Is It Bad To Leave My Windows Open When The AC Is On?

by | Aug 4, 2022 | Energy Saving Tips

In the heat of summer, air conditioning provides some welcome relief from the scorching temperatures outdoors.  But many people also want to have fresh air in their homes.

Opening some windows, especially at night when the temperatures are cooler, may seem like a reasonable way to get the best of both worlds.  

But is it?

Actually, no.

Under no circumstances do we recommend having windows open and using your air conditioner simultaneously.  

Let us tell you why:  


Cool Air Escapes

This isn’t rocket science, just thermodynamics.  Cool air can and will escape through even the smallest of cracks—not to mention wide open windows.  So, when you consider the fresh air that will come in, also consider the cool air that will go out.  Not only is this a waste of energy, but it can also damage your air conditioner because…


Fresh Air Isn’t Always Fresh

That’s right.  When air enters your home from outdoors, it isn’t always as fresh as you might think.  Dust and moisture are two major components of “fresh” air.  And guess what?  They both make your air conditioner work double time.

Air conditioners automatically dehumidify the air in your home, so air with higher humidity (even if it’s technically a cooler temperature) puts stress on your AC unit.  And dust can accumulate within the inner workings of your air conditioner, causing malfunctions and the need for repairs.  

In addition, any pollution or allergens that enter your home from outside will just be continually recycled by the air conditioning system once you shut your windows.


High Energy Bills

You may think that turning off your air conditioner at night to let in fresh air is a win-win.  But we at Classic Air Conditioning & Heating disagree.  Your AC unit will have to work twice as hard the following day to lower the temperature and dehumidify the air in your home again.  

In most cases, the best choice for your pocketbook is to leave your air conditioner running full-time in hot weather.  The most efficient temperature will be approximately 78.8F.  

Some great ways to further reduce your energy bill include drawing your curtains during the hottest parts of the day, tinting your windows, and investing in good insulation throughout your home.  


But What if I Still Want Fresh Air?

If, after reading this blog post, you still feel that fresh air in your home is a priority, consider an energy-efficient heat recovery ventilator.  ERVs and HRVs provide balanced ventilation by using heat exchange technology to replace stale air with fresh air without losing as much energy as you would by opening a window.

Questions?  The team at Classic Air Conditioning & Heating is always happy to help.


About The Author

John Magninat

John Magninat

Owner John Magninat is a third generation air conditioning repair man. Classic Services Air Conditioning & Heating is a family company with family values and our customers are our top priority.

See What Our Customers Are Saying!

Read Reviews