When in the market to purchase an air conditioner, the first question that comes to mind is – What size air conditioner do I need?
Whether upgrading your existing air conditioner or buying a new one, either choice is a significant investment.
Buying the wrong air conditioner unit can lead to issues much earlier than anticipated, leading you to regret your purchase.
In this brief guide, we will try to elaborately answer the common question most homeowners have when purchasing an AC unit: What size air conditioner do I need?
How to Size Your Air Conditioner
The size of an air conditioner is measured by its cooling capacity, which is ideally British Thermal Units (BTUs) or British Thermal Units per Hour (BTUh).
For example, a one-ton air conditioner unit removes 12,000 BTUs of heat in an hour.
In other words, an air conditioner needs around 20 BTUs to cool an indoor living space.
Why Does AC Size Matter?
There are numerous reasons as to why you need to research before buying a new air conditioner. A primary reason is that a smaller unit won’t be able to optimally cool its designated area.
It will become a bigger problem during hotter days, when the AC will struggle to keep the internal environment cool. As a result, some pockets of the indoor area won’t be evenly cool.
In the end, the smaller air conditioner will work overtime to achieve the desired temperature and eventually wear out faster than its expected lifespan. It also leads to decreased energy efficiency and higher energy bills.
Similarly, a larger-than-necessary AC unit will wear out quickly because it will turn on and off frequently.
Due to increased capacity, it will cool the space, turn off, and turn on again to maintain the desired temperature. This unsteady pace of operation puts tremendous stress on the air conditioner unit, eventually impacting its longevity.
Also, an air conditioner unit that’s larger than needed won’t be able to remove humidity from the air efficiently. It will lead to making the atmosphere colder and unpleasant and may even potentially cause mold.
What Size Air Conditioner Do I Need?
The air conditioner size you should ideally purchase depends on the square footage of the space it is meant for. However, these dynamics don’t always apply in the case of window air conditioner units.
When purchasing a central air conditioner, you’ll need the total square footage of your property. You can decipher that by multiplying the length of rooms by width rather than adding the areas of each room.
Once you have the total living area of your home, multiply it by 20 to know the amount of BTUhs needed to cool the entire space.
As per the recommendations by Energy Star, the following adjustments should be made to derive the best size –
- If the room is heavily shaded, the air conditioner capacity needed should be reduced by 10 percent.
- If the room is very sunny, the capacity of the air conditioner required should be increased by 10 percent.
- For kitchens, the capacity of the air conditioner should be ideally increased by 4,000 BTUs.
- If there are at least two people in the room at any given time, the capacity should be increased by 600 BTUs per head.
Air Conditioner Capacity by Home Size
| Home Size | AC Size (BTUs) | AC Size (Tons) |
| 600 to 1,000 square feet | 18,000 | 1.5 |
| 1,000 to 1,200 square feet | 21,000 | 1.75 |
| 1,300 to 1,400 square feet | 23,000 | 1.92 |
| 1,500 to 1,600 square feet | 24,000 | 2 |
| 1,700 to 1,800 square feet | 27,000 | 2.25 |
| 1,900 to 2,000 square feet | 30,000 | 2.5 |
| 2,100 to 2,300 square feet | 33,000 | 2.75 |
Window AC Sizing by Room Type
Generally, the cooling capacity of most window air conditioners revolves anywhere between 5,000 BTUs and 12,500 BTUs.
Calculate the size of the room through the method discussed above to determine the size of the window air conditioner unit you should buy.
Also, don’t forget to include the area of any adjoining rooms without doors, as the window AC unit will be cooling those rooms as well.
For your reference, here is how many BTUs are needed to cool the rooms of different sizes –
- Small Rooms of 150-250 Square Feet – 5,000 to 6,000 BTUs
- Medium Rooms of 250 to 350 Square Feet – 7,000 to 9,000 BTUs
- Large Rooms of 350 to 600 Square Feet – 10,000 to 12,500 BTUs
The general rule for calculating air conditioner size is that 20 BTUs are required for every square foot of space. This will give you a good idea of the cooling capacity you should look for.
If not, you’ll end up needing frequent AC repair service Dothan AL, unnecessarily adding to your expense.
Factors to Consider When Buying an Air Conditioner
While the primary factor to consider when purchasing an air conditioner is the total square footage of your residence, there are some other factors you must take into account.
It plays a vital role in ensuring the air conditioner’s performance and energy efficiency aren’t impacted negatively.
These factors include –
- Climate – Buy an AC unit with a higher SEER rating for warmer climates.
- Home Exterior – The type of material on your home’s exterior decides how much heat is reflected or absorbed. This influences the cooling efficiency required by the air conditioner.
- Sun Exposure – South, South-West, and West-facing homes receive direct sun exposure during the summers, which may benefit from AC units with 10 to 20 percent higher capacity.
- Insulation – Proper insulation helps keep cool air in and heat out during summers and vice versa in winters. Better insulation means improved performance and efficiency of air conditioners.
- Windows – The number of windows in your home and whether single, double, or triple-pane can make a massive difference in the AC unit’s efficiency in cooling the space. Single-pane windows are less energy-efficient, requiring higher AC units with higher tonnage.
- Ceiling Height – If your home has higher ceilings than the standard 9-foot ceilings, add 2-3 BTUs more than recommended when calculating the cooling capacity required for your living space. (The standard is 20 BTUs per square foot)
- Heat Generating Appliances – In kitchen and laundry rooms where the appliances generate heat, higher BTUs than the recommended 20 BTUs per square foot will be required for optimal cooling.
Conclusion
We hope this brief guide helps you choose the right-sized air conditioner for your residence. Not buying the right air conditioner can lead to added and unwanted expenses. It can also lead to inefficient cooling, decreased AC unit lifespan, higher energy bills, and an overall uncomfortable home.
If you’re still in doubt about what size air conditioner you need, trust our experts at Long Total Comfort to help you.
As a locally owned and operated HVAC company in Dothan, AL, we understand the needs of customers in our community well. We offer professional HVAC services you can rely on.
For more information or to schedule a free consultation, call us at 334-759-5170.