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

When you come home from a workout or feel flushed for one reason or another, you want the relief of your air conditioning system as soon as you walk in the door. It can get you hot to see the thermostat set to an uncomfortable 80° F when you really want it set at a refreshing 72° F. 

Most estimates claim that it will take 2.5 hours for the average home to cool from 80° F to 72° F, but the answer varies greatly based on your home. 

After you lower the temperature from 80° F to 72° F, how long should you expect your HVAC system to adjust

How Long Should It Take For Air Conditioner To Cool House? 

To measure the power of your air conditioner, we will use the standard measurement of BTUs (British Thermal Units). 

Every air conditioner comes with a BTU rating that indicates just how many BTUs it produces in an hour.

There are two main types of air conditioners when it comes to power: 

  • Window unit – 5,000 – 15,000 BTUs
  • Central air – 18,00 – 50,000 BTUs

If you only need to control the temperature in certain rooms, you may want to consider a ductless mini-split air conditioner that can produce enough power to cool the entire house but also allows you to conveniently cool one room at a time.

How Long Should It Take AC To Cool 1 Degree?

It requires 0.24 BTU of energy to change the temperature of one pound of air by one degree F. 

Assuming .5 pounds per square foot, once an air conditioner generates 600 BTUs, it will reduce the temperature of a 5,000 square foot home one degree. 

If you have a one-ton air conditioner that generates 12,000 BTUs, it generates 200 BTUs per minute. At that rate, it will take three minutes to lower the temperature one degree.  

If cooling a smaller 1,000 square foot home, you will only need 120 BTUs. With the same one-ton air conditioner mentioned above, it will only take about 40 seconds for the temperature to go down one degree

How Long Should It Take AC To Cool 2 Degrees?

To determine how long it will take to cool your home by 2° F, wait for your air conditioner to produce twice as many BTUs as it took to lower the temperature by one degree. 

Do you even notice the difference when the temperature changes by a mere two degrees? 

If you don’t, you may want to consider leaving your thermostat setting about 2 degrees higher than normal in the summer to save 2 – 3% on your utility bills for the year. 

How Long Should It Take To Cool A House 10 Degrees?

The average central air system can cool an average 4 bedroom house 10° F in roughly 3 hours

Of course, you should start to notice the temperature getting lower after about 30 minutes. You just have to be patient while you wait for the temperature to get to your preferred setting. 

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

Many people consider 80° F the ideal AC temperature until they really need to cool off or keep guests comfortable.

Based on the information above, we can expect the house to cool from 80° F to 72° F in about 2.5 hours

However, it’s not necessarily that simple to accurately determine how long it takes for ac to cool a house.  

Numerous factors come into play depending on your home’s unique characteristics, including:

  • Cooling area (cooling a large house or one room)
  • HVAC upkeep (change the filter and get regular inspections)
  • Ventilation and airflow (mini-duct systems can isolate certain rooms)
  • The energy efficiency of the home (insulation, efficient windows, and building materials)

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

Once you have an air conditioner properly installed, the moment you start it, it will work as quickly as expected if not better since it hasn’t had time to develop any debris and buildup. 

Keep in mind that if you had no air conditioner, the air conditioner may have a higher starting point regarding the temperature of your home, especially if it’s an especially hot day. 

If you feel cool air coming from the air conditioner, you can expect the unit to lower the temperature of an average home by roughly 10° F in 3 hours. 

If there’s no change after three hours on a brand new air conditioner, it may not be installed properly. 

Why Is My AC Taking So Long To Cool?

How fast should the temperature drop in a house? 

If you wait hours to experience cool air but don’t notice a difference, something is wrong.  

Here are some possible causes of an AC taking so long to cool. 

Too Small of an Air Conditioner

As a general rule, most experts suggest a size of 20 BTUs for every square foot of space

For a 2,500 square foot house, you will want an air conditioner that produces at least 50,000 BTUs in an hour. If your current air conditioner doesn’t cover your needs, you may need to upgrade. 

Open Doors or Windows

At the risk of sounding like your mom or dad, you don’t want to pay to cool off the entire outdoors. 

Ensure all windows and doors are properly closed before you turn on your air conditioner. 

Even more difficult, get everyone else in your home to follow the same rules. 

Low Home Efficiency

Your home has an efficiency rating which indicates how easily air and water can pass through. 

Start strong by selecting a house with high-end, durable building materials known to be energy efficient. 

Some other ways to increase your home’s efficiency include:

  • Add insulation in walls
  • Fix holes in the roof
  • Install efficient doors and windows 
  • Use blinds
  • Caulk or seal leaks and cracks immediately

Clogged HVAC Unit

Every HVAC unit contains an air conditioner filter that collects dust and debris in the air. 

If you have pets, smoke inside, and don’t clean well, the filter will become clogged quickly. 

You need to regularly clean your HVAC filter so that the air coming from the system is clean, and you promote proper airflow. 


Countless variables play a part in how long it will take your air conditioner to cool your home. 

You should feel cool air coming from the air conditioner right away, though. If you don’t notice sufficient change after a couple of hours, you may need to take steps to fix the problem or call your local HVAC technician. 

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