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Heat-Pump Water Heaters Come of Age

Now that pilot studies show that installed heat-pump water heaters are performing fairly well, it might be time to buy one

Posted on Apr 13 2012 by Martin Holladay

The least expensive way to heat domestic hot water is with natural gas. Homes without access to natural gas usually choose an electric water heater, since electricity is generally cheaper than propane.

Although most electric water heaters use electric resistance elements to heat water, a more efficient method uses a heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump. — in other words, a device that heats the water using a compressor like the one found in a refrigerator or air conditioner. While a refrigerator transfers heat from the interior of the refrigerator to the room where the refrigerator is located — in effect, heating the room — a heat-pump water heater transfers heat from the room to a tank of water — in effect, cooling the room.

Heat-pump water heaters need backup elements

Compared to an electric-resistance water heater, the main benefit of a heat-pump water heater is energy efficiency. While the efficiency of electric resistance elements is 100% — all of the electrical energy sent to a resistance element is converted into heat — the efficiency of an air-source heat pumpHeat pump that relies on outside air as the heat source and heat sink; not as effective in cold climates as ground-source heat pumps. can be as high as 250%. The heat-pump isn't making heat — it's transferring heat from the air to the water. A heat pump is capable of transferring more energy than the energy required to run it.

The type of heat pump used for heat-pump water heaters can’t heat water as quickly as electric resistance elements, however. While the electric-resistance elements in a typical water heater can heat 20 gallons per hour, a heat pump can only manage about 8 gallons per hour (or even less, if the ambient air temperature is below 68°F).

To make up for this basic deficiency in heat-pump performance, heat-pump water heaters are equipped with electric resistance elements that are energized whenever the heat pump can’t keep up with the demand for hot water. This feature improves the performance of the unit but introduces an energy penalty.

Most heat-pump water heaters have controls that allow a homeowner to choose one of three modes of operation:

  • Heat-pump-only mode (a mode that is energy-efficient, but that doesn’t allow long showers).
  • Hybrid mode (heat-pump operation plus electric resistance backup).
  • Electric-resistance-only mode (a mode that you could choose during cold weather, when you might not want the appliance to cool the space where it is located).

Heat-pump water heaters are clearly more efficient than electric resistance water heaters. Possible side benefits include dehumidification of the room where the unit is located, and space cooling (a side effect which is beneficial in hot weather but potentially problematic during the winter).

Measuring the efficiency of electric water heaters

Electric water heaters (both electric-resistance water heaters and heat-pump water heaters) are rated with an Energy Factor (EF) that is based on a standardized laboratory test procedure. The EF rating is the ratio of the energy delivered to the water divided by the energy used by the water heater. An EF test takes 24 hours; the testing standard specifies the volume and spacing of the hot water draws, as well as the temperature of the hot water and the ambient temperature of the room. An EF rating takes into account standby losses but not distribution (piping) losses.

A typical EF for a heat-pump water heater ranges from 2.0 to 2.5, while a typical EF for an electric-resistance water heater is 0.9. (The EF of an electric resistance water heater is always less than 1.0, due to standby losses through the tank insulation and at the pipe connections.)

While a unit’s EF must be measured in a laboratory, researchers can calculate a water heater’s coefficient of performance (COPEnergy-efficiency measurement of heating, cooling, and refrigeration appliances. COP is the ratio of useful energy output (heating or cooling) to the amount of energy put in, e.g., a heat pump with a COP of 10 puts out 10 times more energy than it uses. A higher COP indicates a more efficient device . COP is equal to the energy efficiency ratio (EER) divided by 3.415. ) in any location where the unit is installed, as long as the proper monitoring equipment is in place. While the EF of an appliance is fixed, the COP of an installed water heater will vary, depending on the ambient temperature of the room where it is installed and the water use habits of the family using the water heater.

A heat-pump water heater with a COP of 1.8 is twice as efficient as an electric-resistance water heater with a COP of 0.9.

Factors that affect performance

A recent pilot study by researchers from Steven Winters Associates monitored the performance of 14 heat-pump water heaters installed in the basements of 14 homes in Massachusetts and Rhode Island. The study was sponsored by three electric utilities: National Grid, NSTAR, and Cape Light Compact. Robb Aldrich presented the results of the study on March 7, 2012 at the NESEANorth East Sustainable Energy Association. A regional membership organization promoting sustainable energy solutions. NESEA is committed to advancing three core elements: sustainable solutions, proven results and cutting-edge development in the field. States included in this region stretch from Maine to Maryland. Building Energy 12 conference in Boston.

The monitored water heaters included ten GE GeoSpring units, two A.O. Smith Voltex units, and two Stiebel Eltron Accelera 300 units. The water heaters were installed in older existing homes, not new high-performance homes.

The cost to operate a heat-pump water heater is hard to predict, because performance depends on the ambient temperatures of the room where it is located and the percentage of time that the electric resistance element is on.

The researchers identified the following factors that affect the performance and efficiency of heat-pump water heaters:

  • The higher the ambient temperature in the room where the unit is located, the better its performance and the better its energy efficiency. A unit that might perform at a COP of 2.35 at 68°F will only perform at a COP of 1.8 at 50°F.
  • The units installed in homes that used a lot of hot water (up to a point) had a higher COP than those installed in low-use homes. “If you don’t use much hot water, your COP is low due to the standby losses,” said Aldrich. “If you use more, the standby losses are smaller, so the COP is higher.”
  • Large volume draws of hot water cause the electric-resistance elements to kick in, thereby lowering the COP. “Concentrated draws of hot water make it hard for the heat pump to keep up,” said Aldrich. “A larger tank or a hotter tank might solve this problem.”

Energy use monitoring data

The measured performance of the 14 heat-pump water heaters enrolled in the study was fairly good. On average, the monitored COP was 1.9 — meaning that the units were more than twice as efficient as an electric-resistance water heater operating at a COP of 0.9.

The best-performing unit (located in a warm basement) had an average COP of 2.6, while the worst-performing unit (located in a small room in a very cold basement) had an average COP of only 1.0.

Where would I put a heat-pump water heater?

There are three places where you might put a heat-pump water heater:

  • If you live in a warm climate and you have an attached garage, put it in the garage.
  • If you don’t have an attached garage or you live in a cold climate, put it in the basement.
  • If you don’t have an attached garage or a basement, put it in a utility room — as long as the utility room is big enough.

It’s important to note that these three locations aren’t equivalent, and the performance of the heat-pump water heater will vary depending on the conditions of the room where it is installed. Many homes don’t have a good place to put a heat-pump water heater.

