When Paula Summers opened her electric bill last week, she couldn't believe her eyes: It was for $818.

That was $520 more than the last two-month bill for her all-electric Poolesville house. At Sally West's house the bill was $647.66.At Nancy Fost's it was $794.61. Everywhere in this western Montgomery County development there was shock and then outrage as the Potomac Edison Co. sent home to its customers a legacy of the nationwide coal strike.

"It was the first time they'd ever put the bill in an envelope instead of mailing it like a postcard," Summers noted, "I guess they didn't want anybody to pass out at the mailbox."

Potomac Edison has been warning its 240,000 customers - 55,000 of them in Maryland - for weeks that bills would be "substantially higher" because the utility has had to buy expensive oil-generated power from neighboring eletric companies during the coal strike. Potomac Edison normally generates electricity by burning coal at a cost of 1 to 1 1/2 cents per kilowatt hour, but had to buy power at 4 1/2 to 5 cents per kilowatt hour in order to meet the demand.

The "fuel adjusment" section of the bill, where such costs are passed on to comsumers, reflects those purchases this month. It will be worse next month, potomac Edison spokesmen said, since the strike isn't over yet and coal reserves keep dwindling. To rub salt in the wound, the company announced yesterday it will seek another rate increase within the next two weeks.

"I don't think we should have to pay for the coal strike," said Summers. "If (the bill) goes up again next month that will mean $1,600 for four months. I don't know what we'll do. We can't sell the house - who'd buy it with bills like that?"

The Summers' electricity usage of 16,142 kilowatt hours in January and February is admittedly high - "phenomenal," according to Potomac Edison executive Paul Horst, who met with in angry crowd of Poolesville residents Monday night. "The few bills I looked at didn't indicate that people were trying to conserve electricity," he said then.

All the homes in the upper middle class community of Poolesville (population 3,500) are all-electric. The Summers family of three has lived in its split-level, detached frame house for 2 1/2 years. They have three bed-rooms, 2 1/2 baths, plus family, living and dining rooms and kitchen. The Summers family has two television sets, a stereo and the usual can openers and appliances. There are no storm windows or a heat pump, however, and Summers did not know whether her house is insulated.

"I never used to pay any attention to all that until this bill," she said, "but I am now."

The entire community is paying attention. At the urging of a special committee created by the town commissioners, residents sent Acting Maryland Gov. Blair Lee III about 300 telegrams complaining about the bills and asking for help in paying them.

A delegation met yesterday with Sen. Charles McC. Mathias Jr. (R.Md.) and a representative of Sen. paul Sarbanes (D.Md.) in Washington , and is scheduled to meet today with Lee. Town clerk Fost said the committee would mobilize as many people as possible to attend a special Monday morning session on the problem scheduled by the Maryland Public Service Commission, which regulates utilities.

"We expected maybe $50, $100 more, but not this much." said Fost. Her fuel adjustment cost alone went from $55 to $450, she said, and her entire bill totaled $794.61. Her house and appliance inventory is similar to the Summers family's. "I'm sure going to find out about insulation standards," she said.

Bills averaged 25 to 30 percent higher than normal, and most of the 400 samples the special committee collected showed fuel adjustment section higher than the basic charge.

"If it costs Potamac Edison $365 in fuel to produce $239 worth of electricity for just me, they have very poor management," West said. What rankles most, she said, is that she had been trying to converse electricity all along and still got a $647.66 bill on usage of 14,550 kilowatt hours. A kilowatt hour is the amount of electricity it takes to light 10 100-watt bulbs for an hour.

"I never doubted we'd have to pay it, but I sure would like to see a little bit of investigation," she said.

The Montgomery County Council voted Tuesday to send a letter to Lee and the state's Public Service Commission, askin gan investigation of the way utility costs are computed and controlled.

"I'm saying anyone is ripping anyone else off," said council member John Menke, who drafted the letter. "I think they (Potomac Edison) are as horrified as we are by these huge bills. I'm not arguing that they are illegal; I'm asking if they are appropriate."

Meanwhile, Maryland people's counsel John J. Keane Jr. asked the Public Service Commission to order billing changes that would put a ceiling on the fuel costs that a utility can recover in any one bill.

The commission will hear that request on Monday.

Horst of Potamac Edison told the Poolesville meeting Monday about a level payment plan designed to ease the impact of the high prices, but he said people at the meeting were not satisfied. "They feel we should have been able to warn them last December, but there's no way we can tell the price of borrowed power until we go to buy it," he said. CAPTION: Picture, Paula Summers electric bill for two months on her Poolesville home was $818. By Bob Burchette - The Washington Post