Optimum Temperature for Furnace Efficiency

Indoor Comfort

• The first consideration for determining what temperature to set your furnace's thermostat for maximum efficiency is the comfort of those inside the home. Savings on energy bills are surely not worth keeping the inside of your home uncomfortably cold, so first determine the lowest possible temperature at which you can keep the furnace to keep everyone inside the home comfortable. Achieving this lowest possible temperature is the first step to using your furnace at its maximum efficiency.

Consistent Temperatures

• In its guide to reducing winter and summer energy costs, the Kansas State University Extension notes that "the longer [a furnace] runs during each cycle, the more closely it operates to its designed efficiency." In other words, your furnace is not operating efficiently when it has to frequently cycle on and off; efficiency is much more easily achieved when the furnace can run for long periods uninterrupted. For whatever temperature you determined will maintain comfort in the home, make sure the thermostat stays at that temperature and is adjusted as little as possible.

  Also make sure the thermostat is set substantially above the outdoor temperatures. A furnace thermostat set at 70 degrees will run more continuously -- and thus more efficiently -- than a thermostat set at 60 degrees when the outdoor air is 40 degrees.

Furnace Efficiency

• The age and mechanical condition of your furnace plays a role in how efficiently or inefficiently it will run. Technological advancements in ventilation and other furnace components mean that new furnaces are substantially more efficient than their older counterparts. A 15-year-old furnace with a thermostat set 60 degrees above outdoor temperatures will operate with less efficiency than a new furnace with its thermostat set 20 degrees above outdoor temperature. Consider replacing your old, inefficient furnace with a newer, more efficient model.

Other Considerations

• Programmable thermostats can vastly increase your furnace's efficiency by allowing you to set custom thermostat temperatures based on times of the day when people are expected to be away and when people are expected to be home. Consider replacing the furnace's old, analog thermostat with a newer digital and programmable model.