How a Furnace Works

How a Furnace Works

Furnaces heat your home by circulating heated air through your ductwork. That air is heated by the burning of fuel within the furnace. Furnaces can be fueled by natural gas, propane or oil. As the fuel burns, the hot gases that are generated move through the heat exchanger, and are vented outdoors through the flue pipe. Simultaneously, the air circulating through your ducts pass over the heat exchanger, and that hot air is then circulated throughout your house.

Furnaces can vary widely in efficiency.

That efficiency is measured by the furnace’s annual fuel efficiency, or AFUE rating.

Standard Furnaces

Standard furnaces have an average AFUE rating of around 80%. This means that for every dollar you spend 80 cents is used to heat your home and 20 cents is lossed in the burning process and exhausted outdoors through the flue pipe

.High Efficiency Furnaces

High Efficiency Furnaces go one step further, and use a secondary heat exchanger to extract even more heat. High-efficiency furnaces can have ratings as high as 96% AFUE, which translates to an energy loss of only 4% or 4 cents. So it’s very easy to see how much more energy is used to heat your home and translates to a far more efficient heating system.