What Is a Variable or Fixed‑Speed Furnace?

A fixed-speed furnace, or a single-stage furnace, has two settings—on or off. It's either running at full capacity or not at all. This means that when your furnace turns on, it uses its maximum power to generate heat. It may turn your unit on and off multiple times in an hour to maintain your home's temperature. Fixed-speed options were the standard for decades, but in 2005, variable options became more popular.

Why did homeowners start switching to variable-speed furnaces when they became available? Because these units, also called two-stage furnaces, have an alternative to full-blast heat. With the two-stage operation, the furnace has a low and high setting, depending on the heat needed at a specific time. While your variable-speed furnace might run for longer, it's using less electricity while it does.

In this blog, we’ll look at:

  • How do variable and fixed-speed furnaces work?
  • Pros & cons of fixed-speed furnaces
  • Pros & cons of variable-speed furnaces
  • Which furnace is best for Portland homes?

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How Do Variable and Fixed-Speed Furnaces Work?

Furnace diagram with cool air, return register, return duct, power switch, gas shutoff valve, burners, exhaust stack, draft hood, filter, blower, blower motor, damper hamper, damper, supply duct, supply plenum, heat exchanger, combustion chamber, burner cover, flame sensor, pilot, electronic igniter, gas control valve, blower chamber, supply register, warm air labeled

A fixed-speed furnace uses electricity or another fuel source to produce heat and blow it throughout your home. With these units, the fan blower is attached to a fixed-speed motor with only a single setting. When on, the blower runs at a consistent speed to deliver heat from the furnace.

A variable-speed furnace comes in two options: the most common two-stage or modulating. While modulating may become the most common option one day, two-stage units are currently most in use when looking at variable-speed options. With these units, there's a low and high setting for the variable-speed blower motor, which means your heater can deliver less heat when you only need things to warm up by a few degrees or more heat when it gets really cold outside. The variable control allows the unit to adjust to the internal temperature as needed.

Pros & Cons of Fixed-Speed Furnaces

Fixed-speed furnaces are often the most affordable to install. These units are durable workhorses that last 15 years or more.

Pros of Fixed-Speed Furnaces

Since fixed-speed units have been around for a long time, it's easy to find experienced maintenance technicians to handle repairs when something goes wrong. And your existing unit is likely a fixed-speed furnace, so you won't need to update your home to support the installation physically.

Cons of Fixed-Speed Furnaces

Single-speed units run at peak energy usage all the time, making them energy-inefficient and causing more wear and tear on the unit. While these furnaces can easily last up to 15 years, a variable-speed option will typically last even longer.

Pros & Cons of Variable-Speed Furnaces

Variable-speed furnaces have a lot to offer. They are more efficient and may use nearly six times less energy than a comparable fixed-speed unit.

Pros of Variable-Speed Furnaces

You likely only need the high-capacity mode during the coldest days of the year, which can significantly reduce your heating costs and the wear and tear on the unit.

They also last longer, with an average usable life of around 20 years. Add in the quiet running and ability to reduce indoor humidity, and they perform better than fixed-speed furnaces.

Cons of Variable-Speed Furnaces

The reason Portland homeowners haven't all converted is pretty simple—the price. Variable-speed furnaces cost more, and it may be years before that upfront cost is paid down by efficiency savings, especially for gas furnaces.

Which Furnace Is Best for Portland Homes?

In Portland, winter gets cold enough to need heat that runs consistently for at least three months. If it's within your budget, we like to look at variable-speed furnaces because they offer benefits in addition to monthly cost savings. While the initial installation cost may make these units slightly more expensive than fixed-speed alternatives, the resulting improvements to indoor air quality and reduced noise make them a big step up for most homeowners.

Call Four Seasons Heating & Air Conditioning to Upgrade to a Variable-Speed Furnace Today!

Our NATE-certified heating technicians at Four Seasons Heating & Air Conditioning will assess your home, heating needs, and budget. Then, we'll recommend variable-speed furnace options and upfront pricing for them. From our Best Price Guarantee to our 100% satisfaction guarantee, Portland homeowners trust us to deliver 5-star installation services.

Call us at 503-538-1950 or request an appointment online today for convenient, 2-hour scheduling windows.

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