gas furnace system installed in garage of home
gas furnace system installed in garage of home

Buying a furnace is a big decision and a significant investment. Your furnace will determine your home’s comfort level for many years, possibly decades. You want to make an informed decision, but where to start?

Furnaces are a popular heating source in the United States. According to a 2020 U.S. Energy Information Administration survey, 58% of American households use furnaces as their primary heating source, but furnaces aren’t the only option. Other families use boilers, baseboard heaters, or heat pumps to heat their homes. Each heating system has pros and cons. Likewise, various types of furnaces are powered by different fuels, each having advantages and disadvantages. Could an alternative system or fuel source be suitable for your home?

When your furnace is on the fritz, you must first decide whether to repair or replace it. Repairs are often a good option, but replacement is better under certain conditions. Buying a new furnace brings about even more decisions about furnace size, efficiency, and cost. The process can be overwhelming if you don't know what you're looking for. This guide will break it down to make your furnace buying experience as painless as possible.

What Is a Furnace?

What is a furnace? A furnace is an appliance that heats a home by generating heat, transferring heat to the air, and circulating the heated air throughout the house. Most furnaces are a component of the home’s HVAC (heating, ventilation, and air conditioning) system.

Furnaces have been used to heat homes and buildings for centuries. All furnaces require an energy source to produce heat. Early furnaces burned wood or coal. Today’s furnaces use natural gas, propane, fuel oil, or electricity. However, some homes still rely on wood furnaces for primary or supplemental heating. All furnaces operate similarly, but they are available in different sizes with various efficiency ratings and motors.

Types of Heating Systems:

Three types of heating systems used in modern homes are forced air, radiant heating, and heat pumps. Each heating system requires a heat source (furnace, boiler, electric coils), a distribution system (forced air or convection), a control system or thermostat, and an energy source (natural gas, propane, electricity, or oil).

Location is one factor that determines which heating system and fuel source a house uses. Furnaces and boilers tend to be used in urban locations with access to natural gas. In fact, according to the U.S Energy Department, 57% of homes use natural gas for heating. Rural locations without access to natural gas typically fuel their systems with propane, oil, or electricity.

Climate is another factor that determines which heating system is used. Heat pumps operate best in mild climates where sub-zero temperatures are nonexistent. On the other hand, radiant systems are popular in cold climates where sweltering temperatures and the need for air conditioning are rare.

forced air heating system illustration

Forced Air System

Forced air heating is the most common system. Forced air systems utilize a furnace fueled by natural gas, propane, oil, or electricity. The fuel source is burned or heated within the furnace, and heat is transferred to the air. A fan in the air handler blows the warm air through the home’s ductwork and heat registers. Each room in the house generally has one supply duct and one return duct. The return duct channels cold air back to the furnace’s air handler to be reheated.

Advantages of a Forced Air System:

  • Warms home quickly
  • An air conditioner can use the same ductwork
  • Highest AFUE (annual fuel utilization efficiency) ratings of any system
  • A humidifier can be added

Disadvantages of a Forced Air System:

  • Can be noisy from loose connections and expanding/contracting metal in ducts
  • Require routine filter changes and regular maintenance
  • Require ductwork and space in walls; installing ducts in an existing home is expensive
  • Can create dry and allergen-filled air
  • Heats the air, not the objects in rooms
radiant heating system delivering heat thought hydronics illustration

Radiant Heating

Radiant heating systems transfer heat from hot surfaces to people and objects in rooms through convection–heated air rises from the system, and cold air sinks to be heated. Typical forms of radiant heating include steam radiators, hot water baseboard heaters, and electric baseboard heaters. Radiant heating panels can also be installed in floors, walls, and ceilings.

Radiant heating systems deliver heat through electric-resistance coils or hydronics. Electric radiant heating systems use coils or wires that heat up inside a baseboard unit, beneath floors, or behind walls and ceilings. A hydronic heating system uses water heated by a boiler and pumped through pipes to radiators, baseboard heaters, tubing in the subfloor, or panels in walls or ceilings.

steam radiant heating system icon

Steam Radiant

Steam radiant heating delivered by cast-iron radiators is more common in older homes. A centralized boiler generates steam and pumps it through pipes to radiators in various rooms. The steam circulates through the radiators’ metal pipes, transferring heat to air, objects, and people. As the steam cools, it condenses into water and returns to the boiler to be heated again.

