How to Find the Right AC Unit for Your Home

To benefit from AC replacement, you must find the right AC unit for your home. It’s important to consult with an air conditioning service contractor. Whether your existing system is reaching the end of its life or is outdated, you have an opportunity to find a more energy-efficient system. However, ignoring important details or making a mistake can have costly consequences.

Finding the right AC unit requires knowing the size of the model you need. We’ll look at numerous factors related to air conditioner sizing and other variables to discuss with your HVAC contractor. 

Square Footage

Square footage isn’t the only size variable to consider when selecting an AC unit. Nonetheless, the square footage of individual rooms and your entire home is usually the first place to start. The larger your home, the more cooling capacity you need. Miscalculating capacity can mean getting too much or too little cool air and spending more on energy.

Ceiling Height

Ceiling heights aren’t included in square footage, but if your home has higher ceiling heights than average, it will require more power to be properly cooled. Ceiling height also influences air circulation. You’ll need a higher-capacity unit to counteract the accumulation of rising warmer air. Irregular airflow patterns caused by sloped or vaulted ceilings must also be considered. 

Number of Windows

It may seem less obvious, but windows have a big impact on an AC unit’s efficiency. If you have a lot of south- and west-facing windows, more sunlight causes higher heat gain, requiring a stronger AC. Other window-related AC sizing factors include:

  • Number of Windows: More windows mean more opportunities for heat gain and air leakage.
  • Age of Windows: Older windows tend to let more air seep in and are less insulated.
  • Window Coverings: Blinds, curtains, and other coverings help windows be more efficient by blocking out sunlight.


Insulation in walls, ceilings, and attics can affect AC efficiency. Each insulating material has an R-value; the higher the number, the greater a material’s thermal resistance (ability to prevent heat transfer). Replacing old materials or filling in poorly insulated gaps or spots with high R-value insulation can reduce energy consumption.


The climate conditions in your area determine how much cooling you need. A smaller air conditioner won’t perform well in soaring summer temperatures, and if your region sees cooler summers, a larger system may not be cost-effective. Nonetheless, you must consider the temperature range throughout the year, along with typical humidity levels.

About Calculating Cooling Capacity

The capacity of an air conditioner is measured in British Thermal Units (BTUs). The larger your home, the more BTUs you’ll need, but the requirements vary. For example, a well-insulated, shaded room generally needs 25 to 30 BTUs per square foot, but rooms with average insulation and moderate sun exposure may need 30 to 35 BTUs per square foot. However, a brightly lit room with poor insulation can require 35 to 40 BTUs per square foot.

Therefore, capacity requirements can vary significantly. Other factors that influence BTU requirements include the number of occupants, lighting fixtures, and the presence of heat-generating appliances. For a novice, working all these variables in a calculation can be overwhelming.

An HVAC professional has an easier way to perform a load calculation and find the right AC for your home. They may use formulas to input specific numbers. Or, they can use load calculation software tools that further streamline the process. This means load calculations can take less time, but this doesn’t minimize their importance at all.

About Efficiency Ratings

Every air conditioning unit has an efficiency rating on its label. You can use this to compare units and predict how a system will operate under standard conditions. Energy efficiency ratings include:

  • Seasonal Energy Efficiency Ratio (SEER): This is an air conditioner’s cooling efficiency throughout a typical cooling season. Higher SEER ACs cost more upfront but consume less electricity and can save money over time.
  • Energy Efficiency Ratio (EER): By measuring a unit’s cooling capacity under standard conditions, its EER can estimate how it will perform during peak demand and predict how it will operate during extreme temperatures.

Finding the Right Type of AC Unit

Sizing, efficiency, and other factors are heavily considered. It’s also important to consider the best type of unit. If you have a small home or a smaller room to cool, a window unit is an option. Central air conditioning systems are often used to cool entire homes; they use ducts to distribute air throughout the space. 

However, a split unit is better suited for cooling a smaller space or individual room. More advanced solutions include heat pumps (provide both heating and cooling) that are even more efficient. Another option is a mini-split; it allows you to zone your home for different levels of heating or cooling in different locations.

Additional Considerations

An AC unit must fit in the available space. If you have a small home, you may have fewer options. Also, consider the HVAC equipment you have. Does it match the AC unit you want to install? Will the new AC and your ductwork be compatible? If your ducts aren’t the appropriate length and diameter, issues with air velocity and pressure drop can affect performance and efficiency. To avoid persistent issues, you may want to consider replacing your entire HVAC system.

Contact Trio Heating & Air

In our years of serving homeowners in and around San Jose, our licensed AC technicians have installed high-efficiency cooling systems tailored to each client’s needs. We use the highest-quality products and brands and guarantee the highest quality of work. During AC replacement, our team advises you on the ideal model for your home and will remove your old unit, install the new system, and test it. To schedule air conditioning installation in Santa Clara County or San Mateo County, call (415) 223-1647 today.


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