Purchase advice, heat pump comparison: Daikin or Vaillant?

I cannot comment on the values, but I recommend, especially if you don't know how to assess them, an independent heating load calculation. We had this done by an engineering firm; they calculated the heating and controlled residential ventilation, including the layout of the underfloor heating and where the supply and exhaust air should go for the controlled residential ventilation. We handed this to the heating technician, and he follows it accordingly.

Thanks for the answers so far! Can you tell me how or with which tool you arrived at this heating load, ? With some online rough calculators, I get many different results: StiebelEltron calculator results in a heating load of 8kW heizleistungsrechner.de calculator results in 2.39kW ibo-plan.de calculator results in 14.5kW wärmepumpe.de calculator results in 4.6kW

I don’t make sense of this either, all made with pretty similar inputs and such different results... :(

And one more question: In the BAFA list, both the heat output and the nominal heat output are given: For "an" Arotherm, for example, 6.99kW heat output at a-7/W35 and 2.77kW nominal heat output at A2/W35. How should these two values be interpreted?!

Take a look at grabenkollektor.Wärmepumpen-verbrauchsdatenbank.de/Energieeinsparverordnung-heizlast html.

This is a simple but very accurate tool for an initial assessment. However, it usually matches the results of MEP planners up to 5%. Deviations mostly occur due to the final geometry of the house.

A heat pump should rather be undersized than oversized.

Thank you, I didn't know it in this form yet. This calculator has "once again" produced a different number than the many other calculators :rolleyes: With controlled residential ventilation I then get 6700W, without controlled residential ventilation 8200W. Which specification (e.g. from the BAFA list) would then be the reference specification? Heating output at A-7/W35 or rated heating output at A2/W35?

Model	Heating output A2/W35	Rated heating output A-7/W35
Daikin Altherma 3 H HT	10.72kW	6.87kW
Vaillant aroTHERM plus VWL 75/6	6.99kW	2.77kW

There are huge differences between the models of both heating manufacturers...on top of that, one would want to install the aroTHERM twice in cascade...

Thank you, I did not know it in this form yet. This calculator "once again" produced a different number than the many other calculators :rolleyes: With controlled residential ventilation, I then get 6700W, without controlled residential ventilation 8200W. Which specification (e.g. from the BAFA list) would then be the reference specification? Heat output at A-7/W35 or nominal heat output at A2/W35?

Sounds quite appropriate already. What kind of wall construction and so on do you have that the Ht is so poor?

Model	Heat output A2/W35	Nominal heat output A-7/W35
Daikin Altherma 3 H HT	10.72kW	6.87kW
Vaillant aroTHERM plus VWL 75/6	6.99kW	2.77kW

Here there are huge differences between the models of both heating manufacturers... moreover, one would want to install the aroTHERM in a cascade twice...

From which list did you get these values? Did you confuse COP with kW there? According to the manufacturer, the VWL 75/6 A still achieves 7kW heating capacity at -7 degrees.

Go to a professional with it... if you already read here that you should rather undersize a heat pump... that may be true, but then you need the exact heating load, no estimate. And neither an online tool nor a master craftsman of the installation trade can provide that for you. Engineers do that...