Air-water heat pump current consumption and data

120sqm old building mid-60s - (still) no ETICS, but upper floor + basement ceiling insulated. 75% new windows. Consumption currently at about 22 degrees indoor temperature +/- 8 kWh including hot water with nights at 3-4 degrees and days at 7-9 degrees.

Oh yes, I have no ERR or actuators at all.

Hello first of all :),

I am new here in the forum, but I have been reading for some time to better understand my new heat pump heating system. Since the summer, we also have a heat pump as a replacement for our old oil heating. We use this to heat our renovated and insulated old building. The energy consultant calculated a heating load of 11 kW (about KFW60) for our house, and we then chose the Vaillant Arotherm plus 125 A /S2 (or were suggested this by the contractor). At the moment, I am using the consumption and energy yield data recorded by the system. We do not yet have a special heat meter or a separate electricity meter. We only have radiators. For hot water, we have a 300L hot water tank and for heating a 200L buffer tank. The system runs as it should and the house (176 m2) is as warm as desired (20-21°C). Although the real test of performance will of course be in the winter.

Here are the data from the system for the month of October.

Status 31.10.21; heating curve 0.6; flow temp. currently 28-37°C; hot water 45 °C

702.6 energy yield heating / month in kWh
4.0 coefficient of performance heating / month
225 electricity consumption / month in kWh
967 total energy yield heating in kWh
3.9 total coefficient of performance heating
145.8 energy yield hot water / month in kWh
2.5 coefficient of performance hot water / month
93 electricity consumption / month in kWh
459 total energy yield hot water in kWh
2.7 total coefficient of performance hot water

Greetings from Bergisches Land

that is already very good for operation with HK.

By now, all rooms are almost as desired at these outside temperatures between 4-7°C everywhere. WEK downstairs is still a bit too warm. But that doesn’t bother much, since our loft door to the hallway/stairwell is still missing. Soon I can get to turning the actuators off. Then there will be no more risks due to the overcurrent valve.

The heat pump ran wonderfully the day before yesterday.


Today it was a bit warmer and it is now making one cycle per hour again.


This will still be a long journey. :)

That is absolutely fine for the transition period. Maybe you have the possibility to adjust the compressor power in the lower modulation range. With my heat pump, I can adjust the compressor power like the heating curve. Of course, that only works in the professional level.

Just a stupid question. I have now set the hot water to Eco so that the heat pump runs throttled. The reason is that the heat pump is otherwise too loud for me when it runs at almost 100% capacity. Unfortunately, there are no diagrams of the efficiency over the modulation range. I would have assumed that the efficiency at 100% is not optimal due to the high lift in hot water.

I will attach myself to this question, I also think that the heat pump does not have to produce hot water with almost 100%. What are the advantages and disadvantages of Eco?