Bafa: Renewable Energy Heat Pumps with Test Certification

look at the Bafa list, the Cop value for A2W35 should be in the range > 4.2-4.3, then it is worth calculating.

Do not undersize the heating system, otherwise it quickly becomes a bivalent operation and then the annual performance factor is ruined. We were almost desperate about that... V used an incorrect U-value (standard value for low energy and not ours) for our building envelope in the calculation and therefore ended up with too high a load - but this was later corrected.

What nonsense. You can achieve 4.5 with a good air-water heat pump!

Just enter the following into the annual performance factor calculator:

Heating limit temperature: 12°
30 flow temperature, 23 return temperature
Buderus, air, Logatherm WPL 8 AR
Standard outside temperature: -16
Monoenergetic
Bivalence: -10°

=> Annual performance factor 4.5 according to VDI 4650.

You can gladly enter that, but it also depends on what you actually achieve. Are your 30° flow temperatures really enough at -16°? (That must be very well insulated/tightly installed). Is the heating limit temperature really appropriate? How warm/cold is it really on average in your region during the heating season (location makes a big difference here!). How warm do you want your hot water to be (that can significantly lower the annual performance factor!).

In the actual tables from people who have an air-water heat pump, it often looks different.

One should know a heating load and then plot it into the performance diagram of the heating system. This way, the bivalence point can be calculated.

This is my heating system, the pink line is the heating load of 9.3 kW including hot water (at -16°).
With the "2er" heat pump, a bivalence point of -9° results, with the "3er" one of -13.2°.

You can gladly enter that there, but it’s also about what you really achieve. Are your 30° flow temperatures really enough at -16°? (That means it has to be very well insulated/tightly laid). Does the heating limit temperature really fit? How warm/cold is it really on average in your region during the heating season (location makes a big difference here!). How warm do you want your hot water (that can significantly lower the annual performance factor!).

In the real tables from people who have an air-to-water heat pump, it often looks different.

30° flow temperature is contractually agreed for me.
Heating limit: no idea. I guess so.
How warm you want the hot water yourself has NOTHING to do with the "normalized" calculation of the annual performance factor according to VDI4650.

It’s not about consumption, but only about the subsidy.

one should know a heating load and then plot it into the performance diagram of the heating system. This way you can calculate the bivalence point.

This is my heating system, the pink line is the heating load of 9.3kW incl. hot water (at -16°). With the "2" heat pump, the bivalence point is -9°, with the "3" it is -13.2°.

Well, the statement regarding the COP values (or the annual performance factor) is basically zero, because it does not say that the heat pump operates at -10° with a performance factor of 1.4 (or whatever). For that, you would need a corresponding additional diagram. Apart from that, the bivalence point does not have to be at the design temperature (that's what the heating rod is for, as is also the case with you); what matters is the region you build in – how often/long does it really get that cold in reality/statistics? You should not choose a "larger" heat pump just to save 5 operating hours of heating rod, since most of the time it runs at higher temperatures where excessive power is counterproductive. Your choice with the "2" looks okay, although the heating load of 9.3kW seems high to me. For me, my self-calculated heating load was lower than the "specified" one and has proven to be accurate in the last two years. Therefore, I see a certain risk of oversizing.

And indeed, when calculating a theoretical annual performance factor, the hot water behavior makes a difference!