How long should AC run to cool?

Author: Prof. Deon Lindgren  |  Last update: Sunday, September 21, 2025

In a perfect situation, an air conditioner should run for 15-20 minutes at a time in mild temperatures. Any less than that and your AC could be too large for your home – more on that below. Obviously, if you hear your air conditioner run constantly, it is taking a toll on your electricity bill.

How long should it take AC to drop 1 degree?

Typically, it takes about an hour for an average-sized air conditioning unit in typical conditions to lower room temperature by one degree Fahrenheit. But remember, 'average' doesn't mean 'always'. Like people, every AC has its personality – some are sprinters while others prefer marathons.

How long should it take to cool a house from 80 to 72?

Cooling a house from 80 to 72 degrees is a common goal for many, especially during the peak of summer. On average, this process takes roughly two and a half to three and a half hours.

How long should an AC run before turning off?

Your AC unit should run its cycles for about 15 to 20 minutes, no more than a couple of times within an hour. If your AC is running for long cycles, it could also indicate a problem. Any AC system failure left unsolved could mean a costly repair and a hefty electricity bill.

How long should it take for AC to get cold?

On average, it can take anywhere from 30 minutes to a few hours for a central air conditioning system to cool a house to a comfortable temperature. For optimal performance, it's best to set the thermostat to a comfortable temperature before the hottest part of the day and ensure the system is well-maintained.

Is it normal for AC to take hours to cool?

The AC System Has a Dirty Air Filter

A dirty air filter is one of the most common reasons why an air conditioning system takes a long time to cool a home. The filter is responsible for removing dust, pollen, and other airborne contaminants from the air.

Why does my AC not feel as cold as it should?

Your AC unit isn't producing cool air as well as it used to because dirty coils may be hindering its ability to remove heat in your home's air. It could also not work properly due to a clogged filter and refrigerant running low, which are also the most common causes why you feel warmer these days.

Is it OK for your AC to run all day?

The constant running will reduce pressure in the cooling coil until it freezes over, which is dangerous as it can cause liquid refrigerant to flood back to the compressor and damage it (the compressor is a very expensive part).

What is the ideal AC cycle time?

Ideally, air conditioning systems should cycle for 15 to 20 minutes.

Is it better for AC to run longer or shorter?

Here are the brass tacks: Your air conditioner is the most efficient when it's running at maximum “speed” for a longer period of time, rather than short cycles in and out of “maintenance” temperatures.

How cool should my house be if its 90 outside?

If it's 90 degrees outside, most people would set their AC to a perfectly comfortable temperature of 68-72°F.

Is 72 degrees to hot to sleep in for a house?

Sleep experts believe the best temperature for great sleep is between 68-72 degrees Fahrenheit. But in addition to making you uncomfortable and interfering with healthy sleep patterns, being too hot at any time of day or night can cause health risks like dehydration and heat stroke.

How cool should my house be if its 100 degrees outside?

Energy Efficiency: Setting the thermostat to 78-80 degrees can help save energy and reduce utility bills. Raising the thermostat during extremely hot days can save you up to 10-15% on your cooling costs, depending on factors like your home's insulation and your AC's efficiency level.

At what temperature does AC become ineffective?

Temperatures Above 100 Degrees Fahrenheit

When temperatures outside become higher than 100 degrees Fahrenheit, the air conditioning system can consume more energy and begin to malfunction or fail. Most air conditioning systems are designed to function with outside temperatures of 100 degrees or less.

What is the 20 degree rule for air conditioners?

Simply put, it means you should never set your thermostat for a temperature more than 20 degrees cooler than the outside air. Why not? Most air conditioning systems can only handle a 20-degree difference between the outside and inside air temperatures.

How fast should an AC unit cool a house?

As a general rule of thumb, a well-maintained air conditioning unit should be capable of lowering the temperature by approximately 20°F within the first hour of operation. However, achieving the desired temperature may take longer depending on various variables.

How long should your AC run before shutting off?

When things are working right, your central air conditioner should run for 15 to 20 minutes and then turn off for a few minutes. It will do this two or three times every hour. It may run longer when it's sweltering outside.

Does an air conditioner need to rest?

Allowing your air conditioner to rest is an excellent way to extend its life and ensure it operates efficiently throughout the years. Air conditioners, like homeowners, require rest in order to recover and perform optimally.

What should my AC schedule be?

The recommended rule of thumb for summertime is to set the temperature to 78 degrees Fahrenheit when you're home and higher when you're away. In general, set it to 82 degrees Fahrenheit when you're asleep and 85 degrees Fahrenheit when you're away.

Does keeping the AC at 72 save money?

Best AC Temperature Settings While You Are Home

As you consider the most comfortable room temperature for your lifestyle and family, keep in mind that for each degree that you set your thermostat above 72 degrees, you can save up to 3% on your energy bill.

What happens if AC runs too long?

You're likely wasting energy, putting stress on your system, and heading toward steep repair bills. Don't let cooling your home become unnecessarily expensive this summer. Use these six simple questions to find out if your AC is running too long (and what you can do about it).

Is it better to turn off AC or raise temperature?

While you might be tempted to simply turn the AC off, it's actually better to adjust the temperature several degrees higher, by about 7-10 degrees. By installing a programmable thermostat and making this simple adjustment you can potentially save as much as 10% on your energy bill.

How to check if AC is cooling properly?

Ways To Check If Your AC Is Working Properly
  1. Check the Air Flow. If your AC is trying to cool a room that continues to stay excessively warm, it may not getting enough airflow through the vents. ...
  2. Check the Thermostat. ...
  3. Check for Refrigerant Leaks. ...
  4. Check the Smart Settings. ...
  5. Check the Outdoor Unit.

How do I know if my thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken
  1. The Thermostat Has No Power. ...
  2. The AC or Furnace Won't Turn On. ...
  3. The Heater or AC Won't Turn Off. ...
  4. The Thermostat Reading Doesn't Match the Room Temperature. ...
  5. The Thermostat Doesn't Respond. ...
  6. The HVAC System Is Short Cycling. ...
  7. The Thermostat Forgets Programmed Settings.

Why is my air conditioner running but not cooling the house?

There are a number of reasons why your air conditioner might be running but not cooling. It could be an issue with the thermostat, the compressor, or the evaporator coils. Or, it could simply be clogged with dust and debris, which is preventing it from working properly.

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