Annual performance factor calculation for funding (parameters and calculation tool)

Hello everyone, who is able to answer the following questions regarding the binding nature of the annual performance factor calculation and its parameters?
Situation:
I am looking for an air-to-water heat pump that achieves an annual performance factor of 4.5. This is almost impossible, but now I have one that nearly achieves it (I don’t know if I’m allowed to name the model), when I change the predefined parameters (especially the standard outdoor temperature) in the online calculator.

Questions:
-1. Which online calculator is allowed to be used so that the calculation is correct and also stands up to BAFA standards?
2. Which parameters am I allowed to change?
3. My most important point: where do the annual performance factor calculators get the standard outdoor temperatures from? Specifically, in my case, on the same page of the annual performance factor calculator, I found a climate map with standard outdoor temperatures that positively influences my calculation and helps me exactly reach 4.5.

Best regards and perhaps someone has an answer

The Federal Heat Pump Association still hasn't managed to incorporate the new climate data with less frosty standard ATs (from the other map) into its annual performance factor calculator. However, you can manually apply the new values, as that is the currently valid standard. You can also point that out to BAFA if you want to be very precise.

Now I am unsure whether I have thought incorrectly: If I go to the climate map and enter my ZIP code, the focus goes to the area with the ZIP code and shows me the NormAT of -13.7. Above that, there is a table with values including the average. There, -11.59 degrees is given. I had referred to this value earlier, but that is probably a mistake on my part.

- What supply/return temperature is taken for a KFW40 house with underfloor heating?
- Am I allowed to reduce the domestic hot water share?
- Does anyone know which value is to be used now?

Eieiei, not an easy matter

The NormAT.

Reducing domestic hot water would require a justification.

I would rather choose the lower supply temperature, but even there your heating engineer might have to justify it. So appropriate actual design of the underfloor heating for this ST at NormAT

Which heat pump do you have in mind then?

The Hoval Ultrasource B comfort C (17) would be interesting, but that is difficult at -14 degrees, unless the other parameters are adjustable.