Boilers are fueled by natural gas, propane, oil, or electricity. Old-fashioned boilers were fueled by coal.

Advantages

  • Doesn’t create dry air like forced air systems
  • Radiators can be updated
  • Modern boilers are energy efficient
  • Radiators are inexpensive to install

Disadvantages

  • Large and unsightly radiators
  • Radiators limit furniture and window covering placement
  • Cannot be combined with air conditioning
  • Expensive to operate
electric baseboard heater icon

Electric Baseboards

Electric baseboard heaters use electric resistance heating elements and convection to provide heat. Three to six-foot-long heaters are mounted along baseboards ¾” above the floor. Electricity is applied to heat metal rods within the heaters. Cold, ground-level air is sucked in, heated, and released through metal fins. Electric baseboard heaters are typically zonal and controlled by individual thermostats.

Advantages

  • Typically the least expensive and easiest system to install
  • Don’t require ducts, air handlers, or other distribution equipment
  • Good for supplemental heating in basements and sunrooms
  • Warm objects in rooms, not just the air
  • Rooms can be set to different temperatures
  • No moving parts and require virtually no maintenance
  • Can be installed anywhere with electricity
  • Silent operation

Disadvantages

  • Pet fur can get sucked in and block airflow
  • Expensive to run; each foot draws 250 watts of electricity
  • Not good for primary heating
  • Can overload circuits
  • Heating elements cool rapidly when the current shuts off
  • Contributes to air pollution if the electricity is powered by coal
  • Cannot be combined with air conditioning
hydronic baseboard heater icon

Hot Water Baseboard Heaters

Hot water baseboard heaters (also known as hydronic baseboard heaters) are essentially modern radiators. A centralized boiler heats water and pumps it through pipes to heating units installed along the baseboards in each room. Heat radiates from the hot water via the units’ metal fins, and cold air sinks to the unit to be heated.

 

Boilers are fueled by natural gas, propane, fuel oil, or electricity. Some are aided by solar power.

Advantages

  • Water in the heaters stays warm longer than the coils in electric heaters, which cool down immediately after the current is shut off
  • Long lifespan; can last several decades
  • Energy efficient
  • Require little maintenance
  • Quiet operation
  • Precise temperature control
  • Can be installed individually or as a whole-house system using a single boiler, similar to a steam radiator system

Disadvantages

  • Pet fur can be sucked in and block airflow
  • More expensive equipment than electric baseboard systems
  • Limit furniture and window covering placement
  • Cannot be combined with air conditioning
  • Heat slowly
  • Pipes can freeze if the system breaks down amid frigid temperatures
home heat pump heating system illustration

Heat Pumps

Heat pumps are becoming a popular heating system. A heat pump can replace a furnace in a forced-air system or be installed as a mini-split (ductless) system with a small outdoor compressor and one or more wall-mounted air handlers. The advantage of heat pumps versus furnaces is that heat pumps can also provide air conditioning. Heat pumps are typically electric, but natural gas models exist.

Heat pumps don’t generate heat; they function like an air conditioner in reverse to transfer heat. An outdoor pump draws heat from outside the house and releases it inside via an air handler. Heat pumps are either air-source (remove heat from the outdoor air), ground-source (use coils buried in a trench to draw heat from the ground), or water-source (draw heat from a lake or pond). Air-source heat pumps are the least expensive to install.

The Inflation Reduction Act of 2022 includes a heat pump subsidy for heat pumps installed between January 1, 2023, and 2032. Consumers can receive rebates and tax credits for installing new heat pumps.

Advantages of Heat Pumps:

  • Provide heating and cooling
  • Ductwork is not required, but existing ductwork can be utilized
  • Energy-efficient
  • Low operating costs
  • Mini-splits provide precise temperature-control for each room and have quiet fans

Disadvantages of Heat Pumps:

  • Unsuitable for cold climates
  • Mini-splits have separate controls in each room
  • High equipment and installation costs
  • Require routine filter changes and regular maintenance

How Does a Furnace Work?

A furnace provides heat by burning or heating a fuel source, such as natural gas, and transferring warmth to the air. A fan or blower distributes the warm air throughout the home or building via ducts and heat registers. A thermostat controls the home’s temperature.

