How to Choose the Right Central Air Conditioner Size

An air conditioner upgrade can get you a more efficient system with better airflow, so your home will be more comfortable and your cooling bills lower.

But getting the correct size air conditioner for a space is critical. There are many things to consider when sizing an air conditioner for your home, including the square footage of your house, ceiling height, sun exposure, and more.

If you’re in the market for a new air conditioner, this article will help you understand how to size the unit for your home.

Note that this article is meant for general information and educational purposes. You should always be dealing with qualified and certified experts to help you appropriately size and install an air conditioner.

In the market for a new central air conditioner? Check out our picks for Best Air Conditioner Brands & Models

Why Air Conditioner Size Matters

When it’s time for a new A/C unit, correct installation of the right central air conditioner size is always one of the most important aspects of the project.

If not done correctly, you could end up overpaying on electric bills and being undercooled when external temperatures call for more.

An undersized unit will struggle to keep up on the hottest days and wear out quicker due to constant operation. An oversized unit, in contrast, will turn on and off frequently (a process called short-cycling), which also causes excess strain on the unit and may lead to fluctuating indoor temperatures.

When upgrading your cooling system, we don’t recommend that you replace it with the exact same size unit without running the calculations. Here’s why:

• The original unit may or may not have been sized correctly
• Your home may have changed over time, especially if additions were added, for example
• Modern units may be more efficient and effective than your old unit and therefore need to be re-sized accurately

Air Conditioner Size Calculator

How Do Air Conditioner Sizes Work? An Introduction to BTUs and Tons

 Measuring Air Conditioners in BTUs

Air conditioners are sized based on British Thermal Units (BTUs), a measurement of the amount of heat your AC will remove from the air. You’ll also see this referred to as cooling capacity.

An air conditioner’s BTU/cooling capacity measures how many tons of air the system can cool per hour.

A good way to think about this is that if your unit is labelled as 12,000 BTUs, it absorbs 12,000 thermal units per hour. The larger the unit, the larger the space it can cool, and the more energy it will consume.

Measuring Air Conditioners in Tons

Air conditioner size/cooling capacity is also measured in tons. Air conditioners are available in sizes ranging from 1.5 to 5 tons. One ton is equivalent to 12,000 BTUs per hour.

For example, a 3-ton air conditioner would have 36,000 BTUs of cooling power.

You want about 0.0016 tons of air conditioning for every square foot in your home for sufficient cooling.

Factors Impacting Air Conditioner Sizing

If you want to know how much cooling power you need, you’ll need to measure the space you want to cool. This is the easiest way to determine what you need for your specific area.

Often HVAC companies will use your home’s total square footage and layout as the main factors in assessing the correct size of a central air conditioner—e.g., bungalow, two-story townhouse, detached two or three-story.

However, other factors must be considered when calculating air conditioner size. Here are some of the most important ones:

• Square footage of the space
• Ceiling height
• Level of insulation
• The air source (the location where the air enters the house) and how long it takes for specific rooms in your home to cool down when the AC is on
• What type of climate or part of the country you live in: People often have larger A/C units in places with high humidity levels, long summers, or heat waves
• The energy efficiency of the unit

You’ll want to pay attention to the CFM (cubic feet per minute) of airflow when choosing an air conditioner.

Energy Efficiency and Air Conditioner Size

The more efficient an air conditioner is, the more effectively it will cool your home. As such, you might be able to get away with a slightly smaller air conditioner if you opt for one with a higher efficiency rating.

A more efficient unit will also cost less to operate, saving you money over time. However, the higher the SEER, the higher the up front cost.

Air conditioner efficiency is measured in seasonal energy efficiency ratio (SEER) and the more updated SEER2. In Canada, air conditioners must have a SEER of at least 13 or a SEER2 of 13.4. Efficiency ratings here typically go as high as 21. A SEER between 16 and 18 is generally ideal for most parts of Canada

A Step-by-Step Guide to Choosing a New Air Conditioner

1. Determine the Square Footage

Measure the length, width, and height of each room. If you want to cool two or more rooms, you should determine the total square footage of each room and consider if you have a single or multi-level home.

