In Upper Marlboro, a $30,000-a-year electrician who has been laid off since January knows his unemployment checks won't cover the $761 he owes the gas company.

He has turned down the hot water heater, and his wife, twin boys and infant son stay by the fireplace to keep warm during the day. "We're behind for the first time and it's very hard when you've had a certain standard of living," said his wife, who was laid off from her job 13 months ago. Unless their income tax refund arrives before the shut-off crews, the warning notices they've received promise an end to gas heat and cooking.

The family has plenty of company. It includes a 55-year-old Beltsville baby sitter on Social Security whose $459 gas bill is out of reach on her income of $5,372, and a Rockville father, who, for the first winter in his 11 years as a homeowner, "just can't keep up" with the family's overdue bill of $516.

They all are among a record number of people likely to lose utility service in the next month as legal protections against shut-offs end in Maryland and 31 other states, according to officials with utilities, public service commissions and social service agencies nationwide.

States imposed the moratoriums, which commonly restrict shut-offs from Nov. 15 through March 31 or April 15, to protect delinquent customers from the cold. But now the day of reckoning is fast approaching.

"When the warm weather sets in, sympathy disappears," said Hal Silvers, director of the Prince George's County low-income energy assistance office. Silvers announced this week the office will stay open one month past its normal April 1 closing date to deal with the "extraordinary" number of shut-offs he predicts will occur.

"Many people's bills are beyond the help of our $200 emergency assistance," said Silvers, who noted the 3,906 households receiving help in the program's first four months already surpass the number seeking aid all of last year.

Government officials and charities report that, in these times of high joblessness and energy prices, overdue fuel bills have grown to unmanageable levels, some because the moratoriums allowed people to temporarily ignore them.

They fear delinquent customers will not be able to amass enough money to get service reconnected before next fall, causing an unprecedented number to face next winter without heat. They also fear people will have to forgo food purchases to get the money to pay the utilities.

While most agree that the problem is much worse this year than last, firm figures are not yet available on the extent of the impending shut-offs. In a recent congressional hearing, the national Citizen/Labor Energy Coalition testified 300,000 households will lose utility service, about a 30 percent increase from 1982.

The author of a study on the effects of delinquent bills and moratoriums for the nation's largest electric and gas trade associations confirms that the volume of unpaid bills definitely means more shut-offs this spring.

"Our company is typical of the industry," said Michael Griffin, manager of customer accounts for Baltimore Gas & Electric Co., who surveyed utilities nationwide last November for the Edison Electric Institute and the American Gas Association. The central Maryland utility cut off 5,300 accounts last April and Griffin expects about twice that number this April.

Some 44,000 BG&E customers--or 50 percent more than last year--currently have unpaid bills totaling $11.6 million. "We predict uncollectables will be $7.9 million in 1983, substantially more than the $6.1 million in 1982," Griffin said. "We are forced to and will have to disconnect." He had harsh words about moratoriums in Maryland and other states: "They hurt the company, the customer who's behind in his bill and the good ratepayer."

The shut-off problem appears to be most severe in the Midwest, where gas prices and joblessness have grown dramatically. Milwaukee utilities, for example, sent out 40,000 disconnect notices at the end of the 1982 moratorium, a number that will rise by 35 percent this spring, according to recent congressional testimony by Tony Maggiore of that city's Social Development Commission.

In the District of Columbia, shut-offs have been allowed since temperatures rose above 32 degrees. In Virginia, where there is no moratorium law, shut-offs have continued all winter. In Maryland, the moratorium officially expires April 1, but earlier shut-offs have been allowed if utilities file affidavits with the public service commission attesting that a shut-off would not endanger the health of a household. Final figures on actual shut-offs in the jurisdictions will not be available for several months.

As has been the case across the nation, utilities in all three local jurisdictions have made humanitarian decisions to spare households from allowable cutoffs if there are disabled or elderly members or young children. But utility officials say they have been stretched to the breaking point and shut-offs must come.

Pepco, for example, after honoring Maryland's moratorium for two years by not shutting off service during the winter, filed affidavits this year to shut off 491 Maryland households during the heating season. "We saw bad debts going up and getting out of hand," said spokesman Nancy Moses, who noted that the amount of uncollected bills rose to $3.6 million in 1982, from $2.9 million a year earlier.

Vepco reported 3,690 shut-offs in January 1983, up 721, or about 20 percent, from the same month a year earlier.

At Washington Gas Light, delinquent accounts rose to $11.5 million in December 1982, an increase of $3.1 million from a year earlier.

In an effort to forestall shut-offs this winter, many utilities, including Virginia National Gas, inaugurated special programs encouraging customers to give an extra dollar when paying their bills to help families pay outstanding bills. Budget plans, where customers were required to pay only a part of their bills, were used nationwide.

Still, the amounts owed to utilities continued to soar, said Michael Foley, director of financial analysis for the National Association of Regulatory Commissioners.

An official of the American Gas Association privately acknowledged the delinquency and disconnection problems are "touchy and getting worse" and said the group is surveying its members on the issues.

Noted Allison Freeman, counsel to the House Subcommittee on Energy, Conservation and Power: "There's no doubt the utilities will be sending out hundreds of thousands of final notices across the country."

"We're extremely worried about what happens this spring when the moratoriums go off," said Carol Werner, of the National Consumer Law Center, whose surveys show terminations were up by one-third in the '81-'82 winter heating season when there were fewer state moratoriums than now.

The shut-offs will put extra demand on the nation's feeding programs, many predict, as food becomes a casualty in the attempt to get service reconnected. "I don't know what people will live on as they try to make up their large bills," said Frances Farrow, a program assistant in Montgomery County's low-income energy assistance program.

The increased demand this winter for government help in paying heating bills also means few offices have much money left for those who are disconnected this spring. Virginia was one of three states that ran out of money this year because of increased demand.

Nationwide, government offices were given $1.85 billion in federal fuel assistance in 1982 to distribute to low-income people, but they also recorded double and triple the number of applicants. The Department of Health and Human Services estimates only 7 million of the 21 million people eligible for fuel assistance received the one-time payment in 1982. The aid, which averaged $184, wasn't enough to eliminate many households' debts.

Shirley Brauer, chief of low-income payments for the D.C. Energy Office, said 7,500 Washingtonians have already applied for the $3.3 million in federal aid and little money is available for help this spring. A surge of applicants last week has nearly exhausted the office's coffers and Brauer is considering tapping money set aside for cooling this summer.

Hundreds of area households, like the Upper Marlboro electrician, the Beltsville baby sitter and the householder in Rockville, already have received the once-a-year government aid and yet still face shut-offs this spring.

All three agree that the humiliation of being unable to pay their bill is almost worse than the inconvenience and discomfort of losing utility service. "My neighbors don't know," said the electrician. "We never thought this could happen to us."

The baby sitter, who has watched as her $60 monthly bills for her home jumped to $100, added, "I just put the bill in the drawer. I get so frightened because I can't pay it. I know they're within their rights to shut me off."