The electric heat pump in Cathie and Cliff Bacon's rambling two-story house wasn't keeping them warm--not in the depths of this Washington winter.

So last month, the Bacons bought a large portable kerosene heater for $289, took it to their Sterling, Va., home and set it up in the family room. Now they light the kerosene heater in the evening, transforming the 24-foot-square, cathedral-ceilinged family room from a drafty chamber into a cozy retreat.

But it's not only comfort that's led many such households as the Bacons to invest this winter in supplemental heating sources ranging from the old-fashioned wood stove to the new generation kerosene heater. Consumers seeking lower bills, advises Ronald A. Fippinger, managing director of the National Housewares Association, should "turn down the primary heating plant within the house and use space heaters to heat the area they are using."

The growing popularity of smaller and more manageable sources of warmth is reflected in rising sales figures, especially for kerosene heaters. In seven years, for example, the number of kerosene heaters imported by this country from Japan, which produces virtually all the heaters sold in the United States, has grown from 3,500 units in 1974 to 3 million units in 1981. And industry officials predict that about 4.5 million units--a 50 percent increase over last year--will be imported in 1982 to satisfy consumer needs.

Demand for electric heaters also has increased. An estimated 4.8 million portable electric heaters were sold in 1981, up from 4.6 million the year before. Sales are down, however, for the quartz heater, which manufacturers initially said could produce more heat for the same wattage than other electric heaters. That claim has since been dropped. And so have sales, from 1.2 million quartz heaters sold in 1980 to one million in 1981.

Despite the willingness of consumers to turn down their furnaces and turn on their heaters, the increased use of the devices has not been without controversy. Fire officials and consumer advocates have raised questions about the safety of the units, especially wood-burning equipment and kerosene heaters; the actual savings delivered by the heaters has become an issue; and there is some uncertainty about the availability of fuel.

Fires resulting from the use of wood- and coal-burning stoves, heaters and fireplaces are up 60 percent, according to the latest available figures compiled for the U. S. Fire Administration. The figures for kerosene heater fires haven't changed significantly, but the International Society of Fire Service Instructors has refused to endorse kerosene units--even the new improved models with built-in safety features--because of the "significant potential for increasing tragic incidents."

The controversy over the kerosene heater is especially bitter, with fire officials squared off against industry officials and retailers in a fight extending from Maryland to California over whether the new generation of kerosene heaters, which are portable and don't require venting, should be used in homes.

Under current laws, the use of the heaters is legal in Virginia but not in the District of Columbia. Maryland's 20-year ban against kerosene heaters was changed in December to allow certain models in one- and two-family homes. The change was approved by the Maryland Fire Prevention Commission after more than a year of struggle between industry representatives and fire safety leaders such as Montgomery County Fire Chief James Dalton.

Kero-Sun, the largest single supplier of kerosene heaters with more than one-third of the market, took the position that the Maryland ban was written to protect consumers against the old-style kerosene heaters marketed during the 1950s and earlier. Those heaters were banned in many areas because of fires caused by heaters tipping over, fires from fuel storage and handling, asphyxiation and other problems. Representatives of Kero-Sun and local Maryland dealers argued that safeguards such as a wide base to minimize the tipping problem and an automatic device extinguishing the heater if it is knocked over should allay those old fears.

Dalton and other fire officials, however, say the heaters, despite the advances, still pose a risk and could result in a new wave of fires, injuries and deaths. According to Dalton, many consumers buy an unsafe grade of kerosene that can create dangerously high levels of sulphur dioxide and carbon monoxide if there is inadequate ventilation.

The Fire Prevention Commission voted 4-2 to amend the ban to allow certain kerosene heaters with approved safety features in one- and two-family homes. The heaters still are illegal in Maryland apartment buildings and schools, however. They are illegal under local codes in Anne Arundel, Wicomico and Baltimore counties and in the cities of Baltimore, Cumberland and Annapolis.

In the campaign to promote the kerosene heater, the companies have formed a trade association, the National Kerosene Heater Association, which contends that modern kerosene heaters are safe when used, maintained and stored properly and that they enable homeowners to cut fuel bills without sacrificing warmth.

However, the examples of savings given by the association are based on kerosene priced at $1.60 per gallon. The special low-sulfur kerosene recommended for kerosene heaters typically costs $2.50 to $4 a gallon in the Washington area.

Regular grade kerosene, which has a higher sulfur content, can be purchased at some service stations for as little as $1.50 a gallon--but it isn't necessarily safe for kerosene heaters. Fire officials say that the higher-sulfur kerosene isn't suitable for unvented heaters because it can gum up the wick, cause incomplete combustion and produce excessive emissions of sulfur dioxide.

As a precaution against ill effects from the kerosene heaters, manufacturers routinely recommend that they be set in well-ventilated areas.

But, says Sgt. Paul Mindte of the Montgomery County Fire Department, the "common person isn't going to go out and spend $200 on a heater, get the correct kerosene, come home, strike up the stove and then open the window." Mindte says that "people won't save money; the heater will stink; and after a while you will see soot all over the windows."