Before you can install a heat-pump water heater, you need to be sure that you can fulfill all of these requirements:

  • You need a room that is big enough; most heat-pump water heater manufacturers advise that the room should measure at least 750 or 1,000 cubic feet, although at least one manufacturer allows its unit to be installed in a room measuring only 500 cubic feet. Remember, in a small room, performance will suffer.
  • Ideally, the room will stay above 50°F all year long; however, if the temperature dips lower occasionally, your water heater will still work, although its efficiency will drop.
  • The room’s ceiling must be high enough to accommodate the water heater. Heat-pump water heaters are taller than electric-resistance water heaters. These units range in height from 63 inches for the G.E. unit to 82 inches for the A.O. Smith unit. Check the manufacturer’s specs before placing your order.
  • The location must allow for the installation of a condensate drain. If a gravity drain (a floor drain) isn’t possible, you’ll need a condensate pump. Since a 120-volt condensate pump that is plugged into a GFCI receptacle will stop working every time the GFCI has a nuisance trip, you probably want to order a 240-volt condensate pump and have it hard-wired.
  • The proposed location must be roomy enough to allow for proper airflow around the unit and for proper maintenance of the filter, the condensate drain, and other parts.
  • The temperature of the room in which the unit is installed will drop when it is operating, by anywhere from 2 F° to 6 F° — and perhaps even more during heavy draws of hot water. The location should therefore be one where such temperature drops don’t lead to comfort problems.
  • The location must be far enough away from occupied areas (especially bedrooms) to prevent noise complaints. “The sound level is about 60 decibels,” said Aldrich. “That’s like a window air conditioner — louder than a refrigerator.”

According to most researchers, garage installations are usually the best. Garages are big, and it’s unlikely that there will be any complaints due to the unit’s cooling effect or noise. Of course, if you live in a climate that is cold enough to freeze pipes in your garage, you’ll have to find somewhere else to put it.

How much space heat do they steal?

Clearly, a heat-pump water heater scavenges heat from ambient air, thereby cooling the space where it is located. However, this is not always a problem.

  • It’s not a problem in a garage.
  • In a hot climate, even if the heat-pump water heater is located inside a home’s conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. , the unit’s cooling effect will be welcome for most of the year.
  • In a cold climate, a heat-pump water heater installed inside a home’s conditioned space will rob space heat, forcing the home’s furnace or boiler to work a little harder.

In the worst-case scenario, all of the heat scavenged by the water heater during the winter is robbed from a home’s conditioned space. However, if the unit is installed in a basement, it’s unlikely that the space heating system will need to supply all of the heat scavenged by the heat pump. After all, most basements aren’t heated directly; all they receive is indirect heat.

Assuming that the basement in not used as living space, some but not all of the heat scavenged by the water heater will come from the furnace, and the basement will stay a few degrees cooler than it would have been otherwise. For many homeowners, cooler basement temperatures aren’t a problem. The fact that there is a slightly higher delta-TDifference in temperature across a divider; often used to refer to the difference between indoor and outdoor temperatures. between the first floor and the basement will have only a very small effect on the home’s heating loadRate at which heat must be added to a space to maintain a desired temperature. See cooling load..

Quantifying these interactions is extremely tricky. “It’s a crazy thing to try to model,” said Robb Aldrich. “So what we have done is to try to bracket it. If the heat-pump water heater robs no heat from the space” — for example, if the unit is in a garage — “then all the measured electrical savings are really savings. On the other hand, the worst-case scenario would be if the heat-pump water heater operated in resistance-only mode for six months of the year. That’s unlikely; it’s the worst-case scenario. What this means is that from the standpoint of energy consumption, a heat-pump water heater is almost always going to be better than just electric resistance, and often quite a bit better. Yes, the heat is coming from the space during the winter, but not every BTUBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. that you take from the basement needs to be replaced by the heating system; that percentage will vary widely.”

Can the exhaust air be ducted outdoors?

At least one heat-pump water heater manufacturer (AirGenerate of Houston, Texas) allows the exhaust air from the heat pump to be ducted to the outdoors. The idea is that if your heat-pump water heater is making your utility room too cold, you might want to send the cold exhaust air somewhere else.

There’s only one problem with this approach. According to David Kresta, a project manager at the Northwest Energy Efficiency Alliance in Portland, Oregon, the temperature of the exhaust air coming off of a heat-pump water heater is in the range of 45°F to 60°F. If you send all of that exhaust air out of the house, an equal volume of makeup air will enter the house from the outdoors. If the outdoor temperature is lower than the temperature of your exhaust air, you’ve made your house even colder than it would have been if you had exhausted the heat-pump inside your house.

Not only that, but the exhaust fan will have to work a little harder (and use a little more electricity) to send the exhaust air through ductwork than it would to just blow the air in your utility room.

How much will I save?

Robb Aldrich calculates that a family in New England could save between $40 and $270 per year by switching from an electric-resistance water heater to a heat-pump water heater. That calculation is based on a family that uses 35 gallons of hot water per day, with an electricity cost of 17 cents/kWh. (If you pay only 8.5 cents/kWh, your savings will only be half as much, of course.)

The low end of the savings scale ($40 per year) is for a heat-pump water heater installed in a bad location (a small, cold room). The high end of the savings scale ($270) is for a unit installed in a good location (a large, warm room).

According to Aldrich, the incremental cost to install a heat pump water heater (compared to an electric resistance water heater) varies from $1,400 to $2,700, depending upon which model was installed.

One of the reports that was issued by the Steven Winters researchers — “Measure Guideline: Heat Pump Water Heaters in New and Existing Homes” — includes a table with somewhat more optimistic conclusions that those summarized by Aldrich during his presentation. (Presumably, the optimistic assumption is based on avoiding bad installations in small, cold rooms.) According to the optimistic assumptions, a family using 35 gallons of hot water per day can expect annual energy savings of 1,750 kWh. If electricity costs 12.6 cents/kWh, the annual saving is $221, and the payback period is 6.6 years (based on a relatively low incremental cost of $1,458 to install the heat-pump water heater).

Families that use more than 35 gallons of hot water per day can expect a shorter payback period.

Choosing a heat-pump water heater

When it comes to integrated heat-pump water heaters — that is, units that come with a tank — five models dominate the market:

  • AirGenerate makes the ATI50 (with a 50-gallon tank) and the ATI66 (with a 66-gallon tank). The larger unit costs about $1,900 to $2,000; it has an EF of 2.40 and a first-hour rating of 75 gallons.
  • A.O. Smith makes the Voltex in two sizes (60 gallon and 80 gallon). The larger unit costs about $1,850 to $2,100; its EF is 2.33 and its first-hour rating is 84 gallons.
  • General Electric makes the GeoSpring. It has a 50-gallon tank and costs about $1,200 to $1,500. Its EF is 2.35 and its first-hour rating is 63 gallons.
  • Rheem makes the HP-40 (with a 40-gallon tank) and HP-50 (with a 50-gallon tank). The larger unit costs about $1,300; it has an EF 2.0 of and a first-hour rating of 67 gallons.
  • Stiebel Eltron makes the Accelera 300. It has an 80-gallon tank and costs about $2,400. Its EF is 2.51 and its first-hour rating is 78 gallons.

