A switch arrangement includes a switch with a source lead and a load lead, a sensor coupled to the switch, and a switch monitor. The switch monitor is in communication with the sensor and is responsive to instructions recorded on a memory to receive a measurement of a switch parameter from the sensor, compare the measurement to a baseline associated with the switch, and determine switch margin using the comparison of the measurement with the baseline associated with the switch. Aircraft electrical systems and methods of monitoring electrical systems are also disclosed.