Flow temperature at 27.5°C, electrical power at 400 W in warm air.
Flow temperature at 37°C, electrical power over 4kW in cold air.
It’s not too surprising to see lower performance when the heat pump is working hard to deliver 12 kW of heat in cold weather, compared to it just ticking over in warmer weather.
This is the 9 kW, Nibe F2050-10 in Bristol
Compared to a similar unit (Cadross, Dumbarton) (red) we’re seeing similar levels of COP vs. Flow Temperature (Jan - April), yet the one in Bristol (blue) is running at much lower temperatures.
Thanks, the maximum carnot efficiency I can see for this system is 65% which is high but plausible. You can enable carnot efficacy under the ‘show details’ section. In this particular example heat pump is delivering a very low flow temperature of 25C with a relatively high outdoor temperature of 10C
However, overall the system has a SCOP of 4.78
This system is using MID approved heat and electricity meter. However, as you can see on heatpumpmonitor this system is not monitoring the electricity used by the internal controller or the circulator pump which is probably around 100W total: https://heatpumpmonitor.org/system/view?id=65. If an extra 100W of electricity was included, this would reduce the COP in this example of 8 to 6. We push all installers to include the energy used by all pumps in the system, but if they choose not to, it’s fine as long as this is clearly stated on the heatpumpmonitor form, which it is in this case.
There’s no data for 25C flow!
Trystan wrote about System Boundaries in this post:
Just wondering on the reasoning behing why pump power should be included in the COP? When I want to compare a heat pump to a gas boiler, I care about how much primary energy is used to get a specific amount of heat into the house. The electrical energy used by the lump goes into the auxiliary energy use of the gas boiler, the heat energy comes from burning the gas. Assuming I’m targeting the same flow temperature, a gas boiler will use the same electrical energy to pump the water around as a heat pump. Now if I want to know exactly how much energy I’m saving by using a heat pump, shouldn’t I look at COP without pump energy included?
I’m wondering what type of system have to be used to manage heating with flow temperature of 25 degrees and return of 23 degrees? I think to heat a swimming pool we need higher temperatures?
Most heat pumps have the primary circulator pump inside the outdoor unit, therefore the energy used is always included.
Because heat pumps are so efficient, the energy used by the circulator pumps or multiple circulator pumps e.g primary, secondary pump(s), UFH manifold pump(s) etc. can have a significant detriment to the performance, therefore its important if possible they are included in the performance monitoring. Some heat pumps have more efficient pump control strategies than others, e.g slowing down the pump between compressor cycles or when less heat is required, it’s all part of the overall system efficiency. On a heat pump system, the circulator pump will generally be running for a lot longer compared to a gas boiler and flow rate will be higher, so direct comparison cannot be made.
It’s a large UFH setup with a lot of thermal mass. 25C is still higher than the required room temperature, so heat is still being delivered, about 2.5kW in the above example. The flow temperature will increase with weather compensation in colder weather when more heat is required.
Hi @glyn.hudson
So when you look at the heatpumpmonitor main page there is no indication that there is any difference between MID monitored systems.
I was only saying to @KnightPhoenix last night that I would now get a NIBE given a choice because it looks great.
But in reality, it’s not as good as my Daikin potentially.
It’s not very clear and you have to dig a lot to find fine details with no easy way to compare.
I know this is all difficult and it doesn’t really matter but a COP. of 8 that is really only 6 when comparing to fully metered systems is quite a difference.
I don’t really have a simple answer and anything I could suggest is probably beyond the scope of the site.
But really, anybody can tick any boxes they like and it can’t be easily verified. It relies on good faith and honesty which I am sure most have but also a bit of knowledge.
The reality is that this NIBE system isn’t quite as good as it appears.
Yes, it’s complicated! This is one example of why looking at COP is not always a very good metric, since the COP in the colder season matters much less compared to the COP in the middle of winter when most heat will be delivered. Your Daikin in working great, I wouldn’t be considering any other heat pump at this point.
