I followed the instructions at https://wiki.ubuntu.com/Bumblebee

sudo add-apt-repository ppa:bumblebee/stable
sudo add-apt-repository ppa:ubuntu-x-swat/x-updates

sudo apt-get update

Instead of installing the proprietary nvidia drivers, via:

sudo apt-get install bumblebee bumblebee-nvidia linux-headers-generic

I did:

sudo apt-get install --no-install-recommends bumblebee linux-headers-generic

How do I determine that power savings mode is active and that my dedicated GPU isn't running?

One thing that bugs me is that if I go to System Settings - Details - Graphics. Driver is shown as Unknown.