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Can You Run an AC With the Windows Open?


In seeking comfort on scorching summer days or humid nights, the battle between saving energy and achieving optimal cooling often leads to the question: Can you run an air conditioner while keeping the windows open?

Air conditioners are designed to regulate indoor temperatures by extracting heat and humidity from the air, creating a more comfortable environment. The process involves circulating the air in an enclosed space, allowing the AC unit to cool down by removing the warmth and moisture.

Opening windows, on the other hand, introduces outside air, potentially leading to conflicting purposes: the cooling efforts of the AC system versus the inflow of warm, humid air from outside.

In this article, we’ll explore the considerations, benefits, and drawbacks of running your AC while the windows are ajar.

Can You Run an AC With the Windows Open?

windows open

Technically, yes, you can, but it’s not recommended. Running an air conditioner with open windows is counterproductive to the AC’s primary function of cooling indoor spaces. While technically possible, it undermines the efficiency of the cooling system and can lead to increased energy consumption and reduced effectiveness in maintaining a comfortable temperature.

When an air conditioner is operated with open windows, it works against the incoming warm outdoor air, causing the unit to run continuously to counteract the heat influx. This not only strains the AC but also increases humidity levels and compromises the system’s ability to maintain the desired indoor temperature.

In most cases, it’s recommended to keep windows and doors closed while the air conditioner is running. This allows the system to effectively regulate indoor temperatures without competing with external heat sources.

You need to utilize the air conditioner in a way that optimizes its performance. If you want fresh air to circulate, it’s better to use the AC to cool the space and then turn it off to open the windows, allowing for natural ventilation without the air conditioner operating.

Pros and Cons of Running an AC with Open Windows

There are both benefits and issues when running an AC with the windows open.


While not generally recommended, there are some benefits to opening windows while running an AC.

Fresh Air Circulation

Opening the windows while running the air conditioner can facilitate the circulation of fresh outdoor air, reducing stuffiness and improving indoor air quality.

Lower Energy Costs

During cooler times of the day, like evenings or early mornings, utilizing the AC with open windows may reduce the system’s workload, leading to potential energy savings.

Reduced Recirculation of Indoor Pollutants

Allowing outdoor air to flow in prevents the constant recirculation of indoor pollutants and allergens, thereby creating a healthier indoor environment.


Here are some reasons you should not open the windows while using an AC.

Reduced Efficiency

An open window allows warm outdoor air to continuously enter your space, making it harder for the air conditioner to cool the room. This decreases the AC’s efficiency as it struggles to combat the incoming heat, leading to longer cooling cycles and increased energy consumption.

Increased Humidity

Open windows introduce moisture from outside, making it harder for the air conditioner to dehumidify the air indoors. This could increase humidity levels, leading to a less comfortable and stickier environment.

Higher Energy Bills

The AC works harder to counterbalance the warm air entering the window, increasing energy usage and utility costs and making it harder to save money while using an AC.

Difficulty Maintaining Desired Temperature

With warm air constantly infiltrating the room, the AC may struggle to maintain the set temperature. This can make your space uncomfortable and even prevent the AC from reaching the desired cooling level.

Dust and Allergens

Open windows allow dust, pollen, and other outdoor allergens to enter your AC and room, possibly causing discomfort or allergies for those sensitive to airborne particles.

Increased Noise and Disturbance

Open windows can allow external noises, insects, and other disturbances into your space, potentially disrupting your comfort and peace.

Final Thoughts

Running an air conditioner with open windows presents a trade-off between reaping the benefits of fresh air and potential energy savings against the reduced efficiency and comfort challenges it might pose, especially in humid climates. Deciding to operate the AC with windows open should consider the local climate, time of day, and individual comfort preferences.

Balancing the advantages of fresh air circulation with maintaining a cool, comfortable indoor environment is critical in making this decision. It’s essential to weigh the pros and cons before running an AC with open windows to ensure comfort and efficiency.

JP Reyes

JP has been in the aircon industry for almost as long as he has been alive. As a child JP would help his tatay fix aircon units at their junk shop in Cavite. After graduating UP in the early 2000's, JP then started his own Aircon servicing business and within 5 years had 10 shops in 8 different cities. Fast forward to today and JP brings all his experience and expertise online to give readers trustworthy advice and reviews about Air-conditioning buying, servicing, cleaning and repair in the Philippines.

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