I see some realism in the logic that a base needs both power plant and a command centre to work, but its redundant in terms of gameplay.
Command Centre is important as a requirement for other buildings to work because it adds a 12 days cooldown for any new base to get operational. Very nice gameplay idea.
Power plant on the oher hand, gets built on same 12 days and is only required for command center to work (or for some buildings that require both) being simply redundant in terms of gameplay and spending an precious base construction slot.
Maybe Power Plant should be removed and command center get its upkeep costs raised a bit, freeing a base slot and eliminating a gameplay redundancy. At the moment, I don't see any gameplay reason for Power Plant to exist.
Obs: However, If powerplant gets any gameplay reason to exist, it starts to get interesting, for instance as a requirement for one particular building type like Missile Battery and supporting SAM sites around the base (they would require power from a nearby base as an adittional prerequisite to be operational).
Other suggestions would be good too, but for any of them, Power Plant function would have to be very specific for one kind of role only. This would add some tatical variety and make Power Plant useful again for gameplay porpouses.