What is the difference between a single-stage and a two-stage furnace?

A single-stage furnace operates at full capacity whenever it is turned on, meaning it only has one speed or stage. This type of furnace provides either full heat or no heat, resulting in quick temperature fluctuations, noise, and higher energy consumption. On the other hand, a two-stage furnace operates at two different heating capacities - a lower stage for milder weather and a higher stage for colder temperatures. By adjusting its heat output, a two-stage furnace provides more consistent and balanced heating, maintaining a more comfortable environment. This increased flexibility results in fewer temperature swings, reduced noise levels, and improved energy efficiency. Overall, the main distinction lies in the performance and control offered by two-stage furnaces, allowing for more precise heating adjustments while offering increased comfort and potential energy savings.