Window AC Units vs. Central Air Conditioning- which is more efficient?

It’s true, central air conditioners are significantly more efficient than window mounted air conditioners, having an energy efficiency ratio (EER) of 14 or 15 compared to window mounted ones, with an EER of about 10 or 11. However, energy efficiency and consumer behavior studies show that window AC units use less energy for cooling. If not properly installed and managed, central air systems are at risk to operating with blowers that circulate cooled air set too high, unsealed ducts that leak cooled air to the environment, control systems that extend operating times, and systems being oversized from specification. This results in a high-efficiency compressor and a low- efficiency duct and control system. When it comes to consumer behavior, people living in homes with central air conditioning tend to keep every room in the house cool, even unoccupied rooms, where people living in home with window-mounted air conditioners have a tendency to cool only the rooms they occupy at that time. Also, since window units are often noisy, users often remember to turn them off when they leave a room, while people with central air leave their AC systems on all day, even when the home is unoccupied.

Consumer behavior plays a major role when determining the efficiency of window-mounted air conditioner versus central air.

AC Tips:
• Buying a bigger AC Unit won’t necessarily make you more comfortable in the hot summer months. A room AC unit that is too big for the area it’s used to cool will be less effective and not as efficient as a properly-sized unit.
• If you have central air, don’t use the system’s central fan to provide air circulation, use circulating fans in individual rooms. You can usually do this by setting the “auto” mode on the fan, which sets the fan to shut off at the same time as the compressor.
• Consider installing a whole-house fan instead of air conditioning. They help cool your home by pulling cool air through the house and exhausting warm air through the attic. They are most effective when used during cooler times of the day, allowing you home to stay cooler through the hottest times of the day without having to turn it on.
• If you’re looking to replace an old AC unit, as always, consider buying an Energy Star model. Room units are 10% more efficient and central units are 14% more efficient than standard models. In particular, look for an Energy Star unit with an Energy Efficient Ratio (EER) of 10.7 or more.

As part of our Whole Building Assessment (Level II Energy Audit), we  provide high quality heating, ventilation and air conditioning audits to help you reduce your HVAC costs.  From the primary mechanical equipment downstream to the wall mounted thermostat, TCorp engineers will identify the different parts of each system, find opportunities to improve the existing system through proper operations and maintenance techniques and when it is cost-effective to do so, recommend changes that will greatly increase the efficiency of the system. Contact us today to find out more. 

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