Pressure wrote: ↑Tue Apr 02, 2024 2:16 pm
However the ASHP feeds UFH in concrete floors across the whole house, everything is a heat store - when the ASHP has failed in the past it’s taken a couple of weeks for us to actually notice.
However I don’t know what the actual power usage of the ASHP, which is pathetic, but it’s hard to know what to install to measure it (or where to put the ct clamps of a monitor…).
I have been trying to answer similar questions prior to getting an HP installed. As you can see from my sig there is quite a lot of kit already.
Your existing thermal storage (slab) is by far the cheapest form of energy storage and by the sound of it will carry you across the 3 hr peak periods. And meets your other criterion <Reliable manufacturer with a good support network - I need this device to be supported in 7 to 10 years time>.
So have you tried setting the HP to switch off at peak times and see if the result is acceptable?
Next cheapest is storage as hot water, do you have any scope for more of this? I am planning a 215 litre thermal store but even so the payback is 12 years if you assume 20% electricity tariff inflation
see this thread.
Batteries are the most expensive option of the lot. Not least because of the limited lifespan. We settled on 10.65kWh; the financially optimal size was only 7.1 but it was running out annoyingly often in winter. Now we charge it on E7 from 0000 to 0700 to a level which depends on the next day's weather forecast and it mostly lasts until midnight. But we have a lot more solar PV and cook on an AGA in winter. So 13kWh may well be the sweet spot for you.
Here is an overview of my annual usage, there is a lot
more detail here.
Yes an external meter is the only reliable way to measure actual HP consumption, I have fitted a 1-module DIN rail mounted one in my CU for £40.
Other ppl on here have got good results by going to either Cosy or Intelligent Octopus Go, worth investigating also.