What could be a sign that a gas furnace is not operating efficiently?

A sign that a gas furnace is not operating efficiently is indeed reflected in higher energy bills than normal. When a furnace is not functioning effectively, it often consumes more energy to heat the home. This can happen due to a variety of issues, such as a dirty filter, a malfunctioning thermostat, or a need for maintenance, which can lead to increased wear and tear on the unit. As a result, homeowners may notice an unexpected spike in their energy costs, indicating that the system is working harder than it should to maintain the desired temperature.

In contrast, a consistent room temperature can be a sign of an efficient system, as it indicates that the furnace is effectively maintaining the set temperature without excessive cycling. Noise during operation can indicate a problem but doesn't inherently suggest inefficiency; it could result from other issues like loose components or airflow restrictions. Lastly, a flame color that remains blue is actually a sign of proper combustion efficiency in gas burners. A yellow or flickering flame would point towards potential issues, such as incomplete combustion or a need for cleaning, which could lead to inefficiency.