We could assume the total cost of electricity bill using ODROID-HC1 : Home Cloud One Server 24hours/7days at home.
We installed the Ubuntu 16.04 minimal image(Kernel 4.9.44) and FTP, SAMBA, NFS, Plex-Media, Seafile, Serviio,
Transmission and WebDAV server applications were running in background.
It consumes 3.6Watt (average) when it is idle and the attached hard disk drive is in spin-down mode.
Here is the detail analysis of power consumption.
Booting : A peak pulse up to 5V/3A(~15Watt) when the HDD starts to run.
Idle, HDD is still spinning : Around 5-6Watt.
Transferring some big files with SAMBA via Gbit Ethernet interface : 7~9Watt approximately.
Idle, HDD spin-down : Average 3.6Watt.
We believe we can make it even lower if we tweak the CPU governor and scaling frequency options.