Ready for the SMA energy meter to be added. By means of the new ready-for-connection and pretested “battery backup distribution” system of enwitec it is no longer necessary for installers to have an cost-intensive and expensive self-construction of the backup function as well as the responsibility for the warranty. So far, the battery backup distribution (abbr. “BBD”) of enwitec is the only product which is recommended by SMA and included in its planning guideline for the application in “flexible storage systems”. The “BBD” for the SMA “flexible storage system” exclusively uses components which are released by SMA and establishes therefore a basis for the maximum of supply guarantee. A backup system surely separates the connected solar construction and the customer distribution in case of power failure from the local grid and simultaneously provide a backup solution to the customer. This switchgear box from Enwitec includes a G59/3 relay suitable for connecting SMA Sunny Island to a single phase supply in the UK.