Kind of a nifty idea. http://www.gizmag.com/cold-water-heater/26941/ Not buffering may be costing the system (as we have found in DSH's).

I suggest that the extra cold domestic water it produces is going to end up being reheated by heat gain from the interior (as it sits in pipes and toilets) and by people mixing it with more hot water. Plus it will cause condensation.

Using a HP to extract heat from a tank of (gray?) water just before it heads out to the sewer - now there is something to think about (in cooler climates).

Not a bad thought jon

Not buffering? It looks to me like they're buffering both the cold AND the hot water!

In the San Diego climate for which it was designed condensation isn't going to be much of an issue. It's delivering a delta-T of 15-20F from 80F water in summer, which is at or above the mean summertime outdoor dew points. They limit the cold-water buffer tank to no lower than 55F, which is above the midwinter dew points. Yes, the warm house will be re-heating the water somewhat, but in an air conditioned house it'll never regain it's 80F incoming temp- it's reducing the sensible cooling load somewhat.

But that's also a climate where cheap series-plumbed batch-solar water heating works pretty well, and very low maintenance to boot. From a water heating point of view batch solar likely to still beat even the hoped for higher efficiency version of the heat-pump/double-tank system as an investment. The heat pump will likely beat active-solar thermal on price/performance though.

I recognize what looks to be a Nyle / Geyser external air source HPWH, converted to sourcing from water.

Cooling 20 gallons of water by 15 degrees at a COP of 2.0 transfers only enough thermal energy to heat 50 gallons of water by 9 degrees. Interesting but not really helpful. Jonr's points about tempering and condensation are spot on, as well. Given that the chilled "colder cold" water gets rewarmed by the surroundings is another way of saying that the proposed system is really an air source HPWH disguised in a complex maze of tanks and pipes.

Any climate warm enough that incoming cold water averages 70*F is already so well suited to conventional tank HPWH that it seems foolish to do anything else.

Recovering heat from a tank that detains grey water on its way out makes much more sense thermodynamically, but the complexity and volume of tanks needed likely render it impractical for single family homes. I've long wondered about doing something like that in a hotel, apartment building or laundromat that consumes 1000+ gallons of hot water per day - raw grey water would likely be at 75-90*F, a large and excellent source for a WWHP making 120*F hot water. In addition, there is a nifty coincidence of supply and demand - hot water draws would 'freshen' the grey water detention tank with thermal energy right as it is needed to reheat hot water supply tank. A WWHP based on a 5-10 nominal ton compressor should be able to quickly transfer heat between the two tanks at a rate of 100-200k BTUH at a COP of 4-6

The inventor of the product offers this as well;

What it is: The GWHP is a new, highly efficient water heating design for single or multi-family residences in temperate and tropical climates.
How it works: The GWHP extracts excess heat from the cold water used throughout the home with a water-to-water heat pump to heat the hot water used throughout the home. The key factors are that: 1) the typical residence uses three to four times as much cold water as hot water, 2) in some climates the cold water is about 15º-20ºF warmer than it needs to be and 3) water-to-water heat pumps are, on average, more than twice as efficient as air-to-water heat pumps. See http://www.halslater.com/ashp_vs_gshp.pdf
Testing done so far: Four prototype units were built and the ASHRAE 118.2-2006 standard water heater efficiency test to determine Energy Factor (EF) was performed on one of them at UC San Diego Department of Mechanical and Aerospace Engineering. The other three units were installed in homes in different climate zones with meters and thermometers to monitor usage, performance and efficiency. The test report is available at: http://www.halslater.com/FinalReport_56957A-10-04G.pdf
Test results: Lab results yielded 2.14 EF at 58ºF incoming cold water temperature but the system is designed for climates where the water temperature is 60º-80º or more. Since the ASHRAE test does not account for system losses, the in-home test rating metric (created by Oak Ridge National Laboratories) used is Overall Delivery Efficiency (ODE) which for the initial two months averaged 1.08, after repairs and adjustments the average has risen to 1.28 even though it is winter. In March, at only 65ºF incoming water temperature and a low 2:1 ratio of cold to hot water use, the CZ7 (coastal) system’s ODE is 1.52.
How it compares to the current leader in water heater efficiency, the Air-to-Water Heat Pump (AWHP): The second-generation prototype AWHP operated at an EF of 1.92 compared to our first generation prototype unit which operated at 2.14. The third generation AWHP has an average ODE of 1.27 in the field, which is about the same as the first generation GWHP of 1.28. Fully optimized per the final report’s Recommendations, the GWHP should be able to reach an EF over 3.25 and an ODE above 2.5.
See complete report at: http://www.halslater.com/Optimized-AWHP.pdf
How the total installed cost compares: The cost to manufacture the GWHP should be under $200 higher than that of the AWHP. Installation is slightly more complicated since the system must supply cold water to the home as well as the hot but no difficulties were encountered in the three system installed for the tests. These added costs should be more than offset by the fact that, as a geothermal appliance, the unit qualifies for a 30% personal tax credit. If this design is powered by solar electric panels it can lower the cost of solar hot water by 20% compared to solar thermal and provide a net 100% solar hot water fraction with no maintenance or risk of freezing, boiling or scaling.
A frequent question has to do with the effect of mixing the cooled water with hot water and whether that would diminish the savings achieved from extracting the heat from the cold water. This effect was considered in the grant application and it was determined by Dr. Kleissl from UC San Diego that, in his words... “If all hot water used were to be mixed down to105ºF, it would increase hot water consumption by 10%. Mixed hot water applications are typically only half of that so the effect is estimated to be an increase of one gallon per person per day."

