Revisiting hot water heat pumps

Forums › Home Workshop DIY › Revisiting hot water heat pumps

1 | ... | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12

13755 posts

Uber Geek
+1 received by user: 6236

ID Verified

Lifetime subscriber

#3414175 12-Sep-2025 13:35

timmmay:

I was thinking of replacing our standard cylinder with a heat pump cylinder, but when I looked at the payback period it was fairly long - I can't remember exactly.

Realistically, it's what you do when you need to replace the HWC. Because you would have to pay for most of the other work anyway, you're really just having to pay the premium of the Heat pump over the regular HWC.

We average about 9kW/h per day for hot water, up to about 6kW/h of that is during the day (hopefully covered by solar) so without solar 6kW/h x $.2343 ($1.41) + 3kW/h x $.1123 ($.34) = $1.75 per day to heat water if you save 70% with a heat pump, that's $1.23 per day or about $450 per year saving.

Comparing like for like outdoor cylinder (3kW) vs outdoor heat pump unit 280L
$2295.00 vs $4799.00

So payback period of about 5.5 years for just an upgrade of cylinder. Yes there is more too it with instillation over and about a regular cylinder so your mileage my vary.

DjShadow

4228 posts

Uber Geek
+1 received by user: 1325

ID Verified

Trusted

Subscriber

#3414178 12-Sep-2025 13:45

timmmay:

What's the payback time on a $8400 hot water cylinder? It would depend on your water use I guess. I wonder how that compares with a standard hot water cylinder. You'd probably assume power price rises of maybe 5% per year.

I was thinking of replacing our standard cylinder with a heat pump cylinder, but when I looked at the payback period it was fairly long - I can't remember exactly.

I've not worked out the payback time yet, I'm doing this with a Solar install but working on the idea of 80% less power consumption. Also the 1% loan from ANZ helped with this.

mattwnz

20542 posts

Uber Geek
+1 received by user: 4813

#3414301 12-Sep-2025 18:55

timmmay:

What's the payback time on a $8400 hot water cylinder? It would depend on your water use I guess. I wonder how that compares with a standard hot water cylinder. You'd probably assume power price rises of maybe 5% per year.

I was thinking of replacing our standard cylinder with a heat pump cylinder, but when I looked at the payback period it was fairly long - I can't remember exactly.

plus replacement cost as how long is it designed to last for. 10 years? I am not sure it adds up unless you are using a lot of hot water. I ssh hair with an infinity hot water heater which heats on demand. I guess if gas runs out there could be bio gas

rphenix

990 posts

Ultimate Geek
+1 received by user: 127

ID Verified

Lifetime subscriber

#3414870 14-Sep-2025 15:04

mattwnz:

plus replacement cost as how long is it designed to last for. 10 years? I am not sure it adds up unless you are using a lot of hot water.

I did the sums 8 years ago and it made sense then - it paid itself off ahead of time thanks to power cost increases and now with more people in the house so higher consumption - ours is a split system so you can fall back to using the resistive element in the tank if the heat pump plays up - something I would highly recommend for anyone considering one.

Handle9

11995 posts

Uber Geek
+1 received by user: 9815

Trusted

Lifetime subscriber

#3414944 14-Sep-2025 19:19

rphenix:

mattwnz:

plus replacement cost as how long is it designed to last for. 10 years? I am not sure it adds up unless you are using a lot of hot water.

I did the sums 8 years ago and it made sense then - it paid itself off ahead of time thanks to power cost increases and now with more people in the house so higher consumption - ours is a split system so you can fall back to using the resistive element in the tank if the heat pump plays up - something I would highly recommend for anyone considering one.

What were the numbers?

jjones

30 posts

Geek
+1 received by user: 5

#3415254 15-Sep-2025 20:38

DjShadow:

Our Carrier HWP just gone in (plumber from A2W plumbing still here as I type), it's a lot bigger than how it appeared in the promotional material. Natural Gas now fully redundant and hoping Genesis will have someone over as early as tomorrow to take the meter out.

Real good timing too as we got an e-mail from Genesis yesterday indicating our line rate was going to $1.63/day and the use rate going from 16c to 24c per kW.

I got a few questions regarding this model as I am planning to get one installed:

Is this the 300L Carrier Blue?

By any chance can you control it via app and what can you do in the app?

Does it also come with a panel inside your house?

How Noisy is it?

In term of energy consumption how is it?

Why did you purchase this over the likes of other HWHP (i.e. Rinnai Hydraheat)?

