The Federal Power Commission yesterday blamed Consolidated Edison Co. for the blackout that left 8.3 million New Yorkers in the dark July 13 and 14. It charged Con Edison with failing to use emergency power units, inadequate manning and emergency procedures, poor planning and excessive dependence on purchased power from nearby utility systems.

Calling the results of the blackout "intolerable," the 80-page report said the FPC doubted Con Edison's ability to provide continous service with out prolonged interruptions." The report recommended that the utility undertake major capital improvements to its generation and power transmission capacity to limit the possibility of massive power outages in the future.

"There isn't any way to escape greater consumer costs," FPC Chairman Richard L. Dunham said.

The cost of these improvements would have to be borne by consumers. FPC officials said Con Edison's rates are how among the highest in the country, nearly twice the national average.

Dunham stopped short of embracing New York City Mayor Abraham D. Beanne's charge that Con Edison was guilty of "gross negligence," but said "we question very seriously the operating procedures."

Asked if he accepted Con Edision Board Chairman Charles F. Luce's explanation that the blackout was due to "an act of God," Dunham said. "We use the term 'incident,' we do not use the term 'act of God.'"

The FPC head carefully avoided accusing the utility of legal negligence.

Con Edison faces about 8,000 damage suits filed by residential and commercial customers.

Con Edison officials say the improvements would cost about $260 million, and most of them are budgeted over the next six years.

The president of the beleaguered utility, Arthur Hauspurg, at a press conference in New York City yesterday, accused the FPC of issuing a report with "inaccurate statements and unsupported conclusions."

Hauspurg disputed the FPC findings, claiming that Con Edison's service reliability is about seven times better than the other utilities in New York State, and "probaly the best in the nation."

Dunham conceded that the FPC, the New York State Public Service Commission, and the Regional Electrical Reliability Council all share in the responsibility for the city's devastating blackout.

Following an outage in 1965. Regional Electrical Reliability Councils were established with the cooperation of the FPC and utilities across the country to ensure utility equipment and operating standards to prevent blackouts. This system failed, Dunham said.

Dunham has called for a thorough re-examination of the reliability standards set by the nine regional councils and a formal report to James R. Schlesinger, Secretary of Energy-designate, the next months.

The FPC report recommended that Con Edison take immediate action to upgrade the utility's interconnections with other systems.One of Con Edison's major tie lines, the report noted, has been out of service since September, 1976. This interconnection, the Hudson-Farragut tie with a New Jersey utility, "contributed to Con Edison's inability to import power needed to maintain the system" the report said.

Con Edison spokesman Dan Walden said the utility expects to have the tie line operational by mid-1978.

The report said Con Edison should increase its own generating capacity, and install automatic controls on stanby generating capacity that was unmanned during the lightning storm which the utility says triggered the blackout.