Worried about your AC performance? Check the blowing temperature!
It's a simple way to check your air conditioner's efficiency and performance at home without professional help.
However, to do this properly, you must know the temperature at which it should be blowing and how to measure it accurately.
In this guide, I'll answer the question 'What temperature should air from AC be blowing?" and show you how to measure the temperature like an HVAC professional so you can see just how your air conditioner is performing.
How Cold Should Your Air Conditioner Be Venting? (Temp Levels Explained)
Air conditioners should typically blow out air 15-20 degrees Fahrenheit colder than the desired room temperature.
This 15-20 degree difference between the thermostat setting and the air temperature is called the 'temperature differential' or ‘evaporator Delta T.’
The exact temperature of the air coming from the supply vents will vary depending on the temperature you want the room to be.
I recommend keeping the temperature in your living space at 70-75 degrees Fahrenheit for maximum comfort.
Therefore, the air coming from the AC should be 50-60 degrees.
Why Air Coming From Supply Vents Should Be 15-20 Degrees Lower
Do All ACs Have the Same Temperature Differential?
No, the temperature differential for air conditioners can vary depending on the size, system type, and specifications.
It can also vary slightly depending on your exact environment, humidity, and airflow, but the air coming out of vents should always be between 10-30°F lower than the set thermostat temperature.
What Is Supply and Return Air?
Supply air is the cold air that has been through your air conditioning system and blown back into your home.
Return air is the air that gets sucked from your house and into your air conditioning system. It’s the warm air that needs to be cooled.
Understanding the basic airflow of your air conditioner can help to explain the difference between the two:
- Warm return air is pulled into the air conditioner.
- The return air passes over the evaporator coil in the AC system.
- The cold air becomes supply air and is pushed back into your home through supply vents.
- Warmer return air is pulled into the air conditioner through return air vents, and the cycle repeats.
The difference between your return air temperature and supply air temperature is the 'temperature differential' or 'evaporator Delta T' - this represents how much heat the AC removes from the air as it passes through.
Supply and return air temperatures will drop as the cooled air lowers the temperature in your home.
How To Accurately Measure the Air Temperature Differential in Your AC System
I recommend using an infrared thermometer for easy measuring and exact temperature readings.
You can pick them up on Amazon for $30-$100, and I recommend a model like the ennoLogic Temperature Gun.
Here are the steps to follow:
- 1Find The Return and Supply Vents:
Look for the vents that air flows in and out (or check the user manual). These are easy to find on most units.
A central AC may have multiple return and supply ducts, so I recommend finding a supply and return vent near the air conditioning unit to get the most accurate readings.
- 2Let The AC Run:
Set the thermostat to the desired room temperature and let it run for 15-30 minutes. This allows the unit to stabilize to give the most accurate readings.
- 3Measure the Supply Vent Temperature:
Point the infrared thermometer at the supply vent with nothing blocking the direct line of sight. Press the measurement button for a few seconds until you get a reading.
This is the temperature of the cooled air coming that’s passed through the AC evaporator coil.
- 4Measure the Return Air Temperature:
Next, use the infrared thermometer on a return vent going into the air conditioner. This is the temperature of hot air entering your AC vent.
- 5Calculate the Temperature Differential:
To calculate the Delta T (temperature differential), subtract the return air temperature from the supply air temperature. This is the heat energy removal as air passes over the AC evaporator coil.
Air Conditioner Output Temperature Chart
Below is a quick summary to help you determine the right temperature for each thermostat setting:
Thermostat Temperature (degrees Fahrenheit)
Ideal AC Output Temperature (degrees Fahrenheit)
What Happens If the Temperature Differential Isn't Within The Ideal Range?
An incorrect temperature differential can lead to:
There are two different issues:
Low Differential: If the differential (Delta T) is under 15°F, the AC isn’t blowing cold enough air to cool the room properly.
This makes it challenging to maintain set temperatures in your home.
High Differential: A high differential (Delta T) of more than 20°F means the air is blowing too cold.
This decreases the efficiency of the unit and can lead to humidity issues.
Have an HVAC professional inspect and perform AC repair on your system annually to keep it in working order.
An incorrect differential is usually caused by one of the following common AC issues:
Commonly Asked Questions
How Cold Should the Air Be Coming Out Of A Mini-Split?
The cold air blowing from a mini-split should be 15-20°F cooler than the temperature set on the thermostat.
What Temperature To Set Air Conditioner in Summer?
The ideal summer thermostat temperature is 70-80°F, but it’s advisable to set lower temperatures for rooms more exposed to the sun as they will regain heat quickly.
What Should AC Be Set at Celsius?
This depends on personal heat preference, but setting your AC to 22-24°C balances efficiency with personal comfort.
Which AC Temperature is Best For Lowering Your Electricity Bill?
The higher the temperature setting, the less you will spend on electricity to power your AC. I recommend setting your AC to 78-80 degrees as it balances efficiency and comfort and can be up to 20% cheaper than setting it to 72 degrees.