What Size Air Conditioner Unit Do You Need?
With summer quickly approaching, you might be wondering if your air conditioner will get you through the hottest months of the year. You need a cooling system that’s the right size for the space, uses the right amount of energy and keeps your whole house comfortable.
If you’re just replacing an old unit, the size you used previously is the best place to start. It is also important to consider the model and energy efficiency of any AC unit you might utilize. This guide can help you figure out the proper cooling capacity for your home air conditioner.
Why Is It Important to Choose the Right Size Air Conditioner?
Selecting the correct size AC unit for your home is essential for sufficient, cost-effective cooling.
An air conditioner that is too small will:
- Run too often and for long periods, often requiring more maintenance.
- Leave your home too warm and create hot or cold spots.
- Supply insufficient airflow to keep your home at a comfortable, consistent temperature.
An AC unit that is too large for your home will:
- Run for short periods without dehumidifying, potentially encouraging mold or dust mites and causing structural damage.
- Decrease the system’s life span and raise energy costs with frequent starts and stops, requiring more maintenance and energy.
- Run loudly compared to a properly sized system, which should be barely noticeable.
How Are Air Conditioner Units Rated?
AC units are typically rated by BTU production and by the SEER rating. While BTUs measure the cooling capacity per hour of an air conditioner, the SEER measures its energy efficiency. Typically, the bigger the cooling system, the higher the BTU and the lower the SEER.
To convert BTU to tons, keep in mind that there are 12,000 BTU in a ton. Room air conditioners have a cooling capacity as low as 5,500 BTU per hour. The cooling capabilities of our DIY ductless mini-split systems range from 12,000 to 34,500 BTU per hour. Our Signature Series central air conditioners can go up to 60,000 BTU per hour.
Use these factors to determine if you may need a more significant BTU-rated AC unit than typical:
- Your ceilings are higher than 8 feet.
- You live in a warmer climate.
- You’re putting the unit in direct sunlight.
- You have little insulation.
- You have large windows in the room.
- You have a large, open-concept house.
This number affects the sizing for your air conditioner because of its energy expenditure in one hour. You would need an AC unit with a smaller BTU for a compact room so you don’t use too much energy to cool your space. A cooling system with a larger BTU for a large room will also adequately cool the area.
A BTU, or British thermal unit, measures the energy that your air conditioner uses to cool the room. When you count calories, you’re measuring how much energy you’re putting into your body and how much you need to burn to maintain your weight. In the same way, when you measure BTUs, you estimate how much energy your appliance can process to regulate the temperature of your home.
2. SEER Ratings
While it does not measure the size of the air conditioner, the seasonal energy efficiency ratio (SEER) number measures how efficient a central AC unit is over the summer. The higher the SEER rating, the more efficient the product.
You might also see information about the energy efficiency ratio (EER), which measures how efficient a cooling system will be at a certain outdoor temperature. The SEER more accurately reflects the overall efficiency of a unit seasonally, but the EER will tell you how the AC works during peak operations.
Energy-efficient appliances have a yellow tag that displays their SEER rating. To have a higher energy efficiency for your AC unit:
- Schedule preventative maintenance at least once a year.
- Change your air filters monthly to protect against debris.
- Set a programmable thermostat to manage comfort correctly.
- Seal and insulate windows and ducts, to prevent air leaks.
While appliances with higher SEER ratings have a higher upfront cost, you’ll save money on energy bills each month with an energy-efficient cooling system. Companies also offer rebates on their energy-efficient products as incentives to purchase them.
The minimum SEER rating for most of the country is 13. If you’re in a state that gets warmer summer climates, the score is 14, so your home could save energy and money. Some of our air conditioning units have a SEER rating of up to 23.
3. AC Tonnage
What is AC tonnage? AC tonnage measures how much heat the unit can transfer in one hour. Each ton of refrigeration can cool 12,000 BTUs each hour. Learn how to calculate air conditioning tonnage by multiplying the unit’s tonnage by 12,000. Using this formula:
- A 2-ton unit can cool 24,000 BTUs per hour.
- A 3-ton unit can cool 36,000 BTUs per hour.
- A 4-ton unit can cool 48,000 BTUs per hour.
What Size AC Do You Need?
