How Long Does It Take To Cool A House

The honest answer to the question of how long it takes central AC to cool down a house is this – it’s very hard to tell. It could take an hour or it could be impossible based on a range of factors discussed below.

How Long Should It Take to Cool a House?

Using the word “should” implies your home has average insulation and is in good condition, your AC is properly sized and the heat outside is typical summer heat – not record-high temperatures.

So, how long to cool an average home?

It takes 75 to 120 minutes to cool a home 5 degrees and 150 to 240 minutes to cool a home 10 degrees.


1 hour 15 minutes to 2 hours = 5 degrees cooler

2 hours 30 minutes to 4 hours = 10 degrees cooler

There’s a more detailed chart below.

Tip: If the AC has been running, then it takes 15-24 minutes to cool a home during a normal AC cycle.

How Fast Does AC Cool a House?

Central air conditioning will cool down a home by 1 degree every 15 to 24 minutes.

That’s true when they are properly sized – meaning the HVAC contractor did a load calculation to make sure your new AC was the right size. Sizes range from 1.5 to 5.0 tons for standard split system and packaged central air conditioner units. Ductless mini split ACs for a whole house range in size from around 24,000 BTUs (2 tons) to 72,000 BTUs (6 tons).

How Long Should It Take AC to Cool 1-10 degrees

Using the data showing correctly sized central AC cools a home 1 degree in 15-24 minutes:

Degrees CoolerHow Long
cool 1 degree15 -24 Minutes
cool 2 degrees30 – 48 Minutes
cool 3 degrees45 Minutes to 1 Hour 12 Minutes
cool 4 degrees1 Hour to 1 Hour 36 Minutes
cool 5 degrees1 Hour 15 Minutes to 2 Hours
cool 6 degrees1 Hour 30 Minutes to 2 Hours 24 Minutes
cool 7 degrees1 Hour 45 Minutes to 2 Hours 48 Minutes
cool 8 degrees2 Hours to 3 Hours 12 Minutes
cool 9 degrees2 Hours 15 Minutes to 3 Hours 36 Minutes
cool 10 degrees2 Hours 30 Minutes to 4 Hours

How long to cool a house by 1 degree?

A home’s central AC will cool it 1 degree in 15-24 minutes.

How long should it take to cool a house 10 degrees?

It takes 2 ½ hours to 4 hours to cool a house by 10 degrees Fahrenheit.

How Long Does It Take to Cool an 80 – 100 Degree House?

This chart is accurate for all homes with all insulation levels and all summer weather conditions. See the Factors below the chart to get a better understanding of how to quickly cool a home – or why it never seems to get cool enough for your comfort!

Tip: We assume that the ideal temperature to cool is 75 degrees

House Starting TemperatureHow Long to Cool to 75 Degrees
80 degrees1 Hour 15 Minutes to 2 Hours
81 degrees1 Hour 30 Minutes to 2 Hours 24 Minutes
82 degrees1 Hour 45 Minutes to 2 Hours 48 Minutes
84 degrees2 Hours 15 Minutes to 3 Hours 36 Minutes
85 degrees2 Hours 30 Minutes to 4 Hours
89 degrees3 Hours 30 Minutes to 5 Hours 36 Minutes
90 degrees3 Hours 45 Minutes to 6 Hours
92 degrees4 Hours 15 Minutes to 6 Hours 48 Minutes
93 degrees4 Hours 30 Minutes to 7 Hours 12 Minutes
94 degrees4 Hours 45 Minutes to 7 Hours 36 Minutes
100 degrees6 Hours 15 Minutes to 10 Hours

How Long Should It Take to Cool a House From 80 To 72

It should take 2 hours to 3 hours and 15 minutes to cool a house by 8 degrees.

Key factors for how long it takes to cool a house from 80 to 72 are the outside temperature, your home’s insulation level, how tight the windows and doors fit and whether the air conditioning system is the correct size.

How Long Should It Take to Cool a House From 80 To 75

Most homes can be cooled from 80 to 75 degrees in 1 hour and 15 minutes to about 2 hours. It will take longer when the outdoor temperature is extremely warm or the home’s AC hasn’t been running for at least 24 hours.

