How Long Should an Air Conditioner Cycle Last?

During hot weather, your air conditioner cycles on and off to keep you at the comfortable temperature of your choice. The length of those cycles can vary based on the weather and unit. But very short or very long cycles can indicate a problem with your air conditioner.

All air conditioners run a cooling cycle that chills the evaporator coil using rapidly expanding refrigerant. Fans draw air over the coil and force the air through the ducts that lead to the rooms in your house to lower the overall temperature. This cooling cycle runs for several minutes until the temperature is right; it then shuts down to save energy and prevent the air from getting too cold inside.

Your air conditioner's cooling cycle should last until it cools the house to your preference. It doesn't run on a set schedule. Instead, the cooling cycle is designed to create colder air in the house until the temperature on the thermostat is reached. It shuts off at that point and starts again when the house begins to warm up naturally.

A normal-functioning air conditioner should have about two to three cycles per hour, each one lasting about 15 to 20 minutes. However, the weather can cause shorter or longer cycles. If it's just slightly warm outside, the cycle is shorter. If it's blazing hot when your temperature is set fairly low, it may need to run much longer to reach the goal temperature.

How long your air conditioner cycle lasts may also be affected by the size of your system. The size of an air conditioner is measured in output BTUs. This indicates the amount of cooling it can produce in a given time. One BTU is equal to the amount of energy needed to raise the temperature of one pound of water by 1 degree Fahrenheit.

If your air conditioner has more BTUs than it needs, it will run very short cycles more often. If it has too few BTUs, it will run much longer per cycle. Both situations can be hard on your air conditioner, which is why it's important to size the unit properly.

The air conditioner does more than blow cold air. It also removes moisture from the air to make the home more comfortable. If properly sized, the air conditioner will cool to the desired temperature and remove the proper amount of moisture within 15 to 20 minute cycles.

If your air conditioner tends to run cycles much shorter than 10 minutes, there is a problem. It can be caused by a unit that's too large, dirty coils, blocked drains, or thermostat malfunctioning. Short cycling will overwork your air conditioner and use up unnecessary energy from starting and stopping cooling. It will also leave too much moisture in the air.

Longer cycles have the obvious downfall in that they use excessive power to run the cycle for long periods of time. This can happen if your unit is too small, it's extremely hot and humid, you need to change a dirty air filter, or the unit is low on refrigerant.