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

Many different factors can affect how fast your house will cool down once you switch on the AC. These include the temperature of your house before you switch on the AC.

The size and shape of your house. And chiefly, how hot it is outside. On sweltering days, AC units might struggle even if in the past they have performed well.

Besides, you also have to look at your house’s insulation level and your AC unit’s type and condition. The more efficient and better quality AC units will cool your house much quicker than an older unit that needs repairs. 

Considering that there are a fair few variables to consider when calculating how quickly your house should cool down after applying AC, it isn’t easy to give an exact answer to how quickly your house will cool down.

How Long Should it Take to Cool a House from 80 to 72

A typical four-bedroom house should drop from 80 degrees Fahrenheit to 72 in an estimated 3h. However, it isn’t easy to give a perfect answer to this question for every household, as mentioned. 

This calculation is assuming that the AC unit is of outstanding performance quality. AC units that are older with a good deal of wear and tear may take significantly longer. 

Cooling a regularly sized house to a point where the occupants notice a significant difference may take as long as 5-6 hours. Again this depends on the collection of variables that have already been discussed. 

How Long should it Take my AC to Drop 1 Degree?

If we use the same four-bedroom house example with an excellent AC unit installed, it should take approximately 18 minutes to decrease the temperature in your home by a degree. This is based on an AC unit’s ability to lower the temperature by 10 degrees over 3 or so hours. 

If your AC unit is running well and your home has well-insulated roof spaces, your home should be noticeably cooler within a few hours. 

How Outdoor Temperature Affects Air Conditioning

High temperatures affect your air conditioning unit in a few ways. In basic terms, your AC will have to work harder the hotter the outside temperature is. When the outside air temperature is in the middle range, your AC works by using the heat exchanger in the unit to move hot air from inside your home to the outside.

However, when temperatures get into the higher ranges outside, your AC starts working differently. When outside temperatures spike, the compressor starts to do more work to create cool air for your residence. 

The hotter the outside air temperature, the harder your AC system has to work to reach the temperature that you have set for it. Most systems are only able to deal with a maximum outside air temperature of 95 degrees Fahrenheit. At this point, most systems are maxed out and will not be able to cool your home any further than approximately 78 to 80 degrees. 

Setting your system lower than this will do nothing to change your home’s temperature, as the unit is working at maximum capacity. 

Why does my AC Take so Long to Cool my House?

There are several reasons why your AC system is not performing as well as it could be. Some are more serious than others. A simple issue that your AC unit might be having is that the air filter hasn’t been changed in a while, meaning that the airflow in and out of the house is significantly slower than it used to be.

This is an imminently fixable issue. All you need to do is clean or, in more serious circumstances, change out your filter. This should help to improve the effectiveness of your AC system. 

Another common problem is that the condenser coils that displace the heat from the refrigerant in the AC system have gotten dirty and therefore are not operating as well as they should be. 

Again this is a problem that you can fix without the need for a professional. All you need to do is wash the condenser coils, located in the outside AC unit, with a special cleaner and water. 

Other more serious problems such as a refrigerant leak or a damaged AC unit should be handled by a professional. 

What to do if your AC is Taking too Long to Cool a House

The first thing you need to do to approach this problem is to understand your AC’s issue in trying to cool your house down.

There may be several reasons why your AC is struggling. One of which could be that it is damaged in some way. In which case, it is recommended that you contact an engineer and have them inspect the unit.

Another is that your AC system is not equipped to deal with the task you have set for it. Your AC unit may be designed for a space much smaller than the one you are asking it to cool and therefore struggling to complete the job. You may need to purchase an oversized unit fit for the space you are trying to cool in this case. 

Your house also might not be very energy efficient or not insulated well enough, meaning that a lot of the cool air generated by the system is being lost unnecessarily.

If this is the issue, it may be worth considering installing better insulation, especially in your roof spaces where a lot of cool and hot air can be lost. 


A regular house should drop from 80 to 72 degrees in most circumstances in 3 or so hours from when you switch the AC. This is if you have a modest-sized home and a very efficient AC system. As we have discussed, though, many different factors go into calculating how long this should take.

These include your AC unit’s condition and size, the level of insulation that you have in your house, and the outside temperature. 

To make sure that your system cools your house quickly, make sure that you have the right-sized AC system for your space, a well-insulated home, and that you keep an eye on the condition of your unit.