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

An air conditioner keeps the house cool and comfortable. This is important during the hot summer days when the outside temperature is soaring. However, your air conditioning system can take a long time to cool the entire house for the first time. The actual time varies with the size of your air conditioning unit, among other factors.

How Long Does It Take to Cool a House the First Time an Air Conditioner Is Started?

It may take about three hours to cool a three-bedroom house fully. This time applies if you turn on the air conditioner first. However, the AC system’s actual time may vary with several factors. Some of the factors include the outside temps and refrigerant levels.

How Long Should an Air Conditioner Sit Before Turning It On?

Air conditioners should sit still for between 12 to 24 hours before you turn them on. This period applies if you have moved or freshly installed your AC. If you turn on your air conditioner system earlier, the AC may become faulty.

An air conditioner unit has a compressor or condenser unit. The condenser unit contains condenser oil. The oil prevents the condenser unit of your ac system from experiencing friction when it is processing the refrigerant. If you move or install your system for the first time, the oil will likely have shifted from its original position. It would help if you gave it time to shift back.

What Temperature Should Air Be Coming Out of the Vent When Cooling?

The cool air that comes from the air vents of your air conditioner should be 20 degrees cooler. For example, if the outside temperature is 80 degrees Fahrenheit, the cold air that comes from the vents of your AC should be 60 degrees Fahrenheit. This temperature difference is important to ensure that the unit cools the entire home.

However, if the AC unit is not working properly, the air from the vents will be warmer than what is ideal. In such a case, the less cool air will not adequately cool your home properly.

What Temperature Should You Set Your Air Conditioning To?

The Department of Energy recommends you set your AC at 78 degrees Fahrenheit. This ideal temperature should balance a cool house’s comfort and manageable energy bills. However, deciding on the ideal temperature for your AC is not an easy thing to do.

You are keen on cooling the entire house fast during those hot summer days. Thus, you will be tempted to set the AC unit thermostat to the lowest temperature levels possible. However, when the AC unit reaches the set temperature and maintains it for a long time, the energy costs will soar.

You should set the thermostat at a higher temperature than 78 degrees Fahrenheit when you are away. Once you get back to the house, set the thermostat to 78 degrees Fahrenheit. This will help you avoid high energy bills. You can also switch on the ceiling fan to cool a particularly hot house.

What Factors Can Slow Down the Cooling Process by an Air Conditioner? 

An air conditioner’s time to cool your home fully varies depending on many factors. Here are some of the most important ones.

Prevailing Weather Conditions

It will take longer to cool your home than a cold one during a hot day. Similarly, the cooling time varies during the summer and winter months. Also, if your home is in a region with particularly high temperatures, it will take a long time for the AC unit to cool the whole home fully.

Your home’s insulation influences the length of time that the air conditioner takes to cool the home. Insulation helps to preserve the heat during the winter. Good insulation also keeps the heat out during the hot summer days. If your home is not properly insulated, the air conditioning system will work harder during the winter and summer.

Leakages in the Ductwork

Having leaky ducts is one of the main factors that affect the length of time your air conditioning system takes to cool the home. Your system has complex ductwork that ensures it effectively moves cool air all around the home.

The movement of the cool air automatically deals with the heat inside your house. A refrigerant leak occurs when your ducts are damaged.

If you have leaky ducts, your cooling system will lose about 30% of the cool air. If this happens, the system will have to work harder. To maintain the airflow. Also, the system has to compensate for the loss of cool air due to leakages in the ductwork.

As your air conditioning system struggles to compensate for the lost air and successfully cool the home, it will consume more energy. Thus, leakages in the ductwork result in high energy bills and lower cooling capacity.

Size of the AC

The size of the air conditioner refers to its cooling capacity. This is usually expressed in British thermal units or BTUs. The higher the BTU value of the central air system, the larger the size of a room that it can cool within a short time. The lower the BTU value, the smaller the air conditioner can cool the home.

You should match the size of your air conditioner unit with your home size. If you get a large air conditioner with a high BTU value, you will be underutilizing it.

Also, purchasing a small air conditioner means not getting to the ideal temperature. Your home will be hotter than what you would expect when you turn on your air conditioner. You may use ceiling fans to keep the humidity and temperature within the range.

Old Air Filters

The air filter in your air conditioner traps contaminants from the air. If the air filter is old and dirty, you will experience many problems with your cooling system. A dirty air filter fails to trap contaminants that trigger allergies.

Also, a dirty air filter can block airflow within the system due to the dirt and other debris. If this happens, you may have high energy bills as your system works harder to maintain the airflow in your home. Thus, having a dirty air filter will prevent the air conditioner from keeping the house cool.

Fortunately, there is a simple solution to this problem. Check and change your air filters regularly. If you start experiencing relatively warm air instead of cool air in the house, it may be time to replace the filters. Also, when you realize the high costs of energy, check the filters for dirt.

Low Refrigerant Level

Your air conditioning system relies on the refrigerant to cool the air inside your home. The refrigerant goes through the condenser unit to absorb the heat from the warm air in your home. The resulting cool air then travels through the ductwork.

If your air conditioner has low refrigerant levels, the system will not cool the home. This is because the air conditioning system will fail to take enough heat from the warm air in your home to cool the house.

You can fix this problem by letting a certified HVAC technician check the cause of low refrigerant levels. If there is refrigerant leakage, the technician will fix the cause of the leak.

How to Quickly Cool a House the First Time an Air Conditioner Is Started 

It is possible to cool your house quickly when you start an air conditioner. The goal is to achieve the perfect humidity and temperature levels without utilizing much power.

Here are a few tips to help you achieve this goal.

  • Ensure your air conditioner is in good shape. Do not wait for the first hot day to turn on your air conditioner. Check the system before the time for any problem and service it. Change your air filter if necessary before switching on the air conditioner on the first hot day.
  • Insulate your house properly. Proper insulation minimizes the loss of cool air during the warm months. It also reduces the entry of warm air during the hot ones. This helps you maintain your power consumption.
  • Cool only the necessary rooms. Strategically cooling rooms where people are helps to speed up the process. This also keeps your energy costs within manageable levels.

Air Conditioner Cooling Time FAQs

How Long Does It Take To Cool a House?

It should take about three hours to cool a house from 80 degrees to 72. The actual time depends on the capacity and status of the air conditioning unit. If it is too small and faulty, it may be longer than three hours.

How Long does it Take for the Ac to Turn On?

It takes about 30 minutes for an air conditioner to turn on. Once you start with the thermostat, you can get on with the entire system after 30 minutes. The system will then be ready to start the cooling process.

How Long Should AC Run after Reaching Temperature?

An air conditioner should run for about 15 minutes after reaching the set temperature. This period applies when the temperatures are mild. If the air conditioner runs much longer, it may be too small for your home.

How Long should it Take to Cool a House 1 Degree?

It should take about an hour to cool a house by one degree. This length of time applies to a standard three or four-bedroomed house. If the house is larger than this, the time may be longer.

How Long does a Window Ac Take to Cool a Room?

A window AC may take about an hour to cool a room. The actual time that the window AC takes depends on its cooling capacity and other factors. The size of the room also influences the time that the window AC takes to cool it.

How Long Should it Take to Cool a House by 2 Degree?

It may take up to four hours to cool a house by two degrees if the air conditioner is in good condition and the house is properly insulated.


Proper and prior maintenance of an air conditioner helps reduce the time it takes to cool a house. Also, getting an air conditioning system with the right BTU rating based on your house helps cool your home fast. You can speed up the process by strategically cooling specific rooms where people sit.