Six Myths About A/C Efficiency Explained

September 22, 2023

Six Myths About A/C Efficiency Explained


When it comes to air conditioning and energy savings, many people misunderstand how air conditioners work and how to save on utility costs. Below we explain six myths about A/C efficiency and clear up some of the confusions around central air conditioning and energy use.

Air Conditioning Myths Explained

Myth 1: Purchasing an energy-efficient A/C system will automatically save me money on utility bills.

This is not necessarily true if your unit is not sized correctly. Even though all new air conditioning systems are rated as 'energy-efficient' according to minimum SEER (Seasonal Energy Efficiency Ratio) ratings, having an oversized unit installed in your home could cost you more money. An air conditioning system that is too large for your home will cycle on and off repeatedly, placing heavy wear and tear on the system, and will use more energy.

Myth 2: Closing vents in unused rooms will boost efficiency.

Another one of the myths about A/C efficiency is that if you close register vents in unused rooms, then more cool air will flow to other rooms that are being used. This is a false assumption because energy has already been expended to cool the air flowing through the air ducts. By closing an air register vent, all you end up doing is cooling the inside of the air ducts, since your system (if sized properly) is designed to manage cooling for your entire home.  

If you want to be able to close off areas where you do not want cooling to occur, then consider a zoned cooling system. A zoned system uses multiple thermostats that control dampers within the ductwork to control room temperatures according to your needs.

Myth 3: Turning off A/C while you are away saves energy.

Turning off your air conditioner allows your home to get much warmer while you are not home. Ultimately, this will only require more energy to bring the temperature back down to a comfortable level when you return. The best thing you can do while you are out is to adjust your thermostat up 10 degrees when you are not home. This will allow the system to still manage humidity while you're away and provide quicker comfort upon your return.

Using a programmable thermostat will allow you to change the temperature to a cooler setting a day or so before you return so your home is cool and comfortable when you arrive. In a related blog post, we further explain the recommendation to leave your system on while away from home.  

Myth 4: Dropping the thermostat setting extra low will cool your house faster.

This is another point of confusion on the list of cooling myths about A/C efficiency that is not true. The air handler in your air conditioning system can only move warm air at a set speed. By setting the thermostat at a very low temperature, you are only wasting energy and your home will not cool any faster.

Another risk you take by setting the thermostat too cold is that components can "ice up" or freeze. In this case, the external evaporator coil can accumulate ice and the internal system can malfunction if dealing with too much moisture inside.  

Myth 5: I won't lose cool air if I keep windows and doors closed.

While keeping windows and doors closed does keep cool air from escaping, you may be losing cool air from leaks through the smallest of places around unsealed doors, windows, recessed lighting, electrical outlets and in ductwork.

To find out where other energy-stealing leaks are occurring in your home, consider having an energy audit done. A professional HVAC specialist can perform blower door and thermographic imaging tests to find leaks. Read more about the benefits of sealing and insulation here.

Myth 6: Leaving a ceiling fan on will cool an empty room.

This myth is a little deceiving in its wording. Ceiling fans DO create a wind-chill effect as the air comes into direct contact with your skin, so YOU will feel cooler. However, a ceiling fan does not reduce actual air temperature. By running a ceiling fan in an empty room, you are only wasting energy. Keep in mind that if you operate a ceiling fan in a room where people are, you can take advantage of the wind-chill effect and save money by turning up your thermostat by a few degrees.

When operating your central air conditioning system this summer, don’t resort to myths about A/C efficiency as they will actually cost you more money in energy use. For more information about energy savings possible with your system, contact a qualified HVAC professional. A reliable technician will be able to answer all of your questions.  

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