Figuring out what size air conditioning unit you need is as simple as taking a tape measure and looking at the length, width and height of your living space. You could also call in a professional to help you find the air conditioner you need to cool off the room. Use these calculations to choose the right size for your AC system.
1. Square Footage AC Calculator
How many tons of AC do you need per square foot? To figure out the square feet within your room, measure the length and width of the room. Use these tips to calculate the area of your living space:
- In rectangular and square areas, multiply the full width by the length.
- In triangular places, use the same formula but cut it in half.
- If you have an abnormal room shape, divide the room into rectangles, triangles and squares and use the previous equations. Add the total square footage of all the various dimensions.
2. AC BTU Calculator Chart
How many BTUs do you need? After you’ve measured the dimensions of each room in the home where you want to put an air conditioner, you can figure out what you need based on the BTU conversion chart.
Find your room’s square footage on the left column, and then use the right column to get the proper capacity for the AC unit. The cooling capacity is measured in BTU per square foot. A 3-ton AC unit can cool a small house, while a 5-ton AC unit can cool a bigger home.
3. Make Adjustments as Needed
While this process seems pretty straightforward, you also need to make some adjustments based on these factors:
- Decrease the cooling capacity of the unit by 10% if the area has shade.
- Increase the cooling capability by 10% if the area is in direct sunlight.
- Increase the total by 600 BTUs for every extra person in a room if the room is occupied by more than two people regularly.
- Increase capacity by 4,000 BTUs if the air conditioner is in the kitchen.
4. Heat Zone HVAC Calculator
Throughout the world, various climate zones indicate the heat that each region experiences. Contractors and builders use climate zones to get the most energy savings in a home. Here are the heat zones in the United States to determine which one you live in and how it affects the size of your AC unit:
- Hot-humid: You are in a hot-humid climate if you live in the southeastern part of the United States.
- Mixed-humid: This climate consists of the central-eastern region of the country.
- Hot-dry or mixed-dry: You may feel hot and dry air if you live in the southwestern part of the United States. The difference between hot-dry and mixed-dry is that mixed-dry sees less warm temperatures throughout the year.
- Cold or very cold: In the northern part of the country, you get colder days more frequently.
- Marine: On the west coast, the weather is pretty consistent, but you’ll see rain each month.
These climates got their names based on the amount of precipitation and the frequency of warmer temperatures compared to the rest of the country. You could figure out what type of air conditioning system you need depending on how often you have sunny days in your region. A house in a hot-humid climate would need a more powerful AC unit than one in a cold part of the country.
5. Bring in a Professional
A professional HVAC contractor will know how to size your cooling system for your living space. They can give you an in-house estimate and explain how much it would cost to install an AC unit that would work best for your living conditions.
If you’re checking out our products, you could contact an expert from MRCOOL. We offer free lifetime tech support on all of our merchandise, so if you’re ever stuck, just give us a call. After years of experience, we know where our products fit best, especially our DIY® Multi-Zone, which can cool the whole house.
Other Important Factors to Consider
While size is a crucial part of choosing an AC unit, you should consider other factors, including:
- Type: Whether you’re sizing a mini split unit or considering a central split system, your family’s needs, such as scheduling temperatures or creating zones, determine the best type of air conditioning for your home.
- Durability: While a properly sized air conditioning unit is essential, you also need a durable system from a reliable manufacturer to ensure the unit lasts as long as possible.
- Maintenance requirements: Ensure you know what maintenance you’ll need to keep your AC unit in good condition, from replacing filters to scheduling professional inspections and repairs.
- Home and insulation: If you own an old house with original or dated insulation, raise the BTUs you need from your AC unit by at least 30% to account for more heat transfer.
- Air quality: The correct air conditioner should dehumidify your space, so look for a unit with a filter capable of keeping dirt, germs and odors out of the air and away from your unit.
- Ceiling height: Ceilings over the standard 8 feet generally require air conditioning units with 20% more BTUs to sufficiently cool the area.
- Fixtures: Everything from windows that let in direct sunlight and hot air to kitchen appliances that make your space warmer affects your air conditioner’s performance.
Find the Right Air Conditioner for Your Home
MRCOOL manufactures reliable, high-efficiency HVAC systems to keep your home comfortable year-round. View our map to find a MRCOOL dealer near you. You can also connect with a service technician or installer. If you have any questions about our products or what size air conditioner you need for your home, please contact our team.