Types of Furnace Systems: Which One Is Best for Your Home?

Natural gas is the most common fuel for heating. 51% of the country, or 54 million homes, depend on natural gas heating, according to the United States Census Bureau. In a natural gas furnace, the gas is ignited in the furnace’s burner to warm the heat exchanger. The heat exchanger warms the cold air returning from the ducts. A fan or blower pushes the warm air through the ducts and registers to heat the home. Exhaust gasses are vented to the outside through a flue.

Natural gas furnaces have numerous advantages. First off, natural gas is convenient. Homes in populated areas can often access their municipalities’ natural gas supply, eliminating the need for a storage tank. Furthermore, natural gas is the most affordable fossil fuel and yields low energy bills. Gas is also an efficient heating fuel due to a large amount of heat it generates. The American Gas Association states that heat from natural gas furnaces is between 120 and 140 degrees Fahrenheit.

Despite the numerous advantages of gas furnaces, they also have drawbacks. Gas furnaces have higher upfront costs and shorter lifespans than electric furnaces. In addition, gas line access is unavailable in some places, mainly rural areas. Finally, there is the potential for CO2 poisoning if the furnace malfunctions or the flue is blocked.

Single-stage Furnace 

• Most affordable to install and repair
• Most basic; turns on and off
• Always runs at 100% capacity
• Produces hot and cold spots
• Might struggle to heat homes during frigid temperatures
• Less energy efficient
• Best for small or single-story homes, mild winters, people on budgets, and short-term heating needs

Two-stage Furnace

• More expensive to install and repair
• High and low power settings
• Produces consistent temperatures
• Less noisy
• Produces better indoor air quality
• More energy efficient
• Best for two or more stories, cold winters, people with flexible budgets, concerns about energy costs, and long-term heating needs

Modulating Furnace

• Most expensive to install and repair
• Dozens of power settings
• Produces the most consistent temperatures
• Less noisy, but the noise is more constant
• Produces the best indoor air quality
• Most energy efficient
• Best for multiple-story homes, bitterly cold and extended winters, people with large budgets, and long-term heating needs

Propane furnaces are similar to gas ones but they use a different fuel. The propane gas is ignited in the furnace’s burner and warms the heat exchanger. The heat exchanger warms the cold air returning from the ducts. A fan or blower pushes the warm air through the ducts and registers to heat the home.

A propane furnace is a good alternative to a natural gas furnace. Propane-fueled furnaces typically have lower upfront costs and don’t require gas line access or flue installation. Like natural gas, propane fuel burns cleanly.

Unlike natural gas, propane furnaces require a supply tank of propane fuel and space for tank installation. The tank must be continuously refilled and maintained. Propane gas is also more expensive than natural gas, so propane furnaces cost more to run.

Oil furnaces function similarly to gas and propane furnaces. A fuel pump brings oil from a storage tank to the furnace’s burning chamber. The oil is sprayed into the combustion chamber and ignited to warm the heat exchanger. The heat exchanger warms the cold air returning from the ducts. A fan or blower pushes the warm air through the vents and registers to heat the home.

Oil furnaces are extremely common in the Northeast but rare in other areas of the country. In fact, propane furnaces are not available in most areas. The only reason to install an oil furnace is to replace an existing oil furnace.

Despite their rarity, oil furnaces have advantages. They heat homes quickly due to the high BTUs emitted by burning oil and are easier to maintain. Compared to electricity, oil is a cheaper fuel.

On the downside, oil tanks require space for installation, and they must be continuously refilled and maintained. Compared to natural gas, oil is a more expensive fuel. Unlike natural and propane gas, burning oil produces tar and soot.

In an electric furnace, heating elements warm the cold air from the ducts, like a toaster warms bread. A fan or blower pushes the warm air through the ducts and registers to heat the home.

Electric furnaces stand out because of their affordability and long lifespan. They are among the cheapest to install and last 20 to 30 years. The lack of a flue or vent makes electric furnaces easy to install and maintain. They are suitable heating systems in mild climates.

Although electric furnace AFUE (annual fuel utilization efficiency) ratings are 95 to 100%, electricity is a highly inefficient heat source. In other words, electric coils heat up slowly, achieve lower temperatures, and consume more energy than other fuel sources. An electric furnace would yield unreasonably high energy bills in a cold climate.

According to the U.S. Energy Information Administration, 10.8 million homes used wood as a heating fuel in 2020, and 2.2 million homes used wood as their primary heating fuel. Wood furnaces, also known as wood stoves, burn wood to provide heat. Smoke is vented through a chimney or vent pipe. Wood stoves achieve high temperatures, and the heat emanates in all directions from the stove. A wood stove can warm a home faster and more efficiently than a forced-air system. Some wood furnaces have blowers to distribute warm air to all parts of the room.

Wood stoves are versatile and can be installed in any room. They can utilize existing chimneys, or vent pipes can easily be added. As a fuel, wood is eco-friendly, carbon-neutral, reliable, available, and less expensive per BTU than oil, gas, and electricity. Wood stoves are great for supplemental and backup heating since they don’t require electricity.

As primary heating systems, wood furnaces have many disadvantages. They are unable to heat large houses; additional stoves are required. Wood furnaces require a steady supply of wood, which is only cost-effective if the supply is readily available. In addition, wood requires splitting, hauling, stacking, and storage space. Fires require regular tending and produce ash and soot.

A geothermal heating and cooling system, also known as a ground-source heat pump, transfers heat from within the earth to the home. During the summer, heat is extracted from the house and deposited in the ground for future heating needs, increasing heating efficiency.

There are three main types of geothermal heating systems. The vertical closed-loop system consists of a U-shaped pipe containing a water/methanol mix buried in a well. The horizontal closed-loop system functions like the vertical system, but the pipes are laid horizontally in a zigzagging pattern within a 300-foot-wide trench buried 6 to 10 feet below ground. The open-loop system transfers heat from groundwater pumped from a 75 to 100-foot-deep well. After the heat is transferred, the water is deposited in a second well.

Geothermal heating has advantages. Firstly, it is a sustainable heat source. Geothermal heating consumes less energy and distributes heat more evenly than traditional furnaces. Geothermal heat is sufficient for homes with mild winters. During summer, geothermal systems can cool homes.

Unfortunately, geothermal systems are costly to install, costing upwards of $30,000 for a 2,000-square-foot home. The return from energy-cost savings would take too long to receive, even though geothermal heating reduces energy costs by 50%. Furthermore, geothermal heat is insufficient in cold climates.