How long should an A/C run to cool the house?

Think your air conditioner takes too long to cool your home?

It’s hard to say exactly how long that should take, as a “normal” cooling time depends on:

  • Your unit’s size
  • Whether you have a single-stage/single-speed, two-stage/two-speed or variable-speed unit
  • The condition of your AC
  • How well your home is insulated

However, if you’re looking for a generic answer, ask yourself:

  1. Does your AC seem to run non-stop but never cool your home?
  2. Does your air conditioner turn on then shut off quickly (within 10 minutes)?

If you answered “yes” to either of these questions, you most likely have a problem with your AC. We’ll get more into what can cause those problems below.

Need a Kansas City tech to repair your air conditioner?

Does your AC run non-stop but never cool your home? These reasons could be why.

If it feels like your AC is running too long, it could be because the outdoor temperature is really high and/or you have your thermostat temperature set low.

See, if it’s a really hot day, your AC will naturally struggle to cool your home quickly. And the lower you set the temperature inside your home, the longer your air conditioner will have to work to cool your home.

If it isn’t super hot outside, your AC could be running for a long time because of:

  • Restricted airflow (dirty air filter or leaky air ducts)
  • Low refrigerant levels
  • An undersized unit

We’ll explain why each problem could cause your AC to run longer than normal.

Problem: Restricted airflow

Your air conditioner will run constantly if it can’t supply enough air to cool your home.

Signs this is the problem:

  • Dirty air filter
  • Closed/blocked vents
  • Improperly sized or leaky duct work
  • Frozen evaporator coil
  • Air from the vents is weak, but cool

How to fix it: To improve airflow in your system, try these tips:

  1. Change your air filter.
  2. Open all supply vents (the ones that send cool air into your home).
  3. Make sure no return vents (the ones the pull warm air from your home) are blocked by curtains, furniture or anything else.

If you tried those solutions and your AC is still running constantly, you’ll need to call a professional. You might have leaks in your duct work, in which case you’d need a duct sealing.

Problem: Low refrigerant levels

Unfortunately, if your AC has low refrigerant levels, it means your system has a leak.

See, refrigerant (the liquid/gas that cools the air going into your home) runs in a closed loop within your system—so it can’t just “run out”.

Signs this is the problem:

  • Warm air from your vents when it’s hot outside
  • Hissing sound near your system
  • Frozen evaporator coil

How to fix it: You’ll need to contact a pro to repair the leak. Don’t try to repair the leak yourself. Only certified HVAC techs should handle refrigerant because it can seriously harm people.

Problem: An undersized unit

An air conditioner needs to be properly sized for a house. If your AC is too small for your home, it will work harder (running constantly) to try to cool your home.

To determine the right size AC, a professional will have to perform a “cooling load calculation”, which is a complex process that measures your entire home and property.

Signs this is the problem:

  • You just bought the air conditioner
  • Frozen evaporator coil
  • Your home doesn’t reach the set temperature on hot days, even when vents blow cool air and airflow is normal

How to fix it: If your current AC is too small for your home, you’re better off getting a new system. You’ll not only save on energy costs, but you’ll be more comfortable in your home (especially on hot days).

Does your air conditioner turn on then shut off quickly? It could be short cycling.

Short cycling is when your air conditioner turns on and off very quickly, usually under 7–10 minutes. This is bad for your AC because it causes:

  • Higher-than-normal energy bills
  • Excessive wear and tear on your system
  • A humid home (bad news in Kansas summers)

What causes an AC to short cycle? It could be one of the following issues:

  • An over-sized AC. As we mentioned above, an AC needs to be properly sized for your home. One that’s too big will cool your home super quickly and then shut off, resulting in a cool but humid home. We recommend having a pro do a cooling load calculation to determine whether your AC is, in fact, too large.
  • High blower motor speed. If your blower motor fan speed is set too high, it will cool your home too quickly. You’ll need a professional to adjust the speed to its correct setting.
  • A supply vent is blowing on the thermostat. This tricks your thermostat into thinking your home is cooler than it really is, which will cause your system to shut off quickly after it turns on. If your thermostat is in a bad location (near your thermostat or a window/door), you’ll want to have a tech relocate it.

Need a Kansas City pro to repair your air conditioner?

We’ll send one of our AC techs to your home to figure out what’s wrong with your air conditioner and get it back up and running.