How to build according to the Building Energy Act or EH55 or EH40

what do you actually want to achieve with this thread? Many strange statements follow one another here without me being able to recognize a goal. Why should an air-to-water heat pump be maintenance-free in EH55, but cost 300€ in EH40? Also funny that you assume 15% higher prices per kWh for EH40. And what do you want to clean every few years for 400-800€ in a centralized controlled residential ventilation? I bought filters for 50ct each and the pipes still look like on the first day. And how do you come to almost 600kWh consumption for a controlled residential ventilation? Ours consumed 300kWh, of which 75% came from photovoltaics at 6ct/kWh.

Well, then I made a mistake.
The system was sold to me as a maintenance-free heat pump.
By the way, I also don’t have my refrigerator serviced.
Surely we have had one problem or another, but that should be normal after almost 19 years.

Everything that has filters needs to be serviced at some point – if your manufacturer claimed back then that the heat pump was maintenance-free (really? not even cleaning the filters? never checking the valves?) and gave you more than 5 years of warranty despite no maintenance, then be glad they were young & dumb back then – most (all?) have learned since.

Therefore, if you buy a heat pump today (for your place or a Gebäudeenergiegesetz/EH55/EH40 building), you will either have it serviced (for X € / year, manufacturer- and not house-dependent!), or do it yourself (for almost 0 €) and live with a residual risk.

Everything that has a filter needs maintenance at some point

Which air-to-water heat pump actually has filters? Mine certainly doesn't.

The only thing you need or can do with the air-to-water heat pump is once a year vacuum/flush the lint from the neighbors' pampas grass out of the heat exchanger.

Which air-to-water heat pump has filters? Mine certainly doesn't. The only thing you have to or can do with the air-to-water heat pump is vacuum/flush the fluff from the neighbors' pampas grass out of the heat exchanger once a year.

I would be very surprised – all systems I have looked at either came with a filter ball valve from the manufacturer or another type of sludge separator/magnet/magnetite filter device for the secondary circuit as standard. Furthermore, I am quite sure that your system also has a filter drier in the refrigerant circuit, although this is usually only replaced when something needs to be done with the refrigerant.

sorry if I made any incorrect statements. This is what I found on the internet. My nephew is building barely 100m away and so one is naturally interested in this or that thing. I can quickly explain the price difference to you. I have a heat pump tariff that does not pay off with low consumption because of the meter rental. I also assume that a ventilation system is not allowed to be operated with it.

Why should an air-to-water heat pump be maintenance-free in EH55, but cost €300 in EH40?

I never claimed that anywhere. I was talking about my place and there is simply a large refrigerator installed. (Figuratively) The cooling fins from the back are in the screed and the cabinet is outside. And for the domestic hot water, the hot gas superheating is simply used.

This is what the evaporator looks like after 19 years without maintenance.