Types of Furnaces

Furnaces are categorized by the fuel that powers them. Regardless of the energy they use, all furnaces operate in similar manners. The five main types of furnaces are natural gas, propane, oil, electric, wood, and geothermal.

Natural gas and electricity are the most popular heating fuels in the United States. According to a 2000 study by the U.S. Census Bureau, 51% of homes use natural gas, and 31% use electricity to power their primary heating sources. Only 9% of homes nationwide use oil. In contrast, oil is the most popular heating fuel in New England.

Type Installation Cost Lifespan AFUE Rating

Natural Gas Furnace

$4,000 - $8,000

15 -30 Years

80% – 98.5%

Electric Furnace

$1,600 - $3,200

20 - 30 Years

100%

Propane Furnace

$3,000 - $6,000

16 - 20 Years

80% – 95%

Oil Furnace

$5,000 - 9,000

15 - 20 Years

80 – 90%

Geothermal

$12,000 - $30,000

25+ Years

400%*

Wood Furnace

$3,000 - $5,000

10 -15 Years

70% – 80%

*For every unit of electricity the system uses, it provides three to four units of heating energy - an efficiency of 300% to 400%.

Furnaces and traditional boilers are referred to as CENTRAL HEATING SYSTEMS because the heat is generated in a central location and distributed throughout the home.

Did you know?

carrier natural gas furnace system in garage of home

Natural Gas Furnaces

In a natural gas furnace, the gas is ignited in the furnace’s burner to warm the heat exchanger. The furnace 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.

Convenience is one benefit of a natural gas furnace. Natural gas is piped to some homes through an underground pipe system, so there are no fuel tanks to fill. On the other hand, some homes have no access to natural gas and cannot implement a gas furnace.

Another benefit of gas furnaces is energy efficiency. Natural gas furnaces are one of the most affordable furnaces to operate. No wonder most homes in the U.S. are heated with natural gas. According to the United States Census Bureau, 54 million homes are heated with natural gas. Gas furnaces are more expensive to purchase than other types, but the savings derived from efficient heating are a leading reason for gas furnace popularity.

Gas furnaces are mostly used in northern climates with harsh winters. Heat derived from natural gas is often warmer than heat from other sources. According to the American Gas Association, heat from a forced-air system with a gas furnace is 35 to 45 degrees warmer than heat from an electric heat pump.

Advantages of Natural Gas Furnaces:

  • Eco-friendly due to clean burning fuel
  • Easy to install
  • Inexpensive to repair
  • Efficient operation results in energy-cost savings and warmer heat
  • Reliable fuel source

Disadvantages of Natural Gas Furnaces:

  • Higher upfront cost
  • Shorter service life (15-20 years compared to 20-30 years on an electric furnace)
  • Requires access to a gas line
  • Potential CO2 poisoning if the furnace malfunctions or the flue is blocked
  • Requires a vent for emissions that must be cleaned and maintained
eletric furnace system in basement of house

Electric Furnaces

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 are among the cheapest to purchase but can be expensive to operate. For this reason, electric furnaces are preferred in climates with mild winters. Electric furnaces are considered 100% efficient since all the heat they create is moved into the home. However, electric furnaces consume more energy than other types, and coal-fueled power plants often produce the electricity they use.

Advantages of Electric Furnaces:

  • No risk of CO2 poisoning
  • Low upfront cost
  • No venting
  • Low maintenance
  • Lasts 20-30 years

Disadvantages of Electric Furnaces:

  • High operating costs in cold climates
  • Produce dry air
  • Less eco-friendly
propane tank outside of house for furnace system

Propane Furnaces

Propane furnaces operate similarly to gas furnaces; 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.

Propane furnaces don’t require the installation of a flue; a vent can be installed beside the furnace on an exterior wall. Another advantage is the vent doesn’t need to be cleaned and maintained like a gas furnace.

Propane furnaces are prevalent in rural areas without access to natural gas lines. The propane is stored in large steel tanks outside individual homes. The downside is the tanks must be installed, filled, and refilled with costly propane.