The results we obtained support that projection as we were unable to see any noticeable change in the hot water consumption rate before or after the installation or during those times when the system was not functioning. Throughout the test period, the daily hot water consumption has been a steady 13.5 gallons per person.

water-to-water heat pumps are, on average, more than twice as efficient as air-to-water heat pumps..... The third generation AWHP has an average ODE of 1.27 in the field, which is about the same as the first generation GWHP of 1.28.

If I read this correctly, it looks like a disconnect between their theory (2x) and their current result (no savings).

To my thinking, in a hot climate (with AC in use), DHW produced by an interior ASHP is free. So there isn't much to improve on.

Testing done by Advanced Energy in NC showed a GE HPWH exceeding EF 2.5 if the setpoint is reduced from 135 (DOE test) to a more-common 120. That was the older GE, newer model adds another tenth to DOE EF, and they do better yet in warm humid environments.

I don't see the product that is the subject of this thread going anywhere. ASHPWH's are a no-brainer in warm climates; more interesting are efforts to make them work in colder climates, accounting properly for added space heat load.

Posted By engineer on 01 May 2013 09:54 AM
.....ASHPWH's are a no-brainer in warm climates; more interesting are efforts to make them work in colder climates, accounting properly for added space heat load.

The comment above caught my attention and thought I would share my experience so far, for what it is worth.... 

In December of 2011, I connected/piped and enabled the desuperheater on my Climatemaster TTV038 (open loop pump and dump, source well has about 45' lift, and consumes ~800 watts at 1st stage flow where it runs a vast majority of the time).  I installed a new GE Heat Pump Water Heater as my powered tank, and repurposed my existing dual element electric tank (50 gal) as the buffer tank.  At about the same time I replaced my old upright frost-free freezer with a new energy star (manual defrost) freezer.  There are several relevant points that took place since the desuperheater was enabled and HPWH was installed:
1. A record or near record warm summer 2012
2. A colder than average winter 2012-2013 (based on local HDD data)
3. Our family grew in size (Based on data logger information from my original standard electric tank heater (prior to the DSH/HPWH tank install) and total cold water consumption read from my water softener…. I’ve assumed the same proportion of hot to cold and estimated that my domestic HW load has gone up by 15-20%)
4. Our family’s comfortable winter t-stat setpoint went from 67 to 68F
5. Added (2) small noise maker fans that run at least 10 hrs per night (sometimes they are left on during the day! :)) 
6. We stopped using our outdoor clothesline to dry most of our clothes, alternate method is electric dryer (we are off the NG grid of course).

After subtracting out the effect of the new freezer (based on before and after KiloWatt meter readings) AND eliminating the data from the record warm weather from 2012 (Jan, Feb, March, April)…. the combined effect of the above changes has been an overall average decrease in energy consumption of 152kWh per month or about $313 per year at current rates (actual monthly savings is greater in the summer months, but there is noticeable savings in the winter/heating months too).

Factoring in the increased HW use over that period, shows that the new equipment DSH/HPWH is actually saving us an additional ~$100 per year (assuming 10.5 gal/day increase, 68 water DT, 0.89 de-rated electric efficiency including average measured stand-by losses).

So for me the combined savings for the GE HPWH & DSH is more than $400 per year or about (17% of my total energy at the time when I installed the units).

Total cost for me - ~ $1,200 (including 10 year labor warranty on HPWH, piping, fittings, insulation, etc.)
Simple payback - ~3 years (less as we continue to use more HW, and local electric rates go up).

This was a pleasant surprise being a more northerly location (West Michigan), where in general the HPWH concept isn’t as favorable. Based on COP data for the GE HPWH and knowing approximately how much HW we use, it is clear that you can’t get to the savings I’m seeing with just cheaper HW. So it would seem that a good amount of the savings I’m seeing is coming from both the longer more efficient run times in the heating mode (as the DSH and HPWH move almost the entire HW load onto the GSHP during the heating season), and the cooling side effect of the HPWH in the hot summer. 

