Progressively higher and higher power usage

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KiwiTT

123 posts

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#323277 14-Nov-2025 06:50

We installed a new Rheem mains pressure hot water cylinder, to replace an old leaking main pressure cylinder.

I have included daily power consumption hourly charts.

23 March - Day before Installation
24 March - Day of Installation
25 March - Day after Installation

As you can see, the daily usage seems pretty usual over those 3 days. I have now included daily examples each month after that, and you can see that in the last 3 months daily power usage has increased excessively, from what was normal.

I may have expected higher power bills due to heater use, but we only have the heaters on for a 1/2 in the morning and a couple of hours at night over winter. However, for the last month or so, we have not used heaters at all.

I got an Electrician friend in and he determined the Hot Water Cylinder is using the high power. I have got the installer to coming in soon to check the cylinder.

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hsvhel

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#3434408 14-Nov-2025 10:44

When he deemed it "High power" did he explain it at all?

Is it heating excessivly or for longer periods than needed? more a thermostat issue

What's the temp set to on the cylinder?

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wellygary

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#3434411 14-Nov-2025 11:12

My first go to would be the thermostat on the cylinder, then a potentially leaky connection,

djtOtago

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#3434512 14-Nov-2025 11:56

Over winter, our Mains pressure hot water cylinder uses more power because the incoming cold water is a lot colder.

fe31nz

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#3434703 14-Nov-2025 23:30

Is there a dripping hot tap somewhere? The shower maybe?

Bung

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#3434704 15-Nov-2025 00:34

Did the plumber use new valves with the new cylinder or reuse the old ones? Is there hot water leaking from the relief valve?

tweake

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#3434728 15-Nov-2025 10:47

i would be looking for leaks first. most common is overflow, especially the pressure relief valve as that leaks hot water. 2nd is the cold water relief valve (i can't remember its correct name). also the pressure regulator. if thats failed the over pressure valves will start letting water out. if no water from those, then taps or pipes somewhere.

it could be stuck thermostat, but that would boil the tank and the pressure relief valve would open letting very hot water out.

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Colin5

8 posts

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#3434767 15-Nov-2025 15:21

I had similar problem years ago.

Ended up being the water inlet valve not shutting off properly, so cold water was continuously feeding into the cylinder.

Check if you can hear water feeding in and/or check if water is coming out the overflow pipe.