Is It More Efficient to Open Windows or Use AC at Night? | O'Brien (2024)

April 19, 2022

The sweltering summer temperatures in most of Pennsylvania make having air conditioning a must. However, leaving your air conditioning running day and night throughout the entire summer can result in huge electricity costs. If you’re like many people, you may attempt to reduce these costs by turning off the AC and opening your windows at night. You may be surprised to learn that this practice has much less of an impact than you think, and here are the reasons why.

Day and Nighttime Energy Usage

To determine how much you can reduce your energy bills, it’s first important to look at how much energy your AC uses during the day and at night. Studies have shown that if an air conditioner is left turned on 24 hours a day, approximately two-thirds of its total energy consumption occurs between noon and midnight. Theoretically, this should mean that shutting off the AC from midnight to noon will reduce your cooling costs by around one-third. Unfortunately, the reality is usually different unless you live in a dry, mild climate.

Calculating Actual Energy Savings

The summers in the Philadelphia area tend to be quite hot and humid, and this has a major impact on your overall cooling costs. It is probably fairly obvious that air conditioners have to work much harder in hotter temperatures. However, many people aren’t aware that humidity also plays a huge role in how efficiently and effectively an air conditioner works. This is because air conditioners don’t just cool the air, they also work to remove excess humidity. As a result, the unit will have to run more frequently and for longer periods when the humidity is high.

In theory, as long as the outdoor temperature is below the temperature in your home, then opening your windows at night will reduce your energy usage and still keep your house cool. However, the fact is that this rarely happens in Pennsylvania. During the hottest parts of the year, it is not uncommon for outdoor temperatures to remain well into the mid-70s or above until at least midnight. This means that opening your windows before going to bed will usually end up making your home hotter, which could result in your air conditioner having to work harder when you turn it back on in the morning.

Numerous studies have been performed on this subject to compare the differences in energy consumption between opening the windows and using air conditioning at night. In one study, researchers saw an average of a 30% decrease in electricity consumption by turning off the AC at night. However, when windows were also opened, the increased temperature and humidity inside the house resulted in the air conditioner using more than 20% extra energy during the day. While this wasn’t enough to completely offset the savings from turning the AC off at night, the difference between the two was still very minimal.

Of course, energy costs are really only one thing that you should consider as your overall comfort is also important. The fact that nighttime temperatures in Drexel Hill and the Philadelphia area are still quite high until after midnight means that opening your windows will often make you hotter. For this reason, it is generally always the best option to keep your home closed tight and the AC running moderately all summer until the temperatures finally start to truly cool off in the fall.

Get Professional AC Maintenance and Services

If you are looking for ways to reduce your cooling costs during the summer, there are other options that can have as much or even more of an impact than simply turning off the AC at night. Regular maintenance of your cooling system is one of the best things you can do for its energy efficiency. At O'Brien Heating & Air Conditioning, we offer maintenance and repairs for all types of cooling equipment as well as heating systems for customers in Drexel Hill and the greater Philadelphia area. We can also replace your old air conditioner with a new, much more energy-efficient model. We specialize in a wide range of other services including indoor air quality, duct cleaning, water heaters and more. Give us a call today to learn more about our services or to find other ways you can reduce your energy costs!

Is It More Efficient to Open Windows or Use AC at Night? | O'Brien (2)

Categories:Air Conditioning

Is It More Efficient to Open Windows or Use AC at Night? | O'Brien (2024)

FAQs

Is It More Efficient to Open Windows or Use AC at Night? | O'Brien? ›

It's a common misconception that turning off the AC and opening windows at night in summer is more cost-effective. But this isn't always the case. As a general rule, if humidity levels are above 65% outdoors, then it's best to keep your windows shut.

Is it better to open windows or turn on AC? ›

The best thing you can do for your air conditioner is to run it at night when it is already coolest and then keep windows and doors shut as much as possible during the day. This will help your air conditioner work less and save you money on your energy bill.

Is it better to sleep with AC or Windows open? ›

If the humidity level outside is much above 65%, you are usually much better off keeping your windows closed at night and using your AC instead. The reason is that opening your windows allows all of that humid air to get inside the house and soak into your furnishings.

