What Are Air Conditioning BTU's?

Choosing the right air conditioner that meets your cooling needs can be easier if you have the correct information. When shopping for an AC, you will most probably come across the acronym BTUs, which stands for British Thermal Unit. It measures the power required to raise a pound of water temperature by one degree Fahrenheit at sea level. You need to match your house size to the BTU rating so that the AC can cool your house adequately. Read on to gain more insights.


When it comes to air conditioning, the BTUs tell how powerful a particular system is. It’s a measure of the amount of energy your AC uses to draw out hot air from a space and recirculate cooled air back. The higher the BTUs, the stronger the air conditioner.


Although a unit with higher BTUs has more power, you shouldn’t go for the biggest AC available. An AC with more BTUs than needed will cool your house faster, which may sound like a good thing, but it does more harm than good. The unit cycles on and off quickly, and with time, it overworks itself causing wear and tear.

Keep in mind that an air conditioner also removes moisture from your indoor air. When a unit turns on and shuts off shortly, it won’t draw out all moisture in the rooms efficiently. You will then begin to have high humidity issues like mold growth. If your AC recirculates mold spores into your house, they can trigger asthmatic symptoms and allergic reactions. High moisture content can also damage your house surfaces.

On the other hand, if you buy a unit with too few BTUs, it might not cool your house adequately. The AC will have to work harder and run for an extended period to maintain the desired temperature. This will translate to higher utility bills. Also, the AC will begin to wear out, calling for frequent repairs and eventually replacements sooner than anticipated.


Calculating the BTUs required for your air conditioning unit is quite simple. All you need to do is get the square footage of your home by measure the room’s length, width and multiplying them. If you intend to cool the whole house, do the same for all rooms. For rooms that open up to another, for instance, an open kitchen with no door to the living room, air freely circulates between the spaces. So you need to treat them as a single space while calculating square footage.

It’s worth noting that some homes are irregularly shaped. You need to divide the house into subsections and calculate the area. If you have a triangular home, multiply the length, width and divide the answer by two. For circular rooms, measure the distance from one end to the center to get the radius, then calculate the square footage. Remember to exclude spaces that you don’t necessarily need to cool, like the sunroom or garage. Sum up the square footage for all the rooms.

You need 20 BTUs per square footage to cool your house adequately. So, multiply your total square footage by 20 to get the approximate size of AC required for your house. Generally, a room of 150 square feet requires an air conditioner of around 5,000 BTUs. An AC of 9000BTUS suits a 400 square feet room, while 14,000 BTUs is ideal for a 700-square-foot space. If you intend to cool a large room or about 1,400 square footage, you can opt for an AC with 23,000 BTUs and 36,000 BTUs for a space of 2,700 square feet.


You should also consider other factors besides the rooms’ square footage to choose the right AC size for your house. Calculating BTUs based on square footage works for rooms with a standard ceiling height of 8 feet. If you have higher ceilings than this, add 10% to your calculated BTUs per room. Note that high ceilings increase the volume of air that needs cooling, so you might need a slightly powerful AC.

On the other hand, your home location will affect the BTUs required for your unit. If you live in warmer regions, your air conditioner will need to work harder to maintain comfortable temperatures. Therefore, people living in warmer climates should add between 10% and 20% BTUs in each room.

Take into account the number of people in a room at a particular time. Note that the human body dissipates a lot of heat, which increases the volume of air that an AC needs to cool. The general square footage calculations account for two people in a room. If you have more than two people in a room, add around 600 BTUs for each extra person.

Your unit will have to work harder to cool rooms that directly face the sun than those shaded. Add 10% cooling BTUs for such spaces. However, if you keep your windows covered with curtains or blinds most of the time, you can lower the BTUs by 10%.

The design of your house also affects your cooling needs. A more compact home layout will need an AC with lower BTUs. If your house has several wings, then it has a large wall area that can contribute to cool air loss, compared to a multistory home. If you have a two-story house, you will need less power to cool the ground floor. However, the top floor will receive more sunlight. Add 10% BTUs for rooms on the top floor and reduce the same for those on the lower floor.

Appliances such as washing machines, ovens, and microwaves generate heat while in operation. This contributes to an additional workload for the air conditioner unit. Therefore, add 400 BTUs to the amount calculated if you wish to cool the kitchen or other areas with heat-generating appliances.

A well-insulated home requires less power to cool. Gaps between your windows, doors, and the floor lets out conditioned air, so you will need more energy for sufficient cooling. Most old homes are less insulated, and they may require higher air conditioner BTUs than newer houses.


When choosing an AC for your house, it’s vital that you select one with a suitable cooling capacity. This way, you will save on energy and make your home comfortable to live in. The above piece should guide you through calculating the number of BTUs needed to cool your house. If you still can’t figure it, it’s a good idea that you consult a professional. AC installation is also a complex task, and only experienced technicians should handle it. A professional has the right tools and extensive knowledge to complete the installation task safely. They will also assess your ductwork’s compatibility to ensure that your AC runs at optimal performance.

If you need professional AC services, get in touch with Air Patrol Air Conditioning. We specialize in air conditioners and heating system installation, repairs, and maintenance services. Our company also offers indoor air quality and HVAC performance audits in Dallas, TX, and the nearby region. Call us today and request any of our services.