Single-stage and two-stage furnaces differ in their heating output capabilities:
Single-stage furnaces operate at only one output level – full capacity. This can lead to uneven heating and fluctuating bills because the temperature fluctuates more than with two-stage furnaces.
Two-stage furnaces offer two levels of heat output: a lower setting for mild weather and a higher setting for colder temperatures. This allows the furnace to modulate its output based on the actual heating demand, resulting in more consistent temperatures, quieter operation, and improved energy efficiency. A two-stage furnace may be a more expensive initial investment, but it can provide greater comfort and savings over time.