mains vs powerhouse

mains

noun
  • The domestic electrical power supply. 

  • The pipes of a centralized water supply that transport the water to individual buildings. 

  • The farm attached to a mansion house. 

  • The main course of a meal. 

powerhouse

noun
  • A power station; the building housing a power station 

  • A very good hand of cards, likely to win. 

  • Any source of power, energy or strength; a source of influence or inspiration 

How often have the words mains and powerhouse occurred in a corpus of books? (source: Google Ngram Viewer )