How Long Does A Portable Air Conditioner Take To Cool A Room?

When the heat rises outside, it’s time to turn on the air conditioner. The type of a/c you use will determine how long you’ll have to wait for sweet relief. How long does a portable air conditioner take to cool a room? The answer depends on several factors.

The time it takes for a portable air conditioner to cool down a room depends on the size of the room, the size, age, and BTUs of the air conditioner, the surrounding temperature, and the level of insulation in the room.

Read on to learn how long it takes a portable a/c to cool a space. 

How long does a portable air conditioner take to cool a room?
A portable a/c unit can provide quick, cool relief!

How long does a portable air conditioner take to cool a room?

When cooling your home, you have several options. Central air. A window unit. A portable a/c unit. A portable unit has several advantages, but how efficient is it at cooling a room?

The amount of time your portable a/c will take to cool the room largely depends on the kind of unit you’re using and the size of the room. Other factors like room temperature, draftiness, and insulation also affect the time. Most portable units will cool a room by 5 degrees in less than 20 minutes.

Portable a/c units are affordable. They also have the advantage of portability that you don’t find with other a/c options. They are easy to install and move from one room to another. You can easily store them when not in use.

Before we look at the factors influencing cooling, let’s look at two other popular a/c styles.

Time it takes a window air conditioner to cool a room

Window air conditioner units work best to cool a single room.

Window air conditioners are more effective than central air conditioners because they are used to cool down one area as opposed to the entire house. Their cooling time is similar to that of a portable a/c unit. However, the unit is fixed in place.

Window units use less electricity than portable units, but sometimes installing a unit into a window isn’t possible. You are limited by the size and style of your windows. These units also produce condensation, which can accumulate around the window casing or on the floor.

A 15’x15′ feet room will feel noticeably cooler after 20 minutes of run time.

Time it takes a central air conditioner to cool a house

Many homeowners prefer central air conditioners. They cool the entire house instead of just individual rooms.

Newer central air conditioners will take 18 minutes on average to cool a house by one degreeAge is a big factor that determines the amount of time the unit takes to reduce temperatures. The older the unit, the longer it will take to cool.

Central units take regular maintenance to cool effectively and efficiently. According to, today’s air conditioners use 30-50% less energy than those of the 1970s.

Factors that determine how long it takes a portable air conditioner to cool a room

Each room’s unique circumstances can affect a portable a/c’s cooling rate.

The factors that determine how long it takes a portable air conditioner to cool a room are the air conditioner size, the room size, temperature, humidity levels, and the number of heat sources in the room.

Air conditioner size & age

The size of the portable air conditioner will affect how long it takes to cool a room.

An a/c with a bigger cooling capacity will cool your room faster than that with a smaller cooling capacity. Cooling capacity is measured in British Thermal Units (BTUs). Air conditioners list their BTU rating on the box so you can choose the correct size for your room.

A BTU is the “quantity of heat required to raise one pound of liquid water by 1 degree Fahrenheit at the temperature that water has its greatest density.” This unit of energy measurement allows us to compare different types of energy. In layman’s terms, a BTU is a measurement that expresses how much energy your unit is using to remove heat from your room.

The larger a room, the more BTUs it takes to cool it down. The older your air conditioner, the more time it will take to cool. Newer models are more energy efficient and don’t have the wear and tear that older models do.

Cooling time by room size 

The size of your room will also determine how long it takes a portable air conditioner to cool it down. Are you trying to cool a small bedroom or a high-ceilinged family room? Size matters when it comes to cooling.

To cool a room effectively, you need to match the room size to an appropriate a/c unit size. The smaller the room’s square footage, the smaller the unit you can purchase. Portable air conditioner units range from 8,000 to 14,000 BTUs. This cooling output can cool up to a 700-square-foot room.

Room size BTU required
150 sq. ft. 5,000 BTU
250 sq. ft.6,000 BTU
300 sq. ft.7,000 BTU
350 sq. ft.8,000 BTU
400 sq. ft. 9,000 BTU
450 sq. ft. 10,000 BTU
500 sq. ft.11,000 BTU
600 sq. ft 12,000 BTU
700 sq. ft. 14,000 BTU
Source: PickHVAC BTU recommendations

There are several online BTU calculators that can help you choose the correct size unit for your individual needs. You can customize insulation type, sun exposure, and climate. It’s always best to have more BTUs than not enough, so size up if in between sizes. Here’s an example:

Calculate how many BTUs are needed for the size of your room.
BTU calculators make it easy to find a portable a/c unit that will work for you.

Important note about portable a/c units and BTUs: Portable a/c units were traditionally rated on BTUs using the same standard as other types of air conditioners (ASHRAE). In recent years, manufacturers have started using a seasonal rating (SACC) which is more suitable for a portable unit. The SACC BTUs will be lower than traditional BTUs but more representative of the true cooling capacity.

Temperature & humidity

Where you live and the location of your room can affect room cooling.

If the heat and humidity levels outside a room are higher, it will take the portable air conditioner extra time to bring the temperature down. A room getting direct afternoon sun will take longer to cool than one in the shade. An area with high humidity levels will take longer to cool than one located in a dry area.