How Long Should AC Run On 100 degree Day?

Your AC will run between 30 minutes and 60 minutes every hour. Yes, that means the AC might run continuously without ever catching up.

Hot Climate – In Arizona, Florida, Georgia, Mississippi and other states that are very hot in summer, your AC might be properly sized for a hot climate.

Moderate and Cool Climate – In other states, where 100 degree temperatures are rare, it is possible that your home’s AC is not designed for extreme heat. In such cases, your AC might run all the time. This is especially true if the house is already hot when the air conditioning is turned on.

Arid Climate –  It is easier to keep a house cool in dry climates. For example, an AC might run for 30 minutes every hour on a 100-degree day in Denver but run for 45-50 minutes every hour in a humid city like Atlanta on a 100-degree day. 

Factors in How Long it Takes to Cool a House with AC

It might take 20 minutes to cool a home with AC – or it might be impossible to get the home as cool as you prefer it.

Here are home AC cooling factors with explanations. These factors will help you determine how long you will have to wait for a cool house – and whether your air conditioning system is doing its job or it is time for a new AC.

Starting Indoor Temperature: Obviously, the hotter the house is to start with, the longer it will take to get it to 75 degrees, for example.

Outside Temperature: The hotter it is outdoors, the longer it takes to cool down a home. That’s obvious too.

Tip: Turn your AC on before it gets uncomfortably hot indoors.

Normal vs Extreme Heat: If the outside temperature is normal for where you live, the AC should be able to keep the house comfortable. But when the outdoor temperature is well above normal during the hottest part of the year, the AC might not be able to get your home cooled to the temperature you like.

For example, 105F is normal for summer in Arizona, so the home’s AC should do the job. But if it is 105 degrees in Minnesota, then a home’s AC likely won’t be large enough to get indoor temperature below about 85 degrees.

Tip: Average outdoor temperatures are rising in some locations. So, the next time you get a new central air conditioner, it might have to be larger than your current unit.

Indoor Humidity: Moisture holds heat, so the more humid your indoor air is, the longer it will take the house to cool down.

Tip: Use a dehumidifier in your basement or crawlspace, if you have one, to allow your home to cool faster in summer. It only makes sense to add a dehumidifier to an AC system in very humid climates. 

Age and Condition of your AC: A new AC is clean, fully charged with no wear and tear. As ACs age, they don’t work as effectively. This is especially true as their indoor coils and outdoor condenser coils get dirty.

Tip: Clean and maintain your central AC system every year in hot climates and every 2-4 years in other locations. Also keep your air handler filter clean or change it when dirty. These steps will keep it cooling as effectively as a new AC.

Condition of your Ductwork: When ducts are coming apart or leaky, cool air will escape, and your home will take a lot longer to cool. 

Tip: Inspect your ductwork for leaks, and seal ducts and wrap exposed ducts with insulation for faster home cooling. 

Your Home’s Insulation Level and Envelope: Homes that meet current recommendations for home attic insulation and have house wrap like Tyvek keep out the heat better. As a result, it takes less time to cool a house with these features.

Tip: Add insulation to your attic, and seal gaps around windows, doors and the foundation to minimize heat gain in summer.


How Long Does It Take To Cool A House The First Time The Air Conditioner Is Started

It takes 30 minutes to 4 hours to cool a house when the AC is first turned on. Average time to cool a house is about 1 hour 30 minutes.

These factors affect how long it takes to cool a house the first time the air conditioner is started:

Starting indoor temperature.

Indoor humidity (humid air takes longer to cool).

Outdoor temperature.

AC Sizing – A properly sized air conditioner will cool a home faster than one that is too small for the house.

What is the best temperature to set your thermostat for AC?

The best temperature to set your AC thermostat is 74F to 80F. The drier the air, the more comfortable it feels, and you can set the thermostat at 78 to 80. If the air is very humid, then set the thermostat lower until the air is dehumidified. 

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

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