Photograph of a split system air conditioner - compressor or outdoor half of the system Portable Room Air Conditioners, Selection, Use, Properties & Functions

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Portable room air conditioners: How to choose an air conditioner for window or through-wall mounting, how much BTU capacity do you need?

How to choose a portable air conditioner that fits the building and your cooling needs?Operating properties of portable room air conditioners, FAQs.

Do portable air conditioners provide outdoor fresh air intake? How big a portable room air conditioner do I need? Details about portable room air . conditioners. Are there energy efficiency & Energy Star Ratings for Portable Room Air Conditioners. BTU capacity & sizing charts for portable air conditioners.

Our page top photo shows the front of a Haier portable room air conditioner. Not shown are condensate accumulator or ductwork/hose extending to outside.

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Portable Room Air Conditioners

SPT portable room air conditionerWhat are the operating properties of portable room air conditioners? Do portable air conditioners provide outdoor fresh air intake? How big a portable room air conditioner do I need?

We also will discuss the energy efficiency & energy star ratings for portable room air conditioners, and portable A/C unit BTU capacity & sizings.

Portable air conditioners are cooling units on wheels that are plugged into an outlet but can be moved room-to-room and do not require a window for their exhaust.

These cooling units are of modest cooling ability, typically around 10,000 BTUh though some producers such as Sunpentown [at reviewers] offer units up to 14,000 BTUh.

Article Contents:

There are quite a few brands of portable room air conditioners, including Friedrich, Haier, New Air, Sharp, Soleus, Supentown, SPT (shown at left). [ has no financial nor any other relationship with any brand or product discussed at this website.]

The U.S. ENERGY STAR program uses the term "Single Package" air conditioning system which is defined as follows:

Single Package: A single package unit is an ASHP or central air conditioner that combines both condenser and air handling capabilities in a single casing.[1]

In this definition, ASHP refers to an Air-Source Heat Pump (ASHP) which is further defined as follows:

Air-Source Heat Pump (ASHP): An air-source unitary heat pump model consists of one or more factory-made assemblies which normally include an indoor conditioning coil(s), compressor(s), and outdoor coil(s), including means to provide a heating function.

ASHPs shall provide the function of air heating with controlled temperature, and may include the functions of air-cooling, air-circulation, air-cleaning, dehumidifying or humidifying.[1]

Reader Question: How can I Avoid Mixing Outdoor Air Into My Room Air with a Window or Portable Air Conditioner?

Do you know of any air conditioners (besides mini split ac's) that don't mix inside air with outside air? Do you know of any ac's that have sealed compressors?

If not, do you know of a solution to not mixing inside with outside air? Do regular window ac's and dual hose portable ac's normally mix inside with outside air? - B.R.

Reply: Close the outside air intake vent on a window air conditioner unit or use a portable room air conditioner

It sounds as if you've been given some confusing information. All residential A/C compressors are sealed units, and outdoor air has no role in the internal operation of the compressor.

Room air conditioners typically have a manual control that permits mixing in outside air or shutting it off.

Central air conditioner systems do or do not have outside air supplied to the return duct system depending on the duct design, having nothing to do with the compressor you cited. Though many residential central air systems we've inspected do not provide for outside air or makeup air, it's a good component to add to the design for a very tight house where IAQ could be a worry; for maximum heating or cooling efficiency we use an air to air heat exchange where outdoor air is entering the system.

How to Close off Outside Air Intake for Window-mounted or Through-Wall Air Conditioners

If you are using a window-mounted or through-wall mounted air conditioner, it is likely to have a mechanical control, a dial or lever that opens or closes a vent that mixes or stops mixing some outside air with room air as it is circulated through the air conditioner unit.

If you don't want to introduce outdoor air (increasing the cooling and dehumidification effectiveness of the system at the expense of fresh air), just be sure that your unit's outside air control is in the "closed" position. These vents may not be perfectly air tight but in a modern air conditioner closing the vent will close off nearly all outside air intake.

Outside Air & Portable Air Conditioners

While some portable air conditioners may make use of outside air to assist in cooling their compressor and in removing condensate, at least some of the models, including dual-hose units that we read about (which is certainly not all of them) provided an outside air intake that adds outside air to the room air being cooled and dehumidified.

The balance point between maximizing the cooling ability (and reducing cooling costs) any air conditioner by closing off outside air from the system and the quality of indoor air in a tight building needs to be decided on a case-by-case basis. If your building is very tight, or has odors, stale air, or high dust or allergen levels

FAQS & Properties of Portable Air Conditioners: Pros & Cons of Portable Cooling Units

Soleus 2 portable air conditioner hosesOne producer of portable air conditioners who provides particularly helpful description of the operating properties of these devices is Sunpentown International (SPT), a California firm. Here are some relevant FAQs that give insight to the operation and use of portable air conditioners, as well as comparing the use of single-hose and dual-hose portable room air conditioners.

