The Supreme Court agreed yesterday to decide whether a state can order a public utility not to propagandize its customers by sending out its views on controversial public issues along with its bills.

Such a use of billing envelopes "is tantamount to taking advantage of a captive audience, since the consumer cannot avoid receiving the utility's message," according to the New York State Public Service Commission.

But Consolidated Edison Co., with 3.5 million customers in the New York City area, defended the use of bill inserts. It is "essential to our democratic process that the free flow of information and ideas...remains unfettered" to inform the public on issues such as the use of coal by power plants otherwise dependent on foreign oil, the utility argues.

The PSC ordered Con Ed in February 1977 to stop using billing envelopes to disseminate its "position on controversial matters of public policy." The ban resulted from a complaint by the Natural Resources Defense Council about a bill insert on the need to develop nuclear power.

Challenging the order, the company contended that its First Amendment right of freedom of expression was being violated.

Last May, the state's highest court upheld the PSC with a 6-0 ruling. The Constitution permits the "facially neutral" regulation that, at most, indirectly restrains speech because utilities remain free to "propagate their views by other means" than billing envelopes, the court said.

Con Ed, in a successful petition for Supreme Court review, contended that alternative means of communication are more expensive, "are less likely to reach...customers and may be less effective."