Comments on: Heat Pump Water Heaters: A Better Way to Heat Water with Electricity?

By: William Munn

William Munn — Sat, 22 Feb 2014 03:43:34 +0000

I live in Orlando, FL and the
I live in Orlando, FL and the heat pump water heater is an ideal solution for my needs. The garage is unconditioned space, and stays well above 80 F most of the year, so it will have plenty of heat to draw upon to heat the water. Just installed the GE Geospring, looking forward to seeing how much I save this summer :)

By: Les Watts

Les Watts — Sun, 07 Nov 2010 18:36:16 +0000

I paid around $1800 installed
I paid around $1800 installed.

The website you posted is not the manufacturer’s website, but a distributor out of Florida.

Since I don’t know how to make a direct link, I will post the website for North Road Technologies which makes the unit.

http://www.northrdt.com/Geyser/index.html 

Also, ACEEE has some good info on the HPWH, but doesn’t even list the Bentley version aka Accelera 300.

http://www.aceee.org/node/3068#lcc 

I do like the advantages of the Geyser retrofit model, and in my climate down in the Lowcountry of SC, I think it makes good cents!

By: Allison Bailes

Allison Bailes — Thu, 04 Nov 2010 21:43:00 +0000

You raise some interesting
You raise some interesting points about the advantages of having an add-on unit, Jamie. Did you pay about $2k for it, as the mfr's website says?

By: Les Watts

Les Watts — Wed, 03 Nov 2010 16:49:25 +0000

Good article Allison and some
Good article Allison and some great comments that followed.

I personally have one of the Geyser units located in a spray foamed attic. I don't have a year of usage prior to install to compare what the cost savings are, but I will tell you that I have my Marathon tank completely unplugged and the Geyser is doing it all with now resistance backup heating(a bit risky maybe). The Geyser has supplied a steady stream of hot water on its own even when our house has been full of guests!

I agree there may be the "robbing peter to pay paul" debate, but I think that should be really looked at and considered. If your holding tank has no insulation value, then yes, the standby losses will be larger, so your HPWH will be running a lot thereby producing more AC and dehumidification while it keeps up with the heat losses. So in this situation, if it is during the winter, there could be some battles. In my situation though, the HPWH runs for 10 - 15 minutes a couple times a day and that is it. When we are showering, cleaning dishes, etc... it runs more of course, but it is not like a whole house AC unit that cycles on due to temp or humidity settings, only when the water needs to be heated.

For the Geyser add-on unit, I think there are several good reasons for using it. First, the cold air can be ducted (as well as the input air if needed) to areas that may need the air more, but once again it is not to replace your HVAC. Second, the unit is separate and can be added on to the existing holding tank in someone's house. With water heating costs ~15% of the bills, waiting until your tank fails to get newer technology is wasting money. If you buy an add-on type, you can start saving right away. Third, if the tank fails, like the GE, Rheem, etc...then the HP component is gone too. With the Geyser it is not, and if you move, you can take your add-on unit with you and continue saving somewhere else. Finally, the versatility of an add-on unit is something that should not be overlooked. If you can't put it right next to the unit due to not enough free air space, you can install it in the crawl space or somewhere else nearby and still get great savings. The EF falls as you get heat loss from transmission the further you get away, but it should not be overlooked.

I completely agree it is the process and not the products, but for the masses that have holding tanks that are extremely less efficient than these HPWH's, moving the ball an inch or a foot forward is a step in the right direction. Maybe I am biased on the HPWH's, but I am a fan.

By: David Butler

David Butler — Mon, 25 Oct 2010 23:56:13 +0000

I certainly wouldn't put a
I certainly wouldn't put a HPWH indoors in a hot climate. You'd give up too much potential from the higher ambients. In cooler climates, it might be worthwhile to rig a seasonal exhaust bypass vent. But that's more of a DIY project, not something I'd ever recommend to a client.

I'm afraid any research involving HPWH's would be so much affected by specifics of the homeowner's water demand and usage patterns that the results would be of little use in the general case.

Although I'm unfamiliar with the Stiebel HPWH (I certainly know the company), it's hard to imagine there'd be enough difference to justify the cost. The manufacturer claims an EF of 2.5, although I couldn't find it in the AHRI certification directory. In any event, given the ambiguities of the certification process I mentioned above, I'd be very skeptical of comparing EF's prima facie.

