emonTX heat pump monitoring - no CoP estimate?

Good evening,

I’ve just setup a new emonTX with WiFi, got it logging to the emonPi emonCMS instance and created the feeds for flow temperature, outside temperature and power consumption.

The heat pump app is not displaying the estimated CoP though as I expected it would from the documentation " * Easy installation on existing system.

  • Estimate COP using flow and outside temperature"

The only estimate visible is via the ‘show detail’ option but this requires manual input of parameters including the outside temperature which goes against what is suggested in the documentation. If the inputs for the estimate are manual then the additional hardware is not required at all.

What am I (obviously!) missing?


I’ve just noticed that @microadam has asked essentially the same question minutes before me here: Basic Heat Pump Monitoring - A few questions

Happy to have this thread closed and just stick with Adam’s query.


Hey Colin! Great timing :smiley:

Sounds like we are going through a similar journey together on this one!

Hello @Aceshigh84 @microadam the estimate of COP is available if you click through from the daily view to the power and temperature view and then click on ‘show detail’ and put a tick in the ‘Simulate heat output using carnot COP equation’ box:

It doesnt give COP estimates on a daily basis and the calculation does have significant limitations, it’s just a basic carnot COP calculation. It works particularly well on my system as my standby system power is very low and there’s only one central heating pump which is a very low power one, the heat pump electricity consumption is therefore mostly the compressor.

While my example above shows only a 1.5% error, I’ve seen the error get to >25% on other systems or periods of rapid cycling, defrosts etc. So it’s really just indicative and it’s accuracy does depend quite a bit on the configuration of the heat pump system being monitored.

It’s useful in giving an idea for what the COP should be at a given outside temperature and flow temperature but it isn’t necessarily what you are actually getting…

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Thank you @TrystanLea . You have confirmed my suspicions - the new emonTX wasn’t required after all for the basic monitoring!

To do it properly requires a heat meter, from the documentation it is only the emonPi or emonBase that can work with a heat meter. Is this the case or can the emonTX be used with a heat meter monitoring solution? I don’t have an emonBase and the emonPi I do have is in another part of the house.

If it can’t it’s likely I’ll be returning the newly purchased kit as it’s not needed.


FWIW, when we put the heat pump in, I moved my emonPi close to the heat pump and put my emonTx doing the main consumer unit.