What is a key indicator that a gas furnace may need replacement?

A low annual fuel utilization efficiency (AFUE) rating combined with an age of over 15 years indicates that the furnace is likely operating at a decreased efficiency and may be nearing the end of its reliable service life. Most modern furnaces have higher AFUE ratings, often exceeding 90%, which means they convert more fuel into usable heat. A furnace with a low AFUE rating signifies that it wastes more fuel compared to newer models, resulting in increased energy costs and potentially diminished performance.

The age factor is also significant because, after approximately 15 years, many gas furnaces begin to suffer from wear and tear, leading to more frequent breakdowns or a decline in heating performance. If a furnace is both inefficient and old, it becomes a prime candidate for replacement as it is less likely to meet current energy efficiency standards and could be costly to maintain.

In contrast, options that mention a high AFUE rating, regular maintenance, or efficient performance do not indicate a need for replacement and suggest that the furnace is functioning well, which is not a concern for replacement.