Before a system can be published to the site, there is a verification process where we do our best to check that what the user claims is being monitored e.g for NIBE we know they have external pumps therefore this requires a 2nd meter, so we’ll make sure we can see data coming from the 2nd meter in the account. We can check the underlaying data inputs and check which meter(s) the data is coming from. For the majority of systems, we’ve supplied the hardware, so we know exactly how many meters are being used.
We did actually supply a 2nd meter for this NIBE installation, but the installer ended up re-purposing it to monitor a booster heater, which had to be retrofitted since this heat pump is undersized and couldn’t provide enough heat in winter. We’ve suggested that fitting a 3rd meter would be preferable.
Thanks Glyn.
I think we all appreciate what you all do and it is a great resource.
It’s so valuable.
I am not considering changing my heat pump, it’s going OK 
I think it would be nice if there was a clearer definition between the grades of monitoring.
I’m no football fan but maybe like football leagues.
Some different way of presenting the information so that a closer look is prompted.
In this case, some clear sign that the electricity consumption is not fully reported.
If it has a pump like my 9kW Daikin then the consumption could be closer to 200w than 100w.
But who knows?
That’s a fair point. We’ll have a think about this. Once option would be to apply a crude offset for systems without primary circulation monitoring. This could intentionally be on the pessimistic side, which would incentivise the installation of a meter to get an accurate reading 
Really? It’s very unusual for a pump to use more than 50W. Looking at data from another NIBE which has monitoring on the controller + circulator. It uses 50W when the pump is running normally and 20W when it’s running at a lower speed in-between cycles.
The circulation pump in the 9kW Daikin is the same as the others in the range up to the 16kW.
It’s a monster, it really is.
See, I wouldn’t know that NIBEs have external pumps and I could have looked at that information and just think they hadn’t ticked the box.
I guess you would only know how much electricity is consumed by getting details of the pump used.
What I might do if the site was mine was have the default view as fully monitored MID systems where you know for a fact that they include everything and then have tick boxes as you do now for MID not fully monitored, non MID without known/suspected errors and then those systems with known errors.
Then it would be clear and visitors to the site would be presented with verified properly metered data by default and if they want to look at others then it is their choice.
Some of us are sad middle aged people who have gone through a lot to make their heat pumps work well.
It’s pathetic I know, but to realise now that a system I thought was just better than mine but actually isn’t doesn’t feel so good.
Heat pumps have a problem, they are too complicated with too many variables for many people.
To get one to work well is quite a task, and sad as it is, many of us judge our work and get satisfaction by comparing to others.
I have spoken to Trystan about this aspect, as great as public data is, it is not always that healthy but it is so hard to avoid getting sucked into trying to be better.
I’m sure I am not alone in this, the nature of optimising a heat pump makes it competitive to some extent.
MID meter doesn’t stop you cooking the numbers though, because you can apply adjustments to data feeds very easily.
I do this to adjust my heat meter power output by +4% because I know it is dirty and under-reporting slightly.
How is this controlled? I tweaked my HP power (see below) because the meter is dirty and I know it’s under-reporting (see Sontex heat meter accuracy over time), but noone has reviewed this or flagged it.
Thanks, I really appreciate the perspective, I always looked at it from a gas vs heat pump view. Of course it makes sense when comparing heat pumps to one another. However it would still be very useful to be able to separate auxiliary energy use from the energy going into the compressor. This would allow to separate intricacies of the hydraulics (multiple pumps etc) from the performance of the heat pump itself.
Perhaps “MID Metering” option should be unticked for this system, if it’s not operating within tolerance?
Probably, until I get service done and things flushed out. I was making a more general point though, that even if MID meters are used, that doesn’t necesarily mean MID values in heatpumpmonitor.org It’s very hard to control validity of results without controlling everything, and therefore heatpumpmonitor.org does rely on people being honest.
Fascinating discussion!
The issues being discussed around data and behaviours that it drives (intended or unintended) are certainly not unique to the heat pump space!
I’ve shared before that in my view data is there to help us ask better questions. The information on heatpump monitor is associated with a forum and a community. I think the two work together well and perhaps all that is needed is to continue to build understanding of the possibilities around variation - there’s a challenge in oversimplification, as much as there is in adding detail.
There is a balance in there somewhere and it’s always going to rely on individuals.
Kevin