Is it cheaper to cool a house at night? ›

Studies have shown that if an air conditioner is left turned on 24 hours a day, approximately two-thirds of its total energy consumption occurs between noon and midnight. Theoretically, this should mean that shutting off the AC from midnight to noon will reduce your cooling costs by around one-third.

Is it cheaper to use central air or window units? ›

If you're looking for the most affordable way to cool an entire house over a long period of time, then central air will be more cost-effective. But when it comes to cooling down a couple of rooms or one floor, a window unit may be the cheaper option, with both a lower cost to install and less energy used to run.

Is it cheaper to only run AC at night? ›

There's some truth that cycling your AC off at night (and running the fan only) can save electricity. But this isn't always so. Whether it promotes efficiency depends on: Outdoor Air Temperature: If the outdoor air is relatively cool at night, you can open some windows and the AC fan will help circulate it.

Is it cheaper to turn AC off at night? ›

Turning off your AC at night saves money

Since 'AC units are among the most energy-consuming appliances in households, sometimes, reducing their usage during times when they are not essential can lead to noticeable savings over time.

Does opening windows cool down a house at night? ›

When you open your windows at night, the cooler air in your home is drawn out and the warmer outside air is drawn in. This will happen even if there is only a couple of degrees difference between your indoor temperature and the temperature outside.

What temperature to open windows at night? ›

Researchers have found out that the best time to open the window and leave off the AC is when the outside temperature is about 70 degrees Fahrenheit, and the humidity levels are low. This keeps the room cool during the night, which ultimately saves money.

Should you open windows at night in summer? ›

Generally, if your house is decently insulated, keep the windows and blinds closed when the sun is shining. Open the windows in the evening and at night. More specifically, keep the windows closed when the outside temperature is hotter than it is inside, and open the windows when it's cooler outside than inside.

What is the best temperature for your house overnight? ›

Bedrooms should be relatively cooler, between 16 and 19°C . Our body temperature decreases during sleep and a cold room can help maintain our internal temperature regulation. Children's bedrooms should be slightly warmer, around 16-20°C, depending on their age.

What is a reasonable temperature for a house at night? ›

The U.S. Department of Energy says an indoor temperature of 65 degrees Fahrenheit at night is best. Setting your thermostat to a lower temperature at night may actually help you sleep better. Medical experts know that our body temperature drops at night.

What is the best AC temperature for energy saving at night? ›

You can also reduce your energy costs significantly by raising the temperature while you are at work, away from home, or asleep. For the greatest savings, consider setting your thermostat to: About 78 degrees while you are at home. About 82 degrees while you are sleeping.

Are fans better than air conditioning? ›

It takes significantly more energy for an air conditioner to move heat around than it takes a fan to blow air onto your skin. As a result, parking yourself in front of a fan is significantly more energy efficient. Fans use around 1% of the electricity consumed by air conditioners.

Is it cheaper to leave window AC on all day? ›

It's more energy-efficient to keep your AC on but set a few degrees higher when you're away from home for the day. Completely turning it off doesn't necessarily save energy as the unit will have to run longer to cool down a hot house upon your return.

Can you leave a window air conditioner on 24 7? ›

Running your air conditioner (AC) all day is not necessarily bad, but it could lead to higher energy bills and may potentially wear down your AC system faster over time.

Does opening windows help cool down a house? ›

Although it's easy to imagine that flinging your windows wide might invite some hint of a cool and pleasant breeze, in all likelihood, you'll just be bringing warm air in – making your living space even hotter.

How to cool down a room fast with AC? ›

Close the windows and doors while you keep the AC on

When you keep the AC on, ensure that the doors and windows in the room are closed tightly. Also, it is advisable to avoid opening and shutting the door frequently to prevent the cool air from escaping the room.

Is it better to keep windows closed on a humid day without AC? ›

Keeping humidity out

You should also keep them closed while you're gone during the day, even if you turn the AC off. Keeping your house sealed will prevent humid air from filtering in while you're gone, making it easier to cool the space upon on your return.

At what temperature should you open your windows? ›

Best Time for Open Windows

Researchers have found out that the best time to open the window and leave off the AC is when the outside temperature is about 70 degrees Fahrenheit, and the humidity levels are low. This keeps the room cool during the night, which ultimately saves money.

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