What Size Furnace Do I Need For My Home? | Day & Night Air

Winter is coming. Game of Thrones may be over, but the world turns on, and the seasons still arrive. While Phoenix winters aren’t as cold as winters in the Midwest, a fully functioning heater is critical for the family’s comfort. The home’s furnace must be appropriately sized to handle the home’s needs and to ensure the family’s comfort during the winter. So how do you know what heater size is suitable for your home? We’ve put together a few factors to consider when purchasing a new HVAC system or furnace for your home.


Factors to Consider When Purchasing a New Furnace

With every big home improvement project comes a list of considerations. No two homes are exactly alike, and no two families need the same things when it comes to a new HVAC system.


Size of the Home

The most obvious factor to consider when considering a new heater installation is the size of the home. Bigger homes require more powerful systems. Homeowners should estimate the square footage of the home. This information is usually easily found on an appraisal, realty listing, or a lease. However, if you can’t find the square footage listed anywhere, follow these steps to estimate it:

1. Measure Each Room’s Length and Width.

Take a tape measurer and run it along the perimeter of each room. Write these numbers down and make sure to measure them consistently (for example, if you start measuring in feet, don’t switch to meters or yards).

2. Calculate the Square Footage

To calculate the home’s square footage, multiply the width by the length of each room, and then add those numbers up. For example:
Living Room: 24 feet x 20 feet = 480 feet
Master Bedroom: 20 feet x 14 feet = 280 feet
Bedroom 2: 18 feet x 13 feet = 234 feet
Bathroom: 10 feet x 16 feet = 160 feet
Kitchen: 25 feet x 10 feet = 250 feet
Dining Room: 10 feet x 18 feet = 180 feet
Total Estimated Square Footage = 1,584 square feet
Additionally, keep in mind that a professional HVAC technician will have experience estimating square footage and choosing the correct furnace size for your home.


The climate where you live is another important factor when deciding on the proper size heater for your home. If your home is in Phoenix, then your climate is considered to be “semi-arid.” Semi-arid climates are classified as such because of the level of precipitation. Phoenix doesn’t see much rainfall, but not as low as a typical “desert” climate. The climate is important because it determines the number of BTUs needed for a properly functioning heating system. A BTU, or British Thermal Unit, is a unit of measurement for energy, and it is vital when determining the size heater you need for your home.


For semi-arid climates, approximately 40-50 BTUs of output per square foot are required. To determine the number of BTUs needed to heat your home efficiently, though, you’ll need to do a little more math.

The following equation estimates the output required for a new heater in our example 1,584 square foot home:
1,584 square feet x 45 BTUs/square foot = 71,280 minimum BTUs needed.
However, this doesn’t mean that a 72,000 BTU furnace will sufficiently heat the home. Keep in mind the furnace’s efficiency rating. Say the furnace you want to install has an 80% efficiency rating:

71,280 BTUs x 80% = 57,024 BTU output
A 57,024 BTU output is inadequate for our example. Therefore, you’ll need a higher BTU output furnace or a higher-efficiency HVAC system. For our example, a 90,000 BTU unit may be more appropriate:
90,000 BTUs x 80% = 72,000 BTU output.

A licensed professional heating and cooling technician can help homeowners estimate the BTU output needed for their specific home depending on a variety of factors.

The Home’s Layout

Another critical element when deciding the right size heater for your home is the home’s layout. An open floorplan needs a different heating strategy than a home that has many small rooms. Additionally, the orientation of the home is important, as well. A home with a living room facing the south will stay warmer in the winter due to the sun.

The Home’s Construction

The materials used to build your home make a difference when considering the installation of a new HVAC system. Brick homes have better natural insulation than homes with wooden siding. Features as simple as shrubbery surrounding the home can affect the size furnace you need. A professional technician considers all of these factors when planning a new heater installation.

Software Estimates

An inappropriately sized furnace wastes resources such as water and energy, many local governments require contractors to use software to choose the correct-sized furnace for their projects. The software, combined with real-world experience, helps contractors and heating and cooling experts pick the right furnace.

How Can Day and Night Air Help?

Day and Night Air uses the latest technologies in the industry when planning new heater installations. This technology includes top-of-the-line software to help our experts determine the right furnace for your home. Whether your new heater is gas or electric, ductless, or vented, we can help. Our team of skilled technicians has decades of combined experience.

Free Estimates for Heater Installations

Do you need a new furnace installed in Phoenix, AZ? Worry no more because Day & Night Air has what it takes to ensure that all your needs are met. Contact our experts today to schedule an appointment for a free estimate.

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