gas company vs public utility

gas company and public utility both are nouns.

Word	Noun	Adjective	Verb	Adverb
gas company	Yes	No	No	No
public utility	Yes	No	No	No

As nouns, public utility is a hypernym of gas company; that is, public utility is a word with a broader meaning than gas company:

gas company: a public utility that provides gas
public utility: a company that performs a public service; subject to government regulation

Other hypernyms of gas company include public-service corporation, public utility company, utility.

gas company (noun)	public utility (noun)
a public utility that provides gas	a company that performs a public service; subject to government regulation