All You Need to Know About Air Conditioner Sizing
When buying an air conditioner, there are many considerations one has to keep in mind: efficiency ratings, inverter technology, reversibility, Energy Star certification, and a few more. But perhaps one which is the most important is the air conditioner sizing or cooling capacity.
Wondering, what size air conditioner do I need? You’ll know exactly the right size for you in this article. It’s also vital to understand what cooling capacity is, how it affects air conditioner operation, and how to choose the right sized air conditioner for your room. Let’s go over these questions and help you get the best air conditioner for you!
If you’re all set to make an air conditioner purchase, you may also be interested in smart AC controllers. You can make any sized aircon or type (mini-split, window, portable) smart! They work like a smart thermostat for your air conditioning unit and allow you to control it with your phone. Moreover, you can enable intelligent features such as geofencing, weekly scheduling, comfy mode, and more!
What Is Air Conditioner Cooling Capacity?
When talking about an air conditioner’s cooling capacity, we mean the amount of area an air conditioner can effectively cool. Properly sizing any type of air conditioner according to the area to be cooled is very important. This is not only for achieving a comfortable environment but also to cut down your energy costs.
But first, we have to understand how the cooling capacity of an air conditioner is measured. The most common way in America to measure an air conditioner’s cooling capacity is by noting the BTU’s/hr of the air conditioner.
What are BTUs? BTU stands for British Thermal Unit. In technical terms, it is the amount of heat required to raise the temperature of one pound of water by one Fahrenheit. All you need to know is that a higher BTU rating of your air conditioner means that it is capable of cooling a larger interior space.
What Air Conditioner Size Do I Need?
Wondering how to size an AC unit correctly? Here are some important considerations to keep in mind based on which you can determine the correct BTU requirement for you.
While the general calculation used as a rule of thumb to determine your air conditioning sizing needs is the size of your room, extremely accurate determination of your air conditioning sizing needs would need to include a whole host of other factors. These can include wall insulation, wall material, the volume of air coming into the room compared to that exiting, the temperature difference between the inside and outside, humidity levels throughout the year, location of the room in the house, and flooring material, and much more.
Let’s look at some of the major factors and how they can affect your air conditioning requirements.
To perform air conditioner sizing for your space, you first need to calculate the size of your room. This is pretty straightforward: simply multiply the length and width of your room to get the space’s area to be cooled (or heated).
If your room is not a perfect rectangle or square, you can make your task easy by dividing the room into separate sections to calculate the precise size. Here is a nifty room size calculator to help you out.
The next part is the tricky one. You need to calculate the right number of BTUs that would be suitable for your room. As a general rule of thumb, you can multiply your room’s total area with 25 to get the BTU required.
This number is a safe figure and caters to different daily weather conditions such as rain and humidity. For example, a room with a length of 10 feet and a width of 14 feet has an area of 140 square feet. Multiply this number by 25 to get the minimum cooling capacity needed for your air conditioner, which comes out to be 3,500 BTU. That is the air conditioner cooling capacity you should be aiming for.
Below is a handy chart, based on the recommendations by Energy Star, to get an idea of the size of the air conditioner you need for your room size.
If you look ahead of the safe figures, your cooling capacity may slightly differ based on your room conditions. If sunshine falls on your room all day, your cooling capacity may need to increase by 10%, or reduce by 10% if the room is in a shaded area. You may need more BTUs if many people occupy the room. Read on to discover more about this in the ‘important considerations’ section.
These calculations only serve to provide a rough estimate of the minimum cooling needed. Actual required cooling power is dependent upon many other factors such as thermal conductivity of the walls and building materials, temperature differences, humidity, amount of airflow in the room, and much more.
Although we have sized air conditioners according to a room’s area, we have so far not considered the height! The height of a room also plays a part in determining how effective a certain cooling capacity is.
Rooms with a very high ceiling will have a much larger amount of air that needs to be cooled. Moreover, wall mounted mini-splits are more effective at cooling all the air present in a room as compared to window-mounted air conditioners. This is because a wall mounted mini split is positioned much higher on the wall, and as we know, warm air rises. The warm air is hence cooled more effectively with a mini-split than a window air conditioner.
