Updated January 29, 2024
The lifespan of most gas furnaces is between 15 to 20 years. A furnace that’s older than 20 years should be replaced, not only because it will be at a much higher risk for a breakdown, additional repairs, and safety hazards. Older furnaces are much less energy efficient than newer models and choosing to retire the aging heating system you currently have for one with a higher AFUE rating will significantly reduce your heating bills.
Furnaces have undergone several technological changes over the last few decades, allowing them to make major strides in improved efficiency. There are high-efficiency furnaces today with AFUE ratings of 97%, which means they only waste 3% of their energy source when producing heat. Below are some of the reasons for these huge improvements:
Electronic ignition systems replacing pilot lights
The standing pilot light was the conventional furnace’s way of igniting the burners whenever gas flowed into them. But this pilot light had to remain burning all through the heating season, draining fuel even when the furnace wasn’t running. The new electronic ignition systems only activate as needed and use much less power over the winter.
Condensing furnaces with second heat exchangers
A specific type of high-efficiency furnace called a condensing furnace contains a second heat exchanger that allows the unit to draw additional heat from the combustion gas. Instead of venting out the vapor left over in the first heat exchanger, it goes to the second exchanger where it is condensed to emanate even more heat.
Variable‑speed blowers and multi‑stage burners
Older furnaces had blower fans and burners that could only operate at one setting: high. Newer furnaces can modulate the blower capacity as well as the strength of the burners to match a home’s heating requirements. These furnaces will run at an energy-saving level of 60% to 80% of the time
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