A new option called Standby Mode is now available on your YouView box which replaces the old Eco-Mode setting found on boxes with the previous software. The new option can be found by pressing the YouView Button> Settings> Device Management> Standby Mode.
I am pleased to announce that this particular update will be completed by Friday. The update will be available to all BT YouView customers using the H3, G4 Z4 YouView boxes on Thursday night 18/02/2016.
The above post by Robbie will give you more information as to what is included.