Gas Hot water systems

I’m in the process of replacing my 18 year old gas hot water tank. It hasn’t failed yet but I’m not taking my chances.
I have looked at tank storage and it seems somewhat wasteful to heat a 200 litre tank and keep it hot over the day. Thought about the instant on Rinnai type gas heaters but a retailer has advised that they are not the economical. Then a plumber who has done some work for me suggested one of the heat pump units are fairly economical to run but pricey to install.
Any suggestions as to where I can go to get independent unbiased advice?
I live in Melbourne with my wife in a three bedroom brick veneer home.
Any suggestions would be greatly appreciated

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I was planning on a continuous flow when my 19 year old service goes, but read they need a minimum flow rate to kick on. Our area seems to get about 22 years to a service. Serendipitously we recently spent a weekend at a home with a continuous flow service and found it challenging. I suspect there is a learning curve to using them as you cannot have arbitrarily slow flow hot water, but that could be model dependent. Most I looked at also required larger gas supply lines than storage systems, so scope and allow for extra installation costs if you need anything upgraded.

Since continuous flow systems only fire up when you use hot water, and have high efficiency heat exchangers, they have higher energy star ratings than storage tank systems. What that means in a gas bill, no idea :wink: Any operating savings need to be balanced against total installation costs amortised over the expected lifetime.

Addenda - the Rinai 26 Continuous Flow model spec states “Compatible with low flow rated shower fixtures (3 Star - 7.0 to 9.0 l/min)” but my shower head max flow is 6.5 l/min, if that reinforces the flow rate problem vs your needs.

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Hi @pgrwrx, In addition to encouraging other Community member to share their recommendations in this thread, we recently surveyed our members on their experience with hot water systems (member content) that may be of interest if you haven’t already seen it.

All the best getting it sorted.

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I’ve had 2 Rinnai Infinity instantaneous gas hot water sytem for about 15 years & it’s been great. I had the first one for 12 years without a single problem. The motor burned out & so was covered by my insurance which replaced it with the next current model which has also been working perfectly for 3 years now.
It’s connected to our natural gas but still has to be connected to electricity. Gas bill is OK except for increasing gas prices but don’t really know how much electricity it uses - wold be interesting.
The only thing that I don’t like about it is it taks a while for the hot water to start running - about 25 seconds sometimes. This seems too long & it would be very interesting how much water I waste waiting for the hot water to start?
Other than that very happy & seems reasonably priced & efficient & reliable.

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I have a similar experience with Rinnai instant gas hot water. The running cost is better than storage but the start/stop nature of the supply can be annoying in some situations. It means that you cannot have the hot water running slowly as it will turn off if the flow is too small. It also means you cannot turn it off and on again quickly as there will be a delay in the re-start and give you a cold segment in the flow. This leads you to keep it running when with storage you can turn off and on with the only penalty being a little cooling in the pipe.

When our Rinnai reached its use-by date we went solar which solved both the gas price and intermittency problems.

Despite the contortions of current governments the domestic price of gas will remain high and is likely to go higher. In your planning do not ever think we are going back to the cheap gas of five years ago - that will never come again. This problem has nothing to do with local supply and everything to do with gross mismanagement over a period of time by successive governments.