How Long Should an Air Conditioner Run to Cool a House in Phoenix?

Wondering if your air conditioning unit is running for a “normal” amount of time?

Well, it’s difficult to say what’s “normal” without considering factors like:

• The outside temperature
• The temperature you set your thermostat to
• The quality of your home’s insulation
• The condition of your AC
• Whether you have a single-stage vs two/variable-stage AC

BUT, we can give you a couple of rules-of-thumb:

Let’s take a look and why your AC is running too short or too long...

If your AC is turning on and off within 10 minutes, then it’s usually a sign your AC is short cycling. Short cycling is when your AC turns on then off too frequently.

Short cycling is bad news for your AC system because it can…

• Raise your energy bills
• Put more wear and tear on your AC
• Decrease your overall comfort

The following AC issues cause short cycling:

If your supply vent is blowing cold air on your thermostat it can trick your thermostat into thinking the room is actually colder than it is. So your AC system will shut off really quickly after it first turns on.

Thermostats should be located centrally, away from supply vents and windows. If your thermostat is in a poor location (a common problem with some manufactured homes), a professional will need to move it to a better location.

If your blower fan motor is set to a high speed, your AC will cool your home too quickly. You’ll need a professional to lower the fan speed if that’s the case.

Has your AC been short cycling ever since you installed your AC? You may have an oversized air conditioner.

If your AC is too big for your home, it will cool your home quickly and then shut off.

You’ll need a professional to inspect your AC and perform a cooling load calculation to determine if you have the right size AC.

Learn more about AC size in our article, “What Size Central Air Conditioner Do I Need?”

First, you should ask yourself the following questions:

1. Is it super hot outside? Hotter days will make your air conditioner work harder to cool your home since the temperature will naturally be higher inside your home.
2. Did you set the thermostat super low? The greater the temperature difference between the actual temperature and your desired temperature, the longer your AC will have to run to cool your home. So, if you set your desired temperature really low, your AC will run longer to cool your home to that temperature.
3. Is your home well-insulated? Homes with poor insulation typically let in more hot air, which raises the indoor temperature so your AC has to work harder to cool your home.
4. Do you have a 2-stage AC? It’s normal for a 2-stage AC to run longer than a single-stage AC. Two-stage systems are designed to run longer to provide greater indoor comfort.

If you answered “yes” to those questions, that could explain why your AC is having to work overtime.

But if you answered “no” to those questions and you feel like your AC is running all day, then you may have some issues a professional needs to fix.

Problems that cause your AC to run all day include:

• Airflow issues: Airflow issues mean your AC isn’t pulling in enough warm air, or cold air is leaking through the ductwork before it reaches your home. Both of these situations make your AC have to run longer to cool your home.
• Refrigerant leaks: Refrigerant is the liquid/gas that actually cools your home’s air. So if you’re low on refrigerant (which means you have a leak) then your AC will often run longer to try and cool your home.
• Undersized AC: An undersized AC will work harder to cool your home’s air, which means it will run longer.
• Condition and age of your AC: If your AC is in poor shape (i.e., it’s old or hasn’t been well-maintained), then it has to work harder to cool your home, so it will likely run longer.

Note: You can read about each of these issues in more detail by reading our article, “Should My Air Conditioner Be Running All Day?”.

If you notice your AC running longer than normal, contact a professional to fix the problem.