Single-stage vs Dual-stage vs Multi-stage Furnaces

The government of Canada has regulated minimum efficiencies (AUFE) to be 90% or greater for a number of years now, but a quick glance at furnace manufacturers product lines show a wide variety of lines ranging for 90% AUFE to 98% AUFE. A top of the line model at 98% efficiency can easily cost 20-30% or more than a base model to install, with only a modest promised fuel savings. So why would you ever want to buy the expensive one?

Most furnace come in roughly three categories these days: single stage, dual stage and multi-stage.

A single stage furnace is either on or it’s off with no middle ground. For example, if you have a 60,000 BTU single stage furnace, and the thermostat sends a signal that the house is below the set temperature and heat is needed, the furnace will fire up at full power and blast the HVAC system until the feedback from the thermostat tells it to stop.

A dual stage furnace can operate at two different output levels, so most of the time it will turn on at a middling ouput level and only turn on at full power on the coldest days. This will lead to more even heating and less strain on your furnace and HVAC system. A dual stage furnace will require less maintenance than a single stage furnace and will require a bit less fuel to keep your house warm under normal conditions.

A multi-stage furnace has an automatic fuel valve which can adjust the amount of natural gas being burned at any time, and often also comes with a variable speed fan to flow the air. This gives you the finest control of heat output and will yield the most consistent temperatures in the house. These furnaces also have the additional benefit of being able to use the fan at low speeds to recirulate air in the house, allowing for more efficient distribution of the heat as well as allowing for air purification services. This can result in savings over-and-above just the fuel-to-heat converting efficiency of the furnace, but it is difficult to know how much you will save as this will vary a lot depending on your specific house, the climate and the variation in temperature programmed over the day.

Multi speed fans can save considerably on your electricity bill, as their power draw at low speed is considerably lower than at full speed. Studies in Wisconsin have found savings between 35%-70% in kWh power consumpion over a wide variety of conditions when comparing variabel rate fans vs single speed fans.

While a multi-stage furnace may be a better the main advantage of a multi-stage furnace is decreased HVAC noise and increased comfort.

All modern furnaces are extremely efficient, but exactly which model you should have depends on how how much you want to reduce your fuel and electrical consumption and how much you value the quietest most consistent environment as possible.

Do you need some advice choosing the right high-efficiency furnace for you? Leave us a message at (587) 773-2612 and we will get back to you as soon as possible, or call (780) 231-0064 if you need to speak to someone immediately. To schedule an appointment, pick your preferred time on our online booking page.

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