Advantages of Propane Furnaces:

  • Easy installation; does not require gas lines
  • Non-toxic propane burns clean
  • Lower upfront cost

Disadvantages of Propane Furnaces:

  • Tank must be continuously refilled and maintained
  • Space is needed for the tank
  • Propane gas is expensive
  • Produces less BTUs, or heating capacity, per gallon than oil
oil furnace in basement of house

Oil Furnaces

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 used primarily in the Northeast, where natural gas and affordable propane are unavailable. Fuel oil costs more than gas, produces tar and soot, and requires a tank that needs to be continuously refilled. Despite the advantages of oil furnaces, the only reason to choose an oil furnace is to replace an oil furnace. In fact, oil furnaces are not even sold in most regions.

Advantages of Oil Furnaces:

  • Emit higher heat BTUs than other fuels; homes warm up quickly
  • Easy to maintain
  • Cheaper than electricity

Disadvantages of Oil Furnaces:

  • Tank must be continuously refilled and maintained
  • Space is needed for the tank
  • More expensive than gas
  • Produce tar and soot
geaothermal heating system illustration

Geothermal Heating

A geothermal heating 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 line extends from the home to 300 feet below the ground. Heat is transferred circuitously between the house and the earth through conduction. The system’s cost is calculated by the foot.

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. Installing a horizontal design is cheaper than digging a well for a vertical system. Still, horizontal systems require more space and damage the ecosystem in the grid area. Horizontal systems are also less efficient than wells because surface temperatures affect them more. Another drawback is that the entire grid must be dug up to locate leaks.

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. Open-loop systems are highly efficient, and installation can be up to 50% cheaper than vertical closed-loop systems. However, open-loop systems require ample groundwater and a high water table.

Geothermal heating is sustainable and efficient but also costly to install.Geothermal heating for a 2,000-square-foot home costs upwards of $30,000. The return from energy-cost savings would take too long to receive, even though geothermal heating reduces energy costs by 50%. It’s wiser to put your money towards heat retention options like better windows, insulation, and possibly a high-efficiency air-source heat pump.

Advantages of Geothermal Heating:

  • Sustainable
  • Provides heating and cooling
  • Consumes less energy than furnaces
  • Distributes heat more evenly than furnaces
  • Suitable for moderate climates with less heating needs

Disadvantages of Geothermal Heating:

  • Extremely expensive to install
  • The cost-savings return depends on energy consumption, so it’s better suited for large buildings
  • Ineffective heating in cold climates
  • Heat’s temperature is lower than a furnace’s and might not feel warm enough
  • May require supplemental heating
wood furnace burning wood inside of home in winter

Wood Furnaces

While most U.S. households are heated by electricity (30.3%) or utility gas (51.2%), the U.S. Census reports that 1.7% of families rely on wood. Wood stoves provide powerful radiant heat emanating in all directions from the stove. A wood stove can warm a home faster and more efficiently than a forced-air system.

Another advantage of wood stoves is their versatility. They can be installed to use existing chimneys, or vent pipes can easily be added. Separate stoves can be installed in multiple rooms to provide zonal heating.

Wood is an eco-friendly and carbon-neutral fuel source; living trees absorb carbon, so burning cordwood doesn’t add additional carbon to the atmosphere.

As a fuel, wood is less expensive per BTU than oil, gas, and electricity. However, your cost-savings depend on whether you have a wood supply or purchase it. Still, wood stoves are convenient for supplemental or backup heating, especially during power outages.

Advantages of Wood Furnaces:

  • Reliable, cheap, and readily available fuel source
  • Doesn’t require electricity
  • Can be installed in any room
  • Powerful and quick heating
  • Eco-friendly and carbon-neutral fuel
  • Great for supplemental and backup heating

Disadvantages of Wood Furnaces:

  • Requires a supply of wood; not cost-effective if the wood is purchased
  • Requires space to store wood
  • Wood must be split, hauled, and stacked
  • Burning wood produces ash and soot
  • Fires require regular tending
  • Modern stoves with catalytic combustors should be inspected three times a season
  • Chimneys should be cleaned and checked once a season for safety reasons

What Size Furnace Do I Need?

Furnace size generally refers to heating capacity. A furnace’s heating capacity rates how much heating power it provides. A correctly sized furnace impacts your home’s comfort and energy costs—a too-small or large furnace results in uneven or insufficient heating and high energy bills.

Your home’s square footage and climate zone are the two most essential factors in approximating your furnace’s capacity. An HVAC installer will provide additional information on the exact size and model you require.

Heating Capacity

Furnace heating capacity is measured in British thermal units (BTUs). A BTU is the energy required to increase the temperature of one pound of water by one degree Fahrenheit.