Wall insulation is a thermally non-conductive material embedded into the walls of the room to help keep it cool in the summer and warm in winters. This is possible because wall insulation is a good thermal insulator, meaning it does not conduct heat efficiently, thus preventing loss of cooling in the summers.
If you have good wall insulation, your air conditioning requirement would be less, since the room will not be losing heat quickly. If you do not have insulation, the room will get warm very quickly after you turn the AC off, so you need to have it running for longer periods and on higher power settings.
Higher humidity means more need for air conditioning. An air conditioner not only works to provide cool air in the room but also works as a dehumidifier. Removing the excess moisture from the air will immediately make a marked difference in the temperature you feel, and make the environment more comfortable.
If you live in an area with a high moisture content year-round, it’s better to invest in some extra capacity for your air conditioner.
Think of Colorado vs. Florida. Depending on a region’s general climate and humidity levels, the same sized houses will have different air conditioning requirements. Houses in cooler or dry regions require a smaller air conditioner size than houses in warmer and humid regions.
Does sunlight fall directly over your house, or you have trees around protecting your space with shade? Energy Star recommends increasing your BTU requirements by 10% if the room in which you plan to place an air conditioner lies in a shaded area. Your cooling capacity will increase by 10% if direct sunlight falls over the room.
The type of room in which you plan to place your AC also affects cooling capacity. Your required cooling capacity will increase by 4,000 BTU if the air conditioner is used in the kitchen.
The type of windows and the number of windows in a room can affect your air conditioner sizing requirements. Energy-efficient windows such as low-e or double-pane windows can reduce the number of BTUs required.
Some windows can be a source of energy loss, and unless treated or fixed, they can increase your cooling capacity or BTU requirements.
Windows also account for incoming light. While natural light is an excellent source to brighten your room, it also a source of unwanted heat gain during hot weather. Numerous windows can add as much as 10% to your BTU requirement. You can also prevent unwanted heat gain from windows by energy-saving treatments such as tinting, etc.
Number of People
Energy Star recommends increasing the required cooling capacity by 600 BTU per person if multiple people are occupying the room for large parts of the day. Human bodies generate heat, making it vital to consider the number of people that a room will occupy at most times.
Why Air Conditioner Size Matters – What If I Go Too Big or Too Small?
You must be thinking, why not play it safe and go for a much greater cooling capacity than necessary? A large-sized air conditioner means more cooling and faster! Although this sounds ideal, there are a few problems with this sort of thought.
An air conditioner that is too large for the room will use up more electricity than required and result in higher energy bills. The extra cooling capacity is actually going to waste, which is detrimental to the environment and your bills!
On the other hand, an air conditioner that is too small will be insufficient for cooling. You won’t be feeling the desired cooling effect from the AC, and it will have to run at full power all the time. More energy will again be consumed without having the desired effect on the temperature.
Moreover, having an air conditioner that is larger than required can have another unfavorable effect. Air conditioners not only cool down the room but also serve to reduce the humidity in the room. An oversized air conditioner will cool down the room very quickly, and then turn the compressor off. But, the humidity in the room will not decrease at the same rate as the temperature. Hence, even though the room will be at a lower temperature, humidity can still make it very uncomfortable.
A walk around to this problem can be by using smart AC controllers such as the Cielo Breez Plus. With humidity-based triggers through “Comfy Mode”, you could set your air conditioner to operate to maintain a specific humidity level.
There are a few more ways to achieve your home’s ideal humidity levels, so be sure to check out this blog post.
Make the Most of Your Air Conditioner
By now, you must be on your way to locking down the perfect AC size that you need for your room! You can further make the most of your cooling capacity and energy efficiency by utilizing smart technology.
Smart ACs or smart AC controllers that can make any AC unit smart are excellent options to enhance your comfort and accelerate your energy savings. They allow you to control your AC from anywhere and set intelligent triggers. For instance, you can maintain your room climate at the temperature of your choice during the exact times that you require!
It is always a wise idea to properly size your room and choose an air conditioner that will suitably satisfy your room’s cooling needs. Now that you know how to size an air conditioner, you know that air conditioners that are too large for the room can result is electricity wastage, and those which are too small for the room will not cool the room to the required temperature. Consult the size charts given above for the perfect air conditioner sizing, and choose the best air conditioner for your space!