When the summer heat reaches its peak, your air conditioner becomes the most important appliance in your home. But as temperatures soar into the upper 90s and beyond, you might notice something stressful happening. Your AC turns on in the morning and seemingly never shuts off.
Listening to your air conditioner run all day can trigger immediate anxiety. You might worry about your upcoming electric bill, wonder if the system is being overworked, or fear that an expensive breakdown is right around the corner.
If you are searching online, wondering why your AC will not stop running, take a deep breath. In many cases, during a severe heat wave, an air conditioner running nonstop is actually doing exactly what it was designed to do. However, there is a very fine line between a system working hard and a system actively failing.
Here is exactly how to tell the difference between normal summer operation and a cooling system that needs professional help.
The Short Answer: Yes, It Can Be Completely Normal
To understand why your AC runs constantly during extreme heat, it helps to understand how residential cooling systems are designed. Air conditioners are not sized to handle the hottest possible day of the year with ease. If they were, they would be massively oversized for the other 95 percent of the summer. Oversized systems turn on and off too quickly, which leads to poor humidity control and a clammy, uncomfortable home.
Instead, residential air conditioning systems are designed to maintain a roughly 20-degree temperature difference between the outdoors and your indoor air.
If it is 98 degrees outside and you have your thermostat set to 70 degrees, you are asking your system to achieve a 28-degree temperature drop. In extreme heat, your home absorbs thermal energy from the sun faster than your AC can remove it. To try and keep up with that massive heat load, the system has no choice but to run continuously.
Running Constantly vs. Running Ineffectively
The most important step in diagnosing your system is determining whether your air conditioner is actually cooling your home while it runs. These are two completely different scenarios that require different responses.
Signs Your AC is Operating Normally
If your system is running all day but checking the following boxes, it is likely just working hard to combat the outdoor heat:
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The air from the vents is very cold. * Airflow is strong and steady.
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Indoor humidity is low. The air inside feels crisp and dry, not sticky.
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The indoor temperature is stable. The thermostat might sit a degree or two higher than your set preference during the hottest part of the afternoon, but the house remains comfortable.
Warning Signs of an Underlying Problem
If your system is running constantly but you notice any of these symptoms, you likely have an equipment issue:
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The air from the vents feels lukewarm or room temperature.
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Airflow is weak or barely noticeable.
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The house feels humid and sticky.
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The temperature continues to climb indoors. If the thermostat is set to 74 but the indoor temperature creeps up to 80 degrees by late afternoon, the system is failing to remove heat.
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You notice ice forming on the indoor coil or the outdoor refrigerant lines.
6 Common Reasons Your AC System Runs Nonstop
If your system falls into the “running ineffectively” category, there is usually a specific culprit blocking its performance. Here are the most common reasons an AC struggles in extreme heat.
1. Extremely Low Thermostat Settings
Many homeowners try to cool their house faster by dropping the thermostat to 65 degrees when they feel hot. Air conditioners cool at a steady rate regardless of the setting. Setting the thermostat drastically low simply forces the system to run endlessly trying to reach an impossible target.
2. A Dirty or Clogged Air Filter
This is the most common and easily avoidable HVAC issue. A dirty air filter acts like a brick wall blocking the air trying to return to your system. When the blower motor cannot pull in enough warm air, the system cannot produce enough cold air. This lack of airflow forces the AC to run twice as long to achieve minimal results.
3. Dirty Outdoor Condenser Coils
Take a look at the outdoor unit sitting in your yard. The metal fins on the outside of that cabinet need to breathe in order to release the heat absorbed from inside your home. If those coils are caked in lawn clippings, dirt, or cottonwood seeds, the system cannot expel heat. This drastically reduces cooling capacity and drives up your utility bills.
4. Low Refrigerant Levels
Air conditioners do not consume refrigerant like a car consumes gas. The refrigerant sits in a closed loop. If your system is low on refrigerant, it means there is a leak somewhere in the coils or copper lines. Without the proper amount of refrigerant, the system cannot absorb enough heat from your indoor air, causing it to run continuously without cooling the house.
5. Poor Insulation or Leaky Ductwork
Sometimes the AC is working perfectly, but the house is failing to hold the cold air. If your attic lacks adequate insulation or your ductwork has holes pushing cold air into crawlspaces, your air conditioner has to work overtime to make up for the loss.
6. An Aging or Undersized System
As air conditioners age past the 10 or 15-year mark, their compressors and motors lose efficiency. A system that kept up perfectly a decade ago may now lack the capacity to cool your home during a heat wave.
What Homeowners Can Do First
Before you start worrying about expensive repairs, there are several simple steps you can take to relieve the strain on your air conditioning system today.
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Change the air filter. If you have not replaced it in the last 30 to 60 days, put a fresh, clean filter in immediately.
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Raise the thermostat slightly. Nudging the temperature up just two or three degrees during the hottest hours of the day gives your system a much-needed break and lowers your energy usage.
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Close blinds and curtains. Block out direct sunlight on south and west-facing windows to drastically reduce the solar heat entering your home.
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Ensure all supply and return vents are open. Closing vents in unused rooms actually disrupts the pressure balance of your system and makes it work harder. Keep them open and clear of rugs or furniture.
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Use ceiling fans. Fans do not lower the temperature of the room, but the wind chill effect makes the air feel cooler on your skin, allowing you to tolerate a slightly higher thermostat setting comfortably.
When Is It Time to Call an HVAC Professional?
If you have changed the filter, adjusted the thermostat, and closed the blinds, but your home is still uncomfortably warm while the AC runs continuously, it is time to call for backup.
You should schedule an inspection with a licensed HVAC technician if you notice:
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Warm air is blowing from your vents.
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Ice is building up on any part of the indoor or outdoor equipment.
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Unusual noises like loud buzzing, squealing, or rattling.
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A sudden and massive spike in your summer electric bills without a change in your habits.
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Short cycling, where the system turns on for just two minutes, shuts off, and immediately turns back on.
Frequently Asked Questions (FAQ)
Will running constantly burn out my AC motor?
Modern air conditioning systems are built to endure long run cycles. In fact, running continuously for several hours is actually less stressful on the compressor and electrical components than turning on and off multiple times an hour. As long as the system is well-maintained and properly lubricated, long run times are generally safe.
What is the best thermostat setting during a summer heat wave?
For an ideal balance of comfort and energy savings, the Department of Energy recommends setting your thermostat to 78 degrees when you are home. If 78 feels too warm, aim for 74 to 76 degrees, keeping in mind that every degree lower will noticeably increase your cooling costs and system run time.
Why are my electric bills so high if my AC is working normally?
Your electric bill is based on how many hours your system runs. During a heat wave, your AC might run 15 to 20 hours a day just to maintain a normal temperature. Even if the system is perfectly healthy and highly efficient, that sheer volume of operating hours will result in a higher utility bill.
Keep Your System Reliable All Summer Long
Watching your air conditioner run all day in hot weather can be stressful, but understanding how your system handles extreme heat is the first step to feeling comfortable in your own home. If your house is cool and dry, you can likely let the system do its job.
However, the best way to prevent cooling emergencies is through routine, preventative maintenance. A system with clean coils, fresh filters, and proper refrigerant levels will cool your home faster, run less frequently, and cost less to operate.
If your air conditioner is struggling to keep up with the heat, blowing warm air, or causing your energy bills to skyrocket, do not wait for the system to break down completely. Contact our experienced HVAC contractors in Charleston today to schedule a comprehensive system inspection. We will diagnose the underlying issue, restore your home’s comfort, and ensure your system is ready to handle whatever the rest of the summer brings.