Here’s a blogpost about the DELL T20: Dell PowerEdge T20 with Xeon E3-1225v3 CPU

Extract: Getting the power consumption with Linux below 15 Watt

sudo pacman -S powertop

Add the file /etc/udev/rules.d/10-local-powersave.rules:

# PCI runtime power management
ACTION=="add", SUBSYSTEM=="pci", ATTR{power/control}="auto"

# USB autosuspend
ACTION=="add", SUBSYSTEM=="usb", ATTR{power/control}="auto"
ACTION=="add", SUBSYSTEM=="usb", TEST=="power/autosuspend" ATTR{power/autosuspend}="60"

# SATA active link power management
SUBSYSTEM=="scsi_host", KERNEL=="host*", ATTR{link_power_management_policy}="min_power"

And run sudo udevadm trigger. Afterwards, cat /sys/class/scsi_host/host0/link_power_management_policy should return min_power.

echo auto > /sys/bus/pci/devices/0000:00:14.0/power/control