Which is More Efficient: AC Window Units or Central Air?

June 18th, 2015 by admin

It’s an age-old question: Which is more efficient, AC window units or central air systems? According to the U.S. Department of Energy, air conditioners use about 5% of all the electricity produced in the United States. Each home that uses an air conditioner produces around 2 tons of carbon dioxide and releases it into the atmosphere — that’s just about 100 million tons of carbon dioxide nationwide each year. These stats prove that when choosing between window units and central air, your decision should take both financial and environmental concerns into account.  

Window UnitCentral Air

Energy Efficiency

One of the best ways to determine a cooling system’s efficiency is by finding out its Energy Efficiency Ratio (EER). In order to be rated energy efficient, central air systems must receive an EER of at least 12, while window units only need to score a 9.2 to be certified by Energy Star. While many specific AC window units have higher EERs, central air systems generally tend to score higher in energy efficiency.

In addition to EER, a system’s Seasonal Energy Efficiency Ratio (SEER) examines energy usage over various temperatures and seasonal conditions. This ratio can only be applied to central air systems, which can be set to various cooling levels, unlike window units, which are generally either turned on or turned off. SEER scores can help you determine which central air system is most efficient for your home.

Weighing the Options

Window units do have certain advantages. Unlike central air, window units:

  • Do not require air to travel through ducts. When air travels through ductwork in a central air system, it can gradually warm and leak out through seams.
  • Are turned off more often. Because central air is such a quiet and unobtrusive system, it is possible to forget to turn it off when it does not need to be in use. Many people are more likely to turn off their window units, which are more visible and generate more noise, than their central air systems.
  • Can cool just a single room. This is more efficient than cooling every room in your home, even the ones you rarely use.

But central air is adapting to be even more efficient and competitive. Many central air systems now:

  • Use sensors to tell when spaces are unoccupied. This allows the system to cool the house only while people are home.
  • Divide a house into sections. These separate areas can then be set to different temperatures.
  • Dehumidify much more efficiently than window units. Central air is more efficient when it comes to dehumidifying, and can dehumidify a space to a point at which it feels much cooler than the set temperature.
  • Include more advanced technology. A central air system is much more complex than the On/Off system of a window unit. With this complexity comes more opportunity for customization.


Factors You Should Consider

Ultimately, the efficiency of window units compared to that of central air depends on how you plan to use your cooling system. You should consider:

  • The climate. Do you live in a humid area? Central air will be more efficient if you do. A dry, hot area? You might be able to get away with window units.
  • Your home’s insulation. Don’t just think about your walls — are your windows insulated? How about your attic? In the summer, the heat from your attic could leak down into your home. Without proper insulation, the appeal of window units lessens greatly.
  • Your lifestyle. Can you afford to keep all the rooms in your house cooled, or would it be more convenient for you to stay in one area of your home when the weather is hot? If you need to be comfortable everywhere in your home, then central air might be more convenient for you.

JK Mechanical can answer any questions that you have about the advantages of central air. Call JK Mechanical at 800-JKM-0028 to speak with a professional and find out whether a central air system fits your lifestyle.



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