All of the researchers I talked to emphasized the benefits of a large tank size, so don’t buy the G.E. unit, the Rheem unit, or the smaller AirGenerate unit. “Bigger and hotter tanks are better,” said Aldrich. “It’s counterintuitive.”

According to “Measure Guideline: Heat Pump Water Heaters in New and Existing Homes” by C. Shapiro, S. Puttagunta, and D. Owens, “The units with smaller tanks demonstrated difficulty in maintaining hot water delivery in high demand situations, even if their electric resistance elements are used. The units with larger tanks provide a buffer in times of high demand and therefore are expected to use their heat pump for recovery, rather than reverting to electric resistance heating to maintain outlet temperature. The result is more efficient operation and better performance in terms of availability of hot water. In households with more than two occupants, a HPWH with a larger tank will likely be a better option.”

One other factor to consider: only one manufacturer (AirGenerate) makes a heat-pump water heater with a stainless-steel tank. The material used by the other four manufacturers is enameled steel. In most cases, stainless-steel tanks last longer than enameled-steel tanks.

How long will they last?

We don’t yet know how long the current generation of heat-pump water heaters will last. Nor do we know which parts will fail first — the controls, the compressor, or the tank.

When I asked Aldrich about the longevity of these units, he said, “That’s a big question. I am cautiously optimistic. Ten or 12 years ago, we did a study of the early models available, and we noticed failures during the first few years after the units were installed. We are not seeing anything like that now with the newer units. The controls are more robust. If you think of a refrigerator, how long does a fridge last?”

So I asked a follow-up question: “Well, would you put one in your own house?”

He answered, “If I didn’t have natural gas — yes, I would.”

Last week’s blog: “Are Tankless Water Heaters a Waste of Money?”

Tags: , ,

Image Credits:

  1. A.O. Smith
  2. GE

Apr 24, 2012 12:44 AM ET

Solar Thermal Heating - Dismissed????
by Rhaud Macdonald

Martin: in regards to your outright dismissal of Jasons' comment; Please visit and check it out, might be worth your while. While your at it feel free to contact Bill or one of the others at the sight, the reality might surprise you! Canadian companies, eh!

Regards, smalld

Apr 24, 2012 5:44 AM ET

Edited Apr 24, 2012 5:45 AM ET.

Response to Steve Rust
by Martin Holladay

Q. "Does anyone know of a calculator or comparison chart which includes oil as a source?"

A. Yes; there is such a table on this page published by the ACEEE: Water Heating. You'll notice that an oil-fired water heater has the highest life cycle cost (over 13 years) of any option on the list. The main reason for this is the high cost of oil. Needless to say, the cost to operate an indirect water heater like you have (a domestic hot water tank connected to a space-heating boiler) will differ from the cost to operate a stand-alone oil-fired water heater; but the chart is still useful.

Q. "Could a HPWH be located in a 330 cu. ft. furnace room? The average temperature in that room is easily 5 degrees warmer than the rest of the house."

A. Good question. The short answer is no -- because you would be violating the manufacturer's recommendations. (The room is too small.)

Apr 24, 2012 5:49 AM ET

Response to Rhaud Macdonald
by Martin Holladay

You have provided a link to the web page of a distributor of solar thermal equipment. It doesn't surprise me at all that a company that sells such equipment claims that it's cost-effective to use solar thermal equipment to heat water or provide space heating. However, this does not constitute evidence or even useful analysis.

No third-party researcher or academic team that I am aware of has found that a solar thermal system can heat domestic hot water cheaper than a water heater burning natural gas.

Apr 24, 2012 2:34 PM ET

solar thermal
by Aaron Becker

Hi Martin (and all),

I am curious about the cost effectiveness of solar thermal hot water systems. You have been stating in some of these blogs about their cost have very long "payback". 1) Were you using the DOE comparisons chart that shows a 13 year life cycle cost compared to other hot water energy source systems? If so, I don't think that it is a fair comparison, since the big ticket hardware for solar hot water systems can last longer than 30 years. 2) Is it the solar storage tank that makes it the limiting factor in the solar hot water system lifecycle? 3) And are you including the currently available tax credits in the system cost? I appologize for having missed your source for that statement in any previous postings and asking you to restate the facts.

Apr 24, 2012 2:49 PM ET

HPWH using fridge heat
by Aaron Becker

I've been following the blog on using the HPWH to scavenge the fridge waste heat. What is the fan capability that is in the add on heat pump water heaters (Geyser & Airtap) regarding moving air in a 4" or 6" duct? I have a scenario where the existing 80 gallon electric hot water tank is directly below the refridgerator in the kitchen. The basement (a workshop - zone 5,) is currently heated with thermostatically controlled electric resistance fan convectors, so scavenging heat from them is not a good application during the heating season. The shop size is more than 2800 cu ft volume. The shop also requires dehumidification during the summer, so a hpwh is a good aplication for spring, summer, fall.
If I could route the hpwh intake air from 4 feet above (the fridge) and dump the cool dehumidified air to the shop, perhaps the effective purchase cost & installation (homeowner) would be juistified for 3 season operation. Any thoughts?

Apr 24, 2012 2:58 PM ET

More on solar thermal payback
by Martin Holladay

Aaron Becker,
Here's a well-researched paper on solar thermal payback: Cost, Design and Performance of Solar Hot Water in Cold Climate Homes.

The paper by researchers from Steven Winters Associates provides detailed monitoring data from two solar hot water systems. The respective simple payback periods for these two systems: 58 years and 76 years.

Of course, rising prices for natural gas or electricity will shorten these payback periods. Incentive and rebate programs will also have the effect of shortening these payback periods.

Apr 24, 2012 4:20 PM ET

RE: Martin's Response to Janet Bergman Wilkinson
by John Clarke

One thing I think you have to consider is the duty-cycle of the GSHP and how much hot water your desuperheater will actually produce. If the GSHP is running on a daily basis year round then your argument against the HPWH makes sense. In a case where the GSHP is not operating continuously (such as in our high efficiency house) then the desuperheater doesn't help unless you have a huge storage tank. After much research and discussion as well as the lack of natural gas for our site, we chose to pair the AO Smith HPWH with our GSHP desuperheater. The installation is in a conditioned basement, part of which is living space and I can attest to the noise of the unit. We plan on sound-proofing the mechanical room in the near future since it does have the GSHP, HPWH, ERV, and the obligatory wastewater lift station (below grade bath).

