Revisiting hot water heat pumps

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545 posts

Ultimate Geek

#3348455 27-Feb-2025 17:43

Mik:

Revisiting this as I've just done a bunch of investigations and number crunching.

I've looked at a bunch of units from various manufacturers and settled on the Midea 280L, for a number of reasons.

Thanks for your reply! We're in the market as well, and I'm also interested for the Midea. So, you have the combined version (i.e. not the split one)? Any particular reason why?

I guess the split systems are slightly more efficient is what I read, but harder to install.

Are you still enjoying it?

timbosan

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#3348462 27-Feb-2025 18:24

boland:

Mik:

Revisiting this as I've just done a bunch of investigations and number crunching.

I've looked at a bunch of units from various manufacturers and settled on the Midea 280L, for a number of reasons.

Thanks for your reply! We're in the market as well, and I'm also interested for the Midea. So, you have the combined version (i.e. not the split one)? Any particular reason why?

I guess the split systems are slightly more efficient is what I read, but harder to install.

Are you still enjoying it?

Just an update, I ended up getting a Rheem unit, and it has an in built timer (BEST feature!) so no mucking around with extra work on the switchboard, circuits, CT clamps, Shelly's, etc. I have mine switching off early evening and on in the AM.

It also freed up a LOT of internal space, isn't really noisy (I can hear it running with the windows open) and I am happy :-)

The screen does have a Wifi symbol but I don't think its available on the NZ units, however I don't really need my HWHP on a dashboard ;-)

Mik

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Geek

#3348467 27-Feb-2025 19:45

boland:

Thanks for your reply! We're in the market as well, and I'm also interested for the Midea. So, you have the combined version (i.e. not the split one)? Any particular reason why?

I guess the split systems are slightly more efficient is what I read, but harder to install.

Are you still enjoying it?

It's been fantastic. It uses such a small amount of energy for what seems like unlimited hot water.

Getting it hooked up to WiFi was a little challenging, but once I had it I wondered how I found it so hard the first time :)

We were replacing an existing gas hot water system which was mounted on the back of the house in an alcove and so, for convenience, we decided to use the same fittings - it was as easy as pouring a small concrete slab to put it on and everything else just fitted.

The split systems are no more efficient and cost a bit more to install. We installed ours ourselves.

I've convinced my parents and sister to replace their electric hot water with the Midea. It will pay for itself in power savings in a couple of years.

Mod Edit |Stu| corrected the person attributed to in quote.

DjShadow

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#3388441 30-Jun-2025 20:40

Reopening this thread as I’m now in the market for a Hot Water Heat Pump.

Currently we use Natural Gas to run a Califont (I believe it is over 10 years old) as well as a Hob, plan is to use the Green Loan option with ANZ to install both Solar and a Hot Water Heat Pump.

To date I’m sitting on a quote from HRV to install a 250L Haier Monoblock for around $7500 but wondering if anyone else in the Wellington region has come across anything better?

Mik

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Geek

#3388443 30-Jun-2025 20:48

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

timmmay

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#3388445 30-Jun-2025 20:59

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

Nice option. Our standard hot water heater takes 3.2kw and does 2.5h per day. Something like that would save us about $400 per year, and it's cheaper than a standard Rheam mains pressure cylinder at least at retail prices here. I'm not sure why the heat pump hot water cylinder is cheaper than a standard cylinder.

Stu1

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#3388446 30-Jun-2025 21:00

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

dustysmurf

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#3388448 30-Jun-2025 21:33

Mik:

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

I looked at this a few weeks ago and saw that it needed to download an App to control it, And thought no thanks.
Is it possible to just connect to it over wifi for complete local control?

Thanks

Scott3

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#3388454 30-Jun-2025 23:02

For those upgrading their hot water solution, who are either on a 3 hours of free power plan, or have / are getting a big solar setup, it is worthwhile evaluating a big (ideally 400L) duel element cylinder against a heat pump setup.

They very simple and hence Cheaper, long lasting & reliable.

