Furnace Comparison Guide

8 Signs Indicating You Might Need To Replace Your Boiler

Todayʼs energy-efficient gas furnaces arenʼt the same as your parentʼs furnace. If you find that you need to replace your central heating system, you may want to get familiar with the latest gas furnace units.

Bigger Isnʼt Better

The size of your gas furnace (which is measured in BTUs or ʻBritish Thermal Unitsʼ), is not a feature. Bigger is not always better, and it is important to clarify this! A gas furnace that is too large or too small may not provide the consistent warmth you expect from your heating system. A gas furnace should be sized “just right” for your specific home. Your old gas furnace may look larger than the new energy-efficient model that you are going to purchase. Many of todayʼs gas furnaces are not only more energy-efficient than in yearsʼ past, but they can also reach higher efficiencies in a much smaller sized unit.

Your installation technician should confirm the size or BTUs required by performing a Manual J load calculation. This calculation helps determine the heating needs of your entire home by assessing square footage, number and location of windows, insulation values, and more. When it comes to gas furnaces, the only size that matters is the right size that provides indoor comfort on those cold winter nights!

Stage of Comfort

A gas furnaceʼs stage may be referred to as single-stage, two-stage, or multi-stage (modulating). The stage is all about the gas valve and the burner. The different stages work similarly to how the heat is adjusted on your gas grill, gas oven or gas stovetop.

  • Single-Stage Gas Furnace: When the gas burner is ignited, the fuel enters at one constant flow. It is either ON or OFF and doesnʼt offer the option of adjusting the gas flow.
  • Two-Stage Gas Furnace: A two-stage gas furnace has a high and low setting on the gas burner. This feature allows for two levels of operation — full gas flow for when the demand for more heat is needed or a lower
    flow for milder days. A two-stage gas furnace may increase efficiency and supply a more consistent indoor temperature when compared to a single stage unit. Typically, a two-stage gas furnace is designed to operate at a low speed as much as possible.
  • Multi-stage or Modulating Gas Furnace: The burner electronically adjusts to provide the right amount of heat required to maintain the temperature on your thermostat or control system. This feature allows for precise
    heating control and energy-efficiency when compared to a single stage unit. Similar to a two-stage system, this type of gas furnace is designed to operate at the lowest speed to provide the most energy-efficient heating.


Blower Motor

Just like the name suggests, the blower motor controls the amount of heated air pushed through the air ducts to the spaces of your home. Below are three blower motor options, each with an increasing level of comfort control.

  • Single-Stage: A single-stage or single-speed option has two positions, ON or OFF. When on, the blower is designed to push a specific volume of air through the ductwork. When your thermostat or control system reaches the desired set temperature, the single-speed blower turns off.
  • Multi-Speed: The multi-speed blower is similar to the temperature control fan installed in your car. This type of blower offers a series of set operating speeds, from low to high. This alleviates the “cold air blowʼ often associated with single-speed furnaces.
  • Variable-Speed: A variable speed blower motor operates at various speeds to precisely control the amount of airflow throughout your home. A variable-speed motor running continuously at a half speed may use up to 75% less power than a single-stage motor to move the same amount of air.


Annual Fuel Utilization Efficiency (AFUE): The AFUE rates how effective your gas furnace is at converting gas to heat used to warm your home. This efficiency rating may range between 80% and 98% AFUE. The higher the percentage number, the higher the certified energy-efficiency level.

80% AFUE (non-condensing gas furnace)

  • Equipment may cost less for initial installation but may have a higher operational cost than higher AFUE furnaces.
  • Vents exhaust gases out of the home through chimney liner or metal flue pipe, typically through the roof.


90%-98% AFUE (condensing gas furnace)

Utilizes a second heat exchanger to heat the air from condensed exhaust gases which helps increase the energy efficiency rating.

  • May have higher upfront equipment and installation costs than a lower AFUE model.
  • Certain high-efficiency furnaces may qualify for a rebate
  • Often come with additional energy-efficient features designed to improve your overall indoor comfort.
  • During installation, a 90+% AFUE may require retrofitted venting if your system is upgrading from a less efficient gas furnace.


Heat Exchanger

The heat exchanger is an essential component of a gas furnaceʼs performance. Combustion from burning fossil fuels creates extreme heat inside the heat exchanger. Your indoor air is circulated over the heat exchanger and warmed. This warm air is then recirculated back to your conditioned indoor living areas.

Heat exchanger features may include:

  • One-piece, tubular construction: Joints are eliminated, reducing weak areas.
  • Wrinkle bend technology: This maintains the wall thickness of a curved section of the heat exchanger. Additionally, wrinkle-bend technology provides a “turbulation” effect for excellent heat transfer properties.
  • Sloped design: The sloped angle of the secondary heat exchanger allows for optimal condensate drainage, which helps improve the performance of the heat exchanger.
  • Stainless steel or aluminized steel: Heat exchanger materials with unique thermal and corrosion properties are selected to provide reliable warmth in your home for many years. A gas furnaceʼs heat exchanger is designed specifically to optimize performance.



Select gas furnaces have made significant technological advancements over the past few years. Your new gas furnace is rather smart! Some innovative features may include:

  • A diagnostic control board that may be capable of communicating system performance. This feature may simplify the installation, maintenance, and repair of your gas furnace.
  • Internet connectivity allows for remote control programming and system management from any location.
  • Automated maintenance reminders on the thermostat control system. These may include filter changes, scheduled maintenance reminders, and other indoor air quality-related products.


The Importance of Installation

The performance and reliability of a new gas furnace may be directly linked to a professional installation. The HVAC company, installing your unit, should have a reputation for renowned expertise and professionalism. An improperly installed gas furnace can lead to performance issues that may shorten the life of your system and cost you in the long run. If your high efficiency equipment isn’t installed properly, it may not be running as efficiently as you think!

Whether your homeʼs heating system is in need of routine maintenance, emergency repairs or a total replacement, selecting a qualified HVAC company is essential.

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