power company vs power service

power company and power service both are nouns.

Word	Noun	Adjective	Verb	Adverb
power company	Yes	No	No	No
power service	Yes	No	No	No

As nouns, power company and power service are synonyms defined as:

power company and power service: a public utility that provides electricity

Other synonyms of power company include electric company, light company.

power company (noun)	power service (noun)
a public utility that provides electricity	a public utility that provides electricity