HeatpumpMonitor.org absurd efficiency readings

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.

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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 :slight_smile:

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 :grinning:

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. :slight_smile:

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?

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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.



Perhaps we need to put a disclaimer on the site that says “Performance values are indicative only and may not be accurate in all cases” or something…

"Use these figures for comparison. Your mileage may vary due to speed, trip length, weather. Actual highway mileage will probably be less.”

Something like that - perhaps signpost to the forum and the experience of helpful, kind community that exists!

Not just honest but also knowledgeable. You know your flow meter is incorrect and compensate for it - others might not do that and hence the reported values would be wrong. It would be good to have some gorm of self-consistency checks in those meters.

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Personally I’ve found this resource invaluable to get my heat pump running at what I consider acceptable efficiency for the system that was installed. I’m very grateful that the shared data and associated community that exists. I feel like I’ve ‘used’ OEM and heatpumpmonitor for its intended purpose.

However, I have thought that there is no doubt that installers of systems will be pointing to their installations on the heatpumpmonitor.org “league table” to potentially increase sales/justify an increased price to potential customers (if they aren’t already, I’d imagine the practice would increase as heat pump installations increase). I’m not sure there’s an easy answer to this, as has been mentioned it is straightforward to “cook” the numbers. Even with manual vetting of systems, fudge factors can be introduced after a system is verified (as others are describing in this thread), I’m also not sure that is an approach that will scale as more and more systems are added to the site.

Having said that, as always, it’s caveat emptor for any potential customer who is being shown data on this site to verify the validity of the data they are being shown.


That’s a fair point, we’ll consider this. However, there are so many variables on each system sites, users really need to look at what’s included in the monitoring and notes accompanying the systems. e.g the top performing Vaillant Arotherm was in an unoccupied house! We’re trying to dilute the focus from just using COP as a metric, the Fabric and Cost tabs are trying to do this. In reality, anything above SCOP 4 is fantastic and above this it’s diminishing returns.

The systems in the top 10 in terms of SCOP get more scrutiny because these are the systems which get more attention.

We can check the input processing of any account. We do an initial check when a system is approved, for most system that use our monitoring bundle we setup the input processing for them. After it’s been approved, we probably won’t check it again unless evidence is brought to our attention. Systems with issues are flagged.

HeatpumpMonitor-org (3)

We also have a team of admins which also help with reviewing and flagging data issues. It’s not a perfect system, but we try our best to ensure data is as accurate as possible.

I’ve added a data issue flag with a note

Potentially true, however a heat meter will only ever underreport if it’s dirty rather than over-report which will result in lower COP.

I think it’s great that installers are using real world independently monitored performance data as a sales tool!

If a user is ‘cooking the numbers’ to such a degree that it’s inflating their system, it’s quite easy for us to check the underlying kWh figures reported by the MID meters which are impossible to change. If an issue was found, it would be publicly visible when we flag it. I don’t think any installer would take this reputational risk.


A “monthly accounting sanity check” wouldn’t be too difficult to publish.

Ignore the instantaneous values etc and do an end of month delta end of previous month to show energy use, heat delivery, and COP. You could also show volume weighted deltaT and derive the mean flow rate when in operation using this and delta energy to give an idea of what the operating conditions are. (typical temperature rise from return to supply and typical system flow rate)

Doesn’t prevent incorrect meter location/installation but does eliminate any configuration issues AND makes it possible to key manual values in from manually read heat/elec meters such that those who JUST buy the heat/leccy meters can get some ide of how their unit performs seasonally?

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Not top performing, but ours is currently unoccupied. Is there anything you would prefer I did/add to the listing?
My expectation is that the space heating load would fall once occupied. Certainly don’t intend to mislead or confuse.

The electrical monitoring includes the internal controller inc. 3way valve & EMon monitoring system.