You have to register to the utility, but that's just a form to fill with the model and power of the kit.

With a e-meter, you will get compensated when you're generating a surplus (+/- €0.04/kWh last time I checked).

However, thanks to the battery, I'm self-consuming almost all that electricity, saving around €0.30/kWh.

Expect 800kWh of annual production per 1kW of panels.