power supply vs wattage

power supply

noun
  • A source of power such as the mains or a generator. 

  • That part of a piece of electronic apparatus that provides appropriate voltages for the rest of the electronics from the connected AC source. 

  • Used other than figuratively or idiomatically: see power, supply. 

wattage

noun
  • An amount or power (especially electric), expressed in watts, kilowatts etc. 

  • The power requirement of some electric appliance. 

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