The photo at left shows typical flexduct and other accessories for a portable room air conditioner, in this case from Soleus.

Quoting from Sunpentown's FAQs (Quoting and paraphrasing):

Single Hose Portable Room A/C Unit

This design draws indoor air for both front cold air output as well as exhaust air (used to cool compressor).

PROS of single hose portable room air conditioners:

CONS of single hose portable room air conditioners:

Dual Hose - draws indoor air for front cold air output and draws outdoor air for exhaust air (used to cool compressor).

PROS of dual hose portable room air conditioners:

CONS of dual hose portable room air conditioners:

NOTE about outdoor air: We read no indication in either design that outdoor air is added to or mixed in with room air.

How is Condensate Disposed-of for Portable Room Air Conditioners

Sunpentown Portable AC units are equipped with an advanced condensation removal system: Self-Evaporating Technology (except WA-9000E, WA-1000E & WA-1205E). When running AC mode, this technology recycles the water condensation to cool off the cooling coils, then evaporates the water out with the exhaust air.

This results in increased energy efficiency, cooling performance and reduces the need to empty the water tank. Under extreme humid conditions, the water condensation may collect faster than the unit can recycle. Should the built-in water tank becomes full, the compressor will automatically shut-off and water full indicator will blink. At this time, water should be emptied, which is a simple process.

For units with Self-Evaporating Technology, it is always suggested to not use continuous drainage in cooling mode. Allowing the water to collect and recycle helps cool down the cooling coils, which in turn produce colder air output.

More detail about how to diagnose and cure an air conditioner that is not dehumidifying can be found at Air Conditioning Dehumidification Problems.

Role of Exhaust Flex-Duct or "Hose" for Portable Room Air Conditioners

Outside air conditioning for tents (C) D Friedman

Our photo (left) shows huge portable air conditioning systems that are being used to air condition an enormous tent used for a college alumnae gathering in New York.

The white flex duct you see there is blowing cool air into the tent space and the entire air conditioner is located outside the tent. This is a "total loss" system that pulls outdoor in to the unit, cools it, and blows it into the tent.

In comparison with the commercial outside portable air conditioner supply flex duct you see at left, indoor portable air conditioners provide for an exhaust duct as follows:

All portable AC units require exhaust hose installation. This is for removal of hot air which has been used to cool off the compressor. Standard installation includes venting through a sliding window or through the wall, by cutting a hole.

Sunpentown AC units are supplied with the necessary accessories for either installation: flexible hose (extends up to 5'), window kit and wall adapter.

[End of quote, paraphrase]

Other types of portable or individual-area air conditioners

Portable, window, or through-wall air conditioners are typically described by their manufacturer as suited for:

How to Calculate the BTUs needed to cool a given space follow this procedure

Here we explain how to calculate the BTU capacity needed for a room air conditioner. Below we provide a PORTABLE AIR CONDITIONER BTU CHART based on room size in square feet and with added factors for sun exposure or extra heat load.

  1. Calculate the total square feet to be cooled: Measure the size of the room (or rooms) to be cooled, to obtain total square feet. Multiply room length by width for each room and if there are multiple rooms, add the room areas together to get a single number.
  2. Read the Base BTUs needed from Table 1 below
  3. Add additional BTUs for these factors:
    • + 4,000 BTUs for each room below a ceiling or roof which is not insulated
    • + 4,000 BTUs for a home or residential kitchen included in the cooled area
    • + 1,500 BTUs for each window which receives significant daily sunshine
    • + 1,500 BTUs for a room over a kitchen or boiler room IF the kitchen or boiler room is actively producing heat during the cooling period
    • + 600 BTUs per person over two, if more than two occupants will be occupying the room during the cooling period
  4. Subtract BTUs from the total required if these factors are present:
    • - 1,000 BTUs if the room is on the shaded side of the building
  5. Calculate the final total BTUh needed from the above steps. This should place you in the right range of cooling capacity needed. Review the warning below about buying an oversized air conditioner.

The Air Conditioner BTU Recommendation table found at AIR CONDITIONER BTU CHART gives recommended air conditioning BTU's necessary to cool a single room. The data in the table assumes that the ceiling over the room is insulated and that the room is not over or is not itself a special heat-producing area such as a kitchen or boiler room. Do not buy an air conditioner which is oversized (too many BTUh) for the area you need to cool. You may think that bigger is better, but not in the case of air conditioning.

To make a room comfortable the air conditioner needs to both cool the room air AND dehumidify the room air.

If the air conditioner is too large for the space to be cooled, the temperature will drop quickly and the A/C unit will shut off before the air has become adequately dry.

The room will be either too cold or too humid for comfort.

