Hot Water System. Gas v Heatpump

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andysh

228 posts

Master Geek

#310624 7-Nov-2023 12:42

Hey all,

The Gas unit has finally kicked the can after 25 years so it is time to replace it. With the rest of the house (bar cooking - which we are happy to change to induction) now on electric, including an electric car, we are thinking of moving to heatpump hot water. My biggest concern is noise, as the current hot water unit is outside the ensuite and the neighbours aren't very happy with our 14kw Panasonic (I know!!) ducted heatpump also. We are in Auckland so cold temps shouldn't be an issue.

Has anyone got any thoughts on heatpump hot water, anything to look out for / brands that are worth it? Or shall we stick to gas?

Cheers!

Referrals:

Tesla: https://ts.la/andrew897313

Sharesies: https://sharesies.com/r/XRGS77

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147 posts

Master Geek

#3156950 7-Nov-2023 13:36

I would be interested to see if anyone here has done the calcs on how long it would take a Heat Pump HWC to pay for the increase in cost vs a standard electric HWC?

PolicyGuy

1726 posts

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#3156965 7-Nov-2023 14:05

I bought a Reclaim heat pump hot water system (https://reclaimenergy.co.nz/home-hot-water-heat-pump/) about a year ago as part of my home de-gasification programme - the Infinity it replaced was the last gas appliance and I had the gas disconnected once the heat pump system was in. That saved about $50/month in connection fees.

The economic pay-back is probably past my occupancy, I'll most likely be off to a Rest Home or the crematorium before it has paid for itself, but that's not why I bought it: the justification was reducing my carbon footprint. I reckon that's better for my grandchildren than leaving them a larger monetary inheritance.

It's right outside my bedroom window and I can only just hear it if the window is open, so it's pretty quiet.
Their brochure says "Average noise level 37db = whisper quiet"

SteveXNZ

59 posts

Master Geek

Lifetime subscriber

#3157159 8-Nov-2023 06:14

I've had a Rinnai EHP32 hot water heat pump running perfectly and relatively quietly for the last four years. It's rated at "Noise level: Fan approx. 55 dB(A)" which means it's noticeable when you're standing beside it, just audible inside the house through the external wall at the closest point, and inaudible in the bedroom across the hall. Given your noise sensitivity I'd go with one with the lowest noise rating, but I'm happy with the Rinnai and would choose again. It delivers up to 6kW of scalding hot water with an energy input of 1.9kW.

Two things to watch:

It's very much install and forget. There is no user-adjustable thermostat, external temperature display, or wifi/smart home integration. If you want to turn it on or off at certain times you need to install a simple controllable switch
There's a filter on the plumbing to the HWC. Clean that out every 6-12 months, or if you detect the heat pump cycling on or off too frequently.

Good move getting rid of gas. I'm in an all-electric house with solar/EV, and wouldn't consider any gas appliance now (apart from the LPG BBQ on the patio).

dasimpsonsrule

147 posts

Master Geek

#3157164 8-Nov-2023 07:46

Here is a spreadsheet I put together last year with some comparisons between different heat pump options. If you are using LPG then basically anything is cheaper to run, even an standard electric one.

andysh

228 posts

Master Geek

#3157193 8-Nov-2023 09:33

Thanks all for the input! Think we will be going heatpump.

Anyone happen to have preferred installers based in East Auckland? Normal plumber is more a gas guy so has only put in one.

Cheers

Referrals:

Tesla: https://ts.la/andrew897313

Sharesies: https://sharesies.com/r/XRGS77

Shindig

1585 posts

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Trusted

#3157225 8-Nov-2023 11:34

Brilliant thread!

The little things make the biggest difference.

cddt

1548 posts

Uber Geek

#3157226 8-Nov-2023 11:36

PolicyGuy:

my home de-gasification programme

A bit off-topic but I'm interested in hearing more. We've moved to a new house which has gas for hot water, ducted air heating, and cooking (hob only, oven is electric). I am keen to switch to electric but it seems to be a big capital investment (not the main concern) and that it's going to be fiddly to retrofit a 1920s house for these appliances.

