Air Conditioning Heating and Ventilation Services

Is It Bad to Leave the Windows Open While the AC is On?

In our warm Florida weather, it’s not a good idea to leave your windows open when the heat is high unless you’re looking for through-the-roof energy bills. Air conditioners do their best work in closed-off spaces, and opening the windows can counteract their efforts. 


Our HVAC technicians explain why leaving your windows open while the AC is running is not the best idea for energy efficiency and the load on your unit. Let’s go! 


open window


Could Lead to Excess Humidity (and More HVAC Maintenance) 


In Florida, we deal with high humidity levels regularly. Opening the windows of your home while your AC is running will significantly increase the amount of work your HVAC system has to do, causing more wear and tear in a shorter amount of time.  


Here’s why opening your windows with the AC running, isn’t the best idea… 


  • Opening your windows will draw moisture into your home that your AC has to remove, and there’s no way to stop this dehumidification process.  
  • Air will hit the evaporator coil, and any moisture within the air will condense on the coil and drain.  
  • Dryer air allows for the coil to absorb heat in the space more efficiently, keeping your home cool. Overly humid air, makes the entire system have to work harder (and that means more AC repairs in your future.) 


Longer Cooling Time 


Although you may assume opening the windows will help your home cool more quickly, it actually tends to be the opposite.  


Keeping the windows open, especially during the summer will allow heat to build up in your space, making it more difficult for your unit to drop the temperature. 


Dust Buildup 


In addition to overloading your evaporator coil and making it more challenging for your system to maintain cool air, some other issues may present themselves.  


Most notably, leaving the windows open will let more dust into the space, which your air filter may not be able to trap. This dust can then cover parts such as: 


  • Evaporator coil 
  • Electronic parts 
  • Fan 
  • Ductwork  


The dust can result in damage and breakdowns that come too soon as well as an increase in energy costs as a result of decreased efficiency. You’ll likely also end up with a clogged filter. Pair the clogged filter with a dirty evaporator coil, and you could easily end up with a frozen coil, which can result in some serious damage. 



A dusty evaporator coil combined with a clogged air filter can lead to an AC freeze, which can be a serious and expensive problem. 



Learn More > How Does Humidity Impact My HVAC System? 


close window when AC is on


The Final Verdict: Keep the Windows Closed 


If the temperature outside is between 60 and 65 degrees, and it isn’t too humid, you may be able to get away with shutting off your HVAC unit and cracking the windows. But in most cases, it makes way more sense for you to keep your windows shut and your AC running. Besides, with our indoor/outdoor lifestyle you can sit and relax on your porch or lanai, enjoy a breath of fresh air, and then come back inside to the perfect temperature.  


We’re here to prolong the life of your HVAC unit. For more guidance on the best practices for your air conditioning unit, reach out to ACHV Services. We’ll provide the most reliable team to find solutions to any HVAC concerns you may face!  


Call/text our local HVAC repair team at 727-453-2432 or 813-917-2982 today! We’ll always help you keep your cool.  

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