There is no Manual Power Save feature in the Hub Manager of the BT Business Hub 5.
To help you save energy, the Hub uses the very latest automatic power saving technology. If the Hub detects that a function is not in use, it will automatically power it down. So for example, If no devices were connected to wireless, the wireless would be put into lower power mode.
In fact, Hub 5 is always looking for the opportunity to power down a port or function such as Ethernet or wireless. It will instantly 'wake up' as soon you start to use broadband.