That being said, most homeowners know the square footage of their homes, so that’s an easy number to go by.

If you’re installing a new central air conditioner, you’ll also want to pay attention to the size of your ductwork. Generally, you’ll want to ensure that your AC unit matches the capabilities of your ductwork because having the wrong size could cause your ducts to put unnecessary strain on your AC unit.

2. Determine Your BTU Requirements

Add up the square footage of the rooms you want to cool and multiply that number by the recommended BTU per square foot.

The size of your living space in square feet is then multiplied by the recommended BTU output required, in most cases this is in the 15 – 50 BTU per square foot range.

While this part of the process is simple to navigate, you should still work with a professional to ensure the project is completed safely.

3. Choose the Right Condenser

The condenser unit and outdoor coil help release heat from your home to the outdoors. This is the exterior unit most people think of in a central AC.

These come in different sizes and, to a certain extent, slightly different shapes depending on the model and tonnage of air conditioner you buy.

Choosing a unit with a condenser that will fit your needs and fit well with your home is essential and is something your HVAC professional will assist you with.

There are two main types of air conditioning units:

A. Split Systems

A split system has an outdoor condenser and an indoor evaporator. The evaporator is usually installed on your furnace, which connects to your home’s ductwork.

Split systems are the most common type of central air conditioner, and this is what you will most likely be installing.

Ductless air conditioners or mini-split systems are another type of split air conditioner.

B. Packaged Units

A packaged unit has both the evaporator and the condenser in one unit. These units are often on the roof or a concrete pad next to the home.

Packaged units are less common than split systems in residential settings in Canada. But they’re sometimes used in homes with limited space, for multi-unit properties, and more commonly, commercial properties.

When choosing the size of your condenser, you’ll need to consider the following factors:

• The size of your home (a larger home will require a larger condenser)
• The climate (in hot climates, you’ll need a larger unit to compensate for the higher temperatures)
• Your cooling needs (if you plan on frequent use, you’ll need a unit with more power)

Once you’ve considered all of these factors, you’ll be able to narrow down your choices and choose the right option for your home.

4. Pick the Right Installer

While you can find a central air conditioner that will fit the needs of almost any home, the best way to ensure you get the most suitable AC for your house is to hire a professional. When hiring an installer, you’ll want to ensure they have all the necessary certifications.

You’ll also want to ensure they have insurance and are licensed where they work. An established track record is another vital thing to look for when hiring an installer.

It’s OK to use contractors who are brand new to the field. You only need to ensure they’re insured and stay updated with their progress. As long as they’ve been trained, this is what you should look for in a contractor.

Choosing the Right Voltage for Your New Air Conditioner

When it comes to voltage, it’s a good idea to match the size of your AC with the voltage of your home electrical system. If the voltage of your system is much lower than the voltage of your new AC, you could have serious problems.

If you’re installing a new air conditioner on an existing system, you’ll want to check the voltage of your current AC, and many AC manufacturers publish information about the voltage requirements of their products online.

You’ll also need to know the amperage of your circuit breaker, so it may be a good idea to ensure that you’re working with a professional instead of working on the project yourself, considering what you need.

There could also be chances that you might need to upgrade your wiring or breaker. This is another reason a professional is recommended.

A 100 AMP breaker or greater is usually needed to add a NEW air conditioner if you didn’t have one before. Replacing an old one usually shouldn’t be an issue.

In addition, you need enough connecting space on your breaker if you’re installing a new AC. Otherwise, you may need to install a “pony panel” to add additional plug space.

Expect extra installation costs for these add-ons or upgrades if needed.

The Bottom Line

There’s a lot to consider when choosing a new central air conditioner. You’ll need to consider your house’s electricity requirements, cooling capacity, and dimensions. Furnace Prices can help you with comparing quotes on this.

Choosing the central air conditioner size that will fit your home is also essential. Luckily, there are ACs available for every home and budget.

Now that you know how to choose the right central air conditioner, you can make an informed decision and cool your home efficiently and effectively. 

Compare professional estimates and get recommendations today to get started.