Octopus Heat Pumps

Exiled_Tyke

Magnitio said:

Some of the earlier quotes on here were also with £5000 grant rather than the £7500 grant.

I've an estimate of £6k from Octopus. But it's a large 4 bedroom detached.  Very different from the OPs property which hopefully shouldn't be too difficult and therefore inexpensive. 

Reed_Richards

racingmars said:

Hi all, 

I am new here... i joined as I am looking into replacing our 38 year old (seriously) oil boiler.

We are with Octopus, so I got the initial quote, which came back as £935.  We live in 3 bedroom semi detached 1950s ex council house.  We have cavity wall insulation already.

I am certain our radiators will need upgrading, but the quote said that this would be included.

A number of the posts that I've read on this forum seem to have quotes in the 1000s.  I don't understand the vastly different quotes, pre and post survey.  I have no doubt that extra work will need to be done, but still can't see why such a difference.  What am I missing?  What small print have I missing? 

Thanks all

When you get a full quote it should include a calculation of the rate of heat loss from your house for a particular low outside temperature, typically a few degrees below zero.  In my case my house was calculated to lose 8.95 kW when it is -3.7 C outside.  Your heat pump and radiators will be sized so that they can meet this demand.  In my case this meant a 12 kW heat pump running at a Leaving Water Temperature (LWT) of 50 C and radiators with a large enough surface are that with 50 C flow and 45 C return their total output would be just a bit more than the 8.95 kW required.  But there is no one right answer here, you could achieve the same heat output with larger surface area radiators running at a lower LWT or smaller surface area radiators running at a higher LWT.

Actually there is a right answer, which is to use as low a LWT as you can get away with without making your radiators inconveniently large because that is what will give you the lowest running costs.  Check what values Octopus quote you.     

Spies

My current combi is in the garage where all the heating and water pipes go, could I have a hot water cylinder on the wall in the position that the boiler is or does it need to be higher up in the house? 

Netexporter

Spies said:

My current combi is in the garage where all the heating and water pipes go, could I have a hot water cylinder on the wall in the position that the boiler is or does it need to be higher up in the house? 

They're mains pressure fed, so can be anywhere.

Reed_Richards

If you can squeeze a hot water cylinder inside the insulated fabric of your house that would be far better.  Any hot water cylinder and the pipes to and from it will lose heat and you'll save money if that heat is not wasted.

Spies

On heatpumpmonitor, of the units installed by octopus, the highest cop is only 3.6 

QrizB

Spies said:

On heatpumpmonitor, of the units installed by octopus, the highest cop is only 3.6 

Well, matt_drummer's Ipswich heat pump is showing a 30-day COP of 4.0 at https://heatpumpmonitor.org/, and that's Octopus. Where are you looking?

Spies

QrizB said:

Spies said:

On heatpumpmonitor, of the units installed by octopus, the highest cop is only 3.6 

Well, matt_drummer's Ipswich heat pump is showing a 30-day COP of 4.0 at https://heatpumpmonitor.org/, and that's Octopus. Where are you looking?

That's where I was looking but I was having issues with the filtering so couldnt see that. 

Reed_Richards

Spies said:

On heatpumpmonitor, of the units installed by octopus, the highest cop is only 3.6 

paul991 said:

.... remember the cosy 6 is  for  a higher run temp so if that is what they fit existing rads should be ok see what they say after the survey 

These are different comments from different people but the two viewpoints are diametrically opposed.  Either you want a high COP or you want to keep your existing radiators.  The chances of having both are very slim.   

Meatballs

Spies said:

On heatpumpmonitor, of the units installed by octopus, the highest cop is only 3.6 

The heatpumpmonitor ratings need to be taken with a pinch of salt.

There's only one Altherma on there with 365 days of readings.

SCOP can often drop over the summer as the low hot water COPs bring the average down. I also don't think comparing a combined SCOP is useful in the slightest, climate and DHW SCOPs should be reported separately. A well insulated house with high hot water demand would do worse than a poorly insulated house with low water demand on SCOP for example.

I would suggest Octopus installs are more likely to be taking advantage of TOU tariffs like Cosy/Go/Intelligent. I currently hammer my heatpump overnight on Go to preheat the UFH which drops my COP. I also bump flow temps when I have solar excess bringing down that COP. 

And 3.6 basically brings the cost of heating to almost equivalent as gas anyway (on the standard rate tariffs)