Gas furnaces are rated for efficiency with an Annual Fuel Utilization Efficiency number, or an AFUE. According to the state's Energy Efficiency Standards, Title 24, the minimum AFUE for central furnace systems now sold in California is 0.78, which means that 78 percent of the fuel used by the furnace actually reaches your home's duct work as heat.
The higher the AFUE, the more efficient the furnace. AFUE numbers in today's furnaces range from 0.78 to around 0.90. If you are thinking about purchasing a new central furnace, please check out our Appliance Database that lists the most energy-efficient models.
Gas Furnace Tips
Don't block registers, vents or heating units with furniture or drapes. That makes your furnace work harder and uses more energy.
Consider installing a programmable thermostat. You can save as much as 10% a year on your heating and cooling bills by simply turning your thermostat back 10% to 15% for 8 hours with an automatic setback or programmable thermostat.
Using a programmable thermostat you can adjust the times you turn on the heating or air-conditioning according to a pre-set schedule. As a result, you don't operate the equipment as much when you are asleep or when the house or part of the house is not occupied. Programmable thermostats can store and repeat multiple daily setting (six or more temperature setting a day) that you can manually override without affecting the rest of the daily or weekly program. When purchasing a new thermostat, look for the ENERGY STAR label (www.energystar.gov) and one that allows you to easily use two separate programs; an "advanced recovery" feature that can be programmed to reach the desired temperature at a specific time; and a hold feature that temporarily overrides the setting without deleting preset programs.