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alasta

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#3157238 8-Nov-2023 12:10

I am also quite interested in this.

I live in a small one bedroom unit which has a European gas boiler system that services hot water and hydronic radiator heating. At some stage I would consider replacing it with heat pump hot water, but there would be two pre-requisites:

The hot water tank would need to be outside as there is no space for it inside. I understand this is possible.
The hot water would need to interface with the central heating system. I'm not sure if this is possible?

Jase2985

13457 posts

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#3157247 8-Nov-2023 12:45

alasta:

I am also quite interested in this.

I live in a small one bedroom unit which has a European gas boiler system that services hot water and hydronic radiator heating. At some stage I would consider replacing it with heat pump hot water, but there would be two pre-requisites:

The hot water tank would need to be outside as there is no space for it inside. I understand this is possible.
The hot water would need to interface with the central heating system. I'm not sure if this is possible?

should be dooable for both your pre-reqs

Ge0rge

2052 posts

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#3157259 8-Nov-2023 13:30

alasta:
I am also quite interested in this.

I live in a small one bedroom unit which has a European gas boiler system that services hot water and hydronic radiator heating. At some stage I would consider replacing it with heat pump hot water, but there would be two pre-requisites:

The hot water tank would need to be outside as there is no space for it inside. I understand this is possible.

The hot water would need to interface with the central heating system. I'm not sure if this is possible?

My old have a hot water heatpump with the cylinder outside. Once the cylinder gets up to temperature, the system switches over to heating their underfloor system. The old man has it set up to heat the cylinder whenever it needs it, and do the underfloor when the sun is shining, to make the most of their solar.

What you're after is most definitely achievable.

PolicyGuy

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#3157262 8-Nov-2023 13:43

cddt:

PolicyGuy:
my home de-gasification programme

A bit off-topic but I'm interested in hearing more. We've moved to a new house which has gas for hot water, ducted air heating, and cooking (hob only, oven is electric). I am keen to switch to electric but it seems to be a big capital investment (not the main concern) and that it's going to be fiddly to retrofit a 1920s house for these appliances.

Hot water
If it's an indoor gas hot water system, you can have the heat pump (which has to be outdoors) remote by up to 9 or 10m from the storage cylinder that could be in the place the gas system now is, or you could have the whole new system externally. In either case, you're going to have a hole to be fixed in your roof and in your ceiling where the flue was. If you move from an indoor to an outdoor system, you're going to have quite a bit more plumbing work to be done.
If it's an outdoor gas hot water system (e.g. Infinity type like mine was), then swapping is relatively straightforward. If the existing gas system uses electricity (like the Infinity does), then there might not be any electrical 'infrastructure' work needed.

Ducted air heating
I haven't done this, but I'd have thought that replacing a gas furnace with a heat pump for ducted heat would be a relatively easy one-for-one exchange - there must already be an electricity supply for the blowers. You get the added bonus that the new system will blow cold air in the summer as well as warm air in the winter, which will probably increase your energy bills overall since you will use the air-conditioning when the weather gets sweaty

Cooking
This was the first stage of my de-gasification programme. There are quite a few stand-alone electric stoves with induction cook tops available on the market, in both 600 & 900 widths. If you've got an electric oven already, you've got a power supply that ought to be sufficient. You will have to get a plumber / gasfitter to disconnect the old stove and cap off / remove its gas pipe before you can swap out the stove, and getting a gasfitter and an electrician to turn up in the right order on the right day might be complicated.
Or this could be the excuse you need for a complete kitchen renovation!

My advice: go for it, your conscience will be easier and your carbon footprints will come down from Giant Size to positively dainty 😀

Danite

42 posts

Geek

#3157295 8-Nov-2023 16:07

One thing that has put me from going heat pump hot water from LPG Infinity is not having solar. I think I will at some point put in solar and I would just go for a classic cylinder, no maintenance issues (Electric element/thermostat failures are fairly rare) my reasoning is if I'm using my own power then I'm getting maximum value per kW and the saving between heat pump HW and element HW can go towards getting solar sooner...

