These are high efficiency furnaces. They are 10-14.9% more efficient than the low efficiency furnaces. This means you will save 10-14.9% more off your gas bill with one of these furnaces than if you select a low efficiency model.

Additionally, some of these furnaces have advanced burners with two flame levels, high and low. When your home needs less heat, the furnace will operate on low flame; when your home needs more heat it will automatically operate on high flame. The benefit of this is a more quiet operation, as well as increased comfort due to more even temperatures in the home (including a reduction in cool air-pockets near doors and windows).

• These furnaces have standard burners with one flame level. The flame is either on at full capacity, or it is off.

• These furnaces will operate on low flame, and then automatically increase to high-flame when more heat is needed.  (A two-stage thermostat is required which allows you to determine when high-flame is engaged.) 
• The two stage burner will help maintain a more consistant temperature in your home, keeping your home at nearly the exact temperature you set your thermostat at.