BTW, does $3k for the Steibel include installation? I think the Rheem sells for about $1600 excluding installation. In any case, labor should be almost a wash compared to installing or replacing a conventional electric heater.

As for the Geyser add-on unit, I don't see the point. According to mfr website, it sells for $2k. That's more than the all-in-one Rheem or GE models.

By: Allison Bailes

Allison Bailes — Mon, 25 Oct 2010 23:26:36 +0000

Arthur, first of all, payback
Arthur, first of all, payback may be irrelevant. See my article on payback to see why.

If payback is relevant, it's going to depend on a number of factors, some mentioned in the article and some in the comments above - climate, location of water heater, hot water usage, electric rates, and what you're comparing it to. My estimate for the Accelera 300 is at least 15 years, or about the lifetime of the unit, but it's an expensive, high end model.

You're absolutely right about the complexity potentially reducing the value of heat pump water heaters.

And, yes, a Btu is a Btu, no matter how you make it, but the cost of each Btu, environmentally and monetarily depends on how you make it.

By: Allison Bailes

Allison Bailes — Mon, 25 Oct 2010 23:10:05 +0000

Good points, David. I
Good points, David. I certainly agree that we need to emphasize process and analysis over products, and water heating is about one of the trickiest areas for that. Gas or electric? Storage or tankless? Electric resistance or heat pump? And, as Carl mentioned, the distribution system gets mighty little attention, way less than HVAC distribution gets.

My main point here was that using electricity to move heat can be better than using it to generate heat. I agree that I was a bit too sanguine about the usefulness of heat pump water heaters and not cautious enough in my endorsement. I've added a question mark to the title of the article to help in that regard.

Your comments seem to apply mainly to the GE and Rheem models, though, so I'd be interested in your take on the Stiebel I discussed above and the Geyser, which you can add on to an existing water heater (either gas or electric).

Regarding the negligible cooling benefit, I was surprised that the air coming off the unit wasn't cooler. Water has a high heat capacity, so it should take a lot of Btu's to heat it up, thus making some pretty cool air. At the time we were there, though, no one was home using hot water.

This would be a great research project, and I'd love to see the results if someone has already done it.

By: arthur larsen

arthur larsen — Mon, 25 Oct 2010 23:00:01 +0000

how long is the payback vs a
how long is the payback vs a conventional water heater?
more mechanical parts means a higher and more frequent service ratio.
a btu is a btu....however you make it.

By: David Butler

David Butler — Mon, 25 Oct 2010 21:36:00 +0000

Allison, you probably thought
Allison, you probably thought that was me posting under an alias ;-)

I do agree with much of what the curmudgeon says. With available tax and utility incentives, a HPWH might make sense for some families in warmer climates. But like many energy efficient products, the problem boils down to quantifying benefits for a particular home and set of occupants.

The problem with the HPWH is that the EF rating is much more sensitive to specific operating conditions than is the case with conventional water heaters. In particular, efficiency and performance are greatly affected by ambient conditions at the condenser. More importantly, because electric backup is required, the total operating cost will depend greatly on hot water demand and usage patterns.

When GE and Rheem decided to enter the market, I spoke with technical reps at both companies as well as an engineer at one of the testing labs. Although both manufacturers avoid the inside vs. outside issue in their installation instructions, the Rheem product manager told me the cooling benefit is too small to be worth considering. He recommends their units be installed outside conditioned space, preferably in a garage or attic. The EF rating procedure assumes an average ambient temperature of 67.5F. No data is available on performance at other temperatures, thus site-specific modeling is not possible.

More significantly, a HPWH, by design, will have at least two operating modes. The Rheem HP-50 has three modes -- Energy Saver (HP only), High Demand (HP + element combined) and Electric Heat only modes. As it turns out, the EF procedure does not specify the operating mode. The Rheem product manager expressed concern about this. In particular, he said a manufacturer could test the first-hour rating in one mode and the EF in another mode without disclosing this to the consumer.

In short, recommending a HPWH requires a leap of faith.

I think the more we can steer folks away from specific products and more toward process and careful analysis, the better for the environment and homeowner pocketbooks.

By: Allison Bailes

Allison Bailes — Mon, 25 Oct 2010 19:22:46 +0000

By 'the more air conditioning
By 'the more air conditioning the home uses,' I mean the hotter the climate, not the lower the thermostat setpoints in summer.