electrical power vs steam power

electrical power

steam power

noun
  • Means of transportation, or heavy equipment, based on such power, especially steamboats, steamships, or steam trains. 

  • Power derived from water heated into steam, usually converted to motive power by a reciprocating engine (a steam engine) or turbine (a steam turbine). 

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