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HWHP, worth it?


HWHP, worth it?

Posted 26 Aug '18 11:19 AM

Hey all. Wondering if anyone here can offer some perspective on Hot Water Heat Pumps.

We moved into an early 70s house about 18 months ago and have been steadily renovating. To date we've replaced the roof, insulated (almost everything we reasonably can), added a ventilation system and rewired. Now we're on to replacing the windows (going PVC), but also a complete refit of the original bathroom and in the process we're going to switch over the DHW, which is currently a standard low pressure, electric cylinder.

We're going to move the system outdoors as that's a pretty simple and strightforward change given our layout - and the options we've been looking at are instant gas, standard outdoor electric or a HWHP. Gas is cheap to install but we'd need to be on bottles and well, it's gas, and we don't want to be tied to that. Electric is next at ~$3800 installed or there are various options for HWHPs - the one we're looking closely at is an EcoSpring 300L for ~$7400 installed. Climate is coastal but relatively mild, with ambient air temps in winter rarely getting anywhere near 0, so efficiency should be decent, even in winter.

But, is it worth it? We're a family of 5, and I estimate the payback period at around 3-4 years, which seems worthwhile, but can anyone speak to their reliability? Most HWHPs seem to have only two year warranties, which I find a bit concerning. Anyone here been using one for a decent period of time? How have you found it?

RE: HWHP, worth it?

Posted 14 Jan '19 11:53 AM

How did you get on? Did you look into solar hot water too? Cheers

RE: HWHP, worth it?

Posted 27 May '19 03:11 PM

I know the Mitsubishi Electric HWHP has a warranty of 5 years plus they are a trusted brand in the HVAC market. Price should slightly more expansive but for a extra 3 years warranty it's probably worth it.

RE: HWHP, worth it?

Posted 27 May '19 05:12 PM

I'm not convinced they are necessarily very efficient. The 2010 BRANZ study is worthwhile reading:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.branz.co.nz/cms_show_download.php%3Fid%3Df8bb9154bc556999f28d2c2db0fe6a83249067fa&ved=2ahUKEwjIuMO2-LriAhWMbX0KHTR8AloQFjABegQIBRAH&usg=AOvVaw0--c9FCs3_ms-KL6Q34axY&cshid=1558933895161

RE: HWHP, worth it?

Posted 19 Jul '19 10:52 AM

The Econergy unit is well rated in Consumer. Its a split system so is separate to the HWC. They are NZ manufactured and have a 5 year warranty?!* The star being that their warranty terms on their website are not clear so do your own research. I like the idea of the separate unit as you could take it with you if you move house and if it failed and was out of service the electric element in the HWC is there ready to go.

RE: HWHP, worth it?

Posted 17 Aug '19 03:35 PM

I would say the biggest deterrent for HWHP setups are the installation cost. I'm also amazed how expensive they've become in the past 10 years $7,400 today vs $2,800 back then. You can spend a lot on the hardware and I would of thought the cost of installation would be cheaper than a hot water solar panel on the roof (less hassles with regulations and consents). For retrofitting an existing house I suppose the cost is a lot more but if you make the installation as easy as possible, I can't see how the cost could be $7,400.

Also not all setups are the same. You have the integrated HWHP (ie Rheem's one) where the heat pump is on top of the HWC and you have the whole unit OUTSIDE. Then you have the 'split unit' setup (which IMO is the preferred way) where the HWC is inside the house and the compressor unit heat pump is outside, operated as a loop off the HWC. The biggest drawback with having the HWC outside is you're fighting with ambient temperature. So if it's 0C outside, the 60C temperature shift of hot water is quite demanding. Without a doubt, no matter how well insulated the cylinder is, heat will escape. As with a split system, any heat losses from the HWC goes into the living space.

We chose HJ Cooper stainless steel 300L HWC (included as PC sum by the builder). Then the HWHP unit alone was $2000 + $500 for installation (my help with installer) for split system. The payback was easily within 3 years and coming about 10 years going, the heat pump has not failed. We did not go with a reputable brand but instead, a Chinese one rated 4kW output. Power use max is only 750watts so the COP is not bad. As far as reliability? I can understand your concerns because back in 2009 we heard the same story. What a heat pump is... is basically a refridgerator and most often, they don't last that long (ie. have been told averaging say 3 - 5 years but in the back of my mind, I recall home fridges lasting well over 10 years so that statement doesn't really add up). It's about 10 years for us and we use a lot of hot water, from others using the same unit have also having it last just as long. You could go with a Mitsubishi but the installer said you're paying well over 3 times the price and these made in China units have the same productions. Use Japanese compressors and Chinese assemblies so what you're getting at the end is not much different. Warranties are a bit like TVs. You buy a new TV with a 1 or 2 year warranty but many last easily 10+ years.

Now the only negative is the COP drops as the temperature drops. Here in Christchurch overnight, when the temp goes sub 0 - i've found it takes about half as long to heat up to 60C as when the temp is 15C or higher and i'm heating overnight to take advantage of the low electricity tariff from 9PM to 7AM. The quickest recovery is over 25C where the 300L takes less than 2 hours.

You mentioned having the HWC outdoors? In that case, I would not recommend HWHP. There's simply too much loss in heat from the wide ambient temperatures. These outdoor integraded ie Rheem branded HWHP I see are primarily Australian and we all know Australia is a much warmer climate than here. Going tankless LPG may be the better bet. Don't worry about storage loss and only heat what you use. If you want to do tankless on the cheap, install a dual switchover and conntect 2 x 9kg bottles that you refill on a bi-monthly basis (if you don't want to pay for LPG rental / delivery charges).

RE: HWHP, worth it?

Posted 02 Dec '19 09:11 AM

Thanks for the responses, especially SBQ - the detail you offer here is much appreciated.

We ended up ditching the HWHP plan (for now at least) and installed a good quality electric cylinder with a 10 year warranty. It had to go outside as our old hot water cupboard was in the centre of the house and since it used to be LP had no drain, with no easy way of putting one in (and no other options to locate it). Gas was going to be fiddly in regards to placment and clearance issues. The cylinder we installed has an option to add a secondary source, so we could consider adding a HWHP at a later date, maybe. Our power bill has increased by about $5 a week, but the switch to mains has definitely been worthwhile and is offset by reductions in power use elsewhere (installing much better heating and insulation, including airtight windows).
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