Optimal size and position of the technical room

It should be a pure technical and connection room. Everything else (Waschmaschine, Trockner, Getränke, etc.) goes into other rooms.

I do not yet know the exact devices. Unfortunately, we are not that far yet.

The proximity to the access road is one thing, the non-overbuilding of the [Leitungen] is another. For the house entry, some providers do not want their distributors / measuring devices to be above or below components of others. Also, "working spaces" in front of parts to be maintained and the electrician's return zone would still need to be considered.

this is how it should look for us on 10m²; planning comes from the main contractor; supply and exhaust air are realized via two cellar shafts in the northeast and southwest
with a buffer tank I wouldn’t see any workbench fitting in there anymore. But it will get its own traditional place
there is still hope that in the end the freezer fits in as well.

Thank you for the example. Does that mean the two inlets of the controlled residential ventilation come from another basement room? What do the abbreviations SDD and LDD in the drawing stand for?

What do the abbreviations SDD and LDD stand for in the drawing?

Ceiling openings.

A buffer tank might possibly fit behind the heat pump in the example, a 1.5 m long bench under the window in the northeast, and if the dryer is placed on the washing machine, a freezer would also fit. Or depending on how high the installation of the "Hauswasserwerk" might be, the sink could also fit on top of it there, and the freezer would then move into its place.

It should be a pure technology and connection room.

Then 7-8 sqm are enough some have 6 including a washing machine... that is quite awkward, but doable in an emergency.