Does a Gas Fireplace Use More Gas Than Gas Central Heat?

Fireplace Gas Usage

• In general, natural gas fireplaces run at about 10,000 Btu to 30,000 Btu and can heat spaces up to about 500 square feet. Direct-vent gas fireplaces trap up to 70 percent of generated heat in the home, a startling contrast to wood-burning fireplaces, which lose up to 85 percent of generated heat out the chimney, according to "The Acorn." Gas fireplaces with intermittent pilot ignition systems conserve roughly 70,000 to 230,000 Btu per year compared to fireplaces without intermittent pilot ignition systems.

Fireplace Considerations

• Gas fireplaces allow users to target energy use because it typically heats one room at a time. Using a gas fireplace as a supplementary heat source while still maintaining a central heating furnace may save more gas than using one system or the other. This setup allows users to reduce central heat use, heating only frequently used rooms. The U.S. Department of Energy rates each gas fireplace model using by its annual fuel utilization efficiency, also known as AFUE. It is the same process used to rate the gas furnaces that power central heating systems.

Central Heat Energy Use

• Typically, gas central heating systems use 75,000 to 100,000 Btu to heat a room for one hour, according to "The Acorn." A 1.5-ton central unit can heat spaces between 600 and 1,100 square feet, depending on exterior temperature. Central gas heating systems must have a minimum AFUE energy rating of 78 percent, though some of the highest-efficiency models tout ratings as much as 97 percent. Gas fireplaces, in contrast, have high-end AFUE energy ratings of about 90 percent while older gas furnaces -- such as those from the 1960s or 1970s -- have AFUE ratings of about 60 percent, notes Consumer Reports.

Central Heat Considerations

• Though central heating systems can heat a larger space than gas fireplaces, the heat isn't as targeted. Because these systems rely on ductwork and are integrated into the home, construction factors such as insulation and window seals exert a larger influence on the gas usage of central heaters than gas fireplaces. Gas furnaces labeled with the Energy Star seal meet efficiency standards determined by the U.S. Environmental Protection Agency. These units feature efficient blower motors and utilize energy up to 15 percent more efficiently than standard gas furnaces.