We have been in the house for less than a month so I can't attest to the cost effectiveness but we have been operating it in efficiency mode to avoid using the resistance heaters. There are only two of us living in the house so we don't have the issue of regeneration times but on days when the desuperheater is operating we expect it to reduce the regen time significantly. Again, our GSHP is very low duty-cycle at this time of year so no empirical data to back up our designed efficiency.

We also have a 40 gallon storage tank (resistance water heater w/o electricity connected) for the desuperheater which feeds the HPWH and therefore our 60 gallon HPWH effectively has 100 gallons of hot water (when the GSHP is operating).

Your comment on the need for the condensate pump is well advised. We piped the condensate out to be added to our rainwater collection tanks (as opposed to adding it to our septic system). A little mentioned advantage is that the basement humidity is reduced while the HPWH is operating which is generally a good thing. No more need for that dehumidifier (which was noisy, generated lots of hot air, and required emptying or a condensate pump attached). I wouldn't suggest that as a reason to buy a HPWH but it does provide an added benefit to us.

Apr 24, 2012 11:24 PM ET

Edited Apr 24, 2012 11:28 PM ET.

Response to several
by Curt Kinder

I agree with the point made that just because heating degree days are based on 65*F doesn't mean houses start needing heat at 64*. When I lived in Mass we didn't reach for ther thermostat until outdoor temps dipped into the 40s.

An attic can be a great place for extra heat to pull into a HPWH at very favorable COP factors, but make sure the weight of the HPWH is well supported and that proper provision is made for both condensate water and possible plumbing leaks.

I have EXACTLY what Martin H tells Janet NOT to combine...My WaterFurnace geo-sourced heat pump has the desuperheater option that warms water in an 80 gallon preheat tank. The preheat tank supplies a second 80 gallon tank heated by a Geyser HPWH. The result is water heating costs no more than $15 per month, and often less than $5 for a family of 4-5.

During summer and what passes for winter in north Florida, the Geyser runs little since water leaving the preheat tank is 100-130*F. During spring and fall, the Geyser carries most of the load since there is little HVAC load. The Geyser's dehumidification is a nifty added bonus.

If I rebuilt the system today I'd use a 60-80 gallon integrated HPWH rather then the Geyser, since the integrated units are now less expensive, quieter, and more efficient than a Geyser heating a separate tank.

An HPWH can be installed in a smaller room warmed by a furnace. A 70 page study of GE HPWH by Advanced Energy in North Carolina extensively tested a small room installation. The GE kept most of its efficiency even as the room dropped to 55*F.

I am concerned that overcooling a small room with an HPWH in a humid climate could lead to dew and mold formation within the walls of a small room cooled to 55*F by an HPWH. The Advanced Energy HPWH study did not address that concern

Apr 25, 2012 4:56 AM ET

Response to John Clarke and Curt Kinder
by Martin Holladay

John and Curt,
I stand corrected. Thanks to both of you for sharing information on your experiences combining a ground-source desuperheater with an air-source HPWH. I learn something every day.

Apr 26, 2012 11:24 AM ET

Edited Apr 26, 2012 11:27 AM ET.

Please check my analysis of
by Derek Roff

Please check my analysis of the heat flow relating to HPWH systems discussed in this article. Heat pumps move heat energy from one place to another. When the heat pump is installed inside the conditioned living space, the energy being moved into the hot water can only come from a) the outside world (solar input and heat conduction from the earth or outside air into the living space), or b) energy introduced into the home via electricity or fuel. In a heating situation, all the calculated advantage of the heat pump, either EF or COP, comes from heat that is already in the house, having been purchased, in case b), or "donated" by the environment, in case a). The heat transferred to the domestic hot water is being removed from the living space, and that heat must be replaced.

While a homeowner might not mind a slightly cooler basement, or might not notice the impact of an air to water heat pump on their space heating needs, this doesn't change the fact that all the heat moved by a HPWH is being taken from the living space. Does this not mean that the true EF or COP is roughly 1, regardless of the industry calculation standards which provide much more attractive numbers?

In a cooling situation, heat is moved from the living space, where it isn't wanted, to hot water, where it is. I can see the energy efficiency advantages there, plus the dehumidifying that has been discussed. But for heating, unless the HPWH is drawing heat from the building that would otherwise be lost, then I don't see how it can have a genuine energy advantage.

Apr 26, 2012 11:40 AM ET

Response to Derek Roff
by Martin Holladay

Thanks for your comments. I will add two more situations that you didn't address fully:

1. In a heating climate, a HPWH located in a garage does not steal space heat from the house.

2. If the HPWH is located in a basement that is ordinarily hot (because of the presence of an inefficient boiler, an inefficient furnace, or uninsulated ductwork) and rarely visited, the lowering of the basement's temperature will not necessarily result in the need to burn more space-heating fuel.

Apr 26, 2012 12:33 PM ET

Edited Apr 26, 2012 12:56 PM ET.

Martin, even in your too warm
by aj builder, Upstate NY Zone 6a

Martin, even in your too warm cellar the too warm cellar is aiding heating the home above it. And same for cooling an attached garage. The separation wall being cooler will make the home use more energy.

Basically the idea works as a secondary heat redistributer at the added cost of buying and running a HPHW gadget.

For cooling climates a noise free unit in the home or attic or garage makes much more sense.

Lastly as I have said, heating water is the least expense any of us pay. An easy way to cut the expense is to simply use less heated water. Small tanks that run out of water save and require no fancy added gadgetry.

Apr 26, 2012 12:48 PM ET

Still wanting to clarify
by Derek Roff

Thanks for your response, Martin. I'm still hoping to understand more fully. In you point 1, if the garage is not heated space, then I agree that HPWH wouldn't impact the heating loads appreciably. But did you not say that an HPWH should be in a room with an ambient temperature of at least 50 degrees F, preferably more? I would imagine that an unheated garage in many heating climates would be below this temperature during some or all of each day for a good percentage of the year.

On your point 2, in a basement that is ordinarily hot, either that heat is being transferred to the living space, or it is being lost to the outside environment. I would hope for more of the former than the latter, but no doubt cases vary. As I mentioned, it seems to me that except to the extent that it uses heat that would otherwise be lost, an HPWH inside conditioned space is using heat that would otherwise contribute to warming the house. What would you imagine is an average amount of heat lost to the outside world in a hot basement of the type that you describe?

Apr 27, 2012 5:40 AM ET

Response to Derek Roff
by Martin Holladay

I understand your basic point about the physics involved. You're right -- lowering the temperature of a basement will probably require the furnace or boiler to work a little harder. The question is, "How much harder?"

To illustrate my point, let's take an exaggerated example. Imagine a house with two big rooms. One is an occupied room that stays at 70 degrees. The other room is an unoccupied room that also stays at 70 degrees. The occupants never enter the second room.

