What Size Air Conditioner Do I Need for My Home?

May 24, 2021 | onestoput | Air Conditioning

Correct sizing is a very vital factor when buying an AC. This doesn’t refer to the physical dimensions of the unit but its cooling capacity. A bigger AC isn’t always better when it comes to air conditioning.

If you buy a larger system than required, you will spend too much money upfront. An oversized AC will also cool your house quickly and switch off and turn on again as temperatures fluctuate. This short cycling doesn’t allow your unit to efficiently draw moisture from the rooms, so you will end up with high humidity. If the AC kicks on and off continuously, it increases your energy usage, damages your AC components, and reduces the unit’s lifespan.

The cost of buying a small size AC can be tempting. However, the unit will not adequately cool your house. You will begin to notice some hot and cold spots. To fix this issue, you might try to run your unit for a more extended period which will only translate into high energy consumption, worn-out parts, increased chances of breakdown, and replacements. Follow the steps below to determine the right AC size for your house.

1. Measure Your Home’s Square Footage

Begin by determining the square footage of the space you wish to cool. For square or rectangular-shaped rooms, multiply the length and width to get the square footage. The formula to calculate the square footage of a triangular room is length times width divided by 2. For a circular space, measure the distance from one end to the center to get the radius and calculate the area. Get the square footage for every room, and add it all together.

Remember to exclude various spaces that you don’t need to cool, such as the sunroom or corridors, when calculating the square footage. Also, if you have rooms that open up to one another, like an open kitchen with no door to the sitting area, treat them as a single room.

2. Determine How Many BTUs You Need to Cool the Entire Space

British thermal units, BTUs, measure the cooling capacity of an AC. BTUs, therefore, tell you the amount of energy your AC uses to pull out hot indoor air and blow in cooler air each hour. Generally, an air conditioner of 20 BTUs adequately cools 1 square footage of the living space. For instance, if you wish to heat a 700-square-foott room, you multiply this by 20, so you need a 1,400-BTU unit to cool your space.

3. Consider the Climate in Your Home Region

A house located in hot and humid regions will have different cooling needs from those in mild, hot areas. If you reside in hotter environments, your unit will have to work harder to maintain the desired temperature. You, therefore, need a more powerful AC. People living in warmer areas should add around 10% to 20% to the number of BTUs for each room.

4. Adjust the AC Size Based on the Number and Types of Windows

Most people prefer having large windows since they let in light and allow a clear outdoor view. However, the windows can be a source of energy loss. A house with large single-panel windows will require a more powerful AC to account for the energy loss. However, if you constantly cover your windows with blinds and curtains or have energy-efficient windows, you can reduce the AC’s capacity by 10%.

5. Consider the Level of Insulation

Insulation plays a significant role in keeping the outdoor heat from seeping into the house. A well-insulated home will therefore require a less powerful unit. However, gaps in the ceiling, attic, doors, and windows let conditioned air seep out and allow sunlight entry. In such a case, you need to increase the AC’s capacity by 10%.

Today, most states have building codes that outline the minimum level of insulation required for a house. Modern homes are thus better insulated than older ones. If you live in a house constructed before the codes went into effect, you will need a larger AC to keep the house comfortably cool. Also, large trees cushion the house from intense sun rays, so if you have those in your yard, you need to account for this as well.

6. Factor in the Number of Occupants in the House

The human body naturally produces a lot of heat, adding to the air volume that your AC needs to cool. The general BTUs calculations account for two people per room. If you need to cool rooms that consistently have more than two people, then add 600 BTUs for each person. For instance, if you need to cool a shared space with three occupants, increase your AC’s BTUs by 1,800.

7. Adjust the BTUs Based on the House Design

You need to make BTU adjustments based on the style of your house. The general BTU calculations work for rooms with a standard ceiling height of 8 feet. If your home is beyond this range, add 10% to the calculated cooling capacity in each room. Also, east- and west-facing rooms get hot during summer, so you need to consider this when calculating your AC size.

Additionally, a two-story and a ranch-style house with similar square footage have different cooling needs. The ranch home has twice as much roof space as the multistory building. Thus, you will need a more powerful AC to maintain a comfortable temperature in a ranch-style home compared to a two-story house.

A multistory building has a compact design, and the top floor acts as insulation for the rooms beneath. The upper floor receives more sunlight, so you need to add 10% BTUs for such spaces and reduce the same for those on the ground floor.

8. Consider the Number of Heat Emitting Equipment in the House

Note that some household appliances like ovens, stoves, microwaves, dishwashers, and washing machines produce a lot of heat while in operation. Hence, rooms with such equipment require a higher cooling capacity. Add about 400 BTUs to your total figure if you wish to cool the kitchen and other rooms with heat-emitting equipment.

Contact the Pros

You need to know the exact BTUs required to cool your space to guide you in buying the correct AC size. When you choose a unit with the proper cooling capacity, it runs efficiently, lowering operational costs and maintains comfortable temperature across all rooms. If the calculations seem somewhat complicated, it’s a good idea that you consult a qualified technician. They have the right tools and hands-on experience to get precise dimensions of your space and analyze your house’s cooling needs to ensure that you get a suitable unit.

If you are still in doubt of the right AC size for your house and need professional help, reach out to One Stop Heating and Air Conditioning. We specialize in AC and furnace installations, repair, and maintenance services. Our company also provides duct cleaning and indoor air quality services in Sandy, UT, and the nearby regions. Contact our friendly team today to book an appointment and try out our incredible services.