How Cold Should the Air coming from my Air Conditioner be?

It’s August. It’s HOT outside. We want to be COOL inside. But just how cold should the air temperatures be coming from the supply vents? While most people just assume that “cold” is the correct answer, there is a range of acceptable temperatures. I’ll get into that in just a minute, but first I feel it’s important to understand (just a little) of how our HVAC system works.

When the air conditioning system is on, and working correctly, the process that is occurring is that warm air is being pulled from the home (let’s say 75 degrees) through the return vent and moving through the A/C units evaporator coil. This is where the magic happens!

Science of evaporative cooling

Through the science of evaporative cooling, when this warm air passes through the evaporator coil, a volume of heat is removed from that warm air and we get cold air coming from the air ducts! It is this process that cools your home! Through this process, humidity is also removed, which helps make us feel more comfortable. Now, from the example above, with 75 degree air being pulled in at the air filter, what temperature should we expect to be blowing out? Well, the general consensus is somewhere between 14 to 20 degrees colder than the intake temperature. From my example, 55 to 61 degrees would be an acceptable range.

properly working ac cooling process

Old ducts affect cooling!

Do keep in mind that this range can vary. Old ducts, with poor sealing and insulation, or ducts that are in an attic with poor insulation can affect the temperature drop, which can negatively affect the room temperature.

Programming your thermostat

You may ask, “Well what temperature should I set my thermostat at to be comfortable?” Well it depends. Everyone is comfortable at different temperature ranges. My wife for example would sleep at 62 degrees year-round if she could, while I would be bundled up in layers shivering. There are two different “philosophies” here:

1) Comfort.

You want what you want, and you are prepared to pay for it. Most homes can generally maintain temperatures between 70-75 degrees in the heat of the summer. Just be aware the lower you set the thermostat, the higher your power bill will be! Happy wife, happy life.

2) Energy savings.

The recommended thermostat setting of 78 degrees in the summer is designed to balance energy savings and comfort. However, not everyone is comfortable at the same temperature.

Also, higher home temperatures mean less air-conditioning run time and potentially higher indoor humidity levels, which can cause health issues

Using a programmable or “Smart” thermostat that allows you to either set a daily program that raises the homes temperature while you are away, and lowers it when you are home, or one with Wi-Fi control will do a much better job of striking the perfect balance between personal comfort and energy savings.

While the Department of Energy recommends 7-10 degrees, I disagree and my personal experience says it’s best to make the “home” and “away” set points within 3-5 degrees of each other and give the system at least an hour to reach the desired setpoint.

It’s important to keep in mind that the temperature you set on the thermostat will not make the air coming out of the supply registers any colder. If the air conditioning system is working correctly, it will always maintain the 14 to 20-degree differential.

One other important thing to keep in mind about your home air conditioner is that ALL air conditioners are only designed and rated with a 95 degree outdoor temperature in mind. Since we live in the South, where temperatures can get in excess of that, sometimes we might see the thermostat rise – and that doesn’t necessarily mean anything is wrong, there is simply more heat coming into your home than your system is designed to remove!

It doesn’t matter what time of day it is, or even what day it is. When your AC unit needs repairs right now, then our emergency HVAC technicians are ready 24/7 to help. If you have an AC emergency that just can’t wait, then call us to get the best emergency service in South Carolina.


5636 Bush River Rd.
Columbia, SC 29212
SC License – #M104545
NC License – #32356

Phone: (803) 794-5526