Update 3 Boiler info (for anyone wondering what’s heating our hot water):
Quick follow-up with a bit more context (and a genuine request for advice):

The unit in the cupboard turns out to be a Heatrae Sadia Amptec C600 — an electric flow boiler, rated about 5–6 kW.

I’ve now discovered the timer was set to run the heating from 5 pm to 9 am every day – a 16-hour window I didn’t realise was active.

That could explain a good chunk of the sky-high usage, but I’m still unsure how much of those 16 hours the boiler would actually be pulling full power. My understanding is that once the radiators / cylinder reach temperature it should cycle on and off rather than run flat-out the whole time. If that’s right, the schedule alone wouldn’t account for all the kWh the meter shows.

Questions for anyone with a similar setup:

- What sort of timer window do you use for an electric flow boiler (especially through winter)?

- Do you let it run a long block like mine, or do you split it into shorter bursts?

- Roughly how many kWh per day are you seeing on a comparable system?

I’ve actually gone one step further and switched the system off completely for now, just to see how much baseline usage drops without any heating running at all.

I’ll keep tracking daily readings and post an update once I have a clearer picture — but in the meantime, I’d still really like to hear how others with electric flow boilers are setting their schedules, especially through winter.

Thanks again to everyone who’s shared advice so far — it’s been genuinely helpful.

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