Phoenix Heating & Cooling Experts
What Makes a Furnace Efficient?

What Makes a Furnace Efficient?

The unfortunate reality of your average furnace is that a large portion of the heat it creates is wasted. As much as 40 percent goes out the exhaust flue and into thin air. The poor performance of your furnace isn’t doing your comfort or your wallet any favors.

Let’s take a look at how high-efficiency furnaces work to improve your comfort and save you money.

A New Standard for Efficiency

Top-performing furnaces are 98 percent efficient. This means that the furnace converts 98 percent of the fuel into actual heat, wasting only two percent of natural gas. A few decades ago, furnaces had a much lower efficiency rating, somewhere between 60 to 70 percent. Even today, standard furnaces might only achieve 80 percent annual fuel utilization efficiency (AFUE), leaving a lot of room for improvement.

How a High-Efficiency Furnace Works

High-efficiency gas-powered furnaces make better use of fuel and feature new advances in heating technology that minimize waste. These features can include…

Electronic ignition: Instead of a gas-powered pilot light, modern furnaces rely on electronic ignition which only turns on when the furnace needs to begin a heating cycle. This is a vast improvement over the standard pilot lights which burn continuously, whether the furnace is on or off.

Variable-speed blower: Older furnaces force warm air out of the vents at maximum capacity and switch off when it reaches the desired temperature. A variable-speed blower operates more efficiently, running for longer cycles but at lower levels, saving you money.

Two-stage furnace: Similar to a variable-speed model, a two-stage furnace operates full-blast but throttles down to a slow speed.

Sealed combustion: A conventional furnace uses the air inside the home to fuel the combustion process -- basically reheating warm air and exhausting it to the outside.

Sealed-combustions models draw from the air outside, preserving your heated air inside.

But what really separates a high-efficiency furnace from the rest of the pack is its ability to use exhaust to create more heat. Normally, a standard furnace includes a heat exchanger. When combustion gas goes into the chamber, it heats up the walls. When air is blown into the exchanger, the air absorbs the heat. The airflow cools down the gas so that it becomes a vapor. Then, the vapor is sent out of the exhaust flue.

With a high-efficiency furnace, the vapor is not sent out the exhaust flue. Instead, a second heat exchanger makes use of this exhaust material. The vapor goes into a chamber that condenses it into a liquid. This condensation process produces extra heat that warms up the heat exchanger's walls. At the end of the process, liquid exhaust drains out of the second heat exchanger.

In short, a high-efficiency furnace basically uses the same fuel twice to produce extra heat.

Is a High-Efficiency Furnace Right for You?

A high-efficiency furnace is considerably more expensive than a conventional heating system. It may also require a more complicated installation due to the sealed-combustion process, which is another cost consideration.

Keep in mind, the AFUE isn’t the only measure of efficiency by which to judge performance. Many standard models also come with some of the same energy-saving features, such as two-stage operation and electronic ignition. So, while a standard furnace may only use 80% of fuel, it’s curbing energy consumption in other ways.

Bottom line: Whether or not a high-efficiency furnace is right for you will depend on a number of factors -- among them, budget, installation requirements and the size of the unit you’ll need. It could be that you’d be better off with a standard furnace. We’re happy to walk you through your options! To schedule an appointment, call (602) 428-9007.


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