How Big of An Air Conditioner Do I Need?

"How big of an air conditioner do I need?" is an age-old question every homeowner asks. Here, the HVAC experts at Comfort Specialists, Randolph's top HVAC contractor, give their professional take on keeping your home perfectly chilled.

Understanding BTU and SEER Ratings

Before answering the question "how big of an air conditioner do I need?" you need to understand the metrics worth measuring. While the actual size of your AC unit does factor into its cooling ability, its Seasonal Energy Efficiency Ratio (SEER) and British Thermal Unit (BTU) ratings are more important.

BTUs measure how much warmth your air conditioner will remove in an hour of constant operation, measured in tons. For example, a one-ton cooling capacity has 12,000 BTUs, and residential units can reach up to five tons.

On the other hand, SEER ratings measure how effectively an AC unit cools a space based on how much energy it consumes. The average SEER rating is 16, but some systems reach as high as 22. SEER ratings don't impact an AC unit's pure cooling ability, but a higher-rated system will save you money and power during operation.

Traditionally, a larger-size air conditioner will have better BTU and SEER ratings than a smaller one. Still, these are the metrics you want to analyze when asking, "how big of an air conditioner do I need?". Larger doesn't automatically mean better.

For an Individual Room

Now that you know what to look for in an AC system, we can finally answer the question, "how big of an air conditioner do I need?" starting with window-mounted and portable units cooling isolated rooms.

You can cool individual rooms reliably with a smaller, less powerful air conditioner since they have lower square footage than spacious living areas. For example, the average bedroom is around 300 square feet and, as a rough estimate, only needs a 6,000 BTU (half-ton) system to cool, while entire homes require nearly double the power.

Of course, you must measure the space you need to cool before installing an air conditioner. The rule of thumb is that you need 20 BTUs for every square foot, and you should avoid exceeding that number for reasons we'll examine later.

For an Entire House

Most people have central air conditioning units rather than portable or window-mounted ones, and for those, you may wonder how large of a unit you need to cool your entire home adequately.

You can follow the 20 BTUs per square foot for central air conditioning. However, as a shortcut, most HVAC experts agree that you need a 1.5-ton (18,000 BTU) unit for a 1,000-square-foot space, a 2-ton unit for a 1,500-square-foot home, and one additional ton for every 500-square-foot increment. Remember that your area's average climate also plays a role in that average since you won't need as much cooling strength to chill a home during mild summers. 

If you follow the guide above, you can subtract one ton from the estimate if you live where the warm season rarely exceeds triple-digit temperatures, like New Jersey. So, rather than needing a 2-ton unit to cool your 1,500-square-foot home, you'll likely only need a 1-ton system.

Why The Size of Your Air Conditioner Matters

Now that we've answered the question, "how big of an air conditioner do I need?" we can break down why properly-sized units are crucial to adequate cooling. Let's start with what your life will look like with an undersized system.

Air conditioners that are too small for your living space will have to run constantly to get your home to the desired temperature. Even then, they won't have enough strength to make a noticeable impact. Unfortunately, that means you'll spike your energy bills to overwork and eventually wear down an AC unit that can't generate enough cold air to fill the area.

Most people hear this and buy the biggest AC system available to avoid poor cooling and wear and tear, but oversized air conditioners have as many issues as undersized ones. Giant air conditioners will get your home to your desired temperature within minutes, shut off, and power on moments later when the chilled air fades. Unfortunately, that rapid cycling wears down AC systems quickly, and they'll break within months if you don't move them to a larger area. 

Get in Touch

 If you're still asking, "how big of an air conditioner do I need?" or want to learn more about split air conditioners and their benefits, call Comfort Specialists at (973) 490-4881 to speak to a professional or schedule a service.