How Efficient Is Your Furnace?

We live in a world where the phrase “they don’t make things like they used to” often rings true. Antique furniture and old appliances sometimes seem to last forever.

But when it comes to your furnace, older is definitely not better.

An aging furnace can quietly waste large amounts of energy every day, increasing your heating bills throughout the winter. Understanding how furnace efficiency works can help you determine whether your system is costing you more than it should.

What Is an AFUE Rating?

Furnace efficiency is measured using something called an AFUE rating, which stands for Annual Fuel Utilization Efficiency.

The AFUE rating is expressed as a percentage and shows how much of the fuel used by the furnace is actually converted into heat for your home.

For example:

• A furnace with a 90% AFUE rating converts 90% of its fuel into heat.
• The remaining 10% is lost through exhaust gases or other inefficiencies.

In Canada, modern building codes require new furnaces to be at least 92% efficient. Many older homes still operate with furnaces that fall far below this standard.

Standard-Efficiency Furnaces

Homes built before the 1990s often contain what are known as standard-efficiency furnaces.

These systems typically operate at only 50% to 60% efficiency. That means nearly half of the energy they consume is wasted.

Standard-efficiency furnaces usually have:

• A single combustion chamber
• No secondary heat recovery
• A simple on/off operation

These single-stage systems run at full capacity whenever they operate, which reduces efficiency and comfort.

Important: Standard-efficiency furnaces are no longer allowed under current Canadian building codes.

Mid-Efficiency Furnaces

Mid-efficiency furnaces became common in homes built between approximately 1990 and 2010.

When newly installed, these furnaces typically operate between 78% and 82% efficiency. While this is an improvement over older systems, it still means roughly 20% of energy is wasted.

As these furnaces age and components wear down, their efficiency can drop significantly, sometimes falling to 55% to 70%.

That means a large portion of the energy you are paying for may never heat your home.

High-Efficiency Furnaces

Modern high-efficiency furnaces are designed to extract as much heat as possible from the fuel they consume. Because of this, they have become the standard for new furnace installations in Canada.

Since 2016, Canadian building codes require furnaces to have an efficiency rating of at least 92% AFUE.

These systems use advanced heat exchangers and combustion technology to capture more heat that would otherwise be lost.

Higher efficiency means:

• Lower heating bills
• Reduced energy waste
• Improved environmental performance

Furnace Stages Explained

The number of stages in a furnace refers to how many levels of heating output the furnace can produce.

Older furnaces typically had only one stage, meaning they were either fully on or fully off.

Modern furnaces may include:

• Two-stage furnaces that operate at both high and low heat output
• Modulating furnaces that adjust heating output more precisely

Multiple stages allow the furnace to provide only the amount of heat required, which improves efficiency and comfort.

Furnace Fan Speeds

Another factor that affects furnace performance is the blower fan.

The blower fan moves heated air through your home’s ductwork. Modern systems often include variable-speed fans that adjust airflow depending on heating demand.

Variable-speed blowers can improve comfort, reduce energy consumption, and maintain more consistent indoor temperatures.

Installation and Maintenance Matter

Even the most advanced furnace will not perform efficiently if it is installed or maintained improperly.

A furnace with fewer advanced features that is properly installed and serviced can perform better than a complex system that is poorly configured.

This is why regular maintenance and yearly inspections by an HVAC technician are important.

Is It Time to Replace Your Furnace?

If your furnace is more than 15 to 20 years old, it may be operating far below modern efficiency standards. Upgrading to a high-efficiency system can significantly reduce heating costs while improving comfort and reliability.

If you are considering replacing your furnace or want to evaluate the performance of your current system, The Gentlemen Pros can help with professional heating services and furnace inspections.