gas service vs public utility

gas service and public utility both are nouns.

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

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

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

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

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