How Long Should It Take To Cool A House From 80 To 72?

It isn’t uncommon to become worried that the air conditioner isn’t cooling fast enough. Perhaps it’s a sweltering hot day, and you’re hoping the air conditioner can do its magic. Unfortunately, however, it’s taking “ages” to lower the indoor temperatures.

What could be wrong? Is it broken? Is it too old to keep you comfortable anymore? Or are you missing something?

We answer these and many related questions below, including how long it should take to cool the house from 80°F to 72°F.

How Long Does it Take to Cool a House from 80°F to 72°F?

Typically, it takes 2.5 hours to cool down a house from 80°F to 72°F. Of course, it can take longer (or even shorter), depending on various factors. However, generally, it takes about three hours to cool a moderately-sized house by ten degrees, thus about two and a half hours to lower the temperatures by eight degrees.

How Fast Do Air Conditioners Cool?

Different air conditioners cool at different rates, depending on multiple factors. However, assuming that the air conditioning unit is the right size for your home and that your home is located in a moderate climate (not the extremes), you should feel a change in indoor air conditions by the end of the first cooling cycle, which lasts 15 to 20 minutes, on average.

However, it’s important to note that this isn’t an ideal figure. The actual figure can be much lower or much higher.

For instance, it takes much shorter to feel a difference in mildly hot conditions with low humidity. So, you may feel cool enough within ten minutes or even less.

On the other hand, it takes significantly longer to feel the impact of the air conditioner in scorching hot weather with high humidity levels. It can take up to 30 minutes to feel a meaningful temperature difference in such conditions.

Similarly, it takes a shorter time to feel the temperature change in a tightly insulated room than in one with poor insulation. Why? Because quality insulation keeps out hot air better while also preventing the loss of conditioned air.

A Few Things to Check Before You Panic

It’s understandable to be worried if it takes longer than you expected for the house to cool to the thermostat setting. However, you want to consider a few things before pushing the panic button.

Do you have the Right Size AC?

One of the most likely issues if your air conditioner takes longer than expected to cool down your home is incorrect sizing.

An undersized air conditioner must work for a longer period to remove enough heat to lower the home’s temperature to the desired level.

For instance, a 1,000 square-foot room requires a 2-ton (24,000 British Thermal Units) air conditioner. Therefore, a 1.5-ton unit in the area will take longer than the 15-20-minute average to achieve the desired results.

Similarly, an oversized unit can create a few problems. For example, although the air conditioner will lower indoor temperatures faster, you won’t feel as comfortable as you’d wish because of high humidity levels. So, it’s important to size the unit correctly.

Is your AC Positioned Correctly?

Positioning is just as important. First, you must locate the air conditioner in a place where the airflow can easily reach every corner of the room.

Otherwise, you may have hot spots throughout the room. Hot spots in this context mean small portions of the rooms that are still hot despite the ongoing cooling.

To this end, you must choose a central location that allows uniform cooling. Bundling the air conditioner in an unused corner is asking for trouble.

Similarly, the location must be free from obstacles that may impede airflow. For instance, installing the indoor air handler behind the sofa makes little sense. Instead, make sure there’s plenty of room in front of the unit.  

Do you Run the AC Often?

Many people wonder whether it’s a good idea to turn off the air conditioner periodically, perhaps to let it rest to prolong its life. While this isn’t a terrible idea, it can cause several issues.

For instance, turning off the air conditioner can encourage mold growth when you sleep. Mold is extremely difficult to eliminate once it starts growing.

More importantly, shitting down the air conditioner for long stretches allows indoor temperatures to drop significantly. Your home will essentially become an extension of the hot, humid, and extremely musty outdoor weather.

Returning the home to the desired indoor air quality level takes a lot more time to start from such a bad state. It’s another reason the home can take longer to cool.

So, it’s best to turn the air conditioner on and set it to AUTO. This way, it will initiate cooling as soon as indoor temperatures rise above the thermostat setting, taking much shorter to make your home comfortable again.

Is the Thermostat Set Correctly?

Finally, the thermostat setting also determines how long it takes for the air conditioner to lower your indoor temperatures to the desired level.

For instance, the hottest summer months in Dallas are around 96°F, and Energy Star recommends setting the thermostat to 78°F during this period. Following their guidelines, you will achieve your cooling goals in 30 minutes to 40 minutes.

However, what happens if you set the thermostat to 72°F, as some people do? It will take another 15-20 minutes to achieve your colling goals. So, you may have to wait a full hour to feel as comfortable as you want.

Why your House is Taking too Long to Cool?

So, you’ve confirmed that you have the right size air conditioner, have verified that it’s positioned correctly, run it often, and have also confirmed that the thermostat is set correctly.

However, the unit still takes too long to cool down your house. At this point, you need to consider the following possible issues;

Dirty Air Filters

Dirty air filters slow down the speed of cooling. How? Because all return air (the air entering the air conditioner from your home) passes through the filter for cleaning.

