What indicator shows a gas furnace is operating efficiently?

A consistently maintained AFUE (Annual Fuel Utilization Efficiency) rating is a key indicator of a gas furnace operating efficiently. The AFUE rating measures the percentage of fuel that is converted into usable heat over the course of a year. A higher AFUE rating indicates that a greater proportion of the fuel is being used effectively, leading to lower energy costs and less environmental impact.

Efficient gas furnaces typically have an AFUE rating of 90% or higher, meaning they convert 90% or more of the fuel into heating energy. Monitoring and maintaining this rating ensures that the furnace is functioning properly and optimally, allowing for effective heating with minimal waste. Regular maintenance and inspection can help sustain the AFUE rating over time, ensuring that the furnace remains efficient throughout its operation.

In contrast, indicators like high gas pressure readings, low ambient temperature in the furnace, or frequent cycling on and off do not directly relate to operational efficiency. High gas pressure could lead to safety issues or improper combustion, while frequent cycling can suggest a problem with sizing or settings rather than efficiency. Low ambient temperatures might be indicative of a problem with the furnace or an inefficient heat exchange process, rather than an indication of high efficiency.