What measurement is used to determine the efficiency of furnaces?

The annual fuel utilization efficiency (AFUE) is a crucial measurement used to determine the efficiency of furnaces. It expresses the percentage of fuel that is converted into usable heat over the course of a year, taking into account the heat lost during operation. A higher AFUE rating indicates that the furnace is more efficient, meaning it effectively uses fuel to produce heating, resulting in lower energy costs and less wasted fuel.

In comparison to other measurements, thermal efficiency rating typically refers to the efficiency of a heating system without accounting for the seasonal variations and operational adjustments throughout the year, making it less comprehensive than AFUE. The seasonal energy efficiency ratio (SEER) is more relevant for cooling systems, measuring their efficiency over a cooling season, while the coefficient of performance (COP) is used primarily for heat pumps and does not apply to furnaces. Therefore, AFUE stands out as the specific metric relevant for evaluating furnace efficiency based on actual annual performance.