What Are the Pros and Cons of a Condensing Furnace?

If you're in the market for a new home heating furnace, you may have noticed the wide discrepancy between the prices for standard furnaces and condensing gas furnaces.

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There's a reason for this. Condensing gas furnaces are extremely efficient, justifying their higher cost. They have a significantly higher annual fuel utilization efficiency rating, which means you use appreciably less energy to heat your home in winter.

What Is a Condensing Furnace?

In a conventional gas furnace, the hot gas from the burner passes through a heat exchanger before exiting through the flue pipe. A condensing furnace has a secondary heat exchanger installed above the main heat exchanger. This secondary heat exchanger recovers excess heat in the flue gases. This means the furnace uses less fuel to generate the same amount of heat. Condensing furnaces are known as high-efficiency furnaces.

How Does a Condensing Furnace Work?

Like a conventional furnace, a condensing furnace has a gas burner and a primary heat exchanger. A second heat exchanger is placed next to the primary one in the flue gas chamber. This heat exchanger condenses the vent gases into water and carbon dioxide — hence the name condensing furnace. The heat recovered from the vent gases increases the heating efficiency of the gas furnace by around 10%.

To avoid unnecessary cycling of the burner, condensing furnaces have gas controllers that reduce the burner output. Some types have a two-stage burner controller that provides for full load and part load. Others have a modulating valve that can precisely adjust the output of the burner to ensure an even heat. Many condensing furnaces also have variable-speed blower motors that automatically adjust the speed to maintain an even temperature in the home.

Pros of a Condensing Furnace

Benefits of a condensing gas furnace over a standard unit include higher energy efficiency, improved temperature control and quieter operation.

Enhanced Energy Efficiency

According to the U.S. Department of Energy, the AFUE rating of condensing gas furnaces is between 90% and 98.5%. This is significantly higher than older low-efficiency heating systems with AFUEs of 70% or less and modern mid-efficiency systems that achieve up to 83%.

Improved Home Comfort

A condensing furnace maintains a comfortable temperature in the home with minimal temperature fluctuation.

Quieter Operation

The variable-speed blower reduces noise levels, allowing for almost silent operation except during start-up and when the furnace is working at 100% load.

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Cons of a Condensing Furnace

The primary disadvantages of a gas condensing furnace are higher cost and a more complex vent installation.

Higher Up-Front Cost

High-efficiency gas-fired condensing furnaces are more expensive than standard units. Expect to pay between $1,000 (CAD 1,360) and $2,000 (CAD 2,715) more for a high-efficiency gas furnace, but this figure depends on its features and heating capacity. To offset this cost, you may qualify for a tax credit if you buy an Energy Star-rated furnace with an AFUE exceeding 97%.

Special Venting Requirements

Condensing furnaces have different venting requirements. In most instances, the gases vent through a PVC flue pipe that goes through your wall rather than your roof. You may also need a separate air supply vent.

Payback Period

Apart from the higher initial cost of the furnace, installation is generally more expensive, so the payback period to recover the additional costs compared to a standard furnace is lengthy.

Why Should You Install a Condensing Furnace?

While a condensing furnace installation costs more, there are many good reasons to install one, especially if you:

• Live in a colder climate. A high-efficiency condensing furnace keeps your home warmer and lowers your energy bills.

• Have good home insulation. Good home insulation minimizes energy losses and allows you to capitalize on the energy efficiency of a condensing furnace.

• Face high energy costs. A condensing furnace can reduce your heating costs by up to 20% compared to an older style furnace.

• Plan to live in your home for a long time. It typically takes several years to recover the higher installation cost of a condensing furnace through monthly energy savings.