Selecting the correct AC unit size directly impacts your home’s comfort, energy efficiency, and monthly utility costs. An undersized unit struggles to cool your space adequately, running constantly and driving up electricity bills. On the other hand, an oversized unit cycles on and off frequently, creating temperature fluctuations and excessive humidity while wasting energy. This comprehensive guide walks you through how to choose the right size AC unit for your house.
Calculate the Square Footage
One of the first things you’ll want to do is evaluate the square footage of your home, and there are a few ways to do this. If you have access to your property records, you can look up the total square footage of your home. Another option is to measure each room. Measure the hallways and closets individually, then add everything together. The latter option is more time-consuming, especially for larger houses. Generally, you only measure rooms if you need a mini-split, as it targets a specific zone rather than the entire house.
Factor in Ceiling Height
As you measure your home, you’ll also want to note the height of your ceilings since this can significantly impact heating and cooling needs. A higher ceiling means more space to heat or cool, which can result in higher energy bills. Standard ceiling heights are typically 8 feet for living spaces and 9 feet for entryways and hallways. If your home has taller ceilings, you’ll want to factor this in when calculating the total square footage of your home.
You can calculate ceiling height adjustments by measuring from the floor to the highest point of the ceiling. Multiply your square footage by the ceiling height in feet, then divide by the height to get an adjusted square footage figure for BTU calculations. This method accounts for the actual air volume your AC unit must cool rather than just floor space.
Evaluate a BTU Sizing Chart for Guidance
Once you have the square footage of your home, you’ll want to look at the British Thermal Units (BTUs) of available AC systems. This measures the cooling capacity of air conditioning systems, indicating how much heat the unit can remove from your space per hour. Standard BTU charts provide baseline recommendations based on square footage, typically starting at 5,000 BTUs for 150 square feet and scaling up proportionally. Most residential spaces require between 20 and 25 BTUs per square foot as a starting point.
Account for Windows and Insulation Quality
Windows significantly impact cooling loads through solar heat gain and air infiltration. If you have several large south or west-facing windows, more sunlight will enter your home, which increases temperatures. To keep the house comfortable, you may need a larger AC unit to combat the additional heat.
Moreover, if you live in an older, poorly insulated home, the outside air may seep in, and your AC will have to work harder to maintain desired temperatures. A larger system will be more capable of handling the demands of this kind of space.
Consider Local Climate
Another tip for choosing the right size AC unit for your house is to consider the local climate. In Florida and Texas, year-round heat and humidity require larger AC units than similar-sized homes in the cooler Midwest. This is because high temperatures and moisture levels force the AC to work harder to cool and dehumidify the air. In contrast, homes in milder climates need less cooling power, as the demand for temperature regulation is lower. Adjusting your AC size to match your climate ensures optimal performance, energy efficiency, and comfort.
Number of Occupants
The more people you have living in your house, the more body heat you all generate, which naturally increases the temperature. Typically, each person adds about 600-900 BTUs to the cooling load, depending on activity levels. Activity levels refer to how much physical movement or exertion happens in the space. For instance, someone sitting quietly or working at a desk generates less heat than someone cooking in the kitchen, exercising, or engaging in other high-energy activities.
It’s also important to consider regular guests or gatherings. If you frequently entertain or have a large family, the additional body heat can strain an undersized unit, making it harder to maintain a comfortable temperature. Factoring in the number of occupants ensures your AC unit can handle the cooling demands without overworking, leading to better efficiency and a longer lifespan for the system.
Consult a Professional
It’s best to consult a professional if you’re unsure about the right size air conditioning unit for your home. Technicians from an AC installation company will analyze the size of your home, layout, local climate, and more to recommend the best options.
Professionals use advanced tools, like Manual J load calculations, to precisely determine your cooling needs based on factors like insulation, window placement, and heat-generating appliances. This level of detail ensures you avoid choosing a unit that’s too large (leading to short cycling and inefficiency) or too small (causing overwork and discomfort). Their expertise not only saves you money on energy bills but also prevents costly mistakes during installation or future repairs.
Pro Tip
An expert can also help install and maintain the unit properly, ensuring optimal performance and longevity.
Tips for Buying an AC Unit
Purchasing the right AC unit ensures your home stays comfortable and energy efficient. Consider these three important aspects before purchasing so that you can make an informed decision.
Research Energy Efficiency Ratings
When buying an AC unit, look for models with a high Seasonal Energy Efficiency Ratio (SEER) rating. Generally, modern AC units have ratings between 15 and 18, but for maximum efficiency, look for a SEER rating of 20 or higher. Units with better energy efficiency may cost more upfront, but they provide significant savings on energy bills over time while also reducing your environmental impact.
Choose a Suitable Unit Type
Decide which type of AC unit suits your home and lifestyle best, such as central air, a window unit, or a ductless mini-split system. Each type has its pros and cons; for example, central systems cool larger spaces efficiently, while ductless systems are ideal for targeted cooling in specific rooms.
Likewise, the type of unit(s) you buy impacts the size(s) you’ll need. If you have a mini-split in your bedroom but also want central AC, you’ll need a smaller central unit because the mini-split will already cool the bedroom space.
Hire Professional Installers
Most importantly, when buying a new cooling system, it’s always best to hire professional installers. These technicians undergo training and hold certificates to work on cooling systems, resulting in industry expertise. Attempting to install the AC system yourself risks damaging the appliance or even causing harm to yourself.
Style Crest has over 50 years of business expertise, same-day service, certified technicians, and a commitment to customer satisfaction. Whether you need help sizing your AC, selecting the right model, or maintaining your system, their team is here to ensure your home stays cool and efficient all year long. Take the next step toward a perfectly sized and expertly installed cooling system!