The heating and cooling system in your home is critical in keeping you and your family comfortable.

To get the most out of your furnace and air conditioner, it needs to be the correct size.

A unit too big of a size can cause temperature swings and waste energy, while a unit too small will not be able to sufficiently heat or cool your home.

Choosing the right size for your HVAC installation is crucial to its performing properly and efficiently.

Figuring out what size HVAC system you need for your home ensures that it will work properly.

How to Calculate the Perfect HVAC Size

In order to know the size of the HVAC system you need, you must first calculate how many BTUs are required to keep your home comfortable.

BTU, or British Thermal Unit, is used to measure the amount of heat required to raise 1 pound of water 1 degree Fahrenheit.

There are two methods that calculate the BTUs

Method 1: Manual J Calculation

The Manual J method measures the total amount of heat lost through the home during the winter. This number is compared to the total amount of heat gained in the home during the summer.

This calculation determines the amount of BTUs your home needs. It considers the size and climate of your space to determine the proper size of the HVAC system needed.

Using the Manual J Calculation, HVAC technicians are able to accurately determine the total amount of heat that is lost through the exterior of a home during the cooler months. They can also determine the total amount of heat that is gained through the exterior of a home during the warmer months.

It takes many factors into consideration like:

  • Square footage
  • Climate zone
  • Ductwork
  • Number and style of windows
  • Natural shade or sunlight
  • Quality and amount of insulation
  • Number of people using the space
  • Heat-generating appliances

Many utility companies offer free energy audits, so call your energy provider to schedule an audit today.

Method 2: Climate Method

You can get a good estimation of how many BTUs your home needs based on the climate you live in.

This map from the U.S. Department of Energy shows the different climate zones.

You can determine what size HVAC system you need for your home based on the climate you have in the area you live.

First, find your location and its correlating zone.

The hotter climate you live in, the more cooling power per square foot of area your HVAC system needs to have.

Below are the BTUs needed per square foot for each of the climate zones.

  • Zones 1 & 2 (hot): 22-30 BTU/sq. Ft.
  • Zone 3 (warm): 20-24 BTU/sq. Ft.
  • Zone 4 (moderate): 18-22 BTU/sq. Ft.
  • Zone 5 (cool): 16-20 BTU/sq. Ft.
  • Zone 6 (cold): 14-18 BTU/sq. Ft.
  • Zone 7 (very cold): 12-16 BTU/sq. Ft.

Let’s use these numbers in an example to give you a better idea of how they relate to your home:

According to Statista, the average American home in 2023 is predicted to be 6,121 square feet, but for simplicity we will use 6,000 square feet. So…

  • Zones 1 & 2 (hot): 6,000 x 22-30 = a 132,000 to 180,000 BTU
  • Zone 3 (warm): 6,000 x 20-24 = a 120,000 to 144,000 BTU
  • Zone 4 (moderate): 6,000 x 18-22 = a 108,000 to 132,000 BTU
  • Zone 5 (cool): 6,000 x 16-20 = a 90,000 to 120,000 BTU
  • Zone 6 (cold): 6,000 x 14-18 = a 84,000 to 108,000 BTU
  • Zone 7 (very cold): 6,000 x 12-16 = a 72,000 to 96,000 BTU

These numbers can fluctuate based on your home’s construction.

All of these numbers can be a little daunting, so just remember this rule of thumb: The maximum size unit you should buy is 15% over the BTUs you need for cooling and 40% of the BTUs for heating.

Or simply put… a home in a cooler climate requires a smaller air conditioner and a larger size of heat furnace.

A home in a hot climate requires a larger air conditioner and a small heat furnace.

What’s the Best Air Conditioner Efficiency Rating for My Home?

Different homes in different climates require different efficiencies.

HVAC system efficiency is rated using the SEER rating system.

SEER, or Seasonal Energy Efficiency Rating, is a rating of how many BTU’s of cooling the unit can produce for the electricity it uses.

The higher the SEER rating, the more efficient the unit is.

Based on the climate zone you live in from the chart above, here are the SEER ratings that are best for each climate zone, according to PickHVAC:

  • Zones 1 & 2 (hot): 18 SEER and up
  • Zone 3 (very warm): 17-18 SEER
  • Zone 4 (warm): 16-18 SEER
  • Zone 5 (moderate): 15-16 SEER
  • Zone 6 (cool): 15-16 SEER
  • Zone 7 (cool): Up to 15 SEER

Moist air is harder to cool, so if you live in an area where high humidity is common, then getting a more efficient air conditioning system in Roanoke, IN will reduce energy costs and make your home more comfortable.

Factors to Consider When Picking the Right Size Unit

Selecting the perfect sizes of an ac unit and furnace in Roanoke, IN is not a clear-cut, dry answer.

Many factors play into the decision, and it’s helpful to know why some units work better in different homes.

  • The Age of the Home: Older homes do not efficiently hold heat or air conditioning as well as today’s newer homes. It’s important to check to see if the electrical and existing ductwork components can handle the newer unit.
  • Exterior Walls and Windows: The number and condition of the walls and windows that are exposed to sunlight can affect the size of the unit needed and how well it will work. If your windows let a lot of sunlight through, then your heater does not have to work as hard to heat your home. On the other hand, if hot air is seeping through cracks and windows, it makes your ac unit work harder than it needs to.
  • Weather Proofing: Sealed doors and windows can help your HVAC system maintain heat and cool air better.
  • Insulation: Added insulation can also help hold in heat and air conditioning.
  • Existing Ventilation and Ductwork: Be sure to have any pre-existing ductwork inspected to ensure that it can handle the new HVAC installation.

You Are Ready to Make A Decision

The thought of a new HVAC installation can make even the strongest stomach drop to the floor.

Knowing how to select the ideal size for your home can save you time, money, and prevent a bad headache.

Using a zone chart and calculating the size of your space allows you to make the right decision for your home.

Contact Captain Comfort today to begin the HVAC installation process.