Furnaces: to Two-stage or not? That is the Question

If you have been shopping for a new gas furnace you are probably wondering whether or not it is important to spend the extra money for a two-stage model. What are the advantages of a two-stage furnace?

There are several benefits of a two-stage furnace that make them a popular choice for many homeowners.

  • They use energy more efficiently, reducing your energy consumption and your energy bills. A two-stage has 2 settings, low heat and high heat. On low heat, the gas burner runs at 65%-70% capacity, depending on the brand and the model. So, if you have a 100,000 Btu furnace, it will produce 65,000 to 70,000 Btu per hour on low heat. On many days, this is enough to meet the heating demands of the house.  If the furnace cannot heat effectively on low heat, the gas valve will open to 100% and bring the house up to the desired temperature. Running on low heat most of the time means less fuel is used in the long run. A single stage furnace runs full blast and then stops, and does this repeatedly, like a car in stop and go traffic. It will use fuel less efficiently.
  • Two-stage gas furnaces offer more balanced heating, with temperature fluctuations of only 2-3 degrees. Because a two-stage furnace runs at a lower capacity (65-70%), it runs more consistently, and that leads to more even heating. A single stage furnace runs full capacity every time it fires, so temperature fluctuations tend to be more pronounced.
  • Two-stage furnaces are quieter. Combustion makes noise, so 65%-70% combustion will be quieter than 100% combustion. The difference may be noticeable if the furnace is located near living areas.
  • Better air filtration is offered by a two-stage furnace. Two-stage furnaces run more, and that means that air is more consistently circulating through the furnace filters, where more allergens and pollutants are removed. If you choose an advanced air purification system for your furnace, two-stage operation will enhance its functionality.
  • Humidification is improved with a two-stage furnace. If you plan to include a humidifier with your furnace, two-stage operation will improve its performance. The humidifier only does its job when the furnace is running, and since a two-stage furnace runs more often, it will add more humidity to your home during the heating season.

Now that you know the advantages of a two-stage furnace, the decision becomes easier. As you price single stage and two-stage models, you have to ask yourself if the above advantages are worth the extra expense. If you want greater comfort from your furnace, then you should spend the extra money and get a two-stage furnace. If your needs for a furnace are more basic, then a single stage furnace may be perfectly adequate to heat your home.

Which Air Conditioner?

A single stage air conditioner is what you probably already have and if it is still in good working order, you can use it even though you may have chosen a two-stage furnace.  However, if you live in a warm, humid climate or are in need of a new air conditioner, you may want to consider a two-stage air conditioner.

Two-stage air conditioners run at 67% and 100% of capacity. The thermostat controls which speed is used based on the home temperature. Comfort is increased because cool air circulates almost all of the time between noon and 8 pm. This reduces room “heat up” that occurs during the off cycle of conventional, single-speed air conditioners.

The end result of using a two-stage air conditioner is that you will receive a relatively continuous flow of cool air throughout your home.  A two-stage air conditioner will send in a steady but smaller stream of cooled air as opposed to the large blast of cold air you would get from a single stage system.

This results in a more consistent and comfortable environment overall, and it also makes it possible for the air conditioning system to de-humidify your house more effectively. When the air is cooled too quickly, the de-humidification system does not always have time to do its job. With the longer cooling cycles of the two-stage system, there is plenty of time to make sure the right amount of humidity is removed from the air.

Savings are substantial in hot, humid areas of the country. A two-stage air conditioner can save 15 to 30% on a cooling bill. Economic evaluations of two-stage air conditioners have shown that the investment has a greater than 10% Return-on-Investment (ROI) and a 4 to 5 year payout.

Whether you are remodeling, building a new home or just need to replace your furnace or air conditioner, it pays to research your options.

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