Data discrepancies on Daikin units

Hi Ali,

I will apologise in advance!

My honest advice is to buy and fit an OEM level 3 monitoring system, than you will know for sure how your heat pump is performing and how efficiently it is heating your house.

I would never have been able to sort my problems without it.

It has been invaluable and was worth every penny.

It’s my opinion, but EspAltherma, as good as it is, is limited and because I can think of no other way to describe it, a bodge.

It’s not reliable, accurate and doesn’t tell you how much heat is going into your house.

Like I said, I apologise, but it’s how I feel about it.

The data situation is totally up to you. Personally I wouldn’t worry about it as a heat pump is designed to be a long term investment, if you want to mark and track improvements add it into the system notes that you swapped meters for a more accurate one on x date (That’s all I done with the ASHP swap, kept all the old data).

I can’t speak for everyone but I use the site and the comparisons to debate and discuss various configurations and see what if anything can be improved. I am not looking for a gold medal or chest on which to pin it, I would rather just see what we can make these units do in the real world and how many others we can get into the high 4 or COP 5 club and save some energy.

It is always good to see how the flow temperature impacts the performance as you have loads of youtube videos and data telling you low is more efficient and more comfortable but until you actually experience it and can see and compare the stats you really don’t get a good idea of the difference.

I will take a peek at the MMI data and see if I can spot any differences later this evening.


Agreed, I’ll put a note in the profile and keep the data as is.

ESPAltherma is a bit of a bodge, but it’s nice to get some stats with minimal investment. I’ll reconsider the L3 monitor.


I understand the attraction of EspAltherma, I really do.

But I think too many users make the mistake of thinking that the data is accurate enough.

It can be miles out and that makes it completely useless, in fact even worse, it can make a heat pump owner think that their system is working well.

The proper monitoring is not really about getting data for data’s sake.

It is about getting the best from your heat pump, maximising efficiency and minimising electricity consumption. You can only do that with reliable data.

EspAltherma can be ok in its raw form but then people start messing with the data to correct perceived errors, then they are just kidding themselves.

The worst bit is them being presented in the same place as properly monitored systems, they just don’t belong anywhere near each other.

I am sure people will disagree with me but it is how I feel.

Hi Ali,

Do you know why Octopus wanted to install a 9kW Daikin when your heat loss was only 5kW?

No idea, it was at the preinstall check that the plumber remarked at how large the unit was compared to the heat loss. When I queried it and sent them your mega thread as a reference to why I wanted the 8kW there was no reply other than “you can get the 8kW unit instead”.


Hi Ali,

Your electricity consumption looks about right now when the heat pump is running.

But there is a problem when it isn’t running.

I would guess that the meter you are now using isn’t very good at measuring small currents.

Maybe you could fit a couple of SM120 meters in the Octopus consumer unit, there is usually plenty of space on the DIN rails.

You can get them from the OEM shop.

From what I have seen the data collected from the heat pump flow and return temperature sensors by EspAltherma is good and all that matters is the dT in any case.

However, looking at your data this morning when the heat pump was steady, the dT is 5.9c which is suspect if you have it set at 5c

The Daikin heat pump is good at holding the set dT and I think it is the main point of reference for control, it is always trying to maintain the return temperature based on the dT set and the requested flow temperature.

I have my dT set at 10c at the moment because I want to ensure that the pump is always running at its lowest flow rate.

If you look at Zak’s data he has his dT set to 3c and even though the flow temperature varies the dT is maintained at 3c. Just select a period when the heat pump has been running past the initial heating phase and you will see in the summary detail what I mean.

Yes that’s odd as I calibrated it at ~100W and 3kW. I like your idea about the SM120, I’ll look into it. Do you mean two for the pump and immersion heater?

I’ll go back and have a play with dT and see how my sensors react. No heating today though as I’m brewing which depletes my battery, it’s warm enough outside anyways.

I was able to increase the granularity of the Shelly 3EM to report every 10 seconds. I also used on of the other two clamps which reports idle power in similar ranges to other Daikin 8kW systems. Since I did that I decided to set everything to 10 seconds which meant creating new feeds in emoncms it seems. Not to worry, I’d rather have more accurate stats. The pump ran this morning for a few hours, but I’m getting the same odd gaps in the instant COP that I did before, anyone know why that is?

I’m still trying to work out how best to fit an SDM120 as I’ll need that + 5v PSU + esp32 to capture the data and I don’t have space in the consumer unit for all that.