A320 Captain reported experiencing a total electrical power loss during taxi. The flight crew returned to the gate after the power was restored.

Narrative

During 2 engine taxi out and APU off; we experienced a total electrical failure. Even lost the systems; all screens; FCU (Flight Control Unit) data; ACP (Audio Control Panel) panels and radio 1. It looked just like you find a plane at the gate; completely powered down with no ground power and batteries OFF. I immediately stopped the aircraft with no issues. About 5 seconds later; IDG (Integrated drive generator) 2 came back online and aircraft started to power up. At this point I noticed that the systems was staring up just as if the aircraft was initialized from a cold airplane with all the manufacturer labels and version data on the screen and then started the countdown for initialization. The only two ECAMS we had was both FWC (Flight Warning Computer) fault and GEN 1 FAULT. I turned the nose wheel steering and I could tell that NWS (Nose Wheel Steering) was working with no issues and no ECAMS related to it. I had the FO start the APU. All the numbers on the ELEC (Electrical) page were indicating. Once we were able to get some electrical power on the aircraft we were able to make appropriate calls to return to the gate. I notified FAs and made PA to passengers. Made Logbook entry. Once at the gate; had a conversation with mechanics. Called dispatcher and we conferenced with Maintenance Control to try to get some feedback since the ZZZ mechanics were puzzled about what had happened. I did get the same feedback from Maintenance Control. No one could understand how we ended up with a total electrical power failure. Aircraft was eventually swapped from Aircraft X to Aircraft Y. Report filed.Cause:NASuggestions:The report comes up with Aircraft Y. As well as the filed report. However; the event happened on Aircraft X (A320) and we swapped into Aircraft Y (A319).