How To Choose the Right AC Size for Your Home
If it’s time to replace your home’s air conditioner, you might have an idea about the cooling unit type and brand that could work well for your home. Still, many homeowners overlook the importance of HVAC sizing. When it comes to air conditioning installation, going big isn’t always the best approach.
You’re not alone if you’re asking, “What size AC unit do I need?” Understanding the concept of air conditioning sizes goes beyond the physical size of the equipment you install. Several factors determine the ideal cooling load for a property. Before purchasing a new air conditioner, consult the guide below to learn everything you need to know.
Why HVAC Size Matters
Ignoring the size of your HVAC system will cause several problems for your equipment and household. The purpose of having an air conditioner is to maximize your home’s indoor comfort during the summer months. Installing an incorrectly sized air conditioner will jeopardize that.
When you don’t have the right HVAC size for your home, it means it has an insufficient or overpowered cooling capacity. If inadequacy is the problem, your equipment will struggle to produce the proper cooling output to keep each room in your house at comfortable temperatures at a consistent pace. As a result, some, if not all, of the spaces inside your residence will feel overly warm, stuffy, or humid despite the air conditioner running.
On the other hand, an overpowered air conditioner will not only provide even cooling but also impact the equipment’s energy efficiency. Due to its high cooling output, the cooling unit will constantly turn on and off, causing you to spend more on utility bills.
You also have to think about wear and tear. Most well-maintained air conditioners have a lifespan between 15 and 20 years. Still, frequently running the system or letting it short cycle for too long will cause its components to wear down faster. This problem can lead to frequent breakdowns, insufficient cooling, high repair bills, and the need for an air conditioner replacement sooner than typically necessary.
Air Conditioner (AC) Too Small
You might feel tempted to settle for an air conditioner that’s too small for your home to save on HVAC replacement costs or because you don’t know how to determine AC unit sizes. Though it’s reasonable for homeowners not to understand the intricacies of sizing air conditioners, you shouldn’t settle for cooling units simply because of the cost. You’ll end up paying more in the long run.
When an air conditioner is undersized, it’ll run all the time because its cooling capacity is too small to provide the output your home actually needs. Even when the air conditioner is on, your home will feel warmer than it should. This can directly impact your comfort, especially in the middle of summer or during heat waves.
The persistent running will wear down your equipment. If you are uncomfortable with your house’s indoor temperature, you might turn the thermostat down to chill the house faster or more evenly. Doing so will cause the system to stay on longer than it should, resulting in premature wear and tear on its components and inefficient energy use.
Air Conditioning (AC) Too Large
The answer to, “What size AC unit do I need?” isn’t to go bigger. That’s a common mistake homeowners make. A high cooling load is great if your home’s characteristics warrant a large HVAC size. If it doesn’t, you’ll still be uncomfortable.
When cooling capacities are too high, the air conditioner will quickly disperse chilled air throughout the home to reach the temperature setting on the thermostat. Yet, it’ll shut off quickly because it’s too good at its job. So instead of providing a steady cooling pace that delivers optimal comfort, the cooling system will constantly turn on and off or short cycle.
Short cycling is a problem because it’s not efficient. It creates uneven, inconsistent cooling, humidity problems, and drafts. It can also cause your energy bills to skyrocket because the air conditioner isn’t consuming energy efficiently.
Step 1: Find the Air Conditioner Type That Best Fits Your Home
Before you can answer, “What size AC unit do I need?” you must determine what type of cooling system will work best for your home. The three most common options include split-system cooling units, ductless air conditioning, and packaged air conditioners.
Many households have split-system air conditioners or central air conditioning units with an indoor air handler and outdoor compressor unit. These components work together to remove heat and humidity from indoor air and disperse them outside, leaving cooler air circulating throughout the house via ductwork.
Ductless air conditioners also have indoor/outdoor units, yet they don’t rely on ductwork to distribute air. Instead, these systems have one or more indoor units that disperse chilled air directly into different rooms or zones. Each unit has its own thermostat and climate control options, making ductless air conditioning excellent for households with varying cooling needs or a general lack of air ducts.
With a packaged air conditioner, you’ll need air ducts but not an air handler. All of the system’s components are inside the single outdoor unit including the condensing coil, evaporator coil, and compressor.
If you’re looking for the most economical way to cool a space that doesn’t accommodate central cooling or a room that stays warm, you might consider installing a window air conditioning unit. Answering, “What size window AC do I need?” is similar to sizing a cooling unit for a whole house but on a smaller scale. Window air conditioners will only cool one room at a time, but you still want to ensure the unit you choose is right for the space.
Step 2: Review Ratings for the HVAC Size You Need
Once you know what type of air conditioner you want to install in your house, you then must consider the type of rating you prefer for your new system. Ratings for air conditioners refer to their ability to consume and use energy effectively to produce a desired cooling capacity. In other words, you should consider HVAC brands, manufacturers, and models that offer decent ratings at reasonable prices.
