What is the minimum efficiency rating required for a natural gas furnace?

The minimum efficiency rating for a natural gas furnace is commonly set at 78% Annual Fuel Utilization Efficiency (AFUE). This means that for every dollar spent on fuel, at least 78 cents must be converted into heat for the home, while the remaining percentage accounts for energy lost through the flue, radiation, and other factors. The 78% AFUE standard ensures that natural gas furnaces meet a baseline efficiency, helping to promote energy conservation and lower utility bills for consumers.

Higher AFUE ratings indicate better efficiency, but the 78% level is the threshold established by various energy efficiency guidelines and federal regulations. Therefore, the choice indicating 78% AFUE accurately reflects the minimum efficiency standard required for natural gas furnaces in many regions.