Measure heatpump COP and ultimately SPF. With EmonCMS ?


I'm Sander form the Netherlands. I've been using EmonCMS to map our companies energy usage quite successfully. I also have a small setup at home.

At home I use a mono-energetic air-to-water heat pump to heat my house. Mono energetic means I only use electricity to heat my house. When outside temperatures drop, so does the efficiency of the heat pump. This efficiency is called COP (coefficient of performance). You basically divide the heat output (watt) by the electric input power (watt)

You need a COP of 3 or above to be more cost efficient than gas heating. This point should be somewhere around 5deg Celsius. In the Netherlands we have significant time per year with temperatures below freezing point. You will need the most heating in this period. The average COP of the heat pump is called SPF; Seasonal Performance Factor.

I'd like to log my COP and SPF to see if my setup is running efficient and to determine if it's interesting to build a bivalent setup. Bivalent means the addition of a second power source like gas or wood/pellets central heating system. Basically all you need is a flow sensor and 2 temperature sensors to determine heating power output of a heat pump. Input power is already logged by EmonsCMS. Sadly I have too little spare time on my hands to build this myself.

Q1) Is there any foreseen implementation of logging heating power output on the water side of a central heating system ?

Q2) Does anyone have any experience with affordable readily available systems for COP and ultimately SPF measurement ?


Thanks !!

rbreuss's picture

Re: Measure heatpump COP and ultimately SPF. With EmonCMS ?

Hi Sander,

Im from Czech republic and our typical heating season is October - April with usuly very cold January. So, Im using air - water heat pump (F2030/7 from NIBE), which covers energy needs of my house October to December and February to April. During January there is necesseary to help heat pum by some additional electrical heating unit.

For monitoring of my heatpump I modified EMONCMS system, which now calculates seasional COP (what you call SPF we call SCOP) - calculates total energy consumed by heat pump since start of heating season and total energy delivered by heatpump, My system also calculates daily COP (called DCOP) to compare days with various outside temperature.

You can see realtime monitoring of my heatpump activity here (unfortunately is it in Czech, but I think, values and units are clear:




Sander's picture

Re: Measure heatpump COP and ultimately SPF. With EmonCMS ?

This makes me jealous ! I love it. Can you elaborate on how you have done this ? What hardware do you use ?

rbreuss's picture

Re: Measure heatpump COP and ultimately SPF. With EmonCMS ?

It is not so complicated as it seems to be:

1) You need to meassure electricity consumption of heatpump. Im doing it twice, by two independent ways for to get precise values

- by standard 3 phase  power meter designed by boredman here:

as I had problems with calibration of this powermeter, I bought at alitrade this energymeter from Eastron:

for comparison of meassured values. This powermeter is a great piece of hardware with RS-485 Modbus output of measured values

2) You need to meassure energy provided to heating system by heatpump:

​best way is to use calorimeter principle. You need to meassure flow of heating water by some flowmeter - Im using this one from Grundfos (this one is relatively expensive, you can use any other with related parameters:

​And when you know water flow, you need to measure just two more things - input and output temperature (by DS18B20) of water going in and out of heatpump, you need to know water temperature difference before and after heatpump.

Rest is just to calculate easy calorimetric equation and you know power delivered by heatpump to your heating system.

Then you cumulate in EMONCMS daily amount of energy consumed and provided by heatpump and the same for total (season) value. And when you divide daily energy provided by consumed, you get DCOP, when you do the same with season value, you get SCOP.

Not se complicated, isn't truht? :-)



Sander's picture

Re: Measure heatpump COP and ultimately SPF. With EmonCMS ?

Indeed not too complicated, but will still take a lot more time than I have available right now ;) I think the Grundfos sensor is a great idea. I was thinking of getting an eBay sensor but it needs to be reliable and accurate. The Grundfos will much likely be allot better.

I will make my own setup, in 2030, when I expect to have some spare time again ;)

rbreuss's picture

Re: Measure heatpump COP and ultimately SPF. With EmonCMS ?

Regarding flow sensor:

1) I tried some cheap chinese plastic flowmeters from eBay. I can't recommed, as they are made from plastic a heating water pressure is very limited. A when I saw it by my eyes, how is it made, Im worry it would be very risky point of my heating system. That flowmeter form Grundfos is much more expensive, but it is made from stainless steel without any moving parts, so reliability of this is quite another level that that chinese one.

2) Grundfos produces flowmeters for various flow rates. Im using  1" size, which is designed to meassure flow from 5 to 100 litres per minute. But real flow through my heat pump is some 12 liters/min. So, better for me would be probably 3/4" size  with not so high maximum flow. Next time I would buy that 3/4" instead of 1"

So good luck to your setup :-)

goodfidelity's picture

Re: Measure heatpump COP and ultimately SPF. With EmonCMS ?

Hello guys!


I'm happy to see this subject has been opened up and this is probably not so difficult as it might seem, but it might cost some money to get it done properly.

Whay you need is really just three units.

- One unit with two pulse inputs that can upload the data from two pulse inputs to the emoncms.

- One unit who will measure energy on the waterside of the heatpump.

- One unit who will measure electricity side of the heatpump.

You can choose to add a few dallas (DS18B20) sensors for diagnostics in emoncms.

Electrical meter to measure delivered energy for the heatpump can be of different kinds. Price is from €15 and up for single phase energy meter 230V. And about €55 for three phase 3x230V or 3x400V pumps. This unit will output a LED pulse. All that has to be measured is the pulse, no calibration/voltage/CTs needed. 

Energymeter on the water side requires you to add hardware into the radiator circuit. The units to be used is standard energymeters for radiator circuit with pulse output. One pipe is fitted with the mass/volume meter and temperaturmeter, and the other with just the temperature meter. Energy delivered into the house is then calculated from ∆T and volume of water circulated. Energy delivered in to the house from the pump will be displayed on this unit, and output is with LED pulse. 

COP is usualy measured at a certain temperature in datasheets, but with this setup you can monitor the efficiency over different temperature ranges. SPF is interesting in all regards.

The arduino sketch must be very easy for someone who knows how to do it, only two inputs and it has all been done before, just not this way.

It would be very nice to make this a app in the emon CMS and add temperatur for all four pipes, and outdoor and indoor temperature. (six temperature sensors in total)

Price for this installation is estimated  (one phase pump)

- Arduino €5

- Ethernet board for arduino €5

- Optical sensors x2 €9

- Thermal sensors x6 €10

- Electricitymeter one phase €15

- Energymeter for water circuit €250

Total €294.

This arduino setup can be VERY useful for people operating heatpumps as it can be used to

- evalute the pump performance, alert when service is needed

- automaticly switch between different heating systems (gas/heatpump)

- make sure the energy source has enough energy (if it is geothermal heatpump)

- diagnostics to make sure system is operating according to specifications


Also it can be used to fine tune the pump and the temperatures in the system so that the system will always be operating at the optimal efficency.

Adding this unit to the heatpump is a small fee of total installation cost, but just from the data you get in emoncms you can calibrate the pump and make sure it works perfect. The money will come back probably first year.

dBC's picture

Re: Measure heatpump COP and ultimately SPF. With EmonCMS ?

You might want to keep an eye on this project as well: which uses the IC from this reference design:

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