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When it's time to get comfortable, it's a good time to install a new, high-efficiency furnace.

High-efficiency gas furnaces are a step up for any home. That's because modulating gas furnaces continuously adjust their heating level by 1% increments to match the degree of comfort you need exactly and efficiently. In fact, they can maintain indoor temperatures to within 1/2 degree of your thermostat's setpoint. The variable speed blower slowly ramps up and down providing quiet and efficient air distribution while reducing overall utility consumption.

You can identify and compare a system's efficiency by not only its AFUE but also by its equipment features, listed below.

Old, low-efficiency heating systems:

  • Natural draft that creates a flow of combustion gases
  • Continuous pilot light
  • Heavy heat exchanger
  • 68% - 72% AFUE

Mid-efficiency heating systems:
  • Exhaust fan controls the flow of combustion air and combustion gases more precisely
  • Electronic ignition (no pilot light)
  • Compact size and lighter weight to reduce cycling losses
  • Small-diameter flue pipe
  • 80% - 83% AFUE
Annual Estimated Savings for Every $100 of Fuel Costs by Increasing Your Heating Equipment Efficiency*
Existing System AFUE New/Upgraded System AFUE
55% 60% 65% 70% 75% 80% 85% 90% 95%
50% $9.09 $16.76 $23.07 $28.57 $33.33 $37.50 $41.24 $44.24 $47.36
55% ---- $8.33 $15.38 $21.42 $26.66 $31.20 $35.29 $38.88 $42.10
60% ---- ---- $7.69 $14.28 $20.00 $25.00 $29.41 $33.33 $37.80
65% ---- ---- ---- $7.14 $13.33 $18.75 $23.52 $27.77 $31.57
70% ---- ---- ---- ---- $6.66 $12.50 $17.64 $22.22 $26.32
75% ---- ---- ---- ---- ---- $6.50 $11.76 $16.66 $21.10
80% ---- ---- ---- ---- ---- ---- $5.88 $11.11 $15.80
85% ---- ---- ---- ---- ---- ---- ---- $5.55 $10.50
90% ---- ---- ---- ---- ---- ---- ---- ---- $5.30
*Assuming the same heat output
Source: U.S. Department of Energy

High-efficiency heating systems:
  • Condensing flue gases in a second heat exchanger for extra efficiency
  • Sealed combustion
  • 90% - 97% AFUE

Residential heating is done typically two ways: A gas furnace or a heat pump.

A gas furnace runs off electricity and natural gas (or even propane for remote areas that do not have gas lines). Gas is used for the actual heat/flame while electricity is used to power the fan (blower) motor. When running, flames heat up the heat exchanger (a type of metal grid). The fan motor pulls air from the home (return air) and pushes it through the heat exchanger, thus warming the air. The warm air is then distributed through the home via ductwork. When the air is heated, this also removes moisture which makes a whole home humidifier a key ingredient to comfortable air during the winter season.

A heat pump runs off electricity, and is actually an air conditioner that can heat as well. Heat pumps have a higher heating energy efficiency than a gas furnace in milder winter climates . Installations are normally a "split system" design where the system components are split indoors and outdoors. The indoor unit is called a fan coil or sometimes an air handler and it contains a coil system and a fan blower motor. The outside unit is the actual heat pump, and also has a copper coil system in it. When running, it absorbs heat from the outside air and compresses it into the refrigerant contained in copper coil (even cold outside air has heat energy in it). The "heated" refrigerant is sent inside to the indoor coil system. As air from the home is forced through the indoor coil system, the air is heated and then sent back into the living areas via ductwork.

In the cooling season a heat pump acts like an air conditioner: read our air conditioning page for more information.

Hybrid System is used in areas with a more extreme range of seasonal temperatures for the best heating efficiency possible. Heat pumps are all electric devices, and are cheaper to run than a furnace when the temperature is 40° degrees and above. When the air temperature drops, the gas furnace is then used instead because it is more efficient at colder temperatures.

A Variable Speed Fan Motor is a term that you will hear mentioned if you are looking at a new system. A variable speed fan is quieter, more efficient and also keeps the home climate more comfortable due to an ability to regulate fan speed based on humidity and temperature requirements. Old school fan blowers just crank on and run at one speed, are less efficient and can be much louder. This matters when your unit is not down in a basement, but in the ceiling or hallway closet.

Typical Heating System
Below is a diagram displaying what we presented above. In a heat pump installation, there are no flames in the indoor unit.