SMA's robust and versatile automatic backup unit. Enclosure includes an automatic transfer switch designed specifically for use with the SMA Sunny Boy Storage inverter family. In the event of a grid failure, the automatic transfer switch disconnects the PV system, loads and the Sunny Boy Storage from the utility grid and creates a battery-backup grid. The included Backup Unit Controller coordinates grid disconnection and reconnection to ensure minimal downtime while also allowing for up to 5 kVA of unbalanced loads. When paired with SMA Sunny Boy inverters, the Sunny Boy Storage curtails PV power production to match load in the event the battery is full to maximize use of solar production.