If you put a HPWH in the second room, the HPWH might lower the temperature of the room to 60 degrees. It's hard to say whether the home's furnace is working any harder at this point; the temperature of the air has been lowered, and the space heat has been transferred to the water in the water heater. But maintaining the second room at 60 degrees may not take any more heat from the furnace than before the HPWH was installed. You could argue that the comfort in the home has been degraded, because one room is now cooler (a fact that normally -- in the absence of a HPWH -- would lead one to guess that the furnace is burning LESS fuel, not MORE fuel -- all other factors being equal). However, comfort is not an issue -- because the occupants never enter the second room.

Apr 27, 2012 10:34 AM ET

Edited Apr 27, 2012 5:14 PM ET.

Martin, physics or magic?
by aj builder, Upstate NY Zone 6a

Martin, physics or magic? Moving home heat to water then draining the water out of the home is physics. The heat is gone and will be replaced by the heat system that it was taken from. You also know that the delta T across a wall or floor matters but not for HWHP for some magical reason.

You even mentioned refrigerator adding heat to a home. It only adds the net heat waste from the light bulbs and motor inefficiency not the warmth of the coils which is equaled by the cold of the inside coils.

These are worthy discussions but let's stick to physics.

Edit; OK.. even more clear, I agree all the work done by the refrigerator motor is inside the home so yes the watts used converted to btus is the added heat. What I was trying to say is that your average Joe or MaryAnn may think the warm coils on the backside of the refrigerator are the source of net heat gain, while disregarding the cold coils effect. Anyway, we agree about the btus added. Where we will remain apart is the idea that cooling a cellar does not effect the home above. It has to. You with your I=B+R which uses delta T in calculations know that if a delta T is 5 degrees more, the equation will show more btus needed. And so the furnace will be providing the added btus and those added btus are what heat the water in the HPHW gadget.

More thoughts on your 2nd point Martin. If I lower the temperature of any internal part of my home by dumping that heat outside the home continuously, like leaving a window open or running a HWHP that dumps the heat into the water that I dump outside the home, I am effectively removing heat that I paid for and came from my HVAC. And the adjoining partition being colder sets up a delta T that will take more btus than if there were no open window or HWHP. You are close to inventing perpetual heat.

We shall remain in partial harmony as usual. Enjoying the physics.

Apr 27, 2012 10:46 AM ET

Edited Apr 27, 2012 5:19 PM ET.

Response to AJ
by Martin Holladay

1. The heat added to a home by a refrigerator (or any electrical appliance located inside the home's thermal envelope) while it is operating is equal to the current drawn by the appliance. If the refrigerator draws 300 watts, then it adds 1,024 Btu/h to the home when it is operating.

2. All other factors being equal, lowering the temperature of one of the rooms in your house during the winter months will result in energy savings. Maintaining a basement at 60 degrees for 4 months requires less space heating energy than maintaining a basement at 70 degrees for 4 months. If the difference in fuel use between maintaining a basement at 60 degrees and 70 degrees is X gallons of fuel oil with a heat energy value of Y, and that energy is transferred to a tank of water, the net result could be a wash in terms of space heating energy use.

That said, in the real world, it is much more likely that installing a HPWH in a basement will, in fact, require the furnace to work a little harder. As I said earlier, the real question is, "How much harder?"

Apr 27, 2012 2:21 PM ET

From a newbie
by Edwin Booth

This has been a great discussion and the one that got me to join. I'm a newbie but have wanted to add either PV or solar thermal for quite a while. I live in Birmingham, AL and my natural gas DHW heater just bit the dust. I have been considering natural gas tankless heaters, but after reading this discussion I am thinking that electric is the way to go assuming that PV is in my near future. Martin, you said standard electric resistance tank heaters powered by PV are likely to be more efficient than solar thermal, but would that be true of electric tankless heaters as well? Your last blog doesn't really make me want to go tankless but what about smaller, point- of-use units? Is the payback time just terrible?

I also agree with the comment about reducing fossil fuel use. I'm willing to pay a bit more initially if I can reduce a) natural gas consumption now and b) grid electric later when I install PV. Our electricity is made from "clean coal"--an oxymoron if there ever was one.

Thanks for the great topic!
Edwin Booth

Apr 27, 2012 2:32 PM ET

Edited Apr 27, 2012 2:34 PM ET.

Response to Edwin Booth
by Martin Holladay

Q. "Martin, you said standard electric resistance tank heaters powered by PV are likely to be more efficient than solar thermal."

A. I think you misunderstood. My point concerned cost-effectiveness, not efficiency.

Q. "Would that be true of electric tankless heaters as well?"

A. The efficiency of electric tankless water heaters is a little higher than the efficiency of electric-resistance tank-style heaters. Electric tankless water heaters have an EF of about 0.99, while electric-resistance tank-style heaters have an EF of about 0.90 to 0.93.

Q. "What about smaller, point-of-use units? Is the payback time just terrible?"

A. Point-of-use electric water heaters make sense for some applications. (For more information on this topic, see All About Water Heaters.) When you ask about payback time, I'm not sure what you mean. The first question you have to clarify is, "Compared to what?" All payback calculations depend on local energy costs, so I probably can't help you; you'll have to research local energy costs and the cost of the equipment and do the math yourself.

For more information on payback, see Payback Calculations for Energy-Efficiency Improvements.

Apr 30, 2012 12:41 AM ET

Response to Stan Smith
by Greg Winger

With such high performance mini-split technology/equipment availible for forced air systems, I was confused as to why all the HPWH's in the U.S. have indoor evaporators. Trolling the internet a few months ago, it was a delight to discover that there are mini-split type water heaters available somewhere in the world. It is great to have you chime in on your experiences with one and providing some hard numbers (prices, temperatures...) The links you provided confirmed my suspicion that they are built with Asian parts (Toshiba outdoor unit) I'm looking to heat some radiant floors with in and if I could buy a HPWH here in the U.S. for $4500 that would work down to 23F I would do it tomorrow.
thanks for your input.

May 1, 2012 5:03 PM ET

New home water heating decisions
by Stephen Carlton


I am designing a passive solar house to be built slightly north of Seattle. I will use SIPs to super insulate and seal the house. Triple glazing from Cardinal glass will provide solar gain.
One of my last decisions is how to provide hot water for the home. Gas is not avaiable but electricity is. A large amont of thermal mass will store the solar heat gained and I anticipate low heating needs; so the home will not need for a large heater than can produce hot water for heating and other uses.

I am not convinced that solar water heaters are cost effective.

The home is modest at 1825 sq feet and will only have two occupants with what is probably a lower than average hot water usage. We only use cold water in the washing machine.

