The power plant produces 100 power units, this amount is less than sufficient to run a big base. Meaning that the more buildings you will have, the more power plants you will have to build to maintain full functionality.
It is best to build Advanced power plants as they produce a doubled power amount, this is not very recommended in multiplayer.
Power output is directly related to the power plant's condition, so protect them during battles.
The power plant costs 300 Credits, and takes 5 building tiles.
Once built it allows the construction of several buildings, assuming that the construction yard is still standing.