In case you don't know it, there's a whole new generation of high efficiency gas furnaces out there that can help you cut your heating bills significantly.

With efficiency ratings over 90%, these new furnaces are designed to increase the amount of heat obtained from every Btu of fuel you consume.

According to the Trane Home Comfort Institute, a consumer information service on heating and cooling, the efficiency of a gas furnace is indicated by its Annual Fuel Utilization Efficiency or AFUE rating. Developed by the U.S. Department of Energy, the AFUE indicates what percent of the energy used is converted to useable heat.

AFUEs for gas furnaces range from 57% to over 90%. The higher the AFUE, the more efficient the furnace. The more efficient the furnace, the lower the heating bill.

If your present furnace is ten years old or more, it's probably in the 60-70% AFUE range. In effect, that means you're wasting 30 to 40 cents out of every dollar you spend for heat. By replacing an old, low efficiency unit with a new high efficiency model, more of the fuel you pay for is turned into heat.

The Federal government now requires that all new furnaces meet or exceed an efficiency level of 78% AFUE. It also requires that the furnaces be tested according to its standards so that consumers can compare the efficiency ratings of various units.

The Gas Appliance Manufacturers Association (GAMA) publishes a directory of those ratings twice a year. Your heating dealer should have a copy and can show you the rating for the system you're considering.

The Trane Home Comfort Institute says AFUE ratings of gas furnaces have increased over the past few years because of new furnace designs that allow the heating units to recover heat that would have otherwise been wasted. Included among these new designs are induced draft furnaces with AFUEs in the 80% range and condensing furnaces with AFUEs in the 90% range.