The District of Columbia Public Service Commission yesterday rejected Potomac Electric Power Company's request for a $33.9 million "emergency" electric rate increase.

The decision, said PSC chairperson Elizabeth H. Patterson, means only that Pepco cannot raise electric rates immediately.

District of Columbia electric rates could go up the full $22.9 million or more after the PSC holds hearings this fall on the rate request filed by Pepco in June.

But the PSC ruled yesterday that Pepco had failed to prove there was any emergency that required approving the higher rates immediately.

Pepco has asked the PSC for to raise electric rates by a total of $48 million, nearly 15 percent a year. The utility company contended it needs $22.9 million of that amount immediately, because its profit margins have fallen far below the rates set by the PSC in its last rate decision.

Earlier this year the PSC ruled that Pepco was entitled to earn a profit of 9.03 percent on its investment in facilities serving electrical customers in the District.

Claiming its rate of return this year will be only 7.45 percent because costs are rising sharply, Pepco asked for the emergency increase to bring earnings back up to 9.03 percent.

The PSC ruled, however, that the fact that earnings had fallen below the level approved before is not grounds for an emergency increase. Pepco's profit margin, the commission said is "an open issue" that is not determined by the previous case.

The emergency increase asked by Pepco would have raised the average D.C. electric bill from $19.98 a month to $20.25, about a penny a day. The full $48 million increase would raise rates about twice that much.