Pilot acting as a Safety Pilot reported returning to departure airport after experiencing electrical system anomalies that affected their radios.

Narrative

After flying northbound through thought the ZZZ TRSA; at approximately 5-8 miles to the north; our transponder screen went out. I immediately notified the pilot who is currently flying under a view limiting. The radio frequency was congested at the moment so before I was unable to ask ZZZ Approach if we were still transmitting altitude. Before I was able to make my call; ATC said 'Aircraft X say altitude'. As I keyed the mic; our standby radios also went dark. I replied 'Aircraft X level 030. Looks like our transponder went out and we having some electric-'. Our GPS and main communication radios went black in the middle of the transmission and I could no longer hear vocal feedback in my headset. I instructed our a passenger who is also a pilot to call Clearance Delivery and inform ATC of our situation. We decided to divert to ZZZ1 Airport. ATC asked if we were sure we didn't want to comeback to ZZZ; and after consideration; we said we would. They told us to enter base for runway X. Once in the airport vicinity; we're were cleared to land with light gun signs and given a taxi clearance via the tower's phone number.