Key terms of energy storage system -- Usable Storage Capacity
Usable storage capacity is the energy stored in an energy storage system that can actually be used and it is different from battery energy capacity.
For example, the AlphaESS SMILE5 uses a battery of 5.7kWh capacity, but only 96% of it can be discharged (aka a 96% DoD, the Depth of Discharge). Therefore, the battery's usable storage capacity of SMILE5 is 5.5kWh.
In fact, let us think about the icon on the top of your phone screen that tells you how much energy your phone left. Sometimes it shows 3% left but your phone just automatically shuts down. That means the DoD of your phone is 97%.