What does a low AFUE rating indicate?

A low Annual Fuel Utilization Efficiency (AFUE) rating indicates that the furnace uses a lot of fuel for heating because it is less efficient in converting fuel into usable heat energy. AFUE is a measure of how much of the energy in the fuel is actually converted to heat over the course of a year, expressed as a percentage. A low rating signifies that a higher percentage of the fuel is wasted, resulting in increased fuel consumption to achieve the desired heating effect. This not only means higher operating costs for the homeowner but also implies a larger environmental impact due to increased greenhouse gas emissions associated with higher fuel consumption.

In contrast, a high AFUE rating would indicate that the furnace operates efficiently, using less fuel to produce more heat. Therefore, the correct interpretation of a low AFUE rating is directly tied to higher fuel usage, highlighting the importance of efficiency in heating appliances.