I have read three of your recent posts on heating water: All about water heaters, Are tankless heaters a waste of money and this post.

Based on your posts I am currently thinking to add a large uninsulated water tank inside the house that will settle to the average house temperature of ~68 degrees. This will also add thermal mass. Then I will use three point of use devices such as the Stiebel Eltron Mini units. One under the kitchen sink and one near each of the two showers. Under the showers I would install heat recovery devices to ensure the temperature can get hot enough.

I would appreciate comments on this scheme

May 1, 2012 5:46 PM ET

Response to Stephen Carlton
by Martin Holladay

Your plan for water heating sounds fine to me.

My only comment: just because you specify SIPs, doesn't mean that your house is superinsulated.

May 3, 2012 3:10 PM ET

Water heating strategy for Passive House
by Stephen Carlton

I am just completing the design of a home which I will build next year close the the border with Canada north of Seattle. The climate is moderate/marine.

I am using a passive house strategy. The house is 1825 sq ft and uses SIPs to provide high insulation values and sealing. Triple glazing from Cardinal will be used to maximize solar gain. High thermal mass will be built into the slab and be well coupled to the heat gained. A heat recovery ventilator will be used. I estimate my heating needs to be quite low and I am not designing in a large heater than can produce hot water for the house as well.

Two people will live in the house so hot water demand will be modest, we only use cold water in the washing machine and hot water is not used to heat the house.

I believe solar hot water systems, especially at this loactio, are not cost effective compared to other methods.

Based on recent posts on this blog about point of use water heaters, tankless heaters and heat pump water heaters I have come up with the following scheme. I should point out that I believe simple is best and I hate waiting minutes for hot water to arrive at a faucet or showerhead.

I plan to place a large uninsulated water talk inside the home so that it is heated to the homes ambient temperature of ~68 degrees by the solar gain. This will also add to the thermal mass in the home. I will distribute this warm water to three point of use heaters such as the Stiebel Eltron Mini™ Series. One at the kitchen sink and one at each bathroom near the shower. Under the shower I will use heat recovery devices in the drains.

I would appreciate comments as to the scheme and I will use them the modify and finalize the house design.

May 3, 2012 3:15 PM ET

Edited May 3, 2012 3:24 PM ET.

Double post
by Stephen Carlton


Sorry for the double post, I hadn't realized that my post was up and that you had responded.

I understand that SIPs don't equal super-insulated. I started down a passivhaus path but now am following your recommendations on insulation, especially given that my house will be in a fairly moderate climate. I will post some other questions about insulation and the way I use it on the appropriate blog post.

May 29, 2012 1:24 PM ET

hpwh as a dehumidifier
by alan abrams

Hi Martin and fellow readers--

in a current project in a mixed humid climate, we will be adding a two story addition with new basement, to an existing 2 story masonry and frame house on an existing, partially finished basement. we plan to condition the new space with a multi zone heat pump. the existing house will remain heated by a boiler radiator system, and will be cooled by an ingenious but marginal AC system with air handler in the attic.

to get to the point of the issue, the existing AC system is inadequate to prevent mold growth in the existing basement in summer time. since the project will include a new water heater--does it make sense to consider a HPWH located in the existing basement, not only to provide hot water, but also to provide dehumidification in that area? It would require some through-wall fans of course, to accomplish this.

alternately, the new heat pump could include an additional zone to condition the existing basement. but the assumption here is that when you add the dehumidification capability of the HWHP into the efficiency calculation, it might cancel out any other disadvantages, including higher first costs for the equipment.


Alan Abrams - Takoma Park, MD

May 29, 2012 1:39 PM ET

Response to Alan Abrams
by Martin Holladay

My recommendation would be to first try to figure out why you have a mold problem in your existing basement, and if possible to address the moisture problem with something other than dehumidification.

Possible causes of your mold problem include air leaks that introduce humid outdoor air, damp soil around the foundation, or a clogged footing drain.

Jun 1, 2012 9:37 AM ET

heat pumps
by Francesco Amato

Heat Pumps new technology can assure a ROI in a2 years depending on installation and climate conditions.
In Europe the new frontier is the application of multifunctional all-in-one heat pumps, those units can provide cooling, space heating and hot domestic water with a great saving.
For additional information write me at

Aug 27, 2012 5:09 PM ET

heat pump noise
by John Eyles

I am a DIY homeowner, adding a room that requires me to move my direct-vent gas water heater. (It's a State one that has performed flawlessly for 25 (sic) years, but I'm assured it'll start leaking if it's moved, so time for a new one).

Been looking at the bewildering variety of water heaters available to day, and am now convinced that heat-pump style is right for me. I'll add a wrinkle I haven't seen in these comments: my space heat is extremely cheap and PC, since the dual-fuel heat-pump only comes on if the passive solar and catalytic woodstove haven't kept up. So if I put it inside, the HPWH would be using cheap heat in the winter and helping to cool the house in the southern summer. A huge win.

One big fly in the ointment - the noise. Sounds like these things are pretty loud and my house ain't that big. I can locate it pretty far from both bedrooms, but sounds like it's loud enough that even being fairly close to the living room and the study will get annoying. I guess there's no way out of this, since of course it can't be sealed up in a closet. Putting it in the crawlspace might be nice, since I have a serious humidity problem and am converting to a sealed crawlspace. But the most clearance I have down there is 4ft, so I guess that's a no-go too; too bad someone doesn't make a lowboy style HPWH.

Aug 27, 2012 5:17 PM ET

Reply to John Eyles
by Martin Holladay

Once it is installed and operating, report back here -- let us know how loud it is.

Aug 27, 2012 11:42 PM ET

Edited Aug 27, 2012 11:43 PM ET.

I'm thinking I'm not gonna
by John Eyles

I'm thinking I'm NOT gonna install one - the noise is a deal killer. Too bad someone can't come up with a noise cancellation system: like noise-cancelling headphones, except a loudspeaker that cancels the compressor/fan nose.

I'm thinking ERWH is the way to go for me. Just talked to energy-expert buddy, who said utility companies are hoping to get a lot of people on the plan where they can control your ERWH remotely; thus millions of people's ERWH's will effectively become a giant "battery" - when there's spare generating capacity (esp. for inconsistent renewables like solar), that excess energy can be put into people's water heater tanks. Pretty neato ! It's also clearly cheaper for me (than propane) and there is a path to PC-ness by adding PV solar.

Aug 28, 2012 6:02 AM ET

Response to John Eyles
by Martin Holladay

You had me confused there for a while -- ERWH? -- until I guessed that you are probably talking about an "electric resistance water heater."

Aug 28, 2012 2:31 PM ET

Edited Aug 28, 2012 2:33 PM ET.

