Gas furnace pros and cons illustration.

Gas Furnaces: The Pros and Cons

Appolo Heating

Gas furnaces are one of the most energy efficient home comfort solutions you can have installed because they can operate at the highest energy efficiency ratings of any furnace type. But you should know that not all gas furnaces are created equal, and choosing the right one will make a big difference in how effectively you heat your home and the amount of money you save on your energy bill. Let us break down the pros and cons of gas furnaces.

Furnace Efficiency Ranges

The first thing you need to know before you purchase a gas furnace is where it falls on the annual fuel utilization efficiency (AFUE) rating scale. “AFUE is the ratio of annual heat output of the furnace or boiler compared to the total annual fossil fuel energy consumed by a furnace or boiler,” as defined on Energy.gov. It is a basic measure of the amount of heat that is used versus the amount that is allowed to escape via the chimney or other areas.

Most new furnaces will fall into the mid to high-efficiency categories. All high-efficiency furnaces are considered to be condensing furnaces and have a clear advantage over conventional gas furnaces (discussed below).

By definition, mid-efficiency furnaces will typically have an overall AFUE rating between 80-85%, whereas high-efficiency furnaces will have an overall AFUE rating of 90 – 98%. Additionally, most gas furnaces above 94% will also be Energy Star approved.

Understanding the various types of furnaces.

Without getting too granular, we can break down gas furnaces into the two following categories, followed by their corresponding operation type.

The two main categories are:

Conventional gas furnaces – burns gas through a single heat exchanger and allows the remaining heat (in vapor form) to escape through a chimney or through the walls.
Condensing gas furnaces – has a secondary exchanger to collect the excess heat vapor, allowing for more efficient energy consumption.

Furnace Operation Types

Single Stage Furnace. This type of furnace can only operate at maximum heat output. It allows for high heat (gas flow) when the gas valve is open and no heat when the gas valve is closed. These are considered to be the most standard gas furnaces and typically have an AFUE of 80 – 85%. Your better single stage gas furnaces will come with an electrically efficient multi-speed blower motor, commonly referred to as a constant torque or ECM motor that will help you reduce the electrical energy needed to operate this type of furnace. The ideal customer for a single stage furnace is looking for an inexpensive heating solution with maximum heat output.

Pros

  • Less expensive furnace
  • Maximum heating
  • Good for cold temperature regulation

Cons

  • Higher energy consumption
  • No middle setting
  • Not good for milder temperatures

Two-Stage Furnace. Unlike the single stage furnace, a two-stage furnace can accommodate multiple heat output settings. An initial high setting and a mid-level setting is triggered by communicating with a thermostat and adjusting the gas valve accordingly for milder temperatures. These will typically operate at an AFUE up to 96%. Your better two-stage gas furnaces will come with either an electrically efficient multi-speed blower motor, commonly referred to as a constant torque or ECM motor, or a variable speed ECM motor that will help you reduce the electrical energy needed to operate this type of furnace. In most cases, the variable speed ECM motor will do a much better job of providing you a more consistent temperature level. The ideal customer for this type of furnace is looking for a moderately priced alternative to single stage furnaces, lower energy costs, and a more consistent comfort level in their home or business.

Pros

  • Multiple heat outputs
  • Middle setting runs longer allowing for more even heat distribution
  • Regulates mild and colder temperatures
  • Lower energy consumption

Cons

  • Only two settings: mid and high operation

Modulating Furnace. Unlike single and two-stage furnaces, this type of furnace has a modulating gas valve that allows for more precise heat output adjustments. Gas output can be adjusted up to the minute and is closely tied to the temperatures set by your thermostat. A modulating furnace can have an AFUE rating of up to 98%. Almost all modulating gas furnaces will come with a variable speed ECM motor that will help you reduce the electrical energy needed to operate this type of furnace. In most cases, the variable speed ECM motor will do a much better job of providing you a more consistent temperature level. The ideal customer will be looking to maximize energy consumption and is willing to invest significantly more up front to ensure they receive the highest quality and most consistent comfort level for their home or business.

Pros

  • Runs longer, allowing for more even heat distribution
  • Multiple heat outputs
  • Variable speed-blower
  • Adjusts for any temperature
  • Lowest energy consumption

Cons

  • More expensive than single and two-stage furnaces

Gas furnaces have come a long way in recent years and due to the increase in quality regulations, most furnaces are well above the minimum AFUE of 80% and can adequately heat your home regardless of type. However, just like your car, you must be diligent about having your new furnace cleaned and checked by a professional heating Service Technician annually.

Choosing the right furnace based on your preferences and how your current home is set up, will help to ensure that you meet your budget needs while maximizing your overall home comfort, and lowering your energy costs.

If your furnace is 10-years-old or older, it may be time to contact a heating professional to see how they can help you maximize your home comfort solutions.

Additionally, you may want to talk to them about the different options that are available to help increase the comfort level of your home or business, while maximizing your ability to lower your energy costs.

Those options include:

Preventative Maintenance Service Agreements
Upgraded Air Filtration
Humidifiers
Dehumidifiers
Ultra Violet Lights
Heat Recovery Ventilator (HRV) Unit
Programmable Thermostats
WiFi / Communicating Thermostats