Choosing the right size air conditioning (AC) unit for your house is crucial to ensure optimal comfort, energy efficiency, and good working order of your air conditioning system. 

An undersized unit may struggle to cool your home, leading to increased energy bills and wear on the system. The extra work an undersized AC unit is doing to cool your home also puts the system at risk of overheating and malfunctioning, which often requires the entire unit to be replaced. 

On the other hand, an oversized unit can cause frequent cycling—the process of an air conditioning system repeatedly turning on and off to maintain the desired indoor temperature. This happens when the AC unit reaches the set temperature, shuts off, then turns back on when the temperature rises above the set point. While cycling is a normal operation of most air conditioning systems, excessive cycling can cause significant wear.

Choosing the correct size central AC unit

Here are some steps to help you determine the right size AC unit for your house:

Calculate your home’s square footage 

Measure the square footage of each room you want to cool, including the height of the ceilings. Add up the square footage of all the rooms you plan to cool to get the total square footage. For irregularly shaped rooms, you can divide the area into smaller regular shapes (like rectangles) and calculate the square footage of each section individually before adding them together. 

When in doubt or if you want a more precise measurement, you can use digital tools like laser distance meters or smartphone apps designed for measuring distances and areas. These tools can provide accurate measurements and make the process easier, especially for larger spaces or complex floor plans.

Account for insulation

Well-insulated homes generally require less cooling capacity, as the insulation helps to retain the cool air and block heat from outside. Conversely, poorly insulated homes will lose cool air more quickly and will need a larger AC unit to compensate for the additional heat gain. 

It’s a good idea to make sure your home is well insulated, because proper insulation keeps your home more comfortable throughout the year and reduces the strain on your cooling system, extending its lifespan and saving you money on energy costs.

Consider your home’s orientation

The direction your home faces impacts the amount of sun exposure it receives, which can affect your cooling needs. South- and west-facing rooms tend to get more sunlight, especially during the hottest parts of the day. As a result, these rooms tend to heat up more quickly and require additional cooling capacity to maintain a comfortable indoor temperature. 

If these rooms have lots of windows, they will get hotter faster. To help keep your cooling needs in check, consider light-blocking curtains or planting large trees or bushes to help shade those rooms. By shading walls that face south and west, you can dramatically reduce the amount of cooling your AC system has to do, which may allow you to opt for a smaller unit.

Use a cooling load calculation

The most accurate way to determine the correct AC size is to perform a cooling load calculation. This calculation takes into account various factors, including your home’s square footage, insulation, the number and size of windows, the type of roofing materials, and local climate data (like temperature and humidity). It may also take into account heat generated by appliances, electronics, and lighting. A professional HVAC contractor can help you with this calculation.

Once you have the cooling load calculation results, you can select an AC unit with the appropriate capacity (measured in BTUs or tons). An HVAC contractor can guide you in choosing the best unit that matches your cooling load requirements.

Consult with a professional

For accurate sizing and installation, consult with a licensed HVAC professional. They can assess your home, take into account all the necessary factors, and recommend the best AC unit size for your specific needs.

Avoid simply replacing your existing AC unit with one of the same size, as your cooling requirements might have changed over the years due to renovations, additions, or improvements in insulation. By following these steps and seeking professional advice, you can choose the correct size AC unit and ensure a comfortable living environment with optimal energy efficiency.

If you’re ready to install a new air conditioner, our expert technicians can help you get the right size AC unit for your home. Contact today to get started.