Revisiting hot water heat pumps

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#3388606 1-Jul-2025 12:39

Mik:

Stu1:

Mik:

Our Midea has been great - https://tradedepot.co.nz/heat-pump-water-heater-280l/

uses about 500W/h and takes 2 hours a day to heat to 55C

Wifi built in, I have it connected to home automation for monitoring and control

and $5K less than the Haier

I did a lot of research - there are thousands of these installed in Australia with very low failure rate. Midea are one of the largest Chinese manufacturers- millions of units a year

I really struggle with the ROI, even with gas prices I’m still better off keeping the gas continuous water till it craps out. I have just got Solar and the Savings I’m getting help offset the gas line charges. It’s a shame that there is no decent one phase continuous electric hot water systems out there. Worked out payback 10.8 years for a HPWH ouch. Still a lot of local plumbers don’t recommend water heat pumps as a good investment

We had a 3 year old Rinnai infinity 26, but our gas supply charge had gone up to $2.50/day and projected to go to over $4

It was the only gas appliance, so we bit the bullet and wrote off the unit - the plumber did the work, including the concrete pad and capping off the gas in exchange for the Rinnai - so saved a bundle. He was updating a rental he inherited so win:win

The Midea is over 100Kg and difficult to handle, so it was a pig to get in place - couldn’t use anything wheeled

We’ve gone from $90/mo to $0, so ROI is less than 2 years (I paid under $2000 delivered)

Any plumber being hesitant over heat pump hot water just hasn’t got an affordable unit to sell. My mate in Oz is a plumber and he’s installed over 400 Midea stand-alone and split systems with less than a handful of issues - all were installation-related

i probably bite the bullet one day . So far options to degas are over 30k . My gas is $2.11 per day and 9.6 c ( excludes GST). New central heating heat pump 23 k , new water heat pump 8k before installation. Unless both units crap out it’s a massive outlay .

alasta

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#3388658 1-Jul-2025 13:51

I live alone in a small unit and currently spend $660 a year in daily gas charges. To transition away from gas I would need to install:

An induction hob to replace the existing gas unit.
An outdoor hot water cylinder to replace the on-demand gas unit (there is insufficient space indoors).
Either a heat pump or some sort of feed from the new hot water cylinder to the existing heating radiators that are currently fed from the gas hot water.

A 5% ROI on $660 would allow a capital outlay of up to $13k. Am I right in thinking that's well short of what would be required to do all of the above?

cddt

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#3388667 1-Jul-2025 14:27

Stu1:

i probably bite the bullet one day . So far options to degas are over 30k . My gas is $2.11 per day and 9.6 c ( excludes GST). New central heating heat pump 23 k , new water heat pump 8k before installation. Unless both units crap out it’s a massive outlay .

I have the same challenge here. I keep doing the numbers but can't mentally pull the trigger on 30-40k of upgrades when the mortgage is still so large...

My referral links: BigPipe | Mercury

Stu1

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#3388701 1-Jul-2025 17:10

alasta:

I live alone in a small unit and currently spend $660 a year in daily gas charges. To transition away from gas I would need to install:

An induction hob to replace the existing gas unit.
An outdoor hot water cylinder to replace the on-demand gas unit (there is insufficient space indoors).
Either a heat pump or some sort of feed from the new hot water cylinder to the existing heating radiators that are currently fed from the gas hot water.
A 5% ROI on $660 would allow a capital outlay of up to $13k. Am I right in thinking that's well short of what would be required to do all of the above?

I’d say at least 15k minimum

WWHB

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#3388757 1-Jul-2025 18:17

With anything from trade depot you are getting exactly what you pay for. I will give you they are cheap but as a plumber I have to warrant what I install so I don’t install trade depot products. It’s worth paying more and getting back up service and a decent warranty.

I only really install 4 brands and all 4 I can service and repair and with 3 of the brands if I can’t repair on the day I can swap out for a brand new unit. No waiting for parts or a service agent. You want a company that stands by the product.

Scott3

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#3388775 1-Jul-2025 18:56

alasta:

I live alone in a small unit and currently spend $660 a year in daily gas charges. To transition away from gas I would need to install:

An induction hob to replace the existing gas unit.
An outdoor hot water cylinder to replace the on-demand gas unit (there is insufficient space indoors).
Either a heat pump or some sort of feed from the new hot water cylinder to the existing heating radiators that are currently fed from the gas hot water.
A 5% ROI on $660 would allow a capital outlay of up to $13k. Am I right in thinking that's well short of what would be required to do all of the above?

Depends on if you want cheap stuff or flash stuff

For the hop, if you are happy with cheap, you can get one for $250

https://tradedepot.co.nz/60cm-induction-cooktop-with-touch-control/

But an F&P is $1700

https://www.noelleeming.co.nz/p/fisher-paykel-60cm-4-zone-induction-cooktop/N148442.html?