It’s important to note that the higher the ratings on an air conditioner, the higher the price usually is for the equipment. That’s why it’s best to know more about energy efficiency ratings for HVAC; the information can help ensure you get the most energy-efficient system without exceeding your budget.
What Is a SEER Rating?
Seasonal Energy Efficiency Ratio or SEER ratings help explain an air conditioning system’s cooling capacity in relation to its energy consumption. The formula for determining SEER ratings is the system’s output divided by the total energy it uses over a typical cooling season. The less power a system uses to produce the desired cooling output, the more efficient it is.
SEER ratios are the maximum efficiency of air conditioners. The minimum SEER rating is 14 and can go up as high as 22 for some central air conditioning units. However, these ratings refer to energy efficiency under near-perfect conditions, so other factors in your home can impact your equipment’s performance.
What Is a BTUh Rating?
Another rating to consider is an air conditioner’s British Thermal Units per hour or BTUh rating. This rating outlines how much energy a cooling unit uses to eliminate heat from a building within an hour. Tonnage is the measurement for BTUh.
One ton of cooling capacity is the same as 12,000 BTUh. When reviewing the tonnage for a new air conditioner, you’ll see that the ratings are in 0.5-ton increments. Your community’s climate and your home’s square footage play direct roles in how much tonnage your new HVAC should have to cool your space effectively.
Step 3: Estimate the Right AC Size for Your House
You could use an AC size calculator online to help answer questions like, “What size AC unit do I need?” Unfortunately, they aren’t the best way to determine a house’s ideal air conditioner size because accurate calculations rely on multiple factors.
Still, you can get a general idea about the air conditioning size that’ll work best for your home if you know these characteristics of your property and household:
- Home square footage
- Type and quality of your house’s insulation
- Condition of your property’s ductwork
- How much direct sun exposure your residence gets
- Number of household members
- Features inside the house that can alter indoor temperatures like sunrooms and fireplaces
- Building materials for the house
- Number and usage of heat-generating appliances such as washing machines and dishwashers
- Number and quality of windows and exterior doors
- Local climate and average temperatures
Determining Air Conditioner Size
When asking, “What size AC unit do I need?” you need to know the general formula for calculating cooling capacity or air conditioning size, which is the length of a space to be cooled times its width. Then, you want to take that figure and multiply it by 25 BTU.
As a general AC size chart:
| Room Size | AC Size |
| 150 to 250 sq. ft. | 5,000 to 6,000 BTUs |
| 250 to 350 sq. ft. | 7,000 to 8,500 BTUs |
| 350 to 550 sq. ft. | 9,800 to 12,500 BTUs |
You can also measure AC size in tons. For example:
- A 1,000 sq. ft. home would need a 1.5-ton AC
- A 1,500 sq. ft. home would need a 2-ton AC
- A 2,000 sq. ft. home would need a 3-ton AC
- A 2,500 sq. ft. home would need a 4-ton AC
- A 3,300 sq. ft. home would need a 5-ton AC
Factors That Affect Air Conditioner Sizing
One of the most effective ways to determine which size air conditioner you need is with a Manual J calculation. Some experienced HVAC professionals use Manual J to calculate cooling capacities with greater accuracy than simply relying on the cooling load formula. It incorporates various factors that directly and indirectly influence indoor temperatures including the following.
Ceiling Height
Many people overlook ceiling height when calculating their ideal air conditioner size because the basic formula only deals with the length and width of rooms and the home’s total square footage. Yet, a house with tall ceilings in different rooms may need an air conditioner with a greater cooling capacity than a home with short ceilings and similar square footage.
Climate
Where you live will directly impact the cooling capacity of your new air conditioning system. Places with hot, muggy summers will use their air conditioners more frequently than people living in areas with moderate temperatures and low humidity. It’s best to consider a system with more powerful cooling power and a higher SEER rating to offset energy consumption.
Insulation
If your house has excellent insulation, it will keep heat out in the summer and retain warmth in the winter. As such, you might be able to size down your air conditioner.
Windows
The number, size, and quality of your windows determine how much sunlight will penetrate your home’s interior. A house with lots of windows, oversized windows, or drafty windows will need extra tonnage for effective cooling.
Sun Exposure
South-facing windows get plenty of direct sunlight, which can make it harder to cool a house’s interior. You can get a smaller AC unit if your home has less sun exposure.
Choose the Best AC Installation Company
Many factors and calculations go into determining the appropriate sizes for air conditioning. While it might be tempting to install a smaller unit to save money or a larger unit to maximize your home’s cooling comfort, not knowing the best AC size for your home can create more problems than they solve.
Are you still wondering, “What size AC unit do I need?” If so, turn to our professionals at Summit Air Conditioning, the top-rated HVAC contractor serving Las Vegas, Nevada. Our company has more than ten years of experience providing outstanding heating and cooling services such as air conditioner replacement, installation, and repair.
By committing ourselves to deliver stellar workmanship, five-star customer service, and customer education on HVAC equipment usage, we ensure each client’s satisfaction — call (702) 297-6411 for a consultation today.
