American Standard's Freedom® furnaces range in efficiency from 80 to more than 92 percent. Every member of the family is designed to provide maximum heat for minimum fuel usage. However, as you climb the ladder from single-stage, to two-stage and variable speed Comfort-RT furnaces, you'll find an increasing number of benefits along the way. For example, two-stage heating makes a big difference during those transitional seasons when you need just a little heat to take the chill out of the air. And, our variable speed Comfort-RT furnaces are perfect for removing moisture during humid summer months.