+ install

60cm Induction cooktops general need a 32 Amp feed. The cost of will depend widely on the ease of getting a run to the switchboard. Versions which are restricted to a max draw of 16 Amps do exist to serve people replacing induction Cooktops who do not want to run a fatter wire, but you may not have any provision for electricity to the hob.

Also induction cooktops are thicker than gas cooktops and have a cooling clearances. If one is even going to fit in the hole in the bench needs checked.

But lets assume $1000 for the electrical work.

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For the Heat pump hot water, a cheap one can be under $2k

https://www.micromall.co.nz/midea-heat-pump-water-heater-170l?

But a reputable brand seem to start at $5- $6k (and there is little selection of small tanks that would suit a small unit and a lone occupant). Lets assume $5414 incl gst for the stiebel eltron W 222 (non H version).

The Non H version doesn't have a backup electric element so draws a max of 0.55 kW or 2.3A. This one can work down to -5 (perhaps avoid if you live somewhere super cold), so does not need a backup element (but has the option to get one for a rapid recovery of the top 80L, something not required for a person living alone)

Unsure of the regulations, but possible this could be plugged into the gas water heaters power socket, still out of abundance of caution still allowing the same for the sparky as the cheaper option.

https://www.5merchants.co.nz/shop/hot-water-heat-pumps-wwk-222?

https://www.stiebel-eltron.co.nz/wwk-222-heat-pump

Again plus install, but this time both a plumber and sparky is needed.

Plumbing is fairly simple, but including a base for the cylinder, capping the gas etc, I would still expect it be be getting close to $1000.

For the electrical, the Midea 170 only needs 12.3A, but unless the gas water heater is on an existing circuit this still likely needs a new circuit run which will add cost. But lets assume $500

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For high wall heat heat pumps, we had a Mitsubishi AP25 (that brands smallest non-mini) installed (simple back to back) for $2242.50 in 2024. Futizu was $230 cheaper. (note price varies wildly by vendor) I'm guessing the unit is a lounge and a bedroom and two of these 3.2 kW nominal heat pumps would get the job done. For inflation, lets assume 2x $2400 heat pumps for both cases, as I am very fond of my Mitsubishi electric.

For me 3x minisplits ended up being cheaper for the upstairs rooms of our house than either a multisplit setup of a ducted setup (with 3x control zones), so I went with the 3x mini splits.

Of OP thinks they can get away with just a single larger heat pump in the lounge (kind of sucks, but seems to be the NZ way, perhaps allow $3k instead of the $4.8k).

Might be prudent to ensure the lounge heat pump passes the healthy homes sizing requirements, incase the house is ever rented or sold to an investor.

Heating by tapping into the above hot water cylinders to run radiators isn't going to work, The heat pumps outputs are 1500W-1800W, and that is rated at warm ambientes, declines when it is really cold. Simply not enough grunt to handle both water heating and space heating.

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I think a gas disconnection fee is about $200, haven't made allowance for this. Also haven't allowed for decommissioning the gas stuff, or removing the radiatiors.

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Cheap option: $9550

Expensive option: $14,415

So (if I am in the right area with my electrical estimates), the cheap option is comfortably inside you $13k budget, and the flash version is just a little outside budget.

Not sure if the $13,000 is the value to use (this is the NPV of a $660 annuity in perpetuity).

Key factors here:

Gas prices (both kWh and daily) are trending up faster than general inflation. There a few reasons for this:
- NZ's gas fields are in decline, and although there are exploration permits in the wild nobody seems to be keen to do prospecting in this part of the world at the moment. This drives up the cost of the gas itself
- Less gas availability and hence use (and declining numbers of residential connections) means the fixed costs of the gas transmission and distribution pipes needs to be shared around lesser use.
- It seems all involved are keen to eek out as much revenue from the gas infrastructure through it's sunset period.
Most people work on much shorter time horizons. Many consumers expect payback period of say 7 years, ignoring inflation, this only allows $4,620

But of course there is a lot more to consider:

Those gas appliances may be approaching end of life anyway.
The ability co provide summer cooling of heat pump provides additional amenity value.
The heat pump air and water heating will likely be a lot cheaper to run. Natural gas is ~14c/ kWh. a heat pump at COP 3 on 30c power costs 10c / kWh of heat
Indoor air quality & safety advantages of moving away from gas cooking.
May need new cookware for induction
May have a preference between gas an induction cooking.
Aesthetics changes from radiators to heat pumps.

Generally I suggest people on gas ride out the rest of the life of their appliances. Staring down at $2k+ cost to replace the gas water heater would make it a lot more attractive swap to electricity.

alasta

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#3388924 2-Jul-2025 09:15

Thanks Scott for the detailed analysis. It is really helpful.

I'm not keen on taking the 'cheap' route for the reasons noted by the plumber commenting above, so I agree with your final conclusion that it's not really a viable project until my existing appliances are approaching end of life. My home was built new five years ago so the appliances still have a decent amount of life left in them, but in another five to ten years time I will have a go at building a proper business case for the switchover.