Heating capacity is not linked to furnace efficiency, expressed as the Annual Fuel Utilization Efficiency (AFUE) rating. Two units with the same BTU rating will produce the same amount of heat regardless of their efficiency ratings.

Square Footage

Square footage is the most significant factor in determining furnace size. Larger homes require more BTUs than smaller houses. Depending on the climate zone and other factors, homes need 30 to 60 BTUs of heating capacity per square foot.

Your home’s square footage can be found on the blueprints or closing documents. You can also determine the square footage with a measuring tape and a little math. Measure the length and width of each room. Multiply each room’s length by its width to obtain the room’s square footage. Add the square footage of every room to get the home’s total square footage. Basements are not generally included in square footage unless they are finished.

Climate Zone

Your climate zone is the second most crucial factor in determining furnace size. 30 to 60 BTUs of heating capacity per square foot is a wide range; your climate zone helps to narrow it. There are five climate zones in the United States. Zone 1 is the warmest, and Zone 5 is the coldest. Colder climates require more heating capacity than warmer climates.

Homes in Zone 1, which includes Texas, Louisiana, and Florida, require 30 to 35 BTUs per square foot. Zone 1 homes might not require furnaces; heat pumps are probably sufficient for Zones 1 to 3. Homes in Zone 3, which includes Kentucky and most of Missouri and Virginia, need 40 to 45 BTUs per square foot. Homes in Zone 5, which includes Maine, Wisconsin, and Montana, require 50 to 60 BTUs per square foot.

Climate Zone BTUs per Square Foot

Zone 1

30 - 35 BTUs

Zone 2

35 - 40 BTUs

Zone 3

40 - 45 BTUs

Zone 4

45 - 50 BTUs

Zone 5

50 - 60 BTUs

Furnace Efficiency (AFUE rating)

The AFUE (annual fuel utilization efficiency) rating expresses furnace and boiler efficiency. The AFUE rating compares the furnace’s annual heat output to the number of fossil fuels (natural gas, oil, propane) it consumes annually.

Furnaces with higher AFUE ratings are more efficient. The federal minimum AFUE rating is 80%. This means that 80% of the fuel consumed is converted into heat, and 20% is wasted. To earn the ENERGY STAR label, gas furnaces must have ratings of at least 90% in the southern U.S. and at least 95% in the northern states. Oil furnaces must have ratings of at least 85%.

AFUE ratings are essential since heating your home uses more energy than any other system and typically comprises around 29% of your utility bill.

furnace efficiency AFUE rating on energy guide label illustration
56-70% furnace AFUE icon

old, low-efficiency heating systems

80-83% furnace AFUE icon

mid-efficiency heating systems

90-98.5% furnace AFUE icon

high-efficiency heating systems

Other Variables to Consider

While square footage and climate zone are the most significant factors in determining heating capacity, other variables help to narrow down the options even more. Square footage and climate zone give you a range of BTU ratings. Family size, windows, number of floors, sun exposure, roof color, ceiling height, ceiling fans, and insulation indicate your furnace’s capacity should be at the upper or lower end of the range.

  • Family Size - Larger families require fewer BTUs because more people create more body heat dissipating into the surrounding air.
  • Windows and Number of Floors - Two-story homes require fewer BTUs because the second story insulates the first level. Homes with a lot of windows, old windows, or windows with broken seals require more BTUs because heat escapes through them.
  • Sun Exposure and Roof Color - Homes with plentiful sun exposure or dark-colored roofs absorb more heat from the sun, allowing fewer BTUs.
  • Ceiling Height and Ceiling Fans - Houses with high ceilings require more BTUs because heat rises. Ceiling fans circulate air to create more even temperatures and reduce required BTUs. When running in reverse, fans push warm air down from the ceiling.
  • Insulation - Insulation helps maintain temperatures in summer and winter. New homes with good insulation can use fewer BTUs. Older homes or houses with insufficient insulation require more BTUs.

Single-Stage vs. Two-Stage vs. Modulating — Which is best?

Furnaces are available in three modes: single-stage, two-stage, and modulating. No particular type is the best for every house. Home size, climate, budget, and the length of time one plans to live in their home are the top factors influencing preference.

single stage furnace illustration icon

Single Stage Furnace

Single-stage furnaces are the most basic type. They turn on and off. They run at 100% capacity or total power when they are on.