Also see RATED COOLING CAPACITY for an explanation of how to determine the cooling capacity of an air conditioner that is already installed at a building.

Cooling Capacity Charts for Portable Air Conditioners

Portable Air Conditioner Cooling Capacity or BTUh Requirements Table

Example Room Size
Square Feet
Recommended Portable Air Conditioner Size in BTUs/Hour Recommended Portable Air Conditioner Size in BTUs/Hour for Rooms Receiving Strong Sunlight or Having Extra Heat Source[3]
130-165 sq. ft. 5000 BTUh  
180-200 sq. ft. 7000 BTUh  
200-300 sq. ft. 8,000 BTUh Increase to 12k BTUH for extra hot rooms such as kitchens
250-350 sq. ft. 9,000 BTUh  
260-380 sq. ft. 10,000 BTUh Increase to 11k BTUh or 14k BTUh
375-425 sq. ft. 12,000 BTUH Increase to 13k BTUh or 16k BTUh
400-600 sq. ft. 14,000 BTUh Increase to 15.4 kBTUh or 18 kBTUh


These room sizes and thousands of BTUs per hour (BTUh) estimates for portable room air conditioner sizing or choices are only approximate. Specific site conditions including general climate, sun exposure, building heat gain due to siding colour, air leaks, and other factors can push the actual BTUh capacity needed in either direction.

Watch out: do not buy an air conditioner significantly over-sized for the room size you are cooling, or you will find that the system may cool but may fail to adequately dehumidify the space.

Watch out: none of these portable room air conditioner cooling capacities will be accurate if you do not vent the hot air from the unit to the outdoors. Purchase a window venting kit or other outdoor venting accessory as needed for that purpose. We do not recommend venting these units into an enclosed building space such as an attic or crawl space.

[1] This table pertains to portable room air conditioners. Because about 30% of the heat being expelled to outdoors by a portable room air conditioner is heat generated by the machine itself, only 70% of the heat being moved outdoors by the unit is being taken out of the space being cooled.

For this reason the energy efficiency of a portable room air conditioner is likely to be notably less than that of a central air conditioner, a split system air conditioner, and also less than a window air conditioner. For window air conditioner BTU or cooling capacity versus room size please

[2] Presuming an eight-foot ceiling height. Increased cooling capacity may be needed for rooms with higher ceilings.

[3] Example, kitchens

Building & Site Adjustment Factors for Cooling BTU Requirements

Sketch explaining how many square feet of building can be cooled with one ton of air conditioning power (C) Carson Dunlop AssociatesHow Much Cooling Capacity do we need Per Square Foot of Building Area? How Much Space can a Ton of Cooling Capacity Serve?

Maybe 450 sq. ft. to 1000 sq. ft. of a typical home can be cooled per ton of cooling capacity: that is, one ton (or 12,000 btuh) of air conditioning can cool about 500 sq. ft. of space. Sketch courtesy of Carson Dunlop Associates.

But the real answer is, it depends. Some of the factors that affect the ability of an air conditioner to cool a space need to be considered besides just the number of square feet. These include at least the following questions about air conditioning load and cooling requirements:

Energy Efficiency of Portable Room Air Conditioners

Reader Question: Are there any portable AC's Energy Star Rated ?

12/14/2014 Anonymous said:

Are there any portable AC's Energy Star Rated


Some but not all manufacturers of portable air conditioners may provide an Energy Star certification and rating for their units. They are not required to do so. Non-providing manufacturers may say "Energy Star Compliant" without giving a rating - a claim which in my OPINION is simply confusing and not so useful. (See )

The Energy Star Compliant claim is presumably a unilateral statement by the manufacturer that their product meets the U.S. Government's Energy Star Program requirements for a product to earn an Energy Star label and rating, BUT that the company has not in fact applied for such a label. (Who knows?) Here is what "Energy Star Compliant" should mean:

How Does EPA Choose which Products Earn the Label?

Products can earn the ENERGY STAR label by meeting the energy efficiency requirements set forth in ENERGY STAR product specifications. EPA establishes these specifications based on the following set of key guiding principles:

You'll see from the last Energy Star Label requirement that a manufacturer cannot accurately claim compliance without actually complying, since their "claim to comply" label omits "Labeling would effectively differentiate products and be visible for purchasers".

In December 2014 we reviewed some online shopping product comparison websites listing more than 40 models of portable air conditioner, scanning the product description text for the words "Energy Star" without finding a single success - that does not (yet) mean that none of those products carry an Energy Star label, we're still researching the question.

There is another portable air conditioner performance rating standard you might want to review:


Continue reading at COOLING RULES OF THUMB or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see RATED COOLING CAPACITY to determine the cooling capacity of existing air conditioning equipment.


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PORTABLE ROOM AIR CONDITIONERS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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