mains vs power grid

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. 

power grid

noun
  • The infrastructure for distributing electrical power throughout a region. 

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