What is a 80% Efficient Two Stage Furnace

Nowadays gas furnaces are divided into two groups based upon their energy efficiency: the 80% efficient group (standard efficiency or SE), and the over 90% efficient group (high efficiency or HE). When you look at the various manufacturers, they tend to have three models to choose from within each group; a single stage furnace, a two stage, and a variable speed unit.

Learn more about the 80% Efficient Two Stage Furnaces below:

80% Two-Stage Furnace

Two stage 80% efficient furnaces offer quieter operation, more even temperatures throughout the home, and less stress on the equipment for increased reliability and longevity.

  • Furnace will initially come on high fire and high fan if the furnace is calling for heat and there is more than 2 to 3 degrees to satisfy the home.
  • Once the temperature is with-in 1-2 degrees The furnace will then drop down to first stage, low speed low fire.
  • It should satisfy on low not over shooting the thermostat like a single speed will do.
  • Once the system has satisfied the furnace should run on low fire low speed saving money on gas and electric.
  • The temperature will become more consistent (evenly distributed) because of the feathering and consistent heat that is being delivered.
  • Quieter operation because the furnace is running the majority of the time on low speed.
  • 2-stage system will not over shoot thermostat as a single stage will do. A lot of times a single stage furnace will heat the home and will not shut off till the temperature is 2 or 3 degrees higher than desired. This is how you get big fluctuations in temperature. The two stage solves this problem
  • Savings on the two stage verses a single staged will be at least $450.00 a year for a 1200 square foot home and much more as the size of the furnace increases and hours of usage are needed to heat a home.

80% Two-Stage Variable Speed Furnace

Variable speed 80% efficient furnaces do everything standard two stage furnaces do but better, and that's not all!

  • ALL features of a 2-stage mentioned above but the variable takes the two stage to the next step.
  • Quieter operation with the sixteen speed slowly ramping up to speed.
  • A little more dehumidification because the furnace is running longer and on lower speed and really helping to make the temperature consistent through out the home.
  • A minimum of 30% more efficient on electrical draw. Up to 50% more when taking in account fan mode.
  • In fan mode the furnace only draws as much as a 75 Watt light bulb.
  • Low speed will help the air-filtration become more efficient and effective catching more particulate.


  • 5-year parts and 1-year labor warranty on furnace, and installation.
  • 20 year manufactures warranty on heat exchanger.

Contact Alternative HVAC Solutions for a FREE Estimate today!