Your point about heat pumps having cooling capability is notable. My place gets extremely hot in the middle of summer, so I would probably need to get some form of cooling if I ever get pets.

k1w1k1d

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#3388929 2-Jul-2025 09:36

Hi WWHB.

What are the four brands that you recommend?

PolicyGuy

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#3388930 2-Jul-2025 09:41

An alternative analysis is to regard this as an ethical rather than economic issue.

Instead of asking "can I get an acceptable return on the money invested?", ask "what can I afford to do to reduce my carbon footprint?". In my case, part of the answer was to de-gas my house.
Yes I am probably SKIing (Spending the Kids' Inheritance) to some degree, but I hope I'm also contributing - in a tiny way admittedly - to giving the same kids (and grandkids) a chance of living in a more habitable future.

Yesterday, the maximum temperature in Spain & Portugal was over 44°C and it's only June ...

Mik

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#3388947 2-Jul-2025 10:11

Interesting how some on here say “reputable brands’, and then Midea, like somehow they are disreputable because they aren’t F&P (someone who will never get a penny from me)

FWIW, they are the largest HVAC and appliance-maker on the planet, by some margin. In business since the 60s, they have a US$40B annual turnover, are the world's largest producer of industrial robots and appliances.

I spent the last 20 years prior to 2020 living in Asia - Midea is a hugely respected brand. Many of those “reputable brands” are made in Midea’s factories. Panasonic heat pumps are rebadged Midea. Toshiba is owned 80% by Midea and almost all products are made by Midea-group factories

Don't let a lack of familiarity and price snobbery make you think they are ‘cheap’ or low-quality

Mik

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#3388948 2-Jul-2025 10:17

PolicyGuy:

An alternative analysis is to regard this as an ethical rather than economic issue.

Instead of asking "can I get an acceptable return on the money invested?", ask "what can I afford to do to reduce my carbon footprint?". In my case, part of the answer was to de-gas my house.
Yes I am probably SKIing (Spending the Kids' Inheritance) to some degree, but I hope I'm also contributing - in a tiny way admittedly - to giving the same kids (and grandkids) a chance of living in a more habitable future.

Yesterday, the maximum temperature in Spain & Portugal was over 44°C and it's only June ...

That was 90% of my reason for spending nearly $30K on solar and electric appliances - my wife’s was to reduce our outgoings prior to retirement

When our battery has proven itself, we will likely go off-grid-in-town - pretty much all our bill, currently, is service fee

Handle9

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#3389090 2-Jul-2025 14:50

PolicyGuy:

An alternative analysis is to regard this as an ethical rather than economic issue.

Instead of asking "can I get an acceptable return on the money invested?", ask "what can I afford to do to reduce my carbon footprint?". In my case, part of the answer was to de-gas my house.
Yes I am probably SKIing (Spending the Kids' Inheritance) to some degree, but I hope I'm also contributing - in a tiny way admittedly - to giving the same kids (and grandkids) a chance of living in a more habitable future.

Yesterday, the maximum temperature in Spain & Portugal was over 44°C and it's only June ...

In the vast majority of cases the best thing you can do to minimise your actual carbon footprint is to not to replace functional equipment. The carbon emissions of the capital works is significant compared to the ongoing carbon emissions.

Mik

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#3389095 2-Jul-2025 14:57

Handle9:

In the vast majority of cases the best thing you can do to minimise your actual carbon footprint is to not to replace functional equipment. The carbon emissions of the capital works is significant compared to the ongoing carbon emissions.

That's a misconception.

You're never going to reduce or claim that carbon back - going to a carbon-negative appliance as soon as possible at least has a chance to offset that CO2 emitter, somewhat, where hanging on to that old gas appliance just adds more pollution to the environment

It's like the argument of hanging on to your old, cheap car, because it costs X in carbon to build it and you need to get that value out - the best thing you can do is recycle it as soon as you can and get something greener. That's the only way of getting the carbon back

Handle9

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#3389096 2-Jul-2025 15:00

Mik:

Handle9:

In the vast majority of cases the best thing you can do to minimise your actual carbon footprint is to not to replace functional equipment. The carbon emissions of the capital works is significant compared to the ongoing carbon emissions.

That's a misconception.

You're never going to reduce or claim that carbon back - going to a carbon-negative appliance as soon as possible at least has a chance to offset that CO2 emitter, somewhat, where hanging on to that old gas appliance just adds more pollution to the environment

It's like the argument of hanging on to your old, cheap car, because it costs X in carbon to build it and you need to get that value out - the best thing you can do is recycle it as soon as you can and get something greener. That's the only way of getting the carbon back

It's not a misconception, it's maths. One has a bigger number so that is the one that has the biggest carbon impact.

There is also no such thing as a carbon negative appliance just as there is no such thing as creating energy.

Mik

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#3389105 2-Jul-2025 15:28

Handle9:

There is also no such thing as a carbon negative appliance just as there is no such thing as creating energy.

There's no such thing as a pedant, either.

Oh, wait - It seems I'm incorrect about that, too.

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