Building a single-family house in NRW

The equation remains wrong. The supplied auxiliary energy is not in any immediate correlation with the recovered heat energy, so your statement is nonsense.

I only read your conversation after my post (skimmed through it). One kWh used in controlled residential ventilation saves you about 15 to 20 kWh of heating on an annual average. Of course, nothing in summer and significantly more than 20 in winter. This calculation works similarly to heat pumps, and on an annual average, you then get 15 to 20 kWh saved per kWh used (for an average house, etc.).

The equation remains wrong. The supplied auxiliary energy is not in any immediate correlation with the recovered heat energy, so your statement is nonsense.

The question is whether controlled residential ventilation saves heating costs compared to window ventilation. What you have been doing for hours is missing the point.

No, it isn’t. Auxiliary energy is and remains required energy.

That controlled residential ventilation saves heating energy is undisputed. I have never claimed otherwise. But what use is it if I save heating energy but need more auxiliary energy for it.

You are ignoring the reality of the energy required (regardless of what for in the system). Either you cannot understand it or you do not want to understand it. My consideration begins and ends with the electricity (and possibly gas) meter for the entire concept (not just for one part). That is the only relevant measurement point. It does no good to say that (correctly) heating costs are saved, but (unmentioned) ventilation costs are added. In both cases, the electricity bill ultimately states 2000 kWh.

Not at all. But apparently, they don't want to understand you if you don't share their opinion.
Read gryms' posts, it's getting too exhausting for me -_-

That a controlled residential ventilation system saves heating energy is undisputed. I have never claimed otherwise. But what use is it if I save heating energy but require more auxiliary energy.

That is not true, as I said. For every kWh of electricity used in the controlled residential ventilation system, 15 to 20 kWh of thermal energy is saved.

Source? And which kWh is measured at which point?

Let's say 17.5 kWh of heating energy equates to only 4 kWh of primary electricity in a good heat pump.

HeatendEnergy unequal used primaryenergy.