The efficiency ratings of furnaces are measured in AFUE as a percentage. AFUE stands for Annual Fuel Utilization Efficiency, and it’s what furnace manufacturers use to inform us of the efficiency of their equipment.
Standard efficiency gas furnaces have efficiency ratings of 60% to 70%. Mid-efficiency gas furnaces have an AFUE rating of around 80%. High-efficiency gas furnaces (aka condensing gas furnaces) haveefficiency ratings in excess of 90%. To visualize what the percentage means, deduct the efficiency from 100% then whatever you have left is what the furnace doesn’t use. Thus, for an 80% efficient gas furnace, 20% of the gas you purchase is going up the chimney. For a 96% efficient (high-efficiency) gas furnace, only 4% of the gas purchased is being exhausted out.
There are 2 main reasons for purchasing a variable-speed, 2-stage gas furnace: comfort and energy savings.
Comfort: a 2-stage variable speed gas furnace distributes the air around your house more evenly, which results in better heating or cooling distribution. These types of furnaces make much less noise, which means less white noise in the background. Less noise, better heat distribution = more comfort. Do you have allergies? If yes, then a variable speed furnace with a high-efficiency air filter is the solution for you! Remove contaminants from the air cost effectively!
Energy Savings: Variable-speed blowers use about 1/4 of the electricity standard motors use. This translates to a savings of $200.00 to $250.00/ year per household! And to top it off, variable speed furnaces make your air conditioner run more efficiently, and help make your air conditioner remove humidity faster from your home.
Aside from improving your indoor air quality, going the D/C route can save you up to $500 annually in hydro savings. Better air distribution and improved humidity control are also benefits of switching to a D/C equipped furnace!
This depends on the type of furnace you have. If you have a furnace equipped with D.C. (E.C.M) variable speed motor, then yes. This is one benefit of the variable speed motor: you can affordably operate your blower 24 hours a day because it circulates the air in between demand cycles at a lower rate, and uses a lot less energy than a conventional blower motor.
If, however, you have a furnace equipped with a conventional motor, you should operate the fan in Auto mode. That way, the fan operates only when the temperature requires it. This is the most used and the most efficient setting. However, there are advantages to using the “on” setting. Air is constantly filtered through the unit’s air filter, and the constantly circulating air results in an even temperature throughout the house.