These are our best gas furnaces, top-of-the-line. 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 variable speed blower gradually ramps up and down to modulate the air flow, creating a smooth, nearly-continuous, quiet and comfortable fan operation. The benefits of this furnace are that it makes the home more comfortable due to more even temperatures throughout the home, maintains a more steady temperature (keeps the house at nearly the exact temperature you set your thermostat), increases your air conditioning efficiency about 8%, has a lower operating cost (due to a DC voltage variable blower motor), increases efficiency of any attached air cleaner, and is quieter than most furnaces.