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What Size Central AC Do I Need for My New Jersey Home?

Jun. 03, 2021
Central Air Conditioner

When buying a new air conditioner, you likely look at things like the brand, features, and price tag. But there’s one thing you can’t neglect—the size. Whether you’re installing a central air conditioner for the first time or replacing your current system, you need to know what size central AC to get for your New Jersey home. 

Unfortunately, there isn’t a one-size-fits-all solution to your central air conditioning needs. You probably have questions like: 
  1. How are air conditioners sized?
  2. Why does the size of your air conditioner matter?
  3. Why should I avoid using a rule-of-thumb estimate?
  4. What goes into an AC size calculation?
  5. What should I look for in a professional HVAC technician? 
In this blog, we’ll answer all of your questions and explain why proper AC sizing is essential.

Ready to find out what size central AC you need for your NJ home right now? Contact Air Experts, Inc. to get a free in-home estimate for AC installation services. 

Question #1. How air conditioners are sized

Air conditioners are sized according to how much heat they can remove from your home in an hour, measured in BTUs (British Thermal Units). The bigger your AC is, the more BTUs and the more heat your AC can remove from your home. 

Typically, New Jersey homes need air conditioners that have a BTU output ranging from 18,000 - 60,000. For context, one BTU is approximately the same amount of heat produced by burning one match. Therefore, an AC with a BTU output of 18,000 can remove 18,000 matches’ worth of heat from your home in an hour. 

Now, don’t get confused if some resources size ACs by “tons” instead of “BTU output.” Both are just ways to measure your BTU output. One AC ton equals 12,000 BTUs.

Long story short: When you’re wondering what size central AC you need for your NJ home, you’re really asking how many BTUs or tons your system needs to have. 
 

Question #2. Why the size of your air conditioner matters

The incorrect size for your AC can impact everything from energy efficiency to your system’s lifespan. Whether the system is oversized or undersized, the same issues can occur. 
 

The effects of an oversized AC

When an AC is oversized, it cools your home too quickly … which is indeed a bad thing. Why? 
  • Dehumidification: The longer an air conditioner runs, the more moisture it can absorb from your home’s air. But if your AC is oversized, it will quickly come on to cool your home in a blast and then shut off, which doesn’t dehumidify your home well (which can be a nightmare as a New Jersey homeowner in the summer).
  • Energy consumption: Sure, your AC might meet New Jersey’s energy standard with a SEER rating of 13 or more. But, an oversized AC also consumes a lot more energy. The AC consumes more energy because it eats up a lot of “juice” when it starts up. And when an oversized AC turns on, shuts off, then turns on over and over again, it consumes energy with each start, causing higher energy bills.
  • Life cycle: An AC that’s constantly turning ON/OFF (called “short cycling”) strains internal motors/components, resulting in frequent repairs and a lowered lifespan.

The effects of an undersized AC

When an AC is undersized, it runs nonstop but still struggles to keep you comfortable and can cause similar problems to an oversized AC. 
  • Cooling: An undersized AC can’t remove heat as fast as the heat is entering your AC system. Having a lower cooling capacity means your AC may not be able to keep you comfortable, even though your unit is running even longer than usual to meet your thermostat setting. 
  • Energy consumption: ACs that are constantly running drive up your energy bills due to long run times.
  • Life cycle: A continuous running AC quickly overworks itself, which means more repairs and (you guessed it) lowered lifespans. 
     

Question #3. Why you need to avoid using a rule-of-thumb estimate

If you’re doing a quick online search of the central AC size you need for your home, you’ll likely come across generic AC-sizing suggestions like this:
  • 1,000–1,200 sq/ft= 21,000 BTUs
  • 1,200–1,400 sq/ft= 23,000 BTUs
  • 1,400–1,500 sq/ft= 24,000 BTUs
  • 1,500–2,000 sq/ft= 30,000 BTUs
  • 2,000–2,500 sq/ft= 34,000 BTUs
  • 2,500–3,000+ sq/ft= 42,000–60,000 BTUs
But, you should avoid relying on square footage charts and lists like this when trying to size your AC. Square footage is a factor, but it’s not the only factor. 

Looking only at square footage when sizing your AC is what we call the “rule-of-thumb” estimate. If you use the vague rule-of-thumb estimate, you’ll likely end up with the wrong size—and money wasted. 

Your current system size might have been based on a rule-of-thumb estimate, depending on the contractor you or the previous homeowners hired for the install. As a result, you should get your new AC correctly sized even if you’re just replacing your current system. 
 

Question #4. What goes into an AC size calculation

Professional HVAC contractors determine the AC size you need with a “cooling load calculation,” also known as the Manual J Heat Load Calculation. This calculation determines how much heat your AC needs to remove from your home per hour to maintain a consistently comfortable temperature.

In other words, a cooling load calculation tells you the BTU output you need from an AC. A cooling load calculation takes several factors into account, including:
  • Square footage 
  • The geographical location (e.g., New Jersey homes have different sizing guidelines than Florida homes)
  • The direction your home faces 
  • How many windows your home has (and what kind of windows)
  • Number of doors in your home
  • Whether your home has carpet or wood flooring
  • How many people live in the home
  • Your home’s insulation levels
  • Whether your ductwork is located inside or outside
  • And much more
As you can see, your AC size could change as your home changes (e.g., adding a room, insulation, etc.), which is why it’s a good idea to have a technician perform a sizing calculation with each AC installation. A professional loading calculation ensures you won’t end up with an air conditioner that’s oversized or undersized—and the increased energy bills as a result of improper sizing.
 

Question #5. What to look for in a professional HVAC technician

Again, you want to look for a professional HVAC technician who will not use a rule-of-thumb method when sizing your central AC. Instead, you want a technician who will determine size using the cooling load calculation.

When looking for a contractor to install a new air conditioning unit, take a look at the following:
  • Reviews: Are they reputable and experienced? Do they actively encourage their customers to leave reviews about their experiences?
  • Their website: Do they provide a free estimate tailored to your home’s needs? Do they mention the importance of AC sizing? 
Before hiring someone for the job, ask them how they determine AC size. If the contractor sizes your AC based on only square footage, consider moving on to another who uses the proper loading calculation.
 

Trust Air Experts to get the right AC for your home

If you’re ready to learn what size central AC you need, look no further than Air Experts. Our AC installation services all begin with a free in-home estimate, so we’ll help you get the correct air conditioning size for your home. 

We’ve been helping homeowners throughout central Jersey with all their heating and cooling needs since 1994. So, rest assured, we’ll help you get the best deal for your new investment.