Single-stage furnaces are the most affordable to install and repair, but they have drawbacks. Short, powerful run-cycles cause certain rooms to heat up quickly, and other rooms remain cold. Keeping your thermostat set higher to combat this issue leads to higher energy costs.

Single-stage furnaces are most suitable for small, single-story homes, locations with mild winters, people on budgets, and people who plan to move in the near future.

Advantages:

  • Lower initial cost
  • Least expensive to repair
  • Good as a short-term solution

Disadvantages:

  • Inconsistent temperatures; hot and cold spots
  • Struggle to heat houses during frigid conditions,
  • Less effective at heating houses with two or more stories
  • Less energy efficient; higher energy bills
2-stage furnace illustration icon

2-Stage Furnace

The difference between single-stage vs. two-stage furnaces is that two-stage furnaces have two power settings, high and low. A two-stage furnace operates on low (60-65% capacity) about 80% of the time. A longer run cycle at a lower speed creates even temperatures throughout the home and reduces energy consumption.

Two-stage furnaces are suitable for homes with two or more stories, houses with hot and cold spots, cold winters, people with flexible budgets, and people concerned about lowering energy costs. You’ll get the best return on the initial cost if you stay in the home long term.

Advantages:

  • Consistent temperatures
  • Less noise
  • Energy efficient
  • Better indoor air quality
  • Longer equipment lifespan

Disadvantages:

  • High initial cost
  • More expensive to repair
modulating furnace illustration icon

Modulating Furnace

A modulating furnace has dozens of power settings and can adjust its temperature in small increments to create precise temperatures. The blower speed and flame level adjust accordingly. Modulating furnaces operate at 35% capacity about 85% of the time. With AFUE ratings of up to 98%, they are highly efficient.

A modulating furnace is a long-term investment. They are suitable for those who expect to live in their house for at least ten years, multiple-story homes, and locations with unstable and extended winters.

Advantages:

  • Low energy consumption
  • Temperature consistency
  • Reduced operating noise
  • Superior indoor air quality
  • Longer system life

Disadvantages:

  • Very high initial and installation cost
  • Frequent noise due to more continuous operation

How Long Does a Furnace Usually Last?

How long does a furnace last? The average lifespan of a properly maintained gas or oil furnace is 15 to 20 years, though they last 25 to 30 years in some cases. Electric furnaces generally last longer than gas or oil, 20 to 30 years on average.

Furnace Type Average Lifespan

Natural Gas Furnace

15 - 30 Years

Propane Furnace

16 - 20 Years

Oil Furnace

15 - 20 Years

Electric Furnace

20 - 30 Years

Factors That Affect Furnace Life Expectancy

Understanding the factors that affect furnace life expectancy will help you get the most out of your furnace. Size, installation, type of heating system, thermostat temperature, and maintenance impact a furnace’s lifespan.

1. Size

Incorrectly sized furnaces have lower life expectancies, whether too large or small. Furnaces that are too large turn on and off more often to maintain the temperature, while furnaces that are too small run longer cycles. Both situations place additional wear and tear on furnaces.

2. Installation

Installation performed by someone other than a professional HVAC technician can result in impaired wiring, incorrectly installed fuel lines, incorrect drainage systems, and poorly installed, sealed, or sized ductwork.

3. Type of Heating System

Single-stage and two-stage systems are less likely to break down than modulating systems containing a computerized blower motor chip to monitor airflow.

4. Thermostat Temperature

Keeping the temperature too high or low shortens the furnace's life expectancy. The ideal range is between 60 and 80 degrees Fahrenheit.

5. Maintenance

Regular maintenance prolongs a furnace’s lifespan. Maintenance includes:

  • Frequent filter changes
  • Annual tune-ups and inspections
  • Regular cleaning of heat registers
  • Sealing leaks in ducts

A furnace’s age can be determined by locating the model and serial number, contacting the manufacturer, or consulting the manufacturer’s website. These numbers appear on the sticker or metal plate located on the furnace’s exterior or the inside of the chamber door.

Did you know?

Repair or Replace Your Furnace?

It’s usually more economical to repair your furnace than to replace it. In some cases, though, it does make more sense to replace it. Three factors impacting your decision should be the age, repair costs, and performance of your current furnace.

