro-Pak from Turbotec is a retrofit device that uses the waste heat from an air conditioner to heat water.

Posted by: Steven Hult on 12 Apr 08

Hi Clark. Thanks for the article. BTW, our home is the second in WA state to use the super-efficient, zero-emission Hallowell All-climate heat pump. Unlike most HP's where performance & efficiencies are limited to 35F +/- (lower temps then require use of supplemental heat source--often a 10kw heat strip or gas), our Hallowell is designed for continuous performance to -30F! Perfect for cold-climates. Within our all-electric home (albeit energy-starred and harvesting 260w of solar PV for computers, A/V, lights, etc.), we have cut our monthly elec. bill to the tune of 50% or so. He hope to prototype their HP hot water heating unit in coming months. For more info., readers can go to website: or email me. :)

Posted by: Jonathan Scherch on 12 Apr 08

about Alex Steffen's comment. sure, you could produce an entire system of gadgets and gizmos to recycle the energy and reduce the entrophy. you can have an expansive ecosystem of machines to manage your energy consumption for you. but why do that when the ecosystem already in place does it just fine?

Posted by: justin on 13 Apr 08



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