A power plant is a ground-based facility built to provide cheap and reliable energy to a city or even region.
Earth's power plants were based on nuclear fission up until the 22nd Century, when they were replaced with more efficient fusion plants. (I AM ERROR)
The power plants on Cardassia Prime were sabotaged during the final battle of the Dominion War, playing a critical part in the battle's outcome. (DS9: "What You Leave Behind")