Systems and methods for monitoring power supply of refrigeration units including cargo sensors (358) located within a container (307), a power connector (346) configured to receive power, the power connector operably connected to the refrigeration unit, a power supply sensor connected to the power connector configured to detect a lack of power supplied through the power connector and a controller in communication with the cargo sensors and the power supply sensor, the controller configured to store predetermined information related to power requirements including a maximum time period of a powered-off state, receive data from the cargo sensors, receive data from the power supply sensor, and, when the data from the cargo sensors indicates the presence of cargo within the container and data from the power supply sensor indicates a lack of power for a duration that exceeds the maximum time period, the controller is configured to provide an indicator.