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. 

What happens when a Dell server is “off” but still connected to AC power?

Even when the OS is shut down, the server is not truly power off. Several subsystems remain powered by the standby 12V or 5V rails from the PSU.

iDRAC (Baseboard management controller)

iDRAC stays powered so you can remotely power on, monitor sensors, or access KVM.

The power consumption of an iDRAC7 (Integrated Dell Remote Access Controller version 7) is very low, since it’s a small embedded management controller.

It consumes ~2–5 W.

Here’s a detailed breakdown:

• Typical power draw: about 2 to 5 watts

• Idle / standby (server off, iDRAC active): around 2–3 W

• During remote KVM or virtual media usage: up to 5 W

• Impact on overall server power: usually less than 1% of total server consumption.

For example, on a Dell PowerEdge R720, Dell’s documentation indicates:

• iDRAC7 Enterprise adds ~4 W maximum power draw compared to a system without iDRAC enabled.

So in practice:

• Idle server, powered off but with iDRAC reachable: ≈ 2.5 W

• Active remote session (KVM or ISO mount): ≈ 4–5 W 

So, the iDRAC is not the main power consumer, however, each PSU has internal monitoring, fan control, and conversion circuits that stay partially active.

Power supply electronics

Modern hot-swap PSUs can draw 10–20 W each, even when the server is “off”.

System Management Bus / sensors / standby logic

Voltage regulators, NVRAM, and monitoring chips stay alive and adds a few watts more.

Fans (momentarily active) and indicator LEDs

Some models keep status LEDs lit, and fans might spin briefly during thermal checks.

Why the drop is so big (≈ 50 W)

When you unplug AC power

• Both PSUs fully depower, therefore, no conversion losses, no monitoring circuits.
• iDRAC and all standby rails go dark.
• Only residual discharge of capacitors happens (milliseconds).

So that ~50 W represents

• 2 × ~20 W PSUs (standby + conversion loss)
• ~5 W iDRAC
• ~5 W various logic circuits

Summary

Here is the summary table of power consumption in various states. 

State	What’s Powered	Typical Draw
Server fully unplugged	Nothing	0 W
Server shut down but plugged in	PSUs + iDRAC + standby logic	40–60 W
Server running idle	Everything	100–250 W (depends on model/config)