A320 Captain reported refusing the aircraft after electrical system malfunctions were not addressed properly by Maintenance during a return to gate event.

Narrative

We pushed back and during engine start at 25% N2 the aircraft went completely dark and we were left with only one transmitter. This is not the correct electrical configuration that should result from an APU failure. All screens were black and we were left with just one transmitter/receiver. I called maintenance crew and they said to do a gate return. While waiting for the tug we ran through the manual and confirmed that the aircraft was not in fact reacting correctly to the shut down. We were unable to restore any electrical power. We returned to the gate and maintenance told us that the APU had some kind of failure. I insisted that even in the event of an APU failure; the aircraft should not go completely dark; and they just shrugged at me. I am certain the aircraft was very broken and the priority bus system was not working properly. So I refused the aircraft. The aircraft was later dispatched with an APU sensor repair; however; the priority electrical system was not inspected (to my knowledge); which was the reason I refused the aircraft. I was additionally told that no codes were stored due to the sudden power loss; so nothing that I was saying could be confirmed. I am not satisfied with how maintenance handled the pilot report and I am disappointed that this event was listed as a refusal instead of a maintenance issue.