Your furnace’s age is the first factor to consider. The average lifespan of a furnace is 15 to 20 years. It is probably wiser to replace your furnace when a significant component fails, and your furnace is over 15 years old.

Next, compare your repair costs to the remaining value of your furnace. Let’s say that 20 years is the maximum amount of time you’ll get out of your furnace, and its value steadily diminishes yearly. You can estimate your furnace’s remaining value with a simple formula:

Original purchase price / 20 years = decreased value per year

For example, a furnace purchased for $4000 decreases in value at a rate of about $200 per year:

$4000 / 20 years = $200 decreased value per year

HVAC professional replacing gas furnace in home

Factor in how many years remain until your furnace hits the 20-year mark. For example, a furnace installed 14 years ago has six years left. To find its worth, multiply the remaining years in its life by its decreased value per year:

6 years x $200 = $1,200 remaining value

If the repair costs exceed 50% of the furnace’s remaining value ($1,200 / 2 = $600), replace the furnace. If the repair costs are less than 50% of the remaining value, repair it.

The final aspect to consider is your furnace’s performance. Check the amount of gas (not cost) currently consumed and compare it to previous years by examining old bills. If gas consumption has increased over the years without any changes to your home or lifestyle, your furnace may decline in efficiency. Replace it if it’s more than 15 years old.

Signs You Should Replace Your Furnace

What’s more unpleasant than your furnace giving out in the dead of winter? A furnace breakdown is inconvenient and could potentially lead to other problems like burst water pipes. You can avoid catastrophe by replacing your furnace when you observe signs suggesting a total breakdown is in the near future.

 

Signs that your furnace should be replaced:

  • It’s more than 15 years old.
  • Your energy bills have increased.
  • Your furnace turns on and off more frequently, or the cycles are unusually long.
  • Your furnace is struggling to heat your home or heats it unevenly.
  • There are unusual noises or smells coming from your furnace.
  • Your furnace’s components are rusty, corroded, or damaged.
  • Your home is unusually dusty or humid.

How Much Does It Cost to Replace a Furnace?

Home Advisor says replacing a furnace costs $2,000 to $7,000, about $4500 on average. The total cost includes the price of the new unit (60% of estimate), labor (25% of estimate), materials, disposal of the old unit, and any local permit requirements (15% of estimate).

Factors affecting replacement cost include furnace type, size, efficiency, brand, and labor. Electric furnaces are the cheapest to replace, gas furnaces fall in the middle, and oil furnaces are typically the most expensive.

Furnace sizes range from 40,000 BTUs to 150,000 BTUs. Furnaces between 40,000 and 60,000 BTUs cost about $2,000 to $3,000. Furnaces between 125,000 and 150,000 BTUs cost about $3,000 to $6,500.

Highly efficient furnaces cost more than less efficient ones, but they can save you money by lowering your energy bills.

Like everything else, the furnace’s brand impacts its price. A Carrier furnace can cost more than twice as much as a Goodman furnace.

Labor costs for furnace installation by a licensed HVAC professional typically range from $50 to $100 per hour. Additional installers cost another $50 per hour. Issues regarding your current setup, ductwork installation, and ductwork repairs might increase the cost.

Furnace Type Average Replacement Price Range

Natural Gas Furnace

$3,800 - $10,000

Electric Furnace

$2,000 - $7,000

Propane Furnace

$2,200 - $5,700

Oil Furnace

$6,750 - $10,000

Geothermal

$10,000 - $40,000+

Wood Furnace

$3,000 - $3,500

Things to Consider When Choosing a Furnace

You don’t have to be a furnace expert to choose a great furnace that fits your needs. You have to know what factors are essential. HVAC installers are excellent sources of information, but you’ll want to understand what you're buying.

Consider these six things when choosing a furnace: energy efficiency, size, climate, installation cost, maintenance and warranty, and rebates.

Energy Efficiency

Highly efficient furnaces are more expensive, but they save you money by lowering your energy bills. Upgrading from 80% AFUE to 95% AFUE will reduce your bill by about 15% each month. If your usual statement is $300, you'll save about $45. The ENERGY STAR® label identifies highly efficient furnaces.

Efficient furnaces are better for the environment. According to the U.S. Department of Energy, replacing an old 56% AFUE gas furnace with a 90% AFUE gas furnace in a cold climate reduces CO2 emissions by 1.5 tons yearly.

