In terms of electrical capacity, what must be ensured in a Part 23 airplane?

The correct answer focuses on the requirement that a Part 23 airplane's electrical capacity must sustain power for essential loads in the event of a primary power source failure. This is crucial for safety and operational integrity, as essential loads might include vital instruments, navigation systems, and communication devices that are necessary for safe flight operations.

When the primary source of electrical power fails, having an electrical capacity that can support these essential systems ensures that pilots can maintain control of the aircraft and navigate safely. This requirement aligns with the regulations intended to enhance safety and reduce the risk of failures during flight.

In contrast, significantly exceeding operational requirements, while it may seem beneficial, could lead to unnecessary weight and complexity in the system without direct operational advantage. Similarly, restricting power only to non-essential loads does not ensure safety during a failure of the primary power source. Lastly, operating without a backup electrical system is not acceptable; redundancy is a key aspect of aircraft safety to ensure that essential systems remain operational in all scenarios.