The idea being that if you can get free power from your 3 free hours, or power in the middle of the day from your solar setup which has an export opportunity cost of say 8.5c / kWh. to feed the bottom element via a timer or solar controller, and have 24/7 power on the top element to much reduce the risk of running out. Hence getting free or very cheap hot water, without the cost, noise etc of a hot water heat pump.

www.geekzone.co.nz/forums.asp?forumid=141&topicid=316109

That's not to discredit how good hot water heat pumps have got in the recent years. If you want max efficiency this is it.

Handle9

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#3388455 30-Jun-2025 23:16

Scott3:

For those upgrading their hot water solution, who are either on a 3 hours of free power plan, or have / are getting a big solar setup, it is worthwhile evaluating a big (ideally 400L) duel element cylinder against a heat pump setup.

I'd be very hesitant to base my business case for resistive vs heat pump water heating on free power that can be withdrawn at any time.

It's a good idea for solar though if you use enough hot water.

Mik

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Geek

#3388458 30-Jun-2025 23:47

dustysmurf:

Mik:

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

I looked at this a few weeks ago and saw that it needed to download an App to control it, And thought no thanks.
Is it possible to just connect to it over wifi for complete local control?

Thanks

Mik

12 posts

Geek

#3388459 1-Jul-2025 00:03

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

timmmay

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#3388472 1-Jul-2025 07:23

Scott3:

For those upgrading their hot water solution, who are either on a 3 hours of free power plan, or have / are getting a big solar setup, it is worthwhile evaluating a big (ideally 400L) duel element cylinder against a heat pump setup.

The solar buyback rate is quite good in many places in NZ, mine is only 10% less than my power buy price - 19c buyback, 21c buy. If I spend about the same money on a Midea heat pump water heater as a large standard cylinder that means I can push an extra 2600kwh or so to the grid, which is $500 a year extra credit on my power bill.

Let's guess the Midea lasts 10 years to the standard cylinders 15 years - I've heard mains pressure cylinders don't last as long as the older lower pressure. $500 a year means in 10 years we have $5K savings and we spend half of that on the replacement, we're $2K ahead. If it doesn't last as long, or the standard cylinder lasts longer, then the economics become more questionable.

ringbearer

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#3388549 1-Jul-2025 09:49

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

What are the noise levels on the Midea like? Our current infinity isn't silent, but I'm interested if it would be louder. It would be running more consistently, so a bit of a trade off I imagine.

Scott3

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#3388570 1-Jul-2025 10:59

timmmay:

Scott3:

For those upgrading their hot water solution, who are either on a 3 hours of free power plan, or have / are getting a big solar setup, it is worthwhile evaluating a big (ideally 400L) duel element cylinder against a heat pump setup.

The solar buyback rate is quite good in many places in NZ, mine is only 10% less than my power buy price - 19c buyback, 21c buy. If I spend about the same money on a Midea heat pump water heater as a large standard cylinder that means I can push an extra 2600kwh or so to the grid, which is $500 a year extra credit on my power bill.

Let's guess the Midea lasts 10 years to the standard cylinders 15 years - I've heard mains pressure cylinders don't last as long as the older lower pressure. $500 a year means in 10 years we have $5K savings and we spend half of that on the replacement, we're $2K ahead. If it doesn't last as long, or the standard cylinder lasts longer, then the economics become more questionable.

My mains pressure cylinder (indoor) looks very original, and my house is 30 years old. Can't speak to other's experiences.

In term's of financials, elephant in the room is how cheap those Midea units are at around $2.5k. For comparison a Rinnai HydraHeat 275L is $6499 RRP, and a Rheem AmbiPower280e is $5150 at plumbing world.

A Rheme Twin element cylinder is $3125 for 300L or $3435 for 400L. Even allowing an extra $500 for the timer and duplicate run to the circuit board, still comes in more than $1000 cheaper than the top tier brand heat pump options. If one was doing solar at the same time (and had enough roof space), that money could go to adding more panels, and one could run the finical analysis between spending more on panels & compared to spending on a heat pump.

But getting back to elephant in the room, Them Midea heat pump unit is not only half of the price of the Rinnai & Rheme heat pump units, but also undercuts a basic 300L or 400L Rheme twin element cylinder. I can't find any lower tier brand large capacity cylinder to run the comparison against.

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