Photovoltaics with later battery retrofit, what do I need?

I am not aware of any hybrid inverter over 10kW or is there something new by now?

And it definitely makes more sense to install 18kWp rather than mess around with storage gimmicks.

So you would simply have to look for an island-capable battery inverter.

Update: For a true three-phase emergency power solution with the GEN24, you need 2 contactors, 2 relays, and a 12 V auxiliary relay as well as FI and LS. Either you build it yourself according to the wiring diagram or buy it ready-made from an external manufacturer. The switching time to battery is reportedly 90 seconds during a power outage, but this can be bridged for important devices.

If you don't want to burn an insane amount of money, skip storage and definitely the right backup power. That will cost you five figures just for having an extra hour of power every five years compared to others. In case of emergency, there isn’t more in the battery anyway. Build all roofs fully now. (50 kWp is still too small in winter. Especially with storage and an electric car.) And if the inverter dies in 15 years AND prices for storage have fallen to a quarter of the current price, you can easily retrofit/upgrade.