There are many factors involved in determining the size of furnace you need for your home. These things include:
-Size of home
-Type of home
-Attic space and more
If you get a furnace that is too big you run into humidity building in the home causing moisture and mold to build up. If the furnace is too small you run into the unit running constantly making your energy bills climb very high. Ensure you have a qualified professional determine the size of furnace you need for your home. A reputable dealer will ensure that they are selling you the correct size unit for your space.