This task allows you to connect inverters and inverter blocks to transformers in the layout.
If, when adding inverters or inverter blocks you selected a transformer to connect them to, they will already be connected. However, if this wasn't in place the inverters/inverter blocks will not be connected to a transformer and they must be connected for the energy yield calculation to run.
You will see a tree control in the left pane of the Electrical Configuration screen. Simply drag and drop one (or more) inverters or inverter blocks onto their parent transformer to connect them together.