Purchase of an existing single-family house prefabricated house year built 2000

I am of the opinion that the issue with oil consumption is not very meaningful since there is a wood stove; if it is running continuously, I can drastically reduce the consumption, but this is just a thought experiment of mine!

Air-water heat pump also works with radiators. A wood stove for buffering extremely cold days is also available. It should work; getting a new oil burner in 5+ years would be disastrous. I find the financing tight but feasible. Very good equity, in a pinch you’ll have to grit your teeth for a few months.

I am of the opinion that the issue with oil consumption is not very meaningful since there is a wood stove; if it runs continuously, I can drastically reduce the consumption,

Then just add + wood consumption. If it is only a "comfort stove" that is lit 20 times a year, it would be negligible. Wood stacks around the house (in the basement) spotted? And the rest? :rolleyes:

A new oil heating system might be difficult, there are exceptions but not that many. With 70 kWh/sqm you could probably heat the place even with a lower flow temperature, but it’s not really good.

He doesn’t need a new oil heating system since he already has one. Modernizations / replacements are always allowed even after 2025. There are still millions of houses in Germany heated with oil that cannot switch to heat pumps due to insulation, costs, available craftsmen, etc.

I don't worry about the heating. When living there, I would look at how low the flow temperature goes and replace individual radiators accordingly.

There are still millions of houses in Germany that heat with oil

And they also have to switch. Therefore, I consider it risky to calculate only €10,000 for a replacement when prices frequently are already around €20,000.
Currently, there is funding, but who knows how that will be in 10 years? With cars, they also want to shift from subsidizing the new to penalizing the old.

So: a heat pump has to be installed sooner or later. Plan for €20,000 rather than €10,000. But don’t worry too much, with a house from 2000, that is not a problem at all.