What Size Furnace Do You Need For Your Home?

Having the right furnace in your home can make a major difference in the cost of heating and the ability of the furnace to heat the home. When you need to replace the existing furnace in your home, it is important that you get a model that is the right size for the structure. The size of a furnace is measured in BTU or British thermal units. This refers to the amount of heat that the unit has the capability to produce. For every home there is a specific correct size of furnace that will work best and this will be determined by accounting for a variety of factors.

Getting a furnace that is the right size for the home is important for many different reasons. A furnace that is too small might not be able to provide adequate heat to the structure. Not only that, but an undersized furnace will have to work harder and this additional strain will reduce the operating life of the unit. With a furnace that is too large, the unit will continually cycle on and off and this can also damage the unit in the long run. A well-sized furnace will cost less to operate and it will have a longer operating life.


The most important factor that will need to be considered when determining the proper furnace size for the home is the size of the structure or home itself. Some contractors might use this as the sole determining factor when they recommend a replacement furnace for your home. However, there is more to properly sizing a furnace than the square footage of the home. A knowledgeable HVAC technician will determine the proper furnace size for your home by using the Manual J method. This is a scientific model that accounts for the size of the home, the building material that it is constructed from, the climate and the amount of windows in the structure.

Since getting the right furnace size requires the consideration of a variety of factors, it is usually a determination that will best be left to a professional. If you are looking to replace a furnace, it might work to determine the size of the old one and simply replace it with a model of the same size. For the most part that can work, but there is no guarantee that your home had a properly sized furnace to begin with. Another consideration that can make it necessary to resize the furnace is whether the home has been remodeled or added on to. If the structure of the home has been significantly altered, the original furnace might not be the appropriate size.

Consulting with an HVAC technician is probably the best idea if you need to determine the proper furnace size for your home. A professional HVAC tech will be able to weigh all of the necessary factors and determine the right size of furnace for the structure. Many companies offer free estimates when it comes to installing a replacement furnace and most will provide you with an accurate answer to your furnace sizing questions.