DC Coupled system meaning solar panels are connected directly to the inverter increasing efficiency by transferring DC power from your panels directly to DC power stored to the battery.  This also utilises the full features that can be used by the battery in Emergency Power Mode.   AC Coupled mode adds the energy storage system to your existing solar systems, this method is less energy efficient and not all the emergency power features are supported in this mode.  RENON ESS can be configured as both DC Coupled and AC Coupled, which depends on the Inverter used.