Kickinbac

477 posts

Ultimate Geek
+1 received by user: 101

#3415526 17-Sep-2025 08:47

DjShadow:

Got the final invoice and thankful the quoted price was the final price, this is a copy/paste:

Price $8401.29

Carrier are one of the most trusted heat pump brands in the world and offer a market leading 10 year warranty. This R290 unit with a 300L capacity offers excellent efficiency at a remarkable price point.

✅Ideal for medium to large households
✅Recovery time, 71/Lhr
✅10yr warranty
✅Frost protection
✅COP of 4.6
✅R290 Refrigerant

Included in this quote is the following:
- Disconnect and dispose of existing HWU.
- Supply and install Carrier Blue 300L Hot Water Heat Pump complete with associated valves and pipework.
- Connect hot and cold water to existing supplies.
- Electrical connection.
- Cap gas at meter.
- Base for HWC.
- Test and commission.

Not Included in Quote:
- Removal of gas meter. Please note this must be done by your gas provider.

Gas meter coming out today so thankful that is one less headache charge wise on the power bill!

What is the cost of the gas meter removal? Plus could you advise your gas supplier and region.

There is some discussion on another topic so would be great to have some real world numbers.

DjShadow

4228 posts

Uber Geek
+1 received by user: 1325

ID Verified

Trusted

Subscriber

#3415530 17-Sep-2025 09:00

jjones:

I got a few questions regarding this model as I am planning to get one installed:

Is this the 300L Carrier Blue?

By any chance can you control it via app and what can you do in the app?

Does it also come with a panel inside your house?

How Noisy is it?

In term of energy consumption how is it?

Why did you purchase this over the likes of other HWHP (i.e. Rinnai Hydraheat)?

Yep 300L Carrier Blue, its new out hence not a lot of information floating around on it

Uses the Carrier App, same one you’d use for your heat pump. Control wise you can set the temp, set vacation mode and do a manual disinfection cycle. Also shows the current temp so good evidence if you have someone in the house that loves hot showers and uses up all the hot water!

Noise wise, it is noticeable. It’s running as I type this and sounds like a gentle hum. I am running it in Economy mode hence it takes a few hours to heat up but have got the option to use the electric element in it for fast heating if needed.

Can’t comment on energy consumption yet as the app doesn’t show any energy consumption stats, I’m hoping to have my solar up and running in a few days so that might give some clues. One thing I can mention, we had our natural gas meter removed on Friday just been and looking at our Genesis app the predicted bill figure 6 days into our cycle has dropped from around $370 to $190, nothing the weather has warmed a little and we’ve not been using the heat pump as much.

Cost was the driving factor, the Rinnai Hydraheat is made in NZ which the plumber noted contributes to the higher price, but he went on to say the international built units are just as good.

DjShadow

4228 posts

Uber Geek
+1 received by user: 1325

ID Verified

Trusted

Subscriber

#3415532 17-Sep-2025 09:03

I got the bill from Genesis yesterday for removing the meter, it was $230 inc GST

In the Hutt Valley (Wellington Region), Powerco manages the Gas Network here

jjones

30 posts

Geek
+1 received by user: 5

#3415533 17-Sep-2025 09:07

DjShadow:

jjones:

I got a few questions regarding this model as I am planning to get one installed:

Is this the 300L Carrier Blue?

By any chance can you control it via app and what can you do in the app?

Does it also come with a panel inside your house?

How Noisy is it?

In term of energy consumption how is it?

Why did you purchase this over the likes of other HWHP (i.e. Rinnai Hydraheat)?

Yep 300L Carrier Blue, its new out hence not a lot of information floating around on it

Uses the Carrier App, same one you’d use for your heat pump. Control wise you can set the temp, set vacation mode and do a manual disinfection cycle. Also shows the current temp so good evidence if you have someone in the house that loves hot showers and uses up all the hot water!

Noise wise, it is noticeable. It’s running as I type this and sounds like a gentle hum. I am running it in Economy mode hence it takes a few hours to heat up but have got the option to use the electric element in it for fast heating if needed.

Can’t comment on energy consumption yet as the app doesn’t show any energy consumption stats, I’m hoping to have my solar up and running in a few days so that might give some clues. One thing I can mention, we had our natural gas meter removed on Friday just been and looking at our Genesis app the predicted bill figure 6 days into our cycle has dropped from around $370 to $190, nothing the weather has warmed a little and we’ve not been using the heat pump as much.

Cost was the driving factor, the Rinnai Hydraheat is made in NZ which the plumber noted contributes to the higher price, but he went on to say the international built units are just as good.

Thanks for your reply. Apparently this dhw-300n7 has a solar PV mode based on the brochure.

Warranty, featurewise, tank size wize this is a better value than the Rinnai hydraheat. It can also go upto 60-70 which the spec sheet for the hydraheat does not say.