Not sure if I'm right though, but the cost of LPG cylinders is getting heavier and heavier so really should do something.

Edit: Forgot to add that have swapped from Gas hob to Induction this year so HW is all that is left.

mattenz

190 posts

Master Geek

#3157517 9-Nov-2023 10:11

PolicyGuy:

Ducted air heating
I haven't done this, but I'd have thought that replacing a gas furnace with a heat pump for ducted heat would be a relatively easy one-for-one exchange - there must already be an electricity supply for the blowers. You get the added bonus that the new system will blow cold air in the summer as well as warm air in the winter, which will probably increase your energy bills overall since you will use the air-conditioning when the weather gets sweaty

Not necessarily, as the output of a gas furnace is higher than a heat pump, airflow can be lower, and ducts smaller than required. Also electricity to the blowers doesn't help that much, as the major electrical cost is wiring the outdoor unit.

cddt

1548 posts

Uber Geek

#3157520 9-Nov-2023 10:14

mattenz:

PolicyGuy:

Ducted air heating
I haven't done this, but I'd have thought that replacing a gas furnace with a heat pump for ducted heat would be a relatively easy one-for-one exchange - there must already be an electricity supply for the blowers. You get the added bonus that the new system will blow cold air in the summer as well as warm air in the winter, which will probably increase your energy bills overall since you will use the air-conditioning when the weather gets sweaty

Not necessarily, as the output of a gas furnace is higher than a heat pump, airflow can be lower, and ducts smaller than required. Also electricity to the blowers doesn't help that much, as the major electrical cost is wiring the outdoor unit.

Yeah we have been told when we got a quote that the existing ducts cannot be reused.

davidgo2

46 posts

Geek

#3157522 9-Nov-2023 10:36

I went exactly this way about 2 months ago, and couldn't be happier.

I discovered that Rheem do a CO2 based heatpump (more efficent then most heatpumps and despite/because it uses CO2 actually slightly more enironmentally friendly), and the premium was not high. The name is Sanden Rheem GAUS 3000FQS Also, the Rheem technical support aftersales service was phenominal - I threw a few complex questions at them and they answered promptly, correctly and quickly. (Installers were only OK - and there was no choice in installer, they only install through one crowd - I think it was Regency Plumbing.)

As far as noise goes, nothing to worry about. It is as noisy as a typical quiet modern outdoor heatpump unit (because thats what it is). I can't hear it from my bedroom which is 6 feet away. Ironically this unit is much, much quieter then our old gas on-demand hot water system which used to suffer from pipe hammer (I think thats what its called) when it turned on suddenly.

It uses about 4-5 amps (a little over a kw) when on - but the super nice thing is that it has a slow start, so I can [and do] control it with a Shelly IOT relay without any fancy relays or anything - meaning I can take better advantage of off-peak pricing. With low-flow shower heads, we can shower 30 minutes after turning the system on because it generates about as much heat as a low flow showerhead uses, and has, I believe, mechanisms to suck the hottest water off the top of the system. Not sure if its an option - but if I were doing it again, and if it were an option, I'd see if I could couple it with an even bigger tank - the 200 litre tank is more then adequate as long as its on at least 4 hours during the day and 4 hours overnight, but if we had a bigger tank we could go for longer periods without heating and have even more ability to use it as storage/buffer with respect of use of excess solar.

I believe I calculated a payback period of about 6 years (when compared to using gas from bottles for a family of 6). By my calculations this unit, combined with electric solar is more energy efficient and flexible then using solar tubes for hot water.

We also put in an induction cooktop at about the same time - which I find better then gas to use - better temperature control - and in the same heat ballpark as gas with the appropriate cookware - although I have found our particular unit (AEG) a little temperemental.

David Go

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