I live in the hot, humid south. We use a portable air conditioner in our bedroom for this reason. Our central unit will run all day long on 95-degree days and still not cool down our room to my liking. A portable a/c can cool it down to a comfortable level in as little as 20-30 minutes.

Insulation level/air leaks in the room

Are your windows drafty? Do you live in an older home? The construction of your room can affect cooling, too.

Poor insulation allows heat into your room. Air leaks around windows will allow cool air to escape out of the room. Both of these issues will cause the portable air conditioner to work harder and take more time cooling the room.

Adding additional insulation in the walls and sealing off any cracks will increase the efficiency of your air conditioner and your comfort level.

Unnecessary heat sources

Do you have a lot of electronics in the room you are trying to cool? This can have a negative impact on the time it takes to lower the temperature.

If the room you’re trying to cool has several heat sources, it will take the portable air conditioner longer to reduce the temperature. People, light sources, and electronics will increase the heat level in a room.

Reducing the number of warm bodies, turning off the lights, and powering down electronic devices will help your unit run more efficiently.

Faster cooling tips for your portable air conditioner

We only use our portable a/c at night to cool our bedroom. I turn it on 20 minutes before we are ready to hit the hay. The room is a perfect 70 degrees, while the rest of the house is five or more degrees warmer. The result? Perfect sleeping temps without turning the central air super low.

Keeping the portable air conditioner unit out of the sun, closing the doors and windows to the room, and using fans to circulate cool air can speed up cooling.

Ready to purchase a portable a/c unit? Here are a few tips to cool your room down fast:

  • Use curtains or blinds in the room to prevent the heat from the sun from penetrating through. 
  • Place the unit where direct sunlight doesn’t reach it. Too much heat from the sun will make the work harder.
  • Put away heat-inducing appliances that are close to the thermostat.
  • Keep doors and windows closed while cooling.
  • Consider using fans to distribute the cool air throughout the room.
  • Insulate the room well.
  • Do regular maintenance and keep your unit clean and dust-free.
  • Seal the windows and doors to prevent heat from coming in through the holes. 
Cooling test in real-time.

Summary of “How long does a portable air conditioner take to cool a room?”

Portable air conditioners are a great option to cool down a room. The time it takes for a portable unit to lower the temperature depends on several factors. To cool down a room fast, buy a unit that has sufficient BTUs for the room’s square footage. On average, it takes 15-20 minutes to reduce the temperature by 5 degrees.

The temperature and humidity of the surrounding area, the presence of air leaks, and the lack of sufficient insulation can affect the time it takes to adequately cool a room.


What is the difference between a portable and a window AC?

A portable AC is a self-contained cooling unit that can be easily moved from room to room, while a window AC is designed to be installed in an existing window opening. Window a/cs typically have more power than portable a/cs.

Why is my portable AC not cooling my room?

There could be several reasons why your portable AC is not cooling your room. One possibility is that the unit is not properly sized for the space it is attempting to cool. Another issue could be a lack of refrigerant gas, which would cause the compressor to overheat and shut down. Additionally, the evaporator coils may be dirty or blocked, preventing the unit from transferring heat out of the room.

How long should you run a portable air conditioner?

There is no set time frame for how long you should run a portable air conditioner. Some factors that could influence how long you should run it include the size of the unit, the climate, and the humidity level. Generally, it is recommended to run a portable air conditioner for as long as possible in order to achieve the desired results.

How do I make my portable air conditioner colder?

Portable air conditioners draw in hot air from the surrounding room, cool it down, and then release it back into the room. To make a portable air conditioner colder, you can either increase the fan speed or decrease the temperature setting. Increasing the fan speed will cause the air conditioner to work faster and release colder air into the room. Decreasing the temperature setting will cause the air conditioner to release cooler air into the room at a slower rate.

Can portable AC units catch fire?

Portable AC units can potentially catch fire if they are not used or maintained correctly. This can happen if there is too much moisture build-up inside the unit, which can create a fire hazard. It’s important to ensure that the unit is properly vented to the outside and that it is not blocked by furniture or other objects. Regular cleaning and maintenance can help prevent these potential fires.

Can a portable air conditioner make you sick?

Portable air conditioners can make you sick if they are not properly ventilated. If the machine is recirculating the same air over and over again, it can become contaminated with bacteria, dust, and other allergens. This can cause respiratory problems and other health issues. It is important to make sure the machine is properly ventilated to the outside so that fresh air can circulate.

Do you have to put Freon in a portable air conditioner?

Yes, a Freon-based refrigerant is necessary in order to power most portable air conditioners. This liquid helps cool the air as it passes over the coils in the unit, making it more comfortable to breathe. While some newer models do not require Freon, it is still the most common type of refrigerant used in air conditioners.

Can you run a portable air conditioner all day?

Portable air conditioners are a great way to cool down a small space without having to rely on a central air conditioning unit. While it is possible to run a portable air conditioner all day, doing so will likely increase your energy usage and cost.

What temperature should a portable air conditioner be set at?

A portable air conditioner should be set between 68 and 72 degrees Fahrenheit to ensure optimal performance. If the unit is set too low, the compressor will work harder than necessary and could eventually fail. If it is set too high, the unit will not be able to remove enough humidity from the air and may start to drip water.

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