What’s the Difference Between a Single Stage, 2-Stage & Variable Speed Furnace?

If you have been shopping for a new furnace, you may be wondering about the differences between single-stage, 2-stage, and variable speed models – and which one is best for your home.  Several factors come into consideration when evaluating these options:

• heating requirements
• existing ductwork and insulation
• size
• the number levels in your home
• budget

Single-Stage Furnace

Single stage furnaces operate at one speed.  Essentially, they are either “on” or “off.” When they are “on” they produce the maximum amount of heat the unit can provide, with no differentiation between cold and extremely cold.  As a result, they can generate extremely costly energy bills during the coldest months. On the other hand, they are less expensive to purchase and install.

Two-Stage Furnace

Two-stage (or two-speed) furnaces are a step up in energy efficiency.  The first stage operates most of the time, at about 65% of the furnace’s full capacity. When the temperature outside becomes extremely cold and the first stage is not sufficient to heat your home, the second stage kicks on to provide the additional heat.  Since they most often operate at less than full capacity, these furnaces are quieter and create fewer carbon dioxide emissions.  They are also more costly to purchase and install.

Variable Speed Furnace

Variable speed refers to the ability of the furnace’s fan motor to move at different speeds. This allows for better airflow and creates a more comfortable environment in regard to both temperature and humidity. The motor in a variable speed furnace continually circulates air throughout your home, even when the furnace is not “on.” The continuous flow of air passing through the filter has several benefits: healthier indoor air quality, greater efficiency since the furnace itself doesn’t need to be on continuously to warm your home. Although the upfront cost for a variable speed furnace is higher, its intelligent performance results in significantly less energy consumption and lower utility bills.

An HVAC professional can help you weigh the energy cost savings against the cost of the furnace and help you select the best unit for your home.

Contact IAQ today to determine which type of furnace is right for you.