Finding The Right BTU: The Best Size Air Conditioner for Your Home

If you’re searching for a new air conditioner, then you’ve probably come across the term BTU rating. You may be wondering what exactly a BTU rating is and whether or not it even matters.

We’re here to tell you that BTU ratings do matter. Before purchasing any air conditioner system, you should first understand why the BTU rating is important and what rating you should be looking for.

Let’s dive into what BTU means, why it’s important, and which BTU rating is perfect for the room you’re looking to cool down.

What is a BTU, and what does it mean?

Before we go into more detail on BTU selections and recommendations, you first need to understand what BTU refers to.

BTU stands for British Thermal Unit and is used as a unit of measurement that tells you your system’s power. One BTU is equal to the amount of energy used to increase or decrease the temperature of one pound of water by one degree Fahrenheit.

For most air conditioners, the BTU rating or otherwise labeled as the capacity can be found on the unit's nameplate. Image source The Hull Truth

BTU is a common measurement for the cooling and heating capacity of equipment and will often be seen as a BTU rating. Whether it be a heater or window air conditioner, the higher the BTU rating the more powerful it is.

Why is BTU important?

The main function of an air conditioner is to remove heat from the air within your home and maintain a comfortable temperature and in doing so, the unit requires a certain amount of energy.

The BTU rating is important as it determines how much energy your unit uses and accurately indicates its potential output. For example, a room air conditioner with a BTU rating of 12,000 will have the capacity to absorb 12,000 BTUs of heat from your home every hour.

The BTU rating makes it easier to compare different models and find the appropriate sizing. The higher the BTU rating, the more efficiently a system can change your temperature.

BTU recommendations based on room size

When it comes to selecting the best HVAC system for your home, size does matter. If you choose an air conditioner that’s too small, it will struggle to reach the entire space. On the other hand, if you select an AC that’s too big, you’ll be wasting energy and have inconsistent cooling.

Finding the right size air conditioner and BTU range will allow you to efficiently cool your home and save on energy costs in the process.

To find the right BTU rating for a particular room, you can simply multiply the square footage by 20. This will give you an approximate BTU recommendation. For example, if we use this method on a 12x12 room, we would multiply the square footage by 144 by 20. This would provide you with a BTU recommendation of 2,880 for a 12x12 room. 

Below is a table where you can see your air conditioner’s recommended BTU rating based on the square footage of the room.

Factors to consider when selecting a BTU rating

Size of the room

One of the more obvious determining factors when finding the appropriate BTU rating is the size of the room and the ceiling height. A larger room will have a greater volume of air that needs to be kept cool and therefore require an AC unit of a higher BTU rating and cooling capacity. A small room may only require an AC with a low BTU rating such as a portable air conditioner.

Knowing the size of your room and what BTU AC is appropriate is vital to ensure you have an effective system. If you were to install an insufficient AC, you can risk the unit overworking and leading to higher cooling costs.

Room insulation

The purpose of insulation is to regulate the flow and amount of heat within any given room. That’s why the level of insulation a room has will affect the size of AC you require.

For example, in a well-insulated room, you will be able to install an AC unit with a much smaller BTU requirement and lower cooling power to meet your air conditioning needs.

The insulation of a particular room doesn’t just refer to what’s between the walls, but also the construction material, window covers, flooring, and ventilation of the room. 

Number of windows

Windows can greatly affect the overall temperature in your entire house or a particular room. During the summer, the sun exposure coming through windows can cause temperatures to rise drastically within your home, making your AC work harder. Alternatively, heat is also able to escape due to airflow through the window pane.

The number of windows a living space or whole house has should be considered when selecting an AC unit and finding the appropriately rated BTU air conditioner.

Room uses

Your intentions for how the room or space will be used can have a major impact on the effectiveness of your AC unit and as a result, the size of the unit you require. For example, if you’re planning on installing an AC in the kitchen, then you may need to look for a higher-rated BTU unit compared to that of a living room. This is due to having several kitchen appliances that generate their own heat.

Dangers of oversizing your air conditioner

When purchasing a new central air conditioner, you may be thinking that bigger is better, but that is not the case. Oversizing your air conditioner can cause a wide variety of problems.

Here are just some of the problems you could experience from an oversized AC unit.

Shorter, more frequent cycles

Unlike an appropriately sized air conditioner that will gradually cool down your home, an oversized AC unit is less energy efficient and will rapidly blast your home with cool air. This will prompt your AC to start up and shut down in quick succession, which is often known as short cycling.

Short cycling can have a major impact on your AC unit and results in unnecessary wear and tear, without reaping any benefits.

Higher cooling bills

You might think that an oversized air conditioner will cool your home down faster and therefore have to run less frequently, resulting in the system using less energy. However, this is far from the truth.

Due to oversized air conditioners running short cycles, several of their components are having to be powered up and shut down more than units that cycle correctly. This leads to the AC needlessly using energy and giving you even higher energy bills.

Increased humidity levels

With the right size air conditioner in your home, the system can run long enough to control the humidity levels easily. However, if you were to run an oversized unit with too large a BTU cooling power, the system’s short cycles will not allow enough time for the humidity to be sufficiently reduced.

The uncontrolled humidity levels can lead to several issues with both your home and your health, including the growth of mold, damaged paintwork, and deteriorating furniture.

Shorter lifespan

The average air conditioner unit should last between 15 to 20 years if used correctly and with the proper amount of maintenance. However, oversized AC units will have a much shorter lifespan. 

The short cycling of an oversized unit will cause many components to be regularly overworked, which can damage your AC and result in increased repair costs.

Selecting a BTU rating

As we mentioned previously, selecting the right BTU rating is so important to ensure you get the most out of your AC unit. Select a rating that is too high, and you could suffer higher cooling bills and increased humidity levels. Select a rating too low, and your AC won’t be able to effectively maintain the temperature of the room.

When selecting your ideal BTU rating you should consider a number of factors and not rely solely on the size of your room as a guide. Factors such as the room's use and the number of windows can play a big part in your selection of AC.

Seeking the help of a professional is also a useful approach to getting an AC BTU recommendation. With a quick home inspection, an HVAC technician will be able to tell you exactly what BTU rating is appropriate.