Is the house connection capacity of 14.5 kW sufficient?

Charge a 22kw car, plus an 8kw heat pump in winter and then the usual stuff like refrigerators, hairdryer, TV, PC and other energy guzzlers. So I definitely wouldn’t want to go below 40kw.

Ok I need more. How much would a larger dimensioned SLS cost as an additional charge?

In our street, everyone was offered 30KW from the utility company as standard. That was without an extra charge. We then applied for 40KW because of an electric car, and it now costs about 1000 more.

In general, consumers with 6.9 kW and above must be registered with the supplier.
This naturally also includes a charging station.
Charging stations with 22 kW usually require approval,
so for that you need a confirmation/approval from the supplier.
As already mentioned, the complete wiring including meter wiring 50A or larger is not sufficient with the usual 10 square wire.

Do you also have to register the sauna stove with the provider?

In general, for higher power, yes.
Exact information about from how much power is stated in the [Tab] from your supplier, which is accessible to everyone on the WWW — network.
The registration is handled by your [Elektrofirma] that also connected it. In any case, they should initiate it.
It is actually just a formality so that the supplier knows what loads may arise on their supply network.
It doesn't cost extra.