There's a small balance update for Heart of the Swarm, which includes the following changes:
- Mothership Core
- Time Warp energy cost increased from 75 to 100.
- Ghost starting energy increased from 50 to 75.
- The Moebius Reactor upgrade has been removed from the Ghost Academy.
The reasoning behind these changes can be read here.
Battle.net - Heart of the Swarm Balance Update: February 4, 2014