Therefore, a filthy, partially, or completely-blocked filter can result in very little conditioned supply air at the other end.

Solution: The only way to solve or prevent issues relating to dirty filters is to ensure regular maintenance. Make sure to change the filter every two weeks or more often, as the manufacturer recommends.

Dirty Condenser/Evaporating Coils

The condenser coils can also become dirty or blocked. For instance, your condenser lines may develop a thick coat of dust after a long period out, such as after a long winter season.

It may also develop a thick layer of ice if it freezes. These can limit airflow through the unit and impact heat exchange between the cold refrigerant coils and warm indoor air, thus slowing down the cooling process.

Solution: Regularly maintenance is critical here too. Additionally, schedule annual professional maintenance. However, don’t hesitate to call your HVAC technician if it’s an ongoing problem.

A Refrigerant Leak

Your air conditioner may also be taking too long to cool your house from 80°F to 72°F (as you desire) because of low refrigerant. When the refrigerant levels drop, the air conditioner loses its heat-carrying capacity.

As a result, it cannot carry as much heat outside the house as it previously did because carrying capacity depends on the refrigerant volume. The most common cause of lower refrigerant levels is a refrigerant leak.

Solution: It’s best to let a licensed HVAC professional handle the refrigerant leak and all other issues related to refrigerants. 

Leaky/Blocked Ducts

You may also want to probe your air ducts for leaks, especially if you use a central air system or other air conditioning system connecting to the main ductwork.

Leaks in the ductwork can lead to loss of conditioned air. Therefore, getting the rooms to the desired temperature would take longer. The same applies if the partially blocked.

Solution: Regular maintenance is the surest way to prevent or swiftly address leaky or blocked ducts. Also, make sure to schedule an annual AC checkup.

An Old AC

Finally, your air conditioner could be taking too long to lower your indoor temperature from 80°F to 72°F because it’s old and weak. Air conditioners, like all machines, lose their power as they age.

Unfortunately, they also lose their precision. For instance, the moving parts are no longer as smooth, leading to friction and loss of efficiency.

Solution: You have two options. First, you can persist with the aging unit if it’s not too slow. Alternatively, consider supplementing it with a mini-split system. However, if it’s more than 15 years, replace it.

Do Outside Temperatures Impact Time to Cool?

Unfortunately, yes. If it’s scorching hot outside, your home will likely be hotter, too, especially if your doors and windows are open. Your home absorbs and loses heat in so many ways that indoor air will be hotter on very hot days, even with the windows and doors completely shut.

For instance, your home breathes through the exterior walls. It also constantly breathes through the floor and the roof. So, the outside weather will certainly affect the time it takes to cool down your rooms.

How Can I Cool House Down Faster?

Fortunately, you can take several steps to cool down your house faster, even on a very hot day. Consider the following;

  • Reverse your ceiling fan: Change the fan’s direction to run in an anticlockwise motion, and make sure to use the fan frequently.
  • Cover the windows during the day: You want to keep out the hot, sweaty outdoor air as much as possible. Covering the windows and doors can help your cause.
  • Dehumidify the air: Humid air has a greater capacity to hold heat. So, dry out the air a little with a dehumidifier on humid days.
  • Open the windows at night: If you’re confident about your security, opening the windows at night can draw in much-needed cooler air.
  • Promote a cross-breeze: If letting in cool air at night is good, promoting a cross-breeze is even better. For instance, consider placing a fan on each window to blow cool air into the house.
  • Skip using hot appliances: You know too well that some appliances produce a lot of heat during use. You want to keep off them for a while.
  • Cook outside: If it’s practical, bring your portable gas cooker outside and prepare most meals outdoors to minimize indoor heat.  
  • Close unused rooms: All rooms hold heat and happily transfer the heat to nearby rooms. Therefore, closing unused rooms can help limit the spread of warm air throughout your home.

How Long should it Take to Cool a House from 80 to 72 FAQs

How Long should it Take to Cool a House by 10 Degrees? 

Generally, it takes three hours to cool a house by 10°F. However, the exact period will depend on the size and age of your air conditioner and a host of other factors.

How Fast should a House Temperature Drop? 

Most homes remain relatively warm for 8-12 hours after cooling begins. However, you can expect gradual cooling afterward for the next couple of days. Of course, it also depends on factors such as the home’s configuration.

How Long should it Take AC to Drop 1°F? 

The average-sized three-to-four-bedroom house takes about three hours to feel 1°F cooler during air conditioning. If it takes longer, the AC may have a problem.

How Cool should my House be if it’s 90°F Outside? 

The Department of Energy recommends setting your thermostat to 80°F if it’s 90°F outside. On the same note, you should set the thermostat to 85°F if it’s 95°F to 100°F outside.


There you have it. It takes about 2.5 hours to cool a house from 80°F to 72°F. However, this isn’t a fixed number.

It may take much shorter or much longer to achieve the same depending on different variables, including the outdoor temperatures, AC size, and age of the air conditioner, among others. However, if it takes too long, you need to troubleshoot the air conditioner.