Real Dictionary

public utility
countable noun: Public utilities are services provided by the government or state, such as the supply of electricity and gas, or the train network.

public utility in American English
an organization supplying water, electricity, transportation, etc. to the public, operated, usually as a monopoly, by a private corporation under governmental regulation or by the government directly
noun: a business enterprise, as a public-service corporation, performing an essential public service and regulated by the federal, state, or local government

public utility in British English
noun: an enterprise concerned with the provision to the public of essentials, such as electricity or water