@wreckguru ‘Seasonal’ COP suggests that an accurate assessment requires that data is required from a full season, (and I would suggest that for truer figures, this should be from four full seasons). COP may be a measurement of any duration but obviously the longer the sample, the more meaningful it might be. Regards, Toodles.

@toodles I assume, but have not checked, that the adjustment can be made empirically?

@wreckguru With Homely, the estimated COP has the rider that it is only as accurate as the data it is given to work with; I am very sceptical of claims for my system’s COP as I am reliant on the Daikin data obtained from the bog standard measuring equipment fitted as standard.
By the way, I am too lazy to note down my consumption and heating figures every few weeks and my Homely graphs don’t provide historic data so establishing my SCOP would be a PITA!
Should I be allowing +or- 5%, maybe 10% - even 20%? I really don’t know, but I am assuming that any errors are probably fairly consistently erroneous! Homely often reports my COP between 3.8 - 5.5 depending on OAT and I am heating to 22.5 degrees C 24/7. This reported figure may be inaccurate but I suppose comparative. As they say, GIGO. I would be very pleased if the figures could be confirmed as correct - but the bottom line is acceptable as far as we are concerned, we are comfortable and we can afford the bills. Mind you, I am all in favour of reducing the iniquitous ‘Spark Gap’ and paying a more reasonable price for my green energy! Regards, Toodles.

@wreckguru how has your COP been during these last few cold days?

3.46, so pretty decent I think?

@wreckguru, is there any chance you can get the measurements of your 250 litre tank? I'm in the process of having a survey done by octopus and am thinking of locations for the hot water tank to go, and I'm limited on cupboard size inside the house? They have said the tank can go in cupboard but with all vessels and volumisers above in the loft. Thanks mate

There is some sort of association between Octopus and Heat Geek now isn’t there? Heat Geek have been doing work on tank designs and sizing recently; it may be worth having a look at the HG website if like me, you are short of space for a DHW. (I solved the problem by going down a totally different route: the Sunamp Thermino range of immersion heater / solar powered / heat pump driven routes is expensive but solved our difficulty). Regards, Toodles.

Probably better from the picture here.  They also supply Joule cylinders (same manufacturer). 

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@wreckguru, is there any chance you can get the measurements of your 250 litre tank? I'm in the process of having a survey done by octopus and am thinking of locations for the hot water tank to go, and I'm limited on cupboard size inside the house? They have said the tank can go in cupboard but with all vessels and volumisers above in the loft. Thanks mate

Yes -

ABOUT.HEATGEEK.COM "https://about.heatgeek.com/partners"

Partners — Heat Geek

And a video/interview.

https://www.youtube.com/watch?v=ZlvDKiSrvW4

They get a lot of criticism from other installers, but bang for buck it's still a no brainer.  And with winter SCOP now a 3.96 I feel efficiency isn't a real world concern...

Posted by: @toodles

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There is some sort of association between Octopus and Heat Geek now isn’t there? Heat Geek have been doing work on tank designs and sizing recently; it may be worth having a look at the HG website if like me, you are short of space for a DHW. (I solved the problem by going down a totally different route: the Sunamp Thermino range of immersion heater / solar powered / heat pump driven routes is expensive but solved our difficulty). Regards, Toodles.

I am in the fence currently after seeking four quotes including one with octopus. Octopus have quoted me for a cosy 9 for my 4 bed property with microbore throughout. I am worried as the other installers have quoted at least three times more with one even including a microbore upgrade to 15mm pipework. How long have you had the cosy 6 now? I also need 21 to 22C throughout my property so I worry if a 9kw ASHP will be sufficient.

I've had the Cosy6 since August, so we are after the 3rd -ve cold snap of the winter now.  The pump is working very well and I keep my house all day everyday at 21c with a 2c setback overnight. 

I have 10mm microbore and didn't alter any of it (I don't view it as an upgrade if it is not needed.).  I guess it depends how you are plumbed - but Heat Geek say that 10mm microbore can carry 1,150w of energy at 0.9mps.  As I am not an expert I read this to mean that if you have a pipe run with radiators totalling up to 1,150w then you are fine.

My biggest rad is 929w (@dT30) and as best I know each pipe runs individually to each rad. (Although we have not had the floor up to look, but belief is that it runs from a single manifold from primary to each rads flow.)

Either way it works well and even if the ashp was running slightly less efficient due to microbore it would not matter from cost angle.  For my usage (~8kW) and price (13p) my quotes were (after BUS):

Local Quote £18k
Heat Geek £12k
EDF £6k
Octopus £3k

I assume the Heat Geek included some new pipe work as that price is outrageous.  I had a quote to re-pipe at £3k. 

Assuming a more efficient system was just £3k more than Octo (and not £6k!) and further assuming a terrible SCOP of 2.8 (which it isn't) and a brilliant SCOP of 4.2 (which I don't think Heat Geek will guarantee) then the savings per year are £123, return on performance investment is 24 years.  

My SCOP is currently 3.57.  Will probably go up a bit when the bulk of winter is over.

That was the analysis I did, before going for Cosy6 which I find absolutely brilliant.

Posted by: @chansug

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I am in the fence currently after seeking four quotes including one with octopus. Octopus have quoted me for a cosy 9 for my 4 bed property with microbore throughout. I am worried as the other installers have quoted at least three times more with one even including a microbore upgrade to 15mm pipework. How long have you had the cosy 6 now? I also need 21 to 22C throughout my property so I worry if a 9kw ASHP will be sufficient.

@wreckguru that is very reassuring. Thanks. My cosy 9 installation has been postponed to June time due to storms in Ireland probably production problem. They were asking if I will go with Daikin if if I don't want to wait. They are yet to come back to me on that.