So what options do I have?  Here is a description of the several options you have available to you.

Single Stage vs Two Stage vs Modulating Furnaces:

  •  Single Stage Furnace – A single stage furnace means that it only has one stage of heat output, it’s running at full capacity no matter how cold it is outside.  A single stage furnace is not as efficient since every time it turns on, it is working at full output to produce as much heat as possible.  There’s an “off” speed, and then an “on” speed with nothing in between.
  • Two Stage Furnace – A two stage furnace operates much more efficiently than a single stage furnace. The first stage operates the majority of the time and runs at about 65-70% of the furnace’s full capacity. When the temperature outside becomes extremely cold and the first stage is not enough to heat your home, the second stage kicks in to provide the additional heat needed. A two stage furnace provides the right amount of heat to efficiently satisfy your home.  In addition, a two stage furnace is much quieter since it doesn’t operate at 100% capacity every time it runs, and creates less carbon dioxide emissions for the environment.
  • Modulating Furnace –  A modulating furnace takes the idea of a two stage furnace and expands on it to include multiple heat output settings.  If it’s cold outside and your home requires more heat, a modulating furnace responds by increasing heat output in increments of as little as 1%. Typically, they function from around 35% up to 100%.  By continuously regulating the amount of fuel burned, according to the thermostat setting, temperature can be maintained to within about ½ degree of your thermostat’s set point throughout your home. Additionally, since the fan and the gas burner almost never run at 100% full capacity together, the on/off cycling that is typical of a standard furnace can be completely eliminated.  Thus, making these modulating furnaces the most fuel-efficient technology currently available.

PSC/Multi-Speed vs ECM/Variable Speed Blower Options:

  • Multi-speed/Standard/PSC Blower – These units have a conventional split-capacitor electric motors that does not make speed adjustments.  They either cycle on or off at one selected speed (low/med/high), based on whether your thermostat is calling for heat or cool.  These units are usually more cost effective than the variable speed option on other units.
  • Variable Speed/ECM Blower – The difference between the multi-speed and variable speed is that the variable speed is completely variable and could run at any level between 0 RPM and the maximum possible speed designed for the motor.  A variable speed blower can circulate air continuously at lower volumes with few “off” cycles. During the cooling season, this prevents the accumulation of hot air at the ceiling and keeps rooms more consistently comfortable.  Variable speed systems typically result in an efficiency gain of about 1 SEER for the air conditioning efficiency.  During the heating season, a variable speed blower can help reduce the “cold” spots through out your home by running longer at lower speeds to help circulate and mix the air.  Electrical efficiency, heating consistency, noise reduction, and cleaner air are all benefits of this type of furnace, depending on the duct work in your home.

8o% vs 90%+ Gas Furnaces:

  • 80% – This is the most common gas furnace in most older homes, vented through a chimney.  In a 80% furnace, 20% of the heat produced is exhausted up the furnace vent.
  • 90% – 97% – These use a secondary heat exchanger to recover that lost energy. Combustion gases are diverted into a condensing phase where the heat is released as the gases condense to water. This boosts the furnace AFUE percentage and lowers operating costs.


You can see some of the options at one our product lines we install – Rheem.

Posted Under: Blog, Heating