Does a heat pump need eBus and KNX connection? 

No, it doesn’t need it. KNX eBus interface, ISE for Vaillant, control, remote switching on and off via app, vacation home

What is needed for KNX connection?

eBus interface: Switching the heat pump on/off, switching operating modes, switching ventilation, connection via USB cable eBus and ISE KNX interface, ventilation system control (Vaillant), energy consumption in kwH to data

Does it need individual room control, yes

Air heat pumps and subsidies: 

Does it all add up, electricity price at 0.50 cents per kWh, always take a close look, there is the BAFA list Hoval Bellaria Twin A with COP=4.6 only achievable by inverter, inverter= power control according to demand and not on/off as before

Water-to-water heat pump: COP=6.96 Heliotherm heat pump technology

Difference between air and water-water: 

As the outside temperature drops, the air source heat pump gets worse, the thing is supposed to heat!

https://www.bafa.de/SharedDocs/Downloads/DE/Energie/ee_waermepumpen_anlagenliste.pdf?__blob=publicationFile&v=89

COP measured at operating point W10/W35, A10/W35 and B0/W35

Sales figures in Germany, types in Germany

Which heat pump is right for me? Everything has already been said,

How long shelf life: 

Few compressor starts, long running times, Copeland-Emerson compressor 150,000 starts,