What Makes a High‑Efficiency Furnace so Efficient?

If you’re considering installing a new gas furnace this fall to prepare for the winter, take a look at many of the high-efficiency models that are currently available. Where older furnaces might have an AFUE rating (efficiency rating) of around 85%, high-efficiency models can have AFUE ratings of 98%. That means the furnaces only allow 2% of the fuel they burn to go to waste, while the older furnaces would waste 15%. As you might expect, this adds to a large difference in how much the furnaces cost to run each winter.

What’s the secret of these high-efficiency furnaces? Is it just that they’re better built? Well… it’s partially that. Furnace manufacturers are more skilled than ever before when it comes to the baseline furnace models: where the standard for furnaces was once AFUE of 85%, newer models rate over 90%. But there are a few specific improvements in high-efficiency models:

• First is sealed combustion chambers. A sealed combustion furnace doesn’t have its combustion chamber open to the air of the house. Instead, it draws the air it needs to work through a pipe that leads to the house exterior. The sealed chamber means less heat loss as the burners are working.
• Second is ­multi-stage burners. A standard furnace either has the burners on or off. When they’re on, they always run at the same power level. A multi-stage burner adjusts how much power it consumes so that it can run at reduced energy whenever it can.
• Third is variable speed blowers. This is the fan that sends heat from the furnace into the ventilation ducts. As with burners, the fan in the standard furnace can only run at a single speed no matter the comfort requirements of the house. A variable speed furnace can run the fan at a lower speed and consume less power. In most high-efficiency furnaces, the blower will run at the energy-saving speed around 75% of the time.

Call our HVAC professionals today to learn more about your choices for a new furnace.