A two-stage variable speed furnace is the second most efficient type of furnace. Most are 95% efficient. To simply explain how this type of furnace operates, think of your gas pedal in your car. When this type of furnace starts, it is heating at 65% of its capacity on the first stage. This would be like starting your car and hitting the highway immediately. It is still saving on gas and electricity by only using 65%. Most 2-stage furnaces run at the first stage 80% of the time. As the temps drop outside, and it needs to produce more heat (compared to your car climbing a steep incline), it is able to ramp itself up to full capacity or 100%. Like you were pushing your gas pedal all the way to the floor.
The variable speed fan motor will adjust the speed of its air-flow on start-up which allows for adjustment based on existing humidity levels and helps to keep temperatures more consistent. This fan motor is made to run 24/7 so that also helps keep fresh air circulating through your home. The fan uses about the same amount of energy as a 40 watt light bulb. Isn’t that great??