I have just upgraded my macbook air to Mavericks and I noticed now that Activity Monitor has an energy tab that shows which apps consume most energy and Pharo is ��on No1 spot for idle apps.
1) Pharo - > 50-60%
2) Chrome (7 tabs open) -> 10%
3) Blender (3d app) -> 15%
emacs, itunes , maps etc close to 0%
The only way to compete with pharo is playback a youtube video that spikes energy to 80 or play a 3d game.��
I assume Morphic is quite heavy on resources.