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Octopus Cosy Heat Pump Owners & Discussion Thread

AndrewJ · 2025-10-23T11:37:06Z

I'd like to discuss how you find it, how you run it and so on.

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Air Source Heat Pumps (ASHPs)

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AndrewJ

(@andrewj)

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Topic starter 24/10/2025 2:45 pm

Posted by: @jamespa

↑

Yes if it results in the heat pump being cycled on and off, which clearly it does. In this circumstance it's the average you need to think about which is 0.8kW consumption. It's on-off control not proportional control

Thanks. Hopefully others will be along to comment on their experiences and set up.

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JamesPa

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24/10/2025 2:49 pm

The cycling suggests that there may be scope to reduce the WC a bit. This should give a performance improvement overall, although you may not immediately be able to see that.

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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Toodles

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24/10/2025 4:08 pm

@andrewj In case the comparison is worth anything, here is a chart showing the Homely controlled 8 kW Daikin EDLA08 monobloc for the day of 23rd. October. The values are for IAT (set to 22.5 degrees C 24/7) OAT and power used. More details of my home and insulation etc. in my profile if you wish to read it. The COP was reported as being 4.2 over this period. Regards, Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

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AndrewJ

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Topic starter 24/10/2025 4:35 pm

Posted by: @toodles

↑

@andrewj In case the comparison is worth anything, here is a chart showing the Homely controlled 8 kW Daikin EDLA08 monobloc for the day of 23rd. October. The values are for IAT (set to 22.5 degrees C 24/7) OAT and power used. More details of my home and insulation etc. in my profile if you wish to read it. The COP was reported as being 4.2 over this period. Regards, Toodles.

Interesting, thanks. It looks like yours is operating on/off as well (currently) - I don't see the total power input or a kWh scale. The Cosy yesterday, showing input/output and OAT:

It reported a COP of 4.37 so very similar.

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Toodles

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24/10/2025 5:04 pm

@andrewj The power consumption varies between the peaks at switch-on of ~1.7 kW and ‘tickover’ at about ~300 - 400 Watts. I note that today with lower temperatures, the pump is running most of the time - ticking over between ~400 - 800 Watts. Regards, Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

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Toodles

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24/10/2025 5:22 pm

@andrewj Here is a chart of ‘Today so far’, I have added the ‘Heating on/off’ data from which you can see that at the overnight temperatures, the pump stayed on ticking over; the system returned to cycling as the temperature rose this morning of course. Regards, Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

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Toodles

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24/10/2025 5:38 pm

@andrewj In this chart, I have selected just the power demand and this in turn also indicates

when the pump turns on and off. Regards, Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

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AndrewJ

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Topic starter 24/10/2025 5:51 pm

@toodles Thanks - it would seem that apart from the cycling mine does (it can't ever stay continuous) then power consumption is similar.

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wreckguru

(@wreckguru)

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24/10/2025 6:04 pm

@andrewj my house is pretty balance for supply and I have lazily adjusted just 2 TRV in 2 bedrooms from 5 to 3.5 and that's it.

I am running 21c all day everyday and 19c overnight.

I am getting all my energy at 14p thanks to home battery and cosy tariff.

The Octopus "system" of PV, battery ASHP and tariff is a great formula.

Also available at other providers, though.

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AndrewJ

(@andrewj)

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Topic starter 24/10/2025 6:15 pm

Posted by: @wreckguru

↑

@andrewj my house is pretty balance for supply and I have lazily adjusted just 2 TRV in 2 bedrooms from 5 to 3.5 and that's it.

I am running 21c all day everyday and 19c overnight.

I am getting all my energy at 14p thanks to home battery and cosy tariff.

The Octopus "system" of PV, battery ASHP and tariff is a great formula.

Also available at other providers, though.

I'm assuming that it is cycling around the 21c and not running continuously?

I'm on Intelligent Go with 16kW of battery and so far all my electric consumption since May has been at 7p although I've exported enough to cover all my incoming electric and banked £350 (as at end of September)

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wreckguru

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24/10/2025 6:16 pm

I thought I would share some stats here too.

As I said I run 24/7 at 21c and 19c setback overnight. I also do 2x 50c dhw cycles per day at 250L.

With my solar PV and battery I have the following bills for 2024/25 full year - for my whole house...

Usage total: 4886kw

Production total: 2925kw

Import £668 - Export £438 = Paid £229.

Needless to say I am very happy with that.

Less happy it doesn't include the standing charge😂

But also have nearly £100 in credits due to savings and power up sessions, which nearly nets off ...

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AndrewJ

(@andrewj)

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Topic starter 24/10/2025 6:21 pm

Posted by: @wreckguru

↑

I thought I would share some stats here too.

As I said I run 24/7 at 21c and 19c setback overnight. I also do 2x 50c dhw cycles per day at 250L.

With my solar PV and battery I have the following bills for 2024/25 full year - for my whole house...

Usage total: 4886kw

Production total: 2925kw

Import £668 - Export £438 = Paid £229.

Needless to say I am very happy with that.

Less happy it doesn't include the standing charge😂

But also have nearly £100 in credits due to savings and power up sessions, which nearly nets off ...

I'm running 24/7 at 22c with no setback. Not tweaked any of the WC setting yet.

I don't know how else to ask this and I sometimes think I must be speaking Martian as even on the Facebook Octopus group I can't get an answer: is your Cosy running continuously (i.e. ALL THE TIME, low and slow) or does it go on/off based on the temperature read by the Primary Pod letting the temp drop and thing bringing it back up again?

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