How to measure and show COP without a heat meter
ie, just using the data from within the Arotherm Plus and compared to OpenEnergyMonitor heat meter data.
Below are OpenEnergyMonitor / heat meter figures recorded on my 5kW Arotherm Plus during December 2022, where temperatures in Sheffield dropped to -3C (average 4.3C across the whole month).
All figures / COP shown are for both heating and hot water combined.
OpenEnergyMonitor / Heat Meter figures
- Electric input: 647kWh
- Heat Output: 2195kWh
- COP: 3.39 (2195 / 647)
Measure COP Using Vaillant Data
Vaillant explain on this document how to measure COP.
The gist being:
So we need to know where to get “energy yield” and “power consumption” from.
I have the Sensocomfort room controller and you can get the figures from there.
- From the front menu showing “Control”, “Information” and “Settings”, choose “Information”.
- From there, choose “energy data”, which shows you “environmental yield”.
- This is the “energy yield” mentioned in the Vaillant calculation.
(perhaps this difference in terms is lost in translation to English?)
Like me, if you take this snapshot on the last day of the month, you can see the total for that month (current month). Alternatively, just do it when your into the next month and look at “last month”.
For Power Consumption, again from Energy Data, choose the “Power Consumption” option.
In here, the data can be seen as
- Heating Only
- Hot Water Only
- Installation (ie, all the above added together)
As the Yield figures aren’t broken down into the separate elements, i’m not sure how useful the broken down power consumption figures are?
So for us to make a calculation we need to head into the “Installation” option to get the total power used.
So for “Current Month” we’ve got the following figures:
Environmental Yield: 1427kWh
Power Consumption: 631kWh
Remember the Vaillant calc was (Yield + Power) / Power, so
(1427 + 631) = 2058 / 631 = 3.26 COP
Note: You can also get the monthly Yield figures from the heat pump controller, but there is no way of getting monthly power consumption from the controller. So it’s really tough to make your own calcs from the data on the controller.
But the controller does show you its own COP figures, which it calls “Working Figure”
Here are the Working Figure screen grabs for the same day (last day of December) from the Heat Pump Controller (VWZ AI).
The bottom line is that the COP from openenergymonitor / heat meter setup is pretty close to the built-in Vaillant COP figures (using both the Working Figures from the controller or using the raw data from Sensocomfort controller).
So on this evidence, the built-in information on the Vaillant Arotherm Plus is likely good enough for most regular folk.
- Heat Meter COP: 3.39
- Sensocomfort COP: 3.26
- Controller: COP 3.2 heat (2.4 hot water) - AKA “Working Figure”
But whilst the COP are around the same ballpark, we notice that the raw data from the Sensocomfort isn’t exact when compared to the heat meter.
Electric Input (3% out?)
- Heat Meter: 647kWh
- Vaillant: 631kWh
Heat Output (7% out?)
- Heat Meter: 2195kWh
- Vaillant: (1427+ 613) = 2058kWh
But close enough for most people not to care?
Hope this helps.