How Long Does It Take for AC to Cool the Entire House? (By Sq. Ft & BTU’s)

We’ve all experienced hot summer days when we’re dying to get back in our homes and turn on the AC. On the off chance that you left it off to save money or forgot to turn it on, it can become a challenging patience game until your house reaches a reasonable temperature. But how long does it really take for your AC to cool your home?

It takes about 18 minutes for an air conditioner to cool down a house by 1 degree and 1.5 hours to cool it down by 5 degrees as long as it’s the correct size air conditioner for the home. Different factors can affect this like air conditioning size, house size, insulation, and outdoor temperatures.

To learn more about AC cooling your house and how long it takes depending on your living space size, keep reading.

How Long Will it Take For My House to Cool Down?

It generally takes between 15 to 20 minutes for an average 2,000-square-foot house to cool down by 1 degree. However, there are many contributors that go into this, making the answer vary. One of the biggest variables is the house size. The square feet of your house is a huge indicator of when you should expect to start feeling the effects of your AC.

For a typical 3 to 4-bedroom house, it takes about 3 hours for the temperature to drop 10 degrees. If your house only has 1 or 2 bedrooms, it will only take roughly 1 hour 30 minutes for it to be 10 degrees cooler.

Cooling the room

This chart shows exactly the time you must wait for your current house temperature to reach your desired house temperature.

From/To (Fahrenheit)75 degrees80 degrees85 degrees90 degrees95 degrees
65 degrees180 minutes240 minutes360 minutes450 minutes540 minutes
68 degrees126 minutes216 minutes306 minutes396 minutes486 minutes
70 degrees90 minutes180 minutes270 minutes360 minutes450 minutes
72 degrees52 minutes144 minutes234 minutes324 minutes414 minutes
75 degrees0 minutes90 minutes180 minutes270 minutes360 minutes
78 degreesN/A36 minutes126 minutes216 minutes306 minutes
The numbers above are correct if your AC fits the size of your space and has enough BTUs.

British thermal unit (BTU) is a classification of cooling power where the higher the BTU, the more powerful the cooling. This chart references how many BTUs you need depending on the square feet of your house. Having the right air conditioner that supplies the correct amount of BTUs for your home will enable it to cool down quickly.

How Many BTUs Do You Need For Your Home Size?

It’s a general rule that you need 20 BTUs for each square foot of living space. With air conditioning that provides the BTUs needed for your space, the cooling time is accurate and applicable to you. If not, it might take more or less time for your house to drop in temperature.

Room Size BTUs needed
150 sq. ft.5,000 BTUs
300 sq. ft.7,000 BTUs
400 sq. ft.9,000 BTUs
550 sq. ft.12,000 BTUs
1,000 sq. ft.18,000 BTUs
1,400 sq. ft.23,000 BTUs
1,900 sq. ft.28,000 BTUs
2,700 sq. ft.36,000 BTUs
BTUs based on room size chart
setting thermostat

What Factors Affect the Cooling Time?

Whether your house cools off super quickly or sluggishly, these factors could be a reason as to why.

Undersized Air Conditioner

If your air conditioner never stops running because it never seems to be cold enough in your home, it might be because your AC doesn’t have enough BTUs. You could also experience temperature inconsistencies throughout your home if your AC is too small.

Since it’s too small and can’t complete a full cooling cycle, it’s not fully cooling your space down, which will cause you to spend more money cooling your home. You could replace it with an AC that’s the right size or make sure your house is properly insulated.

It’s important to get the right sized AC because if you have one that is too small, it’s hard to keep the room cool, and if your air conditioner is too big, it will lower the room’s temperature quickly but won’t get rid of the humidity in the room.

Size of Your Home

The temperature drops 1 degree Fahrenheit in 18 minutes in an average house that’s 2,200 sq. ft. When it comes to larger houses, it usually takes a bit longer for the temperature to decrease from 80 to 72 degrees Fahrenheit. On the other hand, smaller houses will cool down a lot faster. If you live in a spacious abode, space could be a leading factor in what’s affecting your cooling time.


This is a crucial aspect of the heat exchange between your house and its surroundings. The better the insulation, the quicker your home will cool down. On the other end of the spectrum, bad insulation will make it harder to get your home cold.

Outdoor Temperature

As the temperature increases outside, the process of your house cooling will become slower. Even with great insulation, it will never be perfect, and the heat is bound to seep inside the house while the air conditioner tries to fight off the heat transfer.

Outdoor Temperature

Dirty Air Filter

Your air conditioner’s air filter might be dirty if you notice you are having higher power bills because it doesn’t shut off/run properly, increased allergies because of excessive air contaminants not getting filtered, or there is lower airflow in your home compared to normal. These can be easily fixed. All you need to do is replace it with a clean one every 3 months or vacuum/wash it if it’s reusable.

The State of Your Air Conditioner

Taking care of your air conditioner will make it run smoothly and efficiently, which also extends its life. If you aren’t giving it the necessary attention, then the AC may stop working as well and not last as long as expected. With no upkeeping, it’s not going to cool your house as much and must run longer to get your home to your preferred temperature.

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