As sub-freezing temperatures send home heating bills soaring, more than 4,000 residents of Montgomery and Prince George's counties are staying warm with the help of federal energy assistance money.

With more than two months remaining in the five-month program, Prince George's has helped 2,800 households and spent $585,000 of its allocation of $1,364,000, according to Hal Silvers, director of the county's office of emergency preparedness.

County officials anticipate that about 6,500 households will apply for energy assistance before the program expires March 31. Silvers said that if the county needs additional money, he will apply to the state for supplemental funds. Last year, Prince George's assisted 4,000 households and spent $1,278,000.

Montgomery County has helped 1,396 households and spent $125,855 of its $691,000 allocation, according to Frances Farrow of the county's energy office. County officials estimate that 2,787 households will ask for assistance this year. Applications this year, she said, are slightly ahead of last year when the program assisted about 2,400 persons at a cost of $630,577.

Payments have been reduced this year in all categories, ranging from a 22 percent decrease in electricity payments to a 44 percent decrease for oil and kerosene, according to Stephen Minnich, spokesman for the Maryland department of human resources.

Minnich said the state received $28 million in federal energy funds this year, $500,000 less than last year when 75,000 people were given assistance. This year, 65,000 people already have applied. Thus, Minnich said, the estimated benefit for each household this year will be $248 compared with last year's average of $383.

If overdue utility bills are any indication of unusual heating costs, the record is mixed. PEPCO said that it has only 32,855 accounts that are more than 60 days overdue, compared to 36,911 last year.

But the Washington Gas Light Company said that its overdue bills are up by 9,000. Currently, the company has 102,318 customers who are more than 30 days overdue.

The energy assistance program provides funds to help persons and families pay natural gas, electric, oil, kerosene, wood or coal bills. The one-time-only payments can be supplemented in emergencies. After that the counties will provide space heaters, blankets and other necessities.

Payments are usually made directly to the utility or fuel vendor. In cases where utility bills are included in the rent, however, provisions are made to pay the landlord. When a landlord refuses to participate, checks are sent directly to the recipient.

In both counties, payments range from $162 to $257 for electric bills; from $126 to $200 for natural gas; from $180 to $285 for oil fuel; from $144 to $228 for kerosene; and from $126 to $200 for coal and wood-burning stoves.

James H. Farmer, executive director of the Montgomery County Community Action Agency, said that the energy office had received calls from 25 people seeking additional funds. In such cases, the county can provide up to $200 more.

Farmer said that before the aid is granted, however, people are expected to seek help from friends, family, churches or social service agencies.

One fuel assistance recipient is Elsie McGrady, a 52-year-old secretary from Clarksburg who lives in a three-bedroom rambler with her 89-year-old invalid mother, 70-year-old brother and three of her four children.

This is the third time, McGrady said, that she has been helped by Montgomery County's fuel assistance program. Last year, she said, she received $128 in energy assistance. McGrady, whose electric bills currently average $158 a month, said she finds out how much she received this year when the credited amount appears on her next electric bill.

"Any program that you can fit into or qualify for when you really need it is just excellent," McGrady said. She added that "the people at the county office make you feel good and I am thankful that I have been helped in the past and again this year."

Householders eligible for assistance must be receiving welfare in the form of food stamps, aid to families with dependent children, supplemental security income under the Social Security Act or certain veterans benefits or have income levels not exceeding 150 percent of the poverty level or 60 percent of the median income for a given area.

Residents of Prince George's and Montgomery counties who apply for assistance must take with them their latest fuel bill and prove that their maximum yearly household income has not exceeded an average of:

$5,387 for one person; $8,940 for two people; $11,940 for three people; $13,630 for four people; $16,080 for five people; $18,810 for six people.

Persons seeking assistance should call: Montgomery, 279-1014, from 8:30 a.m. to 3 p.m. Monday through Friday. Prince George's 699-2662, from 9 a.m. to 5 p.m. Monday through Friday.