Furnace efficiency matters most in cold climates where heating costs are the highest. Lower energy bills might not offset the initial cost of a 90% AFUE furnace in locations with mild temperatures.

Install a programmable thermostat for significant savings on your energy bills! According to the U.S. Department of Energy, you can save as much as 10% yearly on heating and cooling by turning your thermostat back 7°-10°F for 8 hours a day from its typical setting.

Energy
Saving Tip

Size of a Furnace

Your ideal furnace size is largely determined by your home’s square footage and climate. Family size, number and quality of windows, number of floors, sun exposure, roof color, ceiling height and fans, and insulation are less significant factors.

An undersized furnace won’t be able to keep your home at a comfortable temperature on frigid days. The furnace will run continuously to maintain the thermostat setting, which wastes energy, increases your bills, and puts wear and tear on the system.

An oversized furnace will heat your home unevenly and turn on and off more frequently. Some rooms will heat up quickly, and other spaces will remain cold. Frequent heating cycles strain the system.

Climate

Your climate region also plays a vital role in your furnace's type, size, and efficiency rating. Homes in moderate temperatures might benefit more from a heat pump over a furnace. Houses in mild climates can also get away with smaller, less-efficient furnaces. Homes in cold climates with long heating seasons require bigger furnaces and reap more benefits from efficient furnaces.

Installation Cost

Remember to factor in the cost of installing the furnace. Furnace installation is complicated and requires an HVAC professional. The old equipment needs to be removed, and ducts and other equipment may need to be installed or moved. Labor costs for furnace installation by a licensed HVAC professional typically range from $50 to $100 per hour. Additional installers cost another $50 per hour.

Maintenance and Warranty

The frequency and cost of maintaining your new furnace are essential considerations. Maintenance is often included in the terms and conditions of your warranty. Understanding your warranty’s length, terms and conditions, and coverage of parts and labor is crucial.

Rebates

Incentives and rebates offered by the government for maintaining energy-efficient homes also affect the decision to buy a furnace. Purchasing specific heating systems or making other energy-related improvements to your home may qualify you for federal tax credits. Additionally, you may be eligible for savings through state and local government rebates by purchasing select Energy Star or Goodman products.

Have any questions?

If you are shopping for a new furnace system, The Furnace Outlet can help. We specialize in direct-to-consumer heating and cooling equipement and offer the lowest prices on residential HVAC supplies online. Please contact our experts with any questions or concerns you may have, and we will be happy to help.


Frequently Asked Questions

Do I need to replace my furnace and air conditioner at the same time?

No, you do not need to replace your furnace and air conditioner at the same time. If you’re replacing one unit and the other is in good working condition, and below its life expectancy, there is no reason to replace both. Replacing both at the same time increases installation costs because the job takes twice as long.

In certain situations, however, it might make sense to replace both:

  • Both units are near the ends of their lifespans (10-15 years for AC and 15-20 years for a furnace)
  • To save more money on your energy bills with two high-efficiency units
  • To produce better year-round air quality
  • To maintain a comfortable temperature year-round
  • The installation process is difficult
  • To avoid repairs and replacements in the near future

What is an ECM motor?

An ECM motor (electronically commutated motor) is also called a variable speed motor. It’s a significant improvement in furnace and air conditioner efficiency. An ECM motor contains a microprocessor that regulates airflow by adjusting the fan’s speed.

Whereas a standard single-stage motor runs at 100% capacity, an ECM motor generally runs at 35% capacity and can ramp up as conditions warrant. Running at a lower capacity reduces energy consumption and costs and provides more consistent and even temperatures in the home.

How much does it cost to convert an electric furnace to gas?

According to HomeAdvisor, converting an electric furnace to a gas system adds $5,000 to $15,000 to the cost of gas furnace installation. Gas line installation costs $20 to $25 per linear foot, ductwork installation and repair costs $8 to $12 per linear foot, and a return air stack costs $1,000 to $5,000.

How much does it cost to relocate a furnace in a house?

According to HomeAdvisor, relocating a furnace can cost anywhere from $1,000 to $20,000. The cost largely depends on how far away from the original position the furnace is relocated. Moving the furnace from one place in the basement to another is significantly cheaper than moving the entire system from the basement to the attic.

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