It is not necessary to contact your energy supplier. After the installation of your solar panel system, the distribution network operator will be informed by the installer and the inspection organization. The distribution network operator will in turn send a message to your supplier to report that you have installed solar panels. The supplier will update some data in their system, which will also adjust your billing:

With an analog meter, you will now pay the prosumer rate.

With a digital meter, you will now also enjoy the injection rate.

Please note that it may take a few months for all adjustments to be made.