Yessir. With all the lingo
by John Eyles

Yessir. With all the lingo from the insiders here, I figured no problem using such acronyms ... :-)

I need to figure out if my electrical service can handle adding that huge electrical load though. Though I am an electrical engineer, I'm not quite sure how. Two issues I suppose - is there space for a double/240v breaker, and is the wiring from the transformer up to that many total amps ? Anyone know of a link to help me with that ?

Aug 28, 2012 2:54 PM ET

Response to John Eyles
by Martin Holladay

The electrical load will only be "huge" if you install a tankless water heater. If you install an electric resistance water heater with a tank -- by far the most common type -- the electrical load is not particularly huge.

In any case, if you are "not quite sure" how to determine whether your existing service can handle any extra electrical load, then you're reached the limit of free Web advice. It's time to call an electrician.

Aug 29, 2012 1:46 PM ET

Yes, I guess 20 amps isn't
by John Eyles

Yes, I guess 20 amps isn't really "huge" - assuming it's true only one of the 4500 watt elements is energized at any given time. Interestingly, if you look at the spec sheet for the AO Smith ERWH's, it says 4500/6000 watts. I called and asked what that meant and they said the 6000 watt was a special order. Never heard of that before.

Apr 7, 2013 7:14 AM ET

HPWH for coastal Massachusetts?
by David White

Lots of good discussion on here, glad I found this forum. Like one or two others here, I've been thinking for a while about whether a HPWH would be a good solution just for the summer months. We have an oil furnace for both heating and water, but during the summer its really only used for hot water. I'm now looking at $750 for a tank of oil and there's only one direction that price is going in the future! Would it make any kind of economic sense to install a HPWH, shut the furnace off for the summer and just use the HPWH, shut the HPWH off for the rest of the year and then just rely on the furnace? Has anyone actually tried this?

Apr 7, 2013 7:39 AM ET

Response to David White
by Martin Holladay

First of all, the space-heating appliance in your basement is a boiler, not a furnace.

Second, you are quite correct that using an oil-fired boiler to create domestic hot water in the summer is extremely expensive. If you have somewhere to put a heat-pump water heater (a basement with a high ceiling, for example), the HPWH will cost far less to run. The HPWH will also help to cool and dehumidify your basement.

The only disadvantage to this approach is the high cost of the equipment and the relatively long payback period. If the high cost scares you, you might consider installing a conventional electric-resistance water heater for use during the summer months. In either case, you can lower your electric bill by investing in a PV system; I hear that Massachusetts has some good incentives.

Apr 7, 2013 2:46 PM ET

Thanks Martin
by David White

Thanks for the advice Martin - and correcting me on what I have. Growing up in Britain, we always called it a boiler. In the US, I've only ever heard it called a furnace. I thought we were just using different words for the same thing - two countries separated by a common language etc. We have space to put a HPWH right next to the boiler and I've always assumed that would make the plumbing easier. I'll look into it further, thanks again.

May 31, 2013 6:17 PM ET

Excellent time to buy
by Cartlund Monson

My 20 year old heater finally burst a month ago and it turned out good karma which led me to the Geospring. There will never be a better time to go to a hybrid water heater.
Apparently, the 2009-2012 blue Gen 1 models were sloppily made in China of substandard plastic and coils that actually corroded each other when wet. The new red-topped Gen 2 ones are made in Kentucky using state of the art techniques, and much upgraded parts. The bad reviews from the old units lowered the price from $1599 to $1199. Until 5/29, it was on sale at Lowes for $999 with an instant $200 rebate, thus $799. With the Fed tax break of $300 and a Puget Power refund of $500, my cost was $-1. Well, I had to pay sales tax and a few bucks for a condensate hose.
The Regime (DOE) is mandating new water heater specs that can only be met by Hybrids as of 2015. Expect all the rebates and discounts to vanish after that. Eventually, element heated units will go the way of the incandescent bulb.
Fortunately, however, the higher total unit cost means the tank itself will be better made; this one is a 10 year ($500 equivalent standard heater) vs. a 6 year ($350 standard heater) tank. As to the heat pump longevity, well, it is pretty much the same as the one in the 25 year old almond fridge you probably still have running in your garage. I think GE likely overbuilt these Gen 2 ones because of the chinese fiasco. The new single fan is quiet, unobtrusive white noise, too.
I did a few things to maximize my benefits. I raised the heater about a foot and made sure there was more than 7" clearance all around for airflow. This allows it to draw air from the hotter air near the ceiling, and gave me better drain options. I will have to punch a small hole in the ceiling to change the anode, oh well.
It is in an unheated but insulated room behind the garage that never freezes due to mild Seattle weather and the washer/dryer on the other side of the wall providing heat that will now be recycled. The room is about 8x14, and the cooling effect is comparable to a compact window AC unit--which is in line with the 700 watt heat pump draw. I am setting it to 140 to get through four showers nightly.
I think if you consider airflow and heat transfer you can get a lot of advantage out of these units. There is no question that moving heat is cheaper than generating it. But there has to be a gradient within the compressor's rating. In this case, I think 55+ degrees f. ambient air (specs say 45 to 120) is the best operating range. Below 55, it will struggle to keep up and you will set it to use the elements.
What makes me especially happy is that it is near my hot tub room and 'conservatory'. There is plenty of waste heat I can duct from both places, and the dehumidification is an extra bonus. It pulls a gallon a day from the air.
The one downside is GE is recalcitrant thus far with providing technical data and parts for DIY repair. So, it will be a $400 service call if it breaks. Again, though, I personally use an air conditioner from 1982 in the aforementioned hot tub room, and it has never been serviced. The hardware on this water heater looks very well designed and built. I'm sure the fan and even compressor are shelf parts you could look up, but doubt anything will break in a ten-twenty year timeframe.
Sorry to be so long winded, I just wanted to summarize all my own research.

Jun 1, 2013 7:50 PM ET

Appreciated the read
by Larry Croome

This topic is still up in the air just like our precious energy dollars. Heat pumps in fact are a little like magic in terms of capitalizing on the phase change of refrigerant and locating the heat loss or gain in the right place. There is a substantial market future for heat pump hot water tanks -ONLY if designers and builders are ready to shape their whole building philosophy around ALWAYS incorporating the synergies of our cooling and heating needs. This can bed more simple than complicated -ONLY with the correct advance design of spacial needs and mechanical. I am building a net Zero home in Canada with R40 walls and roof plus solar mass concrete /insulated foundation. It will be a mechanical process in the works over the next while after the basics are installed. I have been planning the heat pump hot water from day one after calculating all other costs of achieving hot water. The intake to the heat pump will be from warm sun collected -when the sun is shining, warm fireplace air when the fire is burning, and the rest of the time from interior air. The fridge is located with its back to the mechanical room and plan on putting a 'cold-sinc' at the fridge coils as well as the master bedroom shower upstairs will have a drain wrap for warming the cold water into the hot water tank. ETC.
If you build your home efficiently enough... as I am, then domestic hot water is by far the most costly energy -then the cost of ventilation air and then space heating. We will capitalize on passive solar when possible and have 2, 3 and 4 pane windows used. I have a long list of synergistic design elements with some costing near ZERO. Our Electric will be PV and feed back to grid. Later we may put in a small bank of batteries. Electric company is charging $0.105 per kwhr and paying $0.10. That number will only be going up --for BOTH. The home design is such that the pv panel install is easy to go in and easy to keep clean.

