Why does a shut down Dell server consume 50W?

Question: Why does a shut down Dell server consume 50W?

 

Short Answer: Because some hardware components still consume power when the server is not disconnected from power. 

Longer Story with details 

I have Dell PowerEdge R620 with iDRAC7 in my home lab and here is the home power consumption in two scenarios

1. shutdown server still connected to power (531 Watts)
2. server fully disconnected from the power (475 Watts)

Scenario 1: shutdown server still connected to power

 

Scenario 2: server fully disconnected from the power

The difference between above two scenarios is ~ 50W. Why? 

Let's dive deeper.