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Tanklets > Heat-Pump Water Heaters

Q: Does anyone have any experience with HPHW's like the Airtap, Wattersaver, E-Tech, etc? They seem like a great concept. Any feedback on fan noise? Venting? Recovery?

A: Hello: I think I'd look for a good warranty with a solid company. Heat pump heaters have come and gone over and over. It seems to be hard to make a reliable, simple unit. Water and time conspire to do in HPWHs :? I'd keep my eye on the technology, but install things to make the hot water system more efficient. Structured plumbing, insulation, demand control, shower heat exchanger, tempering tank, solar, low flow fixtures... all can help with energy and sometimes water savings. -- Larry (9/4/08)

A1: No experience but I have looked into E-tech. They used to have two residential units. They stopped production on one of them, reengineered and came back with two: the R106H and R060 models. Most of us are looking at ROI or payback time. The higher the cost of electricity and the higher the average temperature the shorter the payback time. The COP ratings on the two units are 3.3 and 3.4.

This means you get 3.3 times as much heat/kWh as a resistance heating WH. Also, the units can replace a small amount of air conditioning. The R106H delivers 12,500 BTU/hr into HW and strips 8800 BTU/hr from the air. The R060 numbers are 5900 BTU/hr and 4100 BTU/hr respectively. But since I pay only $0.047/kWh to heat water I haven't yet bought. I had considered ducting the discharge of the units into the suction side of my air handler and set an additional relay to turn on the air handler fan whenever the heat pump is running to produce HW. This would distribute the cool dehumidified air. -- David (9/5/08)

Q2: I installed two E-tech add on heat pump units last year -- one in the basement of an older apartment building and one in my "green" home.

Do they work? Yes. A great savings in energy costs. Please see note below about placement -- they really are NOT for every application.

Do they last well? The night is young, with just over a year of use, and we will see in the future about longevity. No issues so far, and they are pretty simple --no digital bells or whistles.

Fan Noise? Significant. They compare it to a refrigerator. I'd say about double that, though I am not bothered by it nor has anyone else in the household complained.

Installation? A fantastic headache, not to do with the company particularly, or the units. They were supportive. More to do with nobody had ever done one before and so the learning curve was steep. Now that we know how it would be easier. . .

Re use and placement. #1 E-tech We use the one in the historic building to augment the electric preheat of a tandem tank system. Electric 100 gallon first stage to natural gas final. 150 gallons total storage serving six apartments and two active laundries. The cost per month in electric for that application (it has its own meter) has been $40. I'm not sure about the gas addition as it is shared with the furnace, but I've always felt is was fairly minimal as the water entering the final tank is over 120 degrees and its purpose is fast recovery. Summer NG bills next to nothing.

The E-tech runs a lot in this application -- more so than in my house -- as there is a much larger and sporadic water use. We fondly call the pair of them the "heat suckers" as that is what they are up to -- stealing heat from the air. Fortunately, the apartment building E-tech shares a room with an ancient boiler that gives off a good deal of waste heat into a well insulated basement area. Though a cool area in the summer, it still has enough ambient heat to work effectively. That's the trick -- there has to be a cheaper source of heat than electric in the room you are installing them in. GE glosses over this with their integrated model literature: "Your furnace will work harder in winter. . ." You bet!

#2 E-tech has a more interesting placement. My home runs on grid tie PV panels and has only the option of propane or electric -- no natural gas. Solar hot water was not an option (no unshaded southern exposure). The "heat sucker # 2" takes "waste" heat from the wood burning stove we use to heat the house in the winter -- is there any "waste heat" when you chop wood? -- and grabs natural heat from the environment in summer adding a welcome AC side effect.

I am mindful of conservation, but including pumping water for a small farm our grid tie electric bills run $25-$50 a month -- $30 less a month than before. E-tech is much cheaper than extra PV -- which is never really practical for heating anything, water included. The E-tech is probably about equal to a small solar water heat system, if you had a place for it. . . Hope that helps. And I have a question -- anybody ever combined solar water heating with the new GE hybrid water heater? (if they work as planned it will be a blessing -- certainly easier than a retrofit -- though NOT less expensive by the look of it: both my "add on" units totaled $2000, plus installation, roughly the cost of one new GE. An electric hot water tank pretty cheap after all -- particularly if you have one that is working. . . ) -- Dale (1/11/10)