I am very curious if anyone else as experience or advice on how to best apply these HPWH's in heating dominated climates (piping arrangements, operating modes, etc.).

So why not just run a dedicated water to water heat pump water heater(Waterfurnace makes a 1.5 and 2 ton system specifically for domestic potable water) Here is one that we recently installed so I guess I am missing something because the one we put in averages around 4 COP throughout the year and produces 125 degree water all year round.
http://youtu.be/BmemPHZWbU4

Posted By SkyHeating on 28 May 2013 08:16 PM
So why not just run a dedicated water to water heat pump water heater(Waterfurnace makes a 1.5 and 2 ton system specifically for domestic potable water) Here is one that we recently installed so I guess I am missing something because the one we put in averages around 4 COP throughout the year and produces 125 degree water all year round.
http://youtu.be/BmemPHZWbU4

I had long considered that option, even prepared some plumbing connections to allow the dedicated hot water unit source discharge to supply the water to air unit in the summer, but the payback just didn't seem to be there for me. 

I didn't look at those exact models, but if I remember correctly upfront cost for the unit was between $3000 and $4000 (not including accessories, circ pump, and piping). 
In my case COP is derated due to open system pumping energy (~800 watts), so I figured best case COP around 3.5.

With these two parameters, unless I figured on a TREMENDOUS amount of hot water usage (alot more than we use now), or the electric rates go much higher (already at $0.135/kwh average over the year) the payback was more than 10 years.... compared to about 3 year I'm tracking with my HPWH/DSH setup. 

Long term I'd love a water to water unit as i'd be that much closer to a reasonable cost heat source for my infloor heat..

What you might be missing is the $5K plus price tag. Plus the DSH makes water in the summer for free, you only pay a bit for the circulation pump. No question the dedicated hot water unit is the most elegant solution, but not for everyones pocketbook.

Sky's right, the dedicated W-W heat pump alternative probably provides the highest possible COP or EF for domestic water heating, but the installed cost is prohibitive relative to a DSH / resistance or DSH / HPWH setup.

As I mentioned earlier, a dedicated W-W heat pump solution would likely pencil out in hot water intensive light commercial apps such as hotels or restaurants. I'm itching to try one.

The only time when we use dedicated hot water via a separate heat pump is in cooling dominated applications, where we use it to extract heat from the ground loop, which then allows us to reduce the ground loop size, thus it reduces upfront installation costs. They the extra heatpump pays for itself many times.

Are there many cooling-dominated applications with high water heating demands near Buffalo? I suppose a restaurant would fill the bill owing to high internal gains and high water heating demand.

Does the extra cost of the dedicated W-W HP pencil out against shaving tonnage off a loopfield?

What happens during your REAL winter, when both heat and hot water are needed?

Posted By engineer on 29 May 2013 12:59 AM
Are there many cooling-dominated applications with high water heating demands near Buffalo? I suppose a restaurant would fill the bill owing to high internal gains and high water heating demand.

Does the extra cost of the dedicated W-W HP pencil out against shaving tonnage off a loopfield?

What happens during your REAL winter, when both heat and hot water are needed?

Sure, convenient stores, coffee shops, commercial buildings, machine shops with a lot of electrical equipment. Or apartment buildings with 50 people occupancy and a couple restaurants, we are commissioning one right now, the annual heat load is about 2x the cooling load. Doing the hot water centrally with a 7 ton high temp WF, reducing the size of the loopfield by 7 tons since it is sized for cooling.
We don't know real winter and non-real winters. We just know winters. They usually last from September till June....

Interesting data logger and data to show that your family grew.

Posted By jokin on 28 May 2013 10:01 AM >3. Our family grew in size (Based on data logger information from my original standard electric tank heater (prior to the DSH/HPWH tank install) and total cold water consumption read from my water softener…. I’ve assumed the same proportion of hot to cold and estimated that my domestic HW load has gone up by 15-20%)

my domestic HW load has gone up by 15-20%

You can use lower flow shower heads. It's surprising how low you can go, especially when pressure is high.

Posted By mtrentw on 04 Jun 2013 07:50 PM
Interesting data logger and data to show that your family grew.

Laughed so hard when I read this comment that I disturbed a bunch of people nearby at work.....  You make a fair point.  In the interest of full disclosure there were a few other indicators that my family was growing!  :):)   

I guess this shows how small punctuation and grammer mistakes can REALLY effect the meaning!

Punctuation isn't my strong suite as you may have gathered...   I might as well admit it, I managed to pass the PE test recently but failed the mechanics(punctuation) portion of the ACT (standardized test) in high school.