Command Power Plant is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

: Add one mana of any color in your commander's color identity. If you control a Command Tower and a Command Mine, add two mana of any color in your commander's color identity instead. Command Towers you control have, ": If you control a Command Mine and a Command Power Plant, add three mana of any color in your commander's color identity."