Energy Efficient Furnaces – Reducing Your Gas Bill

Not only can a high-efficiency natural gas furnace warm your home and make it more comfortable, but it can also save you money.

So the next question is: do you have an energy efficient furnace in your home? If your house was built after 1990, you might have, although it may only be a mid-efficiency unit. However, most Canadian homes that were built between 1950 and 1970 have standard gas furnaces that are not energy efficient furnaces at all. Those built during the next decade were generally rated as having mid-efficiency. Since 2010, only high-efficiency furnaces have been available in Canada, so if you have a new house, you furnace will be highly efficient.

The difference between standard gas furnaces and those with high efficiency

When it comes to measuring the energy efficiency of furnaces, we need to establish what percentage of fuel used is turned into heat. This is measured as a percentage by annual fuel utilization efficiency (AFUE). The higher the AFUE, the more energy efficient the furnace is.

Standard gas furnaces installed during the 20th century had an AFUE of about 60% – meaning that 40% of the fuel used was wasted. That is nearly half of it! Mid-efficient furnaces were an improvement, measuring between 78% and 82%. But high-efficiency furnaces need to be at very least 90% efficient, or higher. The more efficient it is, the more you will save.

High-efficiency furnaces are also a lot quieter than other types, and they have the ability to maintain a much more constant temperature.

How high-efficiency furnaces work

High-efficiency furnaces normally use a condensing process to work and they have two heat exchangers. These are able to draw sufficient heat from the combustion gases for the moisture in the gases to condense and then release as usable heat. The natural gas condensate, that must be removed to allow the heat transfer to occur, is piped out of the house. With high-efficiency furnaces, the pipe leads to a floor drain and the exhaust gases are vented out of a side wall. This means you don’t need a chimney, and there isn’t a risk of poisonous carbon monoxide leaking.

How a furnace can improve energy efficiency in your home

Since a furnace can account for as much as 60% of the energy consumed in a typical Canadian home during winter, it stands to reason that if you don’t have an energy efficient furnace you should consider making the switch. Switching to a high-efficiency furnace can save up to 35% on your heating bills. In addition it will radically reduce the gas emissions from your home and in that way help you to reduce your carbon footprint and live a greener life.

But it is also important to ensure that the furnace you install is suitable for your house. Very often furnaces produce considerably more heat than the house requires, and this in itself reduces energy efficiency.

How to assess the right size for your new high-efficiency furnace

A good heating contractor will be able to do a home heat loss calculation to help you make this decision. What the contractor will do is to assess how many BTUs (British thermal units, which is the measure of energy used) your furnace should be in relation to your house. The size is determined by what is termed a “total building envelope heat loss”. But the level of insulation in your house and its air tightness will also need to be considered. If there are places where heat is leaking out, for instance through the roof or through badly fitting window frames, these should be plugged to ensure the furnace operates to peak energy efficiency.

Before you go ahead and have a new furnace installed though, find out if you qualify for provincial and/or federal grants. Chances are you do.

Where to find a new high-efficiency furnace

You need to find both a good quality furnace and a qualified installer that will fit it for you. You could start out at the Heating, Refrigeration and Air Conditioning Contractors of Canada web site ( and ask advice from contractors. Alternatively you could look for a furnace and then find a contractor – or find a system or product from a company that does the installation and will give you all the support you need.

Two major North American companies that manufacture gas furnaces are United Technology ( that produce a number of brands including Carrier, Bryant, Heil, Tempstar and the Comfortmaker brands, and Goodman ( that produces Janitrol and Amana. Others include Rheem (the Rudd brand), American Standard (Trane) and Lennox (from Armstrong).

Bryant Heating & Cooling Systems (, an early US company, was originally founded by Mr. Charles Bryant in 1904. While they initially manufactured some of the earliest gas-fired boilers, today the brand features some of today’s most sophisticated heating systems, including both oil and high-efficiency gas furnaces.

Trane ( is a US company that was launched by a Norwegian plumber who invented a low-pressure heating system that he called the Trane Vapo Heating System. Then his son, Reuben, a mechanical engineer, invented a convector radiator. That was just the beginning, but way back in 1923 it gave the Trane Company a head start, and they haven’t looked back. Today Trane employs more than 29,000 people and does business in more than 100 countries. They manufacture in 29 locations worldwide. Residential furnaces are just one of the products they make – and these are amongst the world’s most energy efficient units.

At the end of the day, when you go shopping for a high-efficiency furnace, check its Canadian EnerGuide label to see how much energy the product uses. ENERGY STAR symbols will also help you make a more savvy choice.

And don’t forget the filter!

How to optimize the efficiency of your high-efficiency natural gas furnace

All furnaces have a filter and this should, in itself, improve energy efficiency. A good filter system will not only protect the furnace, it will also reduce your exposure to air-borne particles that can negatively affect your health and cause allergies. These include:

  • normal household dust
  • dust-type particles that result from a variety of household activities ranging from cooking and doing laundry to burning candles and smoking
  • human and pet dander (which amounts to hair and skin flakes from you, your family and the animals you share your home with)
  • air particles from outdoors that filter their way inside

You will, though, need to make sure that the filter you are using has the ability to competently reduce these particles. Don’t take this for granted.

It is also up to you to replace the furnace filter every couple of months. If you keep going with a dirty filter, this will reduce the flow of air and it will result in the furnace taking longer than necessary to heat your home.

It is also important to keep the furnace itself clean, well lubricated, properly adjusted and regularly maintained. If you care for it and maintain it, you will find that you will use less energy and that it will in fact cost you less to operate.

It is also good practice to lower the thermostat on your furnace to about 4 to 5 °C at night while you are sleeping or when there isn’t anyone at home.