What is a High-Efficiency Furnace?

In the home energy performance industry, we often speak about high-efficiency furnaces and the money they can save in lower energy bills.  But, what do we mean by high-efficiency?

Converting Energy into Heat

If your furnace uses natural gas or LP, then the gas coming into your home contains energy.  If your furnace is able to convert 95% of that energy into heat, then we say your furnace is 95% efficient.  If your furnace is able to do that over the varying temperatures that occur during the course of a year, then we say your furnace has an AFUE of 95.  AFUE stands for Annual Fuel Utilization Efficiency.

Furnace efficiency has increased greatly over the years.  There was a time, not that many years ago, when most new furnaces had an efficiency around 60%.  Then the state of the art grew to 80%.  Today many federal, state, and local governments and many utility company programs recognize 95% as the minimum level for a furnace to be called high-efficiency.

In the real world, other factors and new technology can make a big difference in the efficiency you get from your furnace.  For example, two-stage furnaces can operate at less than full capacity, only calling on the full capability of the furnace as needed in colder weather.  Modulating furnaces can increase this capability beyond two stages.  Additional efficiency can come from fans that circulate heated air through your ductwork.  These fans can operate at variable speeds rather than just off and on.

What's the Best Way to Lower Energy Bills?

If your goal in adding a high-efficiency furnace to your home is to lower your energy bills, don’t assume the new furnace will be the best way to accomplish that.  For example, it doesn’t make much sense to produce heat efficiently and then waste it through air leaks or inadequate insulation.  For many homes, air sealing and insulating can result in a bigger decrease in energy bills than adding a high-efficiency furnace.

Don’t forget the ductwork.  Once your heated air leaves your high-efficiency furnace, it is distributed throughout your home by your system of ductwork.  If some or all of that ductwork passes through your attic or crawlspace, that ductwork may be leaking and wasting your heated air outside your home.  It usually pays to have an energy audit first, then determine whether adding a high-efficiency furnace is the best way to reduce your energy bills.

If a high-efficiency furnace is right for your home, the bar today is set at a minimum of 95% or 95 AFUE. 

Contact us today to schedule a free estimate for our home insulation services, air sealing or duct repair!