[Greenbuilding] Heat pump HWS

[Paul M. Eldridge]

Just as an addendum to my previous message, our municipal government has been actively promoting the adoption of solar assisted DHW systems (see: www.halifax.ca/solarcity). Their website tells us that a typical installation runs about $9,000.00.

There's a map of homes and businesses on this website for which you can access performance data, and out of curiosity, I clicked on the one closest to my home (the Bedford United Church). As at 24 April, it shows that their four panel system has saved a total of 3.3 litres of oil year-to-date. That's about a $2.00 saving at current fuel oil prices. I clicked on another site with a two panel system that shows their year-to-date solar contribution as 69 kWh. Other systems did register higher numbers, but I couldn't find any that would provide what I consider to be a reasonable ROI. 

Our Nyle cost $1,200.00 or about one-eighth that of a typical (I'm guessing) two panel system, and it eliminates about six hundred litres of fuel oil demand per year. The incremental increase in our electricity use has been modest if you factor-in the related dehumidifier savings, and the simple payback in our case was roughly two and a half years. If I'm interpreting this data correctly, for many of the solar installations in our community, it's unlikely that you would recover your investment within the expected life of the system. 

Regards,
Paul
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  Original Message  
From: Paul M. Eldridge
Sent: Saturday, April 23, 2016 18:43
To: greenbuilding-request at lists.bioenergylists.org; greenbuilding at lists.bioenergylists.org
Subject: Re: Heat pump HWS

‎Hi Dan,

We're a two person household, and our domestic hot water is supplied by a Nyle Geyser RO connected to a SuperStor Ultra indirect tank.  The Nyle operates at 120-volts and is plugged into a power monitor so I know precisely how much electricity it consumes each day and this data gets logged in a worksheet.  It's also controlled by a timer so it's limited to one recharge cycle per day or two if we happen to be doing laundry.   The unit draws anywhere from 400 to 675-watts depending upon ambient air temperature and whether it's at the start or end of its recharge cycle (it slowly and steadily creeps upward as the spread between air and water temperature increases).  There's no back-up source of heat unless we fire-up our oil boiler. 

It typically consumes between 1.5 and 2.0 kWh per day, or about 50 kWh per month.  Granted, we're pretty frugal users, but neither of us like cold showers and we wash all laundry in hot water. 
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We live in a maritime climate and so we have to run a dehumidifier to help keep mould and mildew at bay.  Thus, for the six or so months of the year that we would normally expect to operate said device, our Nyle provides us with "free" hot water to the extend that it offsets the run time of the latter; in effect, it provides us with two services for the price of one.  During the winter, it steals heat from a conditioned space, but that heat is supplied by a high efficiency heat pump at one-half to one-third the cost of either oil or electric resistance.  Not a bad trade-off, all things said.  There is some noise, but with the timer we can restrict that to the times when this space is unoccupied so that has never been an issue for us (it's not any louder than our dehumidifier, so if you can tolerate one, you shouldn't have a problem with the other). 

The Nyle is a solidly built product and it serves our needs especially well.

Regards,
Paul

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----  Original Message  ----

Date: Fri, 22 Apr 2016 08:34:35 -0700
From: Antonioli Dan <solardan26 at gmail.com>
To: Green Building <greenbuilding at lists.bioenergylists.org>
Subject: Re: [Greenbuilding] Heat pump HWS

[...]

But with heat pumps now all the rage what I'm looking for are solid numbers, not hypothetical calculations. Real-time testing. How much electricity do the heat pumps use? If you use them in hybrid mode can you achieve the same degree of efficiency and net-zero energy as a thermal system?

[...]

Dan