Getting the Right Size AC Unit for Your Home

June 20, 2022
HVAC Size in Erie County, NY

Whether you’re installing an air conditioner for the first time or have to replace your AC due to age or system failure, it’s a major investment. That’s why it’s so important to get the right one for your home, making sure that it is appropriately sized for the space it’ll be required to cool. Factors like the square footage of your home, how you choose the right size, and efficiency should all be taken into consideration.

How are AC Units Sized?

Air conditioner sizes have nothing to do with the physical dimensions of the unit or how much refrigerant it holds. Rather, size refers to the heat transfer capacity of the unit. Air conditioners don’t produce cold air, but rather remove the heat from the air circulating through the system, and then it transfers that heat to the air outside.

Heat transfer capacity is measured in British thermal units, or BTUs. A single BTU equals the amount of heat needed to increase the temperature of a single pound of water by 1 degree Fahrenheit. Another common way to see air conditioning unit sizes is in tons, which is simply another way to describe a certain number of BTUs. A single ton equals 12,000 BTUs.

Why Is Size So Important?

The higher the capacity of an AC unit, the more heat it will transfer out of your home each hour. You may think that a higher capacity would then cool your home faster. However, this isn’t exactly how it works.

When an AC unit is oversized for a home, the coils tend to freeze, causing the system to shut down prematurely, known as short cycling. This actually prevents the system from ever reaching the desired temperature in the house. Additionally, it fails to remove humidity from the air, leaving your home both too warm and too humid.

An oversized unit will experience more starts, which is the most energy-consuming part of the cycle and causes the most strain. As system size increases, so does the price tag, both at installation and in operation.

Likewise, a system sized too small is just as problematic as an oversized system. Your system will run long cycles, but will again fail to achieve your desired temperature. Just like an oversized system, under-sizing causes excessive wear on your system plus significantly higher energy consumption. You may save a little on the installation, but you’ll end up paying for it in repairs and energy expenses.

Getting a Load Calculation

The way to ensure that you get the right size system for your home is to work with a professional installer to get a proper load calculation. This calculation doesn’t actually tell you what size system you need but tells the installer how much heat your home transfers without the use of your HVAC system. This is called the Manual J calculation.

Some estimates use only the square footage of your home to look at the size. However, the Manual J actually uses the cubic footage, which considers the height of your ceilings. It then also considers how many windows and exterior doors you have and their size, your insulation R-value, which direction your home faces, and your climate’s relative humidity. It also considers how many people live in your home, and any other heat sources on your property.

This is important because the more heat your home transfers, the larger the system you’ll need. Therefore, a better-insulated home with few heat sources means a smaller system and lower expenses.

Considering Efficiency

When it comes to evaluating what size air conditioner your home needs, you must also consider the efficiency of the system. A more efficient system may mean you can opt for a slightly smaller unit.

Air conditioning efficiency is measured in SEER, or seasonal energy efficiency ratio. The ratio divides the cooling output over the summer by the energy used during the summer. The higher the rating, the more the cooling output compared to the energy consumption. For a properly sized system, the higher efficiency means you’ll pay less to cool your home.

Vastola Heating & Cooling has been the heating and cooling service provider of choice for people around Orchard Park for over 60 years. Our team provides cooling and heating installation, maintenance, and service combined with indoor air quality and water heater services. Call to schedule your AC consultation with one of our installation experts today!