May 19--Federal officials have concurred with state experts in concluding that Southern California should have adequate electricity supplies this summer, even in the event of a unusually warm season.

In an assessment published yesterday, the Federal Energy Regulatory Commission said it was "fairly unlikely" that the region would suffer rolling blackouts and then only if a very hot summer was compounded by the sudden loss of power plants or transmission lines.

"Nevertheless, such a scenario is possible," the FERC report said.

A spokesman for the California Independent System Operator, the agency that oversees electric reliability in the state, noted that it was not forecasting a likelihood of blackouts in the region.

"Under normal circumstances, we will be OK," said Gregg Fishman, the ISO spokesman.

But Fishman added that there were some plausible scenarios under which the region could dip below a 7 percent electric generating reserve margin. At that point or slightly below, the ISO often issues a Stage One alert, encouraging additional voluntary conservation.

"We are only talking about the hottest of the hot days of summer," he said. "As long as it doesn't get hot everywhere at once, we should be OK. And it can get very hot and as long as we don't lose power plants or transmission lines, we'll be all right."

The California Energy Commission forecasts an even more positive scenario.

Under normal conditions in September -- typically the hottest month for the region -- the commission believes Southern California will have a reserve margin of nearly 17 percent.

Claudia Chandler, assistant executive director, said that under the hottest likely conditions for September -- a so-called one-in- 10-year heat wave -- the region's electricity reserve would fall to 7 percent.

San Diego Gas & Electric said it was in agreement with other forecasts.

"Are rolling blackouts possible? Yes," said Stephanie Donovan of SDG&E. "Are blackouts likely? No."

Donovan added that the utility's new electric generation plant in Escondido and regional transmission upgrades have allowed it to keep pace with power demand growth -- but just barely.

In the worst likely situation expected this summer, Donovan added, the utility will need the cooperation of customers in reducing demand.