Jun 21, 2014 5:08 AM ET

by Ken S

I thought about simply ducting to and from the Attic - in the south and especially in an older home - cooling the attic a little from its normal 140 plus temp is not a bad idea. I have an Aquatherm heating system in Orlando that is run by Natural Gas - they slam the Gas price in the winter so I am not sure if I am saving anything or not. But I can imagine how well ducting to the Attic would be 9 months out of the year. If the attic is cooler the house can be cooled and kept cool cheaper - but then again how much cooler would that attic be considering the Water heater should not be on 24 /7 or even close to that. Of course seems to me just running pipes back and forth through the attic should keep the water hot and its free most of the year.

Jun 21, 2014 5:55 AM ET

Response to Ken S
by Martin Holladay

Your attic air temperature should be irrelevant to your energy bills or your comfort, as long as your attic floor is adequately insulated, and as long as you don't have any ducts up there.

If you have ducts in an unconditioned attic, you have a problem. But your suggested remedy is definitely not the most logical way to solve that problem (ducts in the attic).

Attempts to save energy by blowing air from the vicinity of a heat-pump water heater to a different location usually don't work, for four reasons:

1. The cost to install the duct and run the fan are more than any energy savings;

2. Homeowners who install these systems usually haven't considered the question of where the makeup air comes from;

3. It's hard to prevent air leakage through the duct (and through your thermal envelope) when the fan isn't operating; and

4. It's hard to choose and program a control system so that this Rube Goldberg fan is only running when you want it to.

Jul 20, 2014 3:14 PM ET

HPHW in Rhode Island
by Stephen Porder

We just installed a GE Geospring in our basement in Providence. The house is undergoing an energy retrofit - R60 roof, r30 walls, r20 basement walls. The basement is currently unheated. Leaving aside for a moment that the product was defective upon installation (a common problem with the geospring), we did this because there is a $750 rebate in RI for this unit, making it a $350 gamble. In contrast, the Steibl unit would cost $1800 after rebate, and is too tall to fit in our basement anyway. So, for the green building gurus, assuming we can get it to work, is a $350 Geospring worth it, or should we just get a natural gas heater ? We are a family of three, and although one of us will be a teenager soon, our hot water use isn't all that much at the moment.

Jul 21, 2014 7:46 AM ET

Response to Stephen Porder
by Martin Holladay

This article explains the type of house (and family) for which a heat-pump water heater might make sense. These appliances aren't for everybody. If you are uncertain about whether it makes sense for you, I suggest that you re-read the article.

Q. "Assuming we can get it to work, is a $350 Geospring worth it?"

A. That question is easy to answer. Yes, it is worth it. That's a great price. However, just because it's a great price doesn't mean that it's best for your house and your family.

Q. "Should we just get a natural gas heater?"

A. If you have already installed the Geospring, and if the Geospring has a warranty, I wouldn't give up on it just yet. Use it for a year and decide whether it meets your family's needs.

Apr 30, 2015 1:38 PM ET

by greg coleman

Does anyone know what's going on with the company?

Apr 30, 2015 2:20 PM ET

Response to Greg Coleman
by Martin Holladay

There was some discussion about the company on an earlier Q&A thread.

According to True South, "The manufacturer is no longer warrantying the units."

According to Dana Dorsett, "It's a relatively small start-up company that got into it without the deep manufacturing & support experience of a big player like GE or AO Smith. I hope they continue to survive as a company."

Jan 15, 2016 7:25 PM ET

Edited Jan 15, 2016 7:25 PM ET.

Response to Cartlund Monson; et al
by Gregory Repucci

Where did you get the data on the updated Geospring units? I continue to see current reviews/comments online (up to December 2015) which reference recently installed units that:
1. still have problems with incorrectly installed anodes which leak at first pressurization
2. have developed leaks on units purchased in 2013 (after the 1st Gen fiasco)

To all:
It seems unfortunate that there's not as much activity/follow-up on this blog as there was during the first year of activity - there's alot of great information here, which would be improved by continued data on HPWH usage.
I'm looking to replace an old fashioned resistance water heater with a newer HPWH, the only difficulty is determining reliability data for the ones out there that have been updated to comply with the 2015 regulation changes. My current unit is in the garage, and Arizona provides plenty of hot air :) during most of the year to make this a worthwhile installation.

Of some concern is the fact that we just recently installed a soft water system, which, from what I've read, will have detrimental effects on the anode of the unit in the short term. I'd prefer to install a powered anode to offset that problem, but haven't seen any information on whether that's possible in these HPWHs. Any information about that would be appreciated.

Mar 29, 2016 4:01 PM ET

WiFi monitoring
by Jan Galkowski

Anyone know what hoops have to be jumped through to put a GE Geospring GEH50DFEJSRB on our home local WiFi network? There's a $35 GE module you can buy, but all it does is (apparently) make the device available from a Smart Phone.

Jun 22, 2018 1:38 PM ET

Rheem's Prestige challenges opening sentence
by Brian Knight

Great article and comments. Rheem's new Prestige offering advertises UEFs of 3.55 for 50g and 3.7 for 65 and 80g models. This seems to make natural gas more expensive than electricity in most markets, especially when using updated UEF ratings of gas model comparisons. Maybe there was an update since this was written but Steibel Eltron advertises a 3.39 EF, not 2.51.

Yes the modeling is complex for colder climates but it now seems opening statement no longer holds up in majority of utility markets. Cautiously optimistic is a great term for this new entry.

Jun 22, 2018 1:53 PM ET

Response to Brian Knight
by Martin Holladay

Thanks for your comments. It might be time for a new article on the topic of heat-pump water heaters, in light of continuing technical improvements.

Jun 22, 2018 2:05 PM ET

New article
by John Semmelhack

Yes, please! Most of the manufacturers are on their 4th or 5th generation of HPWH design. Perhaps you can release it in tandem with “Solar hot water is really really really dead”. ;-)

Jun 22, 2018 2:11 PM ET

Response to John Semmelhack
by Martin Holladay

You made me smile.

I've been itching to write the "really really really dead" article!

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