Furnaces heat the vast number of private homes throughout the United States. They work by heating air and then forcing it through a series of ducts into the various spaces of a house. The useful life of a furnace is typically 12 – 15 years and, with diligent and proper maintenance, they can last for as many as 20 years. Unfortunately, as time goes by, regardless of maintenance, the average furnace becomes less than optimally efficient and one needs a furnace replacement. Couple this with the fact that most older furnaces were not designed to be particularly efficient by today’s standards and it may be time for a high efficiency furnace replacement.

Furnace efficiency is measured in terms of annual fuel utilization efficiency (AFUE). It represents the amount of heat energy utilized versus the total energy consumed by the furnace. Basically, it tells how much energy actually heats the house versus how much escapes through the chimney or elsewhere.

The following list gives a general idea of the furnaces in use today, their benefits and drawbacks and their overall efficiencies. You’ll be able identify if you need a furnace replacement.

Early, low-efficiency furnaces:

· Used a natural draft method for inflow and outflow of combustion gases

· Maintained a continuous pilot light

· AFUE rating is 65 – 70 percent

Mid range, late model furnaces:

· Controlled flow of intake and outflow air

· Electronic ignition instead of pilot light

· AFUE rating is 80 – 85 percent

Modern, high-efficiency furnaces:

· Secondary heat exchanger condenses flue gases for extra efficiency

· Combustion is sealed and only uses outside air

· AFUE rating is 90 – 97 percent

Each generation of furnace was designed with new innovations and technologies that increased their efficiency. The oldest high quality furnaces could only achieve AFUEs of 70 percent. The elimination of the constantly burning pilots light and the increased control of the combustion chamber pushed the next generation of furnaces chamber into the mid 80 percent range in AFUE and the introduction of the sealed combustion process saw AFUEs climb well above 95 percent.

In short, today’s furnaces provide remarkable efficiency. Depending on the age and make of your current furnace, the purchase and installation cost of a furnace replacement could be easily recouped through lower utility bills within a year or two. In any case, with ever rising fuel costs, a new, high efficiency furnace replacement deserves a closer look.