The two-week January cold snap has cost Washington residents as much as $20 million more in bills for natural gas, oil and electric heating than they paid during a more normal January such as last year's, according to calculations based on local utility statistics.

This month is shaping up as one of the coldest Januaries on record for the Washington area, with temperatures averaging 9.6 degrees below normal for the first 13 days of the month. So far, according to the National Weather Service, the month is almost as cold as January 1977, the coldest in 37 years.

A second set of calculations shows that a single super-cold day in the Washington area can mean an additional $2 on that day's natural gas bill for a small, two-bedroom house. Those calculations were made for The Washington Post by a research center at Virginia Polytechnic Institute.

That extra cost for single cold day could be $3.94 for the same house if it is heated by electricity and as much as $4.06 if it is heated with oil. Most Washington-area houses are larger than the hypothetical house used in the study, and most apartments and condominiums are smaller.

Cold weather alone apparently does not account for all of the recent increase in energy consumption. "The customer ceased conserving for the holidays," said one local heat distributor. "People were home for two weeks, and now they're going back to conservation."

While heating costs are soaring during the cold snap, no shortages are in sight even if the extreme cold continues, spokesman for the local natural gas, electric and oil heat industries said. Some natural gas companies in New England are expecting shortages.

On a single day -- Sunday, Jan. 4 -- the temperature ranged from 13 to 25 degrees above zero, an average of 16 degrees below normal for that date. The Washington Gas Light Co. sold more natural gas that day than every before: 916 million cubic feet, or 59 percent more gas than it sold on the previous Sunday, Dec. 28, which happened to be 3 degrees warmer than normal.

The temperature difference between those two non-workdays caused an additional $1.3 million in wgl's sales to its 542,000 customers throughout the Washington area, or a cost of about $2.30 extra to each customer because the day was markedly colder than normal.

Jan. 4 was followed by a Monday on which the area's two electric companies, the Potomac Electric Power Co. and Virginia Electric and Power Co., both experienced historic highs in the demand for electricity.

Then, this past Monday and Tuesday, two more exceptionally cold days, Pepco and Vepco again experienced demand that broke the week-old records. Just after dawn Tuesday, Vepco had a record demand, and that day the company sold more kilowatt hours of electricity than ever before -- 176 million, even more than on the hottest summer day when air conditioners are humming.

An estimated 136,000 homes and apartments in the Washington area are heated by electricity. A day such as Jan. 5 with its record demand meant electricity sales of at least $1.5 million more in the area than if temperatures had been normal.

As natural gas and electric sales have soared, trucks from 50 Washington area heating oil firms have been on the job six and seven days a week to keep about 300,000 area homes, apartments and businesses from running out of oil.

A cold day such as Jan. 4 cost those oil users $1 million more than if the day had been only normally cold.

Most of the figures above are rough calculations made by The Washington Post based on statistics supplied by the utility companies, oil heat industry representatives and the U.S. National Weather Service.

While expensive cold snaps occur during most winters, the total heating bills that people receive for a winter will include warm periods as well. Although the first two weeks of this January are cold, and more cold weather is predicted, this does not mean that this winte as a whole will be colder than normal.

January 4 -- the Sunday when WGL had its record "sendout" of natural gas -- was an exceptionally cold day. It dawned overcast and grim, with the area temperature at 13 degrees with 15 mph winds gusting to 21 mph. Jim Travers of the National Weather Services's forecast office calculated the wind-chill factor at 7 a.m. that day at 20 degrees below zero.

In the Washington Gas Light operations center in Springfield, key operators were up hours before dawn working to get the huge WGL gas system poised to pump gas into chilled homes as people awoke on the last day of the long holidy season and turned up their thermostats.

When they did so, the huge quantities of natural gas began moving through 6,000 miles of underground pipes throughout the Washington area. The winds continued all day, gusting at times to 30 mph, and the temperature never rose above 25 degrees. By day's end, the new record had been set.

"The wind is very important," said WGL spokesman Young. "You can have a snow cover which gives the impression of being colder, but it is a form of insulation. Where you have a wind and low temperatures, that's where gas consumption goes up most dramatically. That wind gets into every corner of a house and sucks the heat right out."

There were only patches of snow on the ground in the area on Jan. 4 -- not enough to provide the kind of insulation Young was talking about.

Travers, the Weather Service man, said that the 25-day period from Dec. 22 through Jan. 16 should be, "on a historcial basis," the coldest period of the year when temperatures "bottom out."

If that turns out to be the case this year, Travers said. "We can begin to get optimistic. Of course, that does not prelude some horrendously cold weather [in the period just ahead]."

Travers said the long-range forecast for